Biological Anthropology Notes PDF

-​ September 4, 2024​ ​ Instructor Class 1 ​ Zarin Machanda - [email protected] Unit 1 – Evolution and Genetics ​ TA...

-​ September 4, 2024​ ​ Instructor Class 1 ​ Zarin Machanda - [email protected] Unit 1 – Evolution and Genetics ​ TA Matt Lem - [email protected] Office hours Zarin: Monday 1:30-2:30, or by appointment - Braker Hall Matt: Wednesdays 2-3pm - Braker Hall 117 Anthropology - the study of humans Chimpanzees and Humans shared a common ancestor 5-7 million years ago - chimps are the most closely related societies to humans 4 Units: 1.​ Evolution and Genetics 2.​ Primates 3.​ Human Evolution 4.​ Modern Humans Fair game for exam: Primatologists use words that don’t have connotations: Smile = silent bare teeth grin In despotic species when a dominant member threatens a subordinate the subordinate smiles. Non-despotic (more egalitarian) species smile in more happy contexts. Since humans mainly smile in happy contexts… this shows we are more egalitarian than other primates. September 9, 2024 Class 2 - Evolution by Natural Selection  -​ 1.​ Evolution as Science 2.​ History of Evolutionary Thought 3.​ Basics of Natural Selection 4.​ Trait Types and Other Caveats Evolution as Science What is Science? -​ A process NOT a body of knowledge -​ Question driven -​ Evidence and data are key! Observations trigger studies but anecdotal evidence is not sufficient. -​ We try to approximate undertaking of natural world ~ might not be perfect -​ Curiosity about the world -​ Do you have questions, have the questions been answered or is there more to ask? -​ “Marriage of skepticism and wonder” ~ C. Sagan -​ We don’t PROVE things, we gather data to SUPPORT ideas. -​ There are not many laws in biology because we only know how life works on THIS planet, we can’t compare our life, how it works, with how it may work on other planets. -​ There are many big ideas called THEORIES. -​ Theories aren’t speculative. They are backed with massive amounts of evidence. We are pretty sure it’s true. -​ We are often wrong so science is constantly updating and self-correcting. -​ We are not descended from Neandertals, they are a sister species. -​ Science doesn’t depend on who proposes the idea rather what the data are saying and how the study was conducted. Evolution as a science… -​ Evolution can’t be seen in a lab but it is a branch of science. -​ It is testable, has explanatory power and we can make predictions based on evolution about what we will find. -​ Definition of evolution: change over time/species changing over time.  -​ -​ Homology is when we have across different species, similar structures that are the result of shared descent. -​ Every mammal has five digits because we all came from the same ancestor. -​ Number of vertebrae in the neck of a human is similar to that of a giraffe. -​ There are also developmental similarities that reflect descent from a common ancestor. (See slide 16) -​ Vestigial organs are another example of descent from a common ancestor. Example: tails. -​ Goosebumps are also something we share with primates. When chimps are scared, their hair sticks up and makes them look bigger. -​ Whales have hip bones → this shows they came from a terrestrial ancestor that used to live on land. Fun fact: whale bones leech so much oil, they still secrete it decades after the whale dies. Genetic evidence for evolution… -​ Every living organism has DNA/RNA -​ When DNA sequences are similar, it shows how closely related two species are. Fossil evidence for evolution… -​ There are fossils in the earth all over the world that show evidence of species that don’t exist anymore. -​ Slide 20 ~ transition between an ape and a human Mistakes and imperfections… -​ Bipedalism caused back injuries, hemorrhoids, varicose veins, bad knees, appendix, impacted molars (not about bipedalism but other uses we don’t have) -​ Animals aren’t machines, evolution can only go off of what already exists, we have these issues because we are still evolving. -​ Slide 22 don’t need to draw this chart or know the names! -​ Tetrapods - 4 limbed animals -​ We predicted that there should be the first tetrapod 375 million years ago and we didn’t know what the animal was until we discovered the Tiktaalik which was in fact around 375 million years ago ~ Predictive Power!!! History of Evolutionary Thought  -​ What is man’s place in nature? -​ Carl von Linnaeus set out to classify life -​ Systema Naturae ~ his book -​ First person to classify humans as primates ~ 1735 -​ He ordered things in a hierarchy of life ~ Natural Taxonomy -​ Groups of species nested within broader groups -​ This can’t be done w nonlife -​ There was a connection between biology and religion at this time. -​ They called themselves ‘natural theologists’ -​ Only ppl that could teach biology were Anglican clergy -​ William Paley ~ Natural Theology 1802 -​ Evidence discovered through biology supported God’s power and perfection -​ If you studied nature you were paying tribute to God -​ Paley says that creatures are well adapted to their environment and he attributes this to God. -​ Erasmus Darwin Zoonomia 1794 (Charles Darwin’s grandfather) -​ He talks about the fact that animals are descended from one another ~ very unpopular idea -​ Jean-Baptiste Lamarck 1809, put through a process by which evolutionary change occurs —> animals inherit acquired characteristics. -​ Charles Lyell Principles of Geology 1830-33 promoted Uniformitarianism is about the idea that the world is changing in Geological ways —> erosion, earthquakes -​ Called in Uniformitarianism because he was making a point that the way the earth is changing is happening the same way it has been for hundreds of thousands of years -​ As the world changes, new species are created to fill new environments -​ Even in 1829, they had started finding fossils of Neanderthals Charles Darwin’s contribution… -​ Evolution VIA natural selection (natural selection is the mechanism by which evolution occurs)  -​ Darwin’s father was a physician, he told him he had to be a doctor. Darwin hated medical school. Instead of going to class he would collect rocks. Darwin’s father didn’t want him to go on the voyage, his uncle convinced his dad (slide 39). Darwin and Wallace -​ Beagle voyage 1831-1836 -​ Darwin picked up an illness so after 1836 he barely left his house, but he THOUGHT. -​ Darwin’s theory development 1837-1859 -​ Wallace spent 7 years in the Amazon. When he’s about to leave, his ship catches on fire. Every piece of specimen he collected burns in front of him. -​ He then went to Indonesia and Malaysia archipelago -​ In 1858 he gets Malaria and over 3 days he dreams of the theory of natural selection, writes it in a letter, sends it to a friend who is a mutual friend of Darwin. -​ Darwin has been thinking about this for 20 years so when the friend gets the letters he finally publishes it in 1859. Both of them independently came up w/ this idea. -​ People recieved it positively Basis of Natural Selection Two observations… -​ Animals are well adapted to their environment (Paley) -​ These adaptations are very complicated ~ lots of moving parts that work together for a certain function to work -​ For example: the eye -​ It’s hard to understand how all these pieces come together… it’s because we can’t watch evolution. Some ppl explain this w/ religion… it must’ve been designed. Natural selection is the process by which traits become more or less common in a population -​ important mechanism of evolution (but not the only mechanism)  -​ -​ 4 postulates: 1.​ Competition ~ animals compete because resources are limited, not everyone can survive and reproduce. 2.​ Variation ~ animals vary in traits that make them more/less competitive ex: animals bigger, stronger, smarter, more fur, etc. 3.​ Reproduction ~ then the animals that win this competition reproduces and reproduces more 4.​ Inheritance ~ these babies inherit the traits that made you a good competitor, these babies are more common and that’s how traits evolve on a grand scale. Galapagos finches are some of the best examples of natural selection we have. Studies started by David Lack and continued by Peter and Rosemary Grant. Slide 54 don’t need to know chart for exam. Big idea: beak shape is very different based on species. -​ Original habitat lush forest… Galapagos is very seasonal. -​ Wet season, easy to procure food, easy to eat -​ Dry season, everything dies, harder to get food, not enough available for everyone -​ Beak shape is correlated to food type for fallback food. -​ The birds that are able to get food during the dry season will survive and their beak traits will be passed on. September 11, 2024 Continuation of Monday’s lecture… How we explain the passing on of big beaks on galapagos finches… need to explain this process on an exam* review slide 17 of lecture 3: genetics ​ Variation is heritable Cross-fostering experiments - take an egg from a big beak beard and have them raised by a small beak bird and vice versa. Found that children of big beak birds will still have big beaks and vice versa ​ More proteins code for bigger, longer beaks.  -​ ​ Bigger beaks are able to crack open a harder, dryer shell during a drought… these are the finches that survive. ​ The ones that survive then reproduce and pass on the bigger beaks. Fitness/Reproductive success (interchangeable): The ability of an organism to survive and pass on their genes. Adaptation: a trait that has been selected for by natural selection; promotes survival. Trait Types and Other Caveats Homology: traits shared due to common ancestry (see visual on slide 24) Homoplasy: traits shared due to convergent evolution (see visual on slide 26) Mutations -​ Accidents of nature, not necessarily adaptive By-product of evolution/pleiotropy -​ Ex: penis tissue and clitoral tissue come from the same place. The clitoris in birds is a by-product of shared developmental origins of penis tissue in birds… humans too? ​ Not all evolution is the result of natural selection Behavior Ecology -​ Behaviors can be adapted and coded for by genes -​ Behaviors survive and reproduce through the same process of competition, variation, reproduction and inheritance Chapter 2 - How Humans Evolved 1.​ Mendelian Genetics 2.​ Cell Division and Inheritance 3.​ DNA and Molecular Genetics  -​ Mendelian Genetics Gregor Mendel -​ Became a priest so he could become a teacher and practice science by conducting experiments -​ Mendel bred pea plants together (slide 35) -​ Slides 36-38: -​ Bred yellow and green plants together and the babies were all yellow -​ Then he took the yellow and bred them together… 3 of the products were yellow, 1 was green (they always showed up in this ratio). -​ No blending occurred (green didn’t mix w/yellow) -​ Slides 39&40: -​ All variations come back in a particular ratio -​ Also no blending -​ All combinations are present in the grandchildren Mendel’s Two Principles (blue = more updated language): 1.​ Principle of Segregation: You get two sets of particles: one set from mother, one from father. Some genes may be passed on but hidden in the next generation. Individuals inherit one copy of each chromosome from each parent. Every cell contains genetic info from a mother and a father. 2.​ Principle of Independent Assortment: Particles for different traits assort independently. Ex. You can have yellow round or yellow wrinkled. Yellow & round don’t have to go hand in hand. Different chromosomes have different genes. Generally, need a full complement for proper development. Cell Division and Inheritance Cell Theory -​ All organisms are made of cells -​ The cell is the most basic unit of life -​ All cells are produced from other cells Chromosome inheritance theory: there are bodies in the nucleus of the cell that are replicated when cells divide in the creation of gametes  -​ ​ Sperm and eggs have ½ the number of chromosomes than every other cell in the body. Each has 23 chromosomes. Somatic cells have 46. ​ If sperm and/or egg cells have fewer or more chromosomes than 23, there are defects in the offspring. Lazzaro Spallanzani is responsible for the discovery that sperm is necessary for the fertilization of an egg. Ploidy: the # of each chromosome in a cell ​ If a chromosome is diploid then it has 2 copies of each chromosome → true of almost all mammalian somatic cells. ​ Gametes are haploid → single copy of every chromosome ​ Polyploidy (more than 2) is common in plants Mitosis -​ Start w a diploid parents cell -​ Chromosomes are replicated -​ Then they split into two diploid daughter cells Meiosis -​ Diploid parent cell -​ Chromosomes replicate -​ Results in 4 haploid daughter cells/gametes *key difference between mitosis and meiosis Alleles: gene variants -​ Alleles that are same: homozygous (AA or aa) -​ Alleles that are different: heterozygous (Aa) Genotype v. Phenotype -​ Genotype: combination of alleles of a particular individual. A description of allelic combination of the cell (AA, aa, Aa) -​ Phenotype: what does the organism look like (yellow, green)  -​ ​ Huntington’s Disease is a dominant trait Dihybrid Crosses: Two Traits Crossing-over and recombination allows for traits that each parent has to be broken up and combined in different ways but not blended. (Slides 72 & 73) Linkage -​ Genes close on a chromosome are more likely inherited together (a package deal) Pleiotropy -​ Some genes affect multiple traits -​ Ex: Beta-globin gene mutation produces blindness, liver failure and heart attacks Incomplete Dominance -​ The dominant gene isn’t 100% dominant: someone w straight hair has a baby w someone w curly hair. Curly hair is dominant but child has wavy hair bc it doesn’t translate 100% Codominance -​ Both traits dominant so both traits expressed -​ Ex: white hair and gray hair in birds results in speckled hair Sex-Linked -​ X and Y chromosomes are not a homologous pair -​ X and X are a homologous pair -​ So… imagine someone with an X X homologous pair. One of the chromosomes has a gene for color blindness, the other is fine. That person will be fine because they have the fine backup chromosome -​ But individuals with X Y heterozygous pairs don’t have a backup chromosome so… they are either colorblind or not depending on what the X chromosome is. Trisomy  -​ -​ Sometimes when the copied chromosomes split in meiosis, the chromosomes don’t split perfectly in half. -​ Usually when this happens the embryo isn’t viable and results in a miscarriage -​ When the embryo survives it results in Down Syndrome Environment -​ Same genotype but something about the environment determines expression -​ Ex: hydrangea are a certain color based on pH of the soil, but they have the same genotype Polygenic Traits -​ Many traits are coded for by multiple genes in the body -​ Ex: height and skin DNA and Molecular Genetics Genome: the complete set of genes or genetic material present in a cell or organism. ​ Genes code for proteins DNA: Deoxyribonucleic Acid -​ Double Helix -​ Base Pairs: Adenine & Thymine, Guanine & Cytosine DNA Replication -​ Ladder of double helix unzips and each side of the ladder creates another strand -​ Mutations are the result of a mistake in the replication of DNA (when a base paired isn’t paired correctly for example) Proteins 1.​ Structural proteins - muscle, collagen, keratin 2.​ Enzymes - affect and allow for chemical reactions 3.​ Regulatory Elements - decide how much proteins to make Amino Acids → Peptides → Proteins  -​ ​ There are 20 amino acids DNA → RNA → Proteins *important! September 16, 2024 Class 4 DNA and Molecular Genetics continued… Study the process of slide 4* (you know this, just review) -​ DNA is grouped in 3 letter ‘words’ called codons. These codons make up amino acids (20 dif variations, 20 dif amino acids) -​ RNA has Uracil instead of Thymine and that pairs w Adenine -​ If a mutation occurs, the amino acids code for a totally different protein Gene Regulation -​ Repressor region → bound in presence of glucose (turns off a gene) -​ Activator region → bound in presence of lactose (turns on a gene) -​ Transcription occurs when activator is bound and repressor is unbound -​ Enhancers decide how much of gene to turn on Chapter 3 - How Humans Evolved ​ Read and study p 65-68 for midterm 1.​ Lactase Persistence 2.​ Modern Synthesis 3.​ Population Genetics 4.​ Agents of Evolutionary Change Lactase Persistence -​ All infant mammals can digest milk -​ Infants produce lactase which lets them break lactose down into glucose and galactose (two digestible sugars) -​ As we are weaned off milk the gene for lactase gets turned off, undigested lactose goes to the colon -​ We turn off this gene to conserve energy at the cellular level  -​ -​ 35% of humans keep lactase gene turned on The Neolithic Revolution → period between 12,000 and 6,000 years ago when humans transitioned from hunter-gatherer lifestyle to farming-herding lifestyle Pastoralism → keeping of livestock and practice of milking livestock -​ Milk was an important source of calories even for adults The Biocultural Coevolution theory proposes that pastoralism and lactase persistence coevolved, occurred around the same time and began to reinforce each other *Lactase persistence varies geographically and areas where lactase persistence is high, so was a tradition of pastoralism A Single Nucleotide Polymorphism (SNP) is a mutation that involves the changing of one letter in the genetic code. → may seem insignificant but can affect how strongly a promoter or activator binds to a gene -​ In lactase persistence an enhancer site has a C replaced with a T. -​ This SNP affects how strongly and how often the transcription factor Oct1 binds to this site. -​ Oct1 is an activator and therefore causes more promoters to bind to the lactase gene → more transcription of lactase → can digest lactose! -​ After adults wean off milk there is normally a decrease in the transcription of lactase, this SNP prevents that so these people can still digest lactose. Convergent evolution is the independent evolution of similar features in separate lineages. Lactase persistence went through convergent evolution in Europe and Africa. *a different gene is sniped in Kenya than in Europe than in Sudan. Modern Synthesis Darwin – evolution is gradual accumulation of small change Mendel – inheritance is discrete and discontinuous Polygenic Inheritance is the inheritance of traits that involves more than one gene  -​ ​ Look at slides 34-38 for example on height Population Genetics Natural selection acts on the phenotype but changes allele frequencies in the next generation *important! Population genetics is the study of how allele frequencies change in a population over time and respond to evolutionary pressure -​ Allele frequency changes result in differences among species Gene Pool -​ All genes and different alleles in a population Allele frequency → “how many big As in a population” Genotype frequency → “how many of a specific gene in a population” Hardy-Weinberg Principle -​ The original proportions of the allele frequencies in a population remain constant from generation to generation (if evolution is NOT occurring). -​ P = frequency of A in a population -​ Q = frequency of a in a population -​ P + Q = 1 -​ Study slide 50-60 for an example *need to know how to calculate number of A and a alleles!! -​ Hardy-Weinberg equilibrium is reached if frequency of aa = q^2, frequency of Aa = 2pq and frequency of AA = p^2 Evolution occurs when allele frequencies change not when gene frequencies change!!! *important Hardy Weinberg Principle holds if… -​ Population size is large -​ Random mating is occurring -​ No mutations occur -​ No alleles transfer in/out of population (no one leaves/enters)  -​ -​ No selection occurs Then allele frequencies will remain the same in the population Agents of Evolutionary Change 1.​ Natural selection -​ Selection against those w PKU for example because homozygous (aa) die and can’t bring their alleles to the next generation. This was originally 16% of the population but then they died and don’t get carried on to next generation 2.​ Mutation -​ Changes in a cell’s DNa -​ Ultimate source of genetic variation -​ New mutation transforms an allele into a diff allele to it affects allele frequencies -​ Mutation rates very slow, little effect on Hardy-Weinberg equilibrium 3.​ Gene Flow -​ Movement of alleles from one population to another -​ Migration of individuals or gametes between populations -​ Migration powerful agent of evolution -​ Migration adds or removes alleles from the gene pool 4.​ Random Mating -​ Members of population mate w/each other w/out regard to phenotypes and genotypes -​ Members of populations are almost equally likely to mate w any other member in the population 5.​ Non-random mating -​ mating between specific genotypes shifts genotype frequencies 6.​ Genetic drift -​ Random fluctuations in allele frequencies over time due to chance events -​ Founder effect is when a few individuals found a new population (small allelic pool) (human example on slide 72)  -​ -​ Bottleneck effect is a drastic reduction in population, and gene pool size and complexity (surviving population doesn’t represent correct allele frequencies because they are small number of population) (human example on slide 73) Important terms: Fitness – The ability of an organism to survive and pass on their genes. -​ Direct Fitness: # of your genome copies you pass directly to the next generation -​ Indirect Fitness: # of your genome copies passed indirectly to the next generation via kin -​ Inclusive Fitness: # of your genome copies that are passed in total to the next generation (Direct + Indirect Fitness) (slide 76, good visual) Adaptation - Feature shaped by natural selection, promoting survival and reproduction Slide 81 & 82 licking removed methyl groups! This behavior changed genetics. *epigenetics September 18, 2024 Class 5 (last lecture for midterm 1 + labs 1 & 2) 1.​ Micro vs. Macroevolution 2.​ What is a species? -​ Biological species concept (BSC) -​ Ecological species concept (ESC) 3.​ Humans and the BSC 4.​ Speciation 5.​ Phylogenies Micro vs. Macroevolution Microevolution: allele frequency change within a population Macroevolution: the origin of new taxonomic groups above the level of a species  -​ Microevolutionary processes: -​ Mutation -​ Gene flow -​ Genetic drift -​ Non-random mating -​ Natural selection Slide 8: moths on the right die because don’t blend into the soot What is a species? -​ There’s a difference between variation within and variation between species -​ Species are real: if we represent individuals as dots on a graph based on traits, they show up in clusters, implying that species exist -​ There are genotypic and phenotypic similarities within a species -​ The longer two species have been separated from each other, the more different they are -​ Species range from extremely similar to extremely different Biological Species Concept (BSC) * Species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups. (closed gene pool) Barriers to reproduction (zygotic)… -​ Ecological (far apart, won’t mate between species) -​ Temporal (time, ex: one species is there in spring, other in winter) -​ Sexual/behavioral (two species are not gonna prefer one another) ​ For example: mating calls are different so they won’t attract mates from the other species -​ Mechanical (mating can’t occur for mechanical reasons) ​ Genetal arches have to come together in specific configurations for example Barriers to reproduction (postzygotic)... -​ Zygotic instability ​ Won’t survive outside of the womb  -​ -​ Hybrid inviability ​ Once an egg is born it’s gonna die soon after -​ Hybrid sterility ​ Can be born but it will be sterile -​ Hybrid breakdown ​ Two species have a baby, its born but the new species isn’t doing well so it doesn’t survive Problems w/BSC… 1.​ Can’t apply BSC to fossils because for fossils we have to define species by their visual similarity 2.​ Can’t apply BSc to asexual species because if they exchange genetic info they only do it with those that are genetically similar to them. 3.​ Reproductive isolation is not always watertight -​ Natural selection may eliminate hybrid species (think ESC) Ecological Species Concept (ESC) -​ reproductive isolation not necessary -​ Natural selection keeps species distinct from one another -​ Almost half of all species are not reproductively isolated -​ Some species have little or no gene flow Humans and the BSC -​ Look at slide 41 to see human evolution from apes What happened to the neanderthals? -​ We used to assume we out competed them, they starved to death and went extinct -​ In 2010, we edited this answer -​ We developed techniques to sequence ancient DNA and discovered that we have neanderthal DNA → there was interbreeding -​ Genomes of all living non-africans are approximately 2% -​ Neanderthals didn’t live in Africa -​ We have acquired some useful traits from neanderthals -​ Because we interbred w/neanderthals BSC would lump us into the same species  -​ -​ However, hybridization will occur between species but if not common enough to compromise identity of species, they are two separate species (loose application of BSC) Speciation Speciation is the process by which lineages split in evolution: a single species becomes more than one species Speciation is based on whether mutations occur quickly, whether geographic isolation persists, etc. (when two populations genetically diverge) Allopatry → populations in different places ​ One reason we don’t see hybrids even though it seems like hybridization should occur is that they are being out-competed Sympatry → populations in the same place Happens in two ways… 1.​ Effectively instantaneous speciation through chromosomal rearrangement 2.​ Gradual divergence between two subpopulations within a single species *confused by this ^^ study! Phylogenies Taxonomy → grouping of organisms based on shared characteristics Phylogeny → the evolutionary relationship between species -​ Genetic data is the best way to compare species -​ Knowing phylogenetic relationships explains why a species evolved certain adaptations not others Knuckle Walking -​ Is it a homology or homoplasy? -​ Rule of parsimony is the keep it simple rule, most likely scenario is true  -​ -​ In this case it would suggest that knuckle walking evolved once. (it’s a homology) Reconstructing Phylogenies… more similar genes, more closely related -​ Sometimes there’s convergence! Homoplasy not homology -​ Characters that are most important when constructing are synapomorphies (derived characteristics that are shared between two different species) -​ We compare non-coding genomes in DNA that accumulate mutations at a particular rate, we can count up number of mutations in a lineage and turn DNA data into a molecular clock; more mutations that have accumulated, more time has elapsed Ancestral → present in the common ancestor Derived → arose since the common ancestor September 23, 2024 Class 6 Unit 2 - Introduction to Primates 1.​ Humans as Primates 2.​ What is a Primate 3.​ Brief Overview of Primate Groups 4.​ Primate Dietary Adaptations Humans as Primates -​ Aristotle noticed that primates look like humans -​ Linnaeus → first biologist to insist that humans are primates -​ Humans: Order = Primates Family = Hominidae Genus = Homo Species = sapiens -​ Gorillas first described in 1847 by Dr. T Savage -​ 1855, Richard Owen, last major biologist to insist that humans are NOT primates → introduces the theory of homology  -​ -​ He thought humans have such different brains that we should be categorized differently → larger, we have hippocampus minor and projection beyond cerebellum -​ Thomas Huxley “Darwin’s Bulldog” (Darwin was sick at home so Huxley would debate his ideas for him) → he believed that Owen was wrong, that great apes do have hippocampus minors and project beyond cerebellum -​ Between 1984 and 1997 we got DNA data that proved that human beings are most closely related to chimpanzees and bonobos. -​ Last common ancestor between humans and chimpanzees looked a lot like a chimp -​ Shared characteristics between primates: ​ Grasping hands and developed vision ​ We take a long time to grow up ​ Have large brains ​ Physiological and cognitive structures that help us process information What is a Primate? What do they all have in common? They share a suite of traits (not all have all of these but all have at least some) -​ Emphasis on vision rather than smell -​ Big brains for their body size -​ Generalized dentition (similar across all primates) -​ Emphasis on manual dexterity ​ Opposable thumbs ​ Mostly nails instead of claws -​ Increased life spans and slow development -​ Social creatures, they live in complex, permanent social groups w relationships and personality Where do primates live? -​ There are about 700 species and subspecies of primates -​ They live in Africa, Asia, South/Central America in tropical regions (all centered around the equator)  -​ Social organization -​ Gregarious → they live in a social group -​ Solitary → Individuals live on their own -​ Philopatry → describes which sex remains in the group -​ Group structure → some are solitary, pair-bonded, one-male units (one male many female), polyandrous (one female, multiple males), multi-male/multi-female, and fission fusion (more on that later) -​ Nocturnal → mostly active during night -​ Diurnal → active mostly during day -​ Cathemeral → active at random times during day -​ Frugivore → eat mostly fruit -​ Folivore → eats mostly leaves -​ Insectivore → eats mostly insects -​ Gummivore → eats mostly gum/sap -​ Carnivore → eats anythings Primate teeth -​ All primates have incisors, canines, premolars, molars -​ Dental formula I-C-P-M (upper)/ I-C-P-M (lower) Brief Overview of Primate Groups Strepsirhini: Lemurs & Lorises Haplorhini: Tarsiers, New World Monkeys, Old World Monkeys, Apes Strepsirrhines: -​ Lemurs (Madagascar) -​ Lorises (tropical Asia) -​ Galagos (tropical Africa) Strepsirrhines retain PRIMITIVE features (features that were prevalent at the beginning of primates before evolution) -​ Longer snouts -​ Wet curved noses -​ No color vision -​ Tooth comb  -​ -​ They also have a reflective layer behind the retina because they are nocturnal Behavioral Characteristics: Lemuriformes (lemurs) Lorisiformes (lorises and galagos) Nocturnal or diurnal nocturnal Solitary and gregarious Often solitary Arboreal & terrestrial arboreal Mainly frugivorous Feed on fruit, gum and insects Slow Loris - endangered in Southeast Asia, illegally captured and posted on tiktok ​ BIG eyes for better night vision Differences between the groups: different skull structures, strepsirhini don’t have bone enclosure around jaw and top of head  -​ Haplorhines: tarsiers (south east asia), new world monkeys (central and south america), old world monkeys (africa and asia), and apes -​ Complete orbital closure -​ Dry, simple noses -​ No tapetum lucidum, color vision -​ Vascularization to brain and of placenta (blood flow) Tarsiers -​ Eyes are huge -​ Nocturnal -​ Each eyeball, bigger than their brains -​ Behaviorally like strepsirrhines (they’re all prosimians, get lumped together when talking about lifestyle) * New and Old world monkeys and apes are anthropoidea New World Monkey: Platyrrhini (latin name) Old World monkeys & apes: catarrhini (latin name) Platyrrhines New World monkeys -​ 2 families: Cebidae & Pithecidae -​ Cebidae subfamilies: Atelinae, Aotinae, Callitrichinae, Cebinae, and Samirinae Behavioral characteristics -​ All diurnal except for Aotus (Owl Monkey) -​ Arboreal → live in trees (almost exclusively) -​ Social systems and diets vary between species ​ Smaller-bodied new world monkeys (marmosets and tamarins) -​ Some pair-bonded, some polyandrous -​ Twins (almost always) -​ Eat gums ​ Larger-bodied New world Monkeys -​ Multimale-multifemale or one male units -​ Frugivores and folivores Pithecidae: red faced, hard to track Catarrhini  -​ Old World monkeys and Apes (including humans) Behavioral characteristics: -​ All diurnal -​ Arboreal or terrestrial -​ Social systems & diet vary between species ​ Platyrrhines have 1 extra tooth and broader nostrils than catarrhines, they also have ear tubes where catarrhines don’t Cercopithecoidea (Old World monkeys) Two major groups: -​ Colobines (leaf eating monkeys) -​ Cercopithecines Colobines -​ Sacculated stomachs (can digest leaves better) -​ Reduced or absent thumbs -​ Mostly arboreal -​ Mostly folivores -​ Babies different color than adults Cercopithecines -​ Cheek pouches for food storage -​ Diet (very omnivorous) and social systems vary -​ Both arboreal (little ones) and terrestrial (big ones) -​ Female philopatry (females stay in group they’re born in to) and strong Female on Female bonds Hominoidea All apes (including humans) -​ Gibbons & siamangs -​ Orangutans -​ Gorillas -​ Chimpanzees and bonobos  -​ -​ Humans (Homo sapiens) Behavioral characteristics: -​ Gregarious (except for orangutans) -​ Mostly frugivores (except gorillas) -​ Arboreal or terrestrial -​ Exhibit diversity of social systems * chimps and gorillas knuckle walk * most hominoidea have arms longer than legs (except humans) and flexible joints * bonobos are more skinny than chimps, sometimes just walk upright * orangutans are larger bodied, very flexible joints * gorillas → largest living primates, terrestrial mammals, big bellies because they eat leaves Diets -​ Meat eating → sharper teeth -​ Smaller-bodied eat small amounts of high quality food -​ Larger-bodied primates eat large amounts of low quality foods.  -​ -​ See slide 80 for examples of high vs. low quality food. -​ Basal metabolic rate not scaled linearly w/body size → larger animals need less energy per unit weight than smaller animals. -​ Ex. the cell of an elephant needs less energy than the cell of a mouse Primates have a lot of dietary adaptations -​ Insectivores ​ Short simple gut, easy to digest ​ Sharp cusps on teeth to chew -​ Gummivores ​ Short incisors ​ Long gut -​ Folivores ​ Well developed molar shearing crests → good for tearing leaves ​ Complex stomach ​ Enlarged large intestine → cellulose hard to digest -​ Frugivores ​ Low rounded molars → good for mashing fruit ​ Long small intestine Class 7 October 2nd, 2024 Primate socio-ecology 1.​ Sexual selection theory 2.​ Female reproductive strategies 3.​ Male reproductive strategies 4.​ Mate choice Primates: the social order -​ Huge diversity of social systems ​ Multi male multi female, one male and many females, one female and many male -​ Mating system vs social system ​ Mating system: how animals find mates and care for offspring  -​ ​ Social system: how many adult males and females are in a group ​ Some terms apply to both – IE pairbonded (when relationship forms out of sexual activity) Sexual Selection Natural selection: process by which traits become more of less common in a population Sexual selection: we expect traits to be beneficial or neutral with respect to fitness (there are showy traits like a peacock's feathers that don’t seem good for survival → reproductive purpose?) -​ Airnaments: showy features that slow an animal down (horns) -​ Ornaments: decorative features ​ Sexual selection tries to explain these traits. Secondary sexual characters: traits that function in reproduction but are not necessary in reproduction. Darwin sexual selection: the advantage which certain individuals have over individuals of the same sex with exclusive regard to reproduction Intrasexual selection: male-male competition → results in armaments -​ Differential reproduction resulting from competition of individuals within a sex for access to the other sex Intersexual selection: female choices → results in ornaments -​ Differential reproduction resulting from differential preferences that one sex has of members of the other sex Definition of sex: male: the sex that produce small motile gametes (sperm) Female: sex that produces large relatively immobile gametes (ova) -​ Can apply to trees, plants etc. -​ Some individuals might do neither, some might do both, some change. Not imposed as a characteristic of an individual but rather a strategy that an individual is using at a given time.  -​ Bateman principle (1948) sought to measure reproductive success of fruit flies. -​ Put various numbers of one sex and then one member of the other to see how many babies would result. -​ The males that had access to more females had more babies vs. female reproductive success was constant regardless of how many men there are 1.​ Male reproductive success is more limited by number of partners 2.​ Male RS is more variable and potentially higher Reproductive success for males and females Females reproduction: costly and time consuming, limited access to food -​ Not limited by partners she has but how much access to food because of energy costs -​ Should be choosier about who they mate with Male reproduction: cheap (sperm) and limited access to females -​ Should always be seeking out partners Primate mating system: rules -​ Sexual reproduction: Sperm and eggs must come together -​ Female gestation: Pregnancy is carried by the female -​ Female lactation: there is lactation and it is more energetically costly than gestation. Need 2x as many during lactation rather than end of pregnancy Language of adaptive explanations -​ “Strategy” as a word for suite of behaviors selected for by natural selection ​ Animal doesn’t need to be aware of evolution for it to happen -​ “Costs and benefits” ​ Not everything is perfectly designed ​ Trying to find a balance between maximizing success and minimizing cost ​ IE it would be good to have 60 kids but w/o the energy to do so other strategies would be better -​ One strategy is parental care ​ Frogs have thousands of eggs and maybe one or two will survive. Minimize quality of care  -​ ​ Birds: female lays the eggs, after both male+female completely invested in caring for the offspring ​ Sea horses: males gestate, have many offspring and don’t do much care ​ Mammals: female critical care giver, male care varies ^ Some males carry babies after vs. male chimpanzees who don’t pay any attention Female Reproductive Strategies -​ Female primates invest heavily in offspring ​ Gestation: long pregnancies, brain growth energetically expensive ​ Lactation: long infant periods – chimp nurses offspring until 5 -​ Importance of energy: net energy gain → RS (birth rate + survival) ​ When animals enter captivity they become horribly obese ​ Provisioning: more food → obesity. More food→bigger populations ​ Reproductive rates skyrocket with food (monkeys at zoo) ​ Waiting time to conception drops significantly as % of diet that is ripe fruit rises ​ 5% more ripe fruit → 4 months quicker to conceive ​ Primates are always on a nutritional edge – access to more food improves fitness. ​ Food enhanced baboons (living near cities w/ human food) have increased maturity and shorter interbirth intervals compared to wild groups ​ Wild groups that have better food sources take short interbirth intervals compared to those w/worse What influences female reproductive success? -​ Longevity: start reproducing earlier and live similarly you’re better off ​ Most female primates don’t go through menopause, so the longer one lives the more babies it can have -​ Age: ​ Young mothers → 50% higher infant mortality rate, lack experience, allocating energy toward their own growth ​ Older mothers → senescence (deterioration of cell functions w/age) -​ Group size  -​ ​ Long-tailed macaques: separated into small and large groups, within split by rank ​ Low-ranking female in a small group can do better than high-ranking female in a large group ​ Small group reduces competition for food ​ Scramble competition: larger groups face more competition bc resources need to be shared -​ Rank ​ Dominant individual: winner of agonistic interaction (approach-retreat, supplant from food site, fight) ​ Gorillas: those Why does it matter for females? ​ Food: high-ranking females eat better (contest competition) ​ Graph (slide 31): higher ranked females eat more grams per minute when feeding and at any time, intake rates of food gradually shifts lower as the rank is lower Reproductive success: -​ W/old world monkeys High ranking tend to have… ​ Earlier age of 1st reproduction ​ Shorter inter-birth intervals ​ Higher infant survival rates ​ Better survival during mortality crisis ​ Graph(slide 33): gray langurs higher rank = more offspring ​ More births, more survive to one year, more survive to 2 years compared to middle-ranking and low-ranking ​ Graph (slide 34): chimpanzees more offspring ​ Quality – graph: long-tailed macaque ​ High-ranking alpha female more likely to have a son who is the alpha male -​ Sociality ​ Female-female bonds (proximity, grooming, coalitions) can promote reproductive success ​ Graph (slide 37): x-axis composite sociality index, y axis infant survival ​ Females who have lots of friends have infants that are more likely to survive  -​ ​ Friendships impact longevity ​ Graph (slide 38): survivorship by age based on female relationship quality ​ Friendship strongly affects length of life ​ Graph (slide 39): humans mortality extended by social relationships, a greater impact than giving up smoking or drinking Female tradeoffs Resources limited -​ Allocation of energy to one offspring comes at expense of others ​ Trade-off between Quality over quantity -​ When to have next child ​ If I wean this kid early it will be small but I can have another? -​ Lactation considers these decisions ​ Lactational amenorrhea: A female can’t ovulate while lactating, not enough energy -​ Weaning ​ Infants become more independent ​ Nursing gradually reduced ​ Energy available for mother to conceive again ​ Time of weaning varies in diff primates ​ Graph (slide 41): as infant starts to forage on their own = nursing decrease Male Reproductive Strategies -​ Driven by access to females -​ Often the larger and more aggressive males will win -​ Results in sexual dimorphism: as they compete with each other = males becoming larger than females Intrasexual selection -​ Pair-bonds have little male-male competition → little dimorphism -​ One male-male, multifemale: huge body and canine dimorphism -​ Multimale, multifemale: large dimorphism -​ Direct competition: males form a linear dominance hierarchy ​ Males with higher rank get priority of access to females  -​ ​ Graph (slide 49): chimpanzees – low-ranking males have babies too, how? Alternative male strategies -​ Sneaky copulations Indirect competition -​ Sperm competition: competition between sperm of two or more males for fertilization of a single female ​ When a female is ovulating she will mate with all the males multiple times a day → Causes evolution of sperm ​ Evolution of testis size ​ Gorillas in one-male groups have small testes because he doesn’t have to compete vs. chimpanzees who have huge testes ​ Male chimpanzees devote as much energy to testes as they do to their brain, size is similar -​ Evolution of sperm speed ​ Graph (slide 57): swimming speeds of sperm show faster sperm of chimps and macaque vs. humans and gorillas ​ Social systems w/ competition have faster sperm -​ Sperm plugs: a gelatinous plug that blocks other males’ sperm from reaching the egg ​ To prevent sperm plugs, many have evolved baculum: penis pone that breaks sperm plugs Behavioral flexibility: some one-male groups sometimes include multiple to help defend territory -​ Peaceful (no detectable dominance) male muriquis that live in a multi-male multi-female group – no fighting. -​ When a female is ready to reproduce the males sit in a line and wait their turn Class 8 October 7th, 2024 1.​ Male Reproductive strategies (continued) 2.​ Mate Choice  -​ Male Reproductive Strategies Investment -​ Pair bonding ​ Increased parental investment ​ Extrapair copulations are common (sometimes mates with a male who isn’t her pairbond partner) ​ Graph (slide 3): Male grooming female a lot more than female grooms male bc male wants to guard his mate. ​ Mate guarding: does not necessarily mean monogamy ​ Examples: Titi and owl monkeys, marmosets and tamarins, gibbons and siamangs, humans -​ Cooperative breeding ​ Males and other individuals in the group help raise young ​ Marmosets and tamarins → obligate twinners, mother can increase reproductive success (RS) by having helpers ​ Humans are cooperative breeders ​ Graph (slide 4) → more males, increased survival of infants bc males do a lot of the caretaking ​ Fathers are caretakers when they have a lot of confidence that the child is actually their offspring Infanticide -​ When a male thinks a baby is not theirs the male will kill the baby -​ It’s not pathological (unreasonable) -​ Change in male residence or status (when a new male takes over the group) -​ Only kill infants that result in resumption of female cycling (when babies are nursing, females not ovulating → kill babies so females start ovulating again and male can have children) -​ Reproductive benefits to males -​ 85 % of deaths follow takeover by new male -​ Infants killed are primarily those who are still nursing -​ Rarely done by sexually active males in groups (if there’s a chance the male could be the father) -​ 45 to 70% of cases, males mated with same female whose baby was killed  -​ Paternity Confusion -​ Females have sex with every male in the group to prevent infanticide and confuse males as to who the father of the offspring is -​ Graph (slide 9) more swelling as ovulation happens, every male mates with the female at peak swelling (ovulation) Friendship -​ Baboon male friendships ​ Male starts by becoming friends with a female when they enter a group ​ Male protects female & eventually infant of female ​ Female grooms male -​ Hormonal profiles (graph slide 10) ​ Cortisol: stress hormone ​ Female stress level rises if no male friend during takeover Bruce Effect -​ Female Geladas ​ Terminate pregnancies after new (infanticidal) male takes over a new group → don’t want to waste energy if the baby will just be killed ​ Graph (slide 11) estrogen levels rise during pregnancy, plummet in estrogen levels means pregnancy over Mate Choice Mandrill -​ males colorful, females brown (dull in color) -​ Graph (slide 15) females approach most colorful males -​ However, most dominant male is also most colorful → possible confounding variable -​ Color is most likely not for female attention, color is correlated with testosterone levels, so color is a sign or testosterone levels (don’t bother fighting me, I have high testosterone and am gonna beat ya) *In Primates, males are the ones who are more choosy with mates -​ Males have a preference for the oldest female who have already had babies -​ Nulliparous means a female who hasn’t had a baby -​ Parous is a female who has had a baby -​ Older parous females don’t care as much about having MORE babies so they invest more energy into the ones they have  -​ Great Apes 1.​ Why do primates live in groups? 2.​ Socioecological Model 3.​ The Great Apes 4.​ Chimpanzees and Bonobos Why do primates live in groups Benefits Costs Vigilance Visibility Finding food Competition for food Guarding food Disease Raising offspring Predation -​ At least 32 primate genera ​ Microcebus → gorilla -​ Most common predators: raptors, felids, snakes -​ May be rare, but important ​ Failing to avoid a predator (being eaten) is catastrophic to one’s fitness -​ Hard to study predation ​ Rare ​ Habituation (predators not habituated to humans) ​ Have to study the predator not the prey -​ Predation can be a serious threat -​ E.g. predation by chimps on red colobus monkeys -​ Graph on slide 23 Why live in a group? 1.​ Dilution ​ Selfish herd effect → in a big group, less likely to get eaten 2.​ Vigilance  -​ ​ Lots of eyes in a group, may be able to see the predator coming 3.​ Active defense ​ Group could mob the predator -​ Graph (slide 28) → when living with high predation groups, more likely to live in a bigger group -​ Expectation: ​ Higher predation risk → higher male to female ratio bc males are important for vigilance and defense -​ Graph (slide 29) → more males, more successful defense Summary -​ Predation pressure is an important determinant of primate grouping and social behavior -​ But hard to study -​ Direct observations and tests are rare Socioecological Model Why do primates live in societies rather than flocks? (flocks/herds are not socially bonded, anonymous group) a.​ Troops -​ Predictable membership: all together all day -​ E.g. gorilla, baboons, capuchins b.​ Fission-fusion -​ Predictable (stable) community membership -​ Unpredictable party (parts of the community) membership (never see all members together all at once) -​ E.g. chimps, spider monkeys 2 Types of feeding competition: 1.​ Scramble competition: occurs when increasing the group size results in less food for every individual 2.​ Contest competition: dominants get access to food over subordinates  -​ ​ Type and degree of competition is affected by abundance, distribution (where food is found in the habitat) and quality of food (how many calories in a food). 1980 → Richard Wrangham proposed the socio-ecological model to account for patterns of relationship among primates. -​ Graph (slide 38) individuals C & D have to sit under tree until they cooperate and kick A & B (who aren’t cooperating) out of the tree, then A & B cooperate to overpower C & D. -​ Females form groups to defend clumped, high quality food resources -​ Females form cohesive kin groups (because this increases the inclusive fitness) and therefore are philopatric -​ When food is evenly distributed or is in small patches, females avoid competing with kin by dispersing (being close to kin is worse because it means competition) The general idea with socio-ecology -​ Habitat effects female foraging strategy which determines female distribution which determines male’s strategy for getting as many females as possible which can then affect female distribution again The Great Apes ​ Study ape phylogeny (slide 48) Gibbons -​ Smallest ape (about 5kg) -​ Low sexual dimorphism -​ Asian tropical forests -​ Pair-bonded Pair-bonds -​ Gibbons and siamangs -​ 50% of diet is fruit fruit -​ Food is in small patches -​ Small, well defended territories -​ Gibbons spend a lot of time grooming their female → pair-bondedness, monogamy  -​ -​ Be able to describe how food availability explains pair-bonds for gibbons (slide 51) Orangutans -​ High sexual dimorphism (males 2x as big as females) (males 100kg, females 40kg) -​ Asian tropical forests -​ Solitary Two male morphs in Orangutans: -​ Flanged → pads on side of face (100kg) -​ Unflanged → no pads (40kg) sometimes mistaken for females -​ We have no understanding of why some males are flanged and others are unflanged -​ Unflanged will definitely go extinct in my lifetime Females: typically solitary, social only when food abundant Males: range very widely ​ Promiscuous mating ​ No known long-term social bonds ​ Female Orangutans are desperate for calories → sometimes eat bark Gorillas -​ Largest living primate -​ High sexual dimorphism (female 100kg, male 200kg) -​ Lowland and montane forests -​ One male units -​ Social uni-male polygyny -​ Prefer fruit but able to eat large quantities of low-quality foliage -​ Group structure: 1+ silverback male, 1-7 females -​ Both sexes disperse but some stay ​ Graph (slide 59) → females don’t need to defend food bc it’s abundant, females need to prevent infanticide, they form a group around the male so he feels like he should protect them and their babies  -​ Chimpanzees and Bonobos Chimpanzees -​ Moderate sexual dimorphism (males 50 kg, females 40 kg) -​ Lowland forest and woodland -​ Spend 50% of their day time hours chewing -​ Graph (slide 66) shows time spent chewing → each point on graph is a dif species -​ Diverse diet → ripe fruit, leaves, flowers, insects, meat Socio-ecology of chimps -​ Food spread out but not as much as with Gibbons -​ Males cooperate to defend a territory of solitary females -​ Males in groups w/kin -​ Females go off to neighboring communities and find a new group to live in -​ Chimps are big, so they’re not as subject to predation pressure -​ Strong male-male bonds bc they stay in the community -​ Fallback foods can’t support females, need to forage for higher quality foods (fruit), so they travel more → creates fission fusion Bonobos -​ Moderate sexual dimorphism (females 30kg, males 40kg) -​ Lowland forest Class 9 October 9th, 2024 Chimps and Bonobos -​ Chimps: P. troglodytes -​ Bonobos: P. paniscus -​ “Fission fusion” -​ Create groups/parties -​ Parties are fluid, they rearrange throughout the day  -​ Female Chimps -​ Disperse at adolescence -​ Relatively solitary -​ Utilize ‘core areas’ -​ Neighborhoods Female Strategies -​ Mean inter-birth interval of 5-7 years (have a baby every 5-7 years) -​ Resume cycling when offspring weaned -​ Swellings indicate sexual receptivity (10-12 days during 35 day cycle) -​ Multiple cycles per conception -​ Typically mate with many males (to confuse paternity) -​ When they are swelling, males have high testosterone, have to fight over female Male strategies -​ Philopatric -​ Range widely, encompass core areas of many females -​ Cooperate to defend community range -​ Social bonds & cooperation ​ Association ​ Grooming ​ Coalitions ​ Food sharing ​ Patrolling -​ Range widely, encompass core areas of many females -​ Cooperate to defend community range ​ Patrols ​ Attacks ​ Lethal raids Bonobos: make love not war ape -​ Solve social tension by having sex with one another Bonobos and food  -​ -​ Females spend more time together, create stronger female-female bonds bc there is enough food to go around -​ Females are able to suppress male aggression because of these coalitions and bonds -​ This explains why bonobos aren’t very aggressive -​ Females control male behavior by having sex with them Cooperation Why do we help each other? 1.​ What is cooperation? 2.​ How does altruism evolve? 3.​ Non-kin cooperation What is cooperation? Cooperation: When an individual acts in a manner that benefits others → often costly to the actor. Reason why animals cooperate: usually the actor DOES benefit too  -​ Altruism harder to understand than selfishness -​ Selfish interactions compatible w Darwin’s postulates ​ Actors increase own fitness & reduce fitness of others ​ Traits that enhance relative fitness will be favored -​ Altruism is more problematic ​ Individuals reduce own fitness and increase fitness of others ​ Doesn’t fit with Darwin’s postulates ​ Someone who is gonna sacrifice his life to save others isn’t gonna live to pass on those genes → how does altruism evolve? How does altruism evolve? Assortment (have to be nice to other altruists) is key -​ Non-random association -​ Altruists direct benefits selectively to other altruists -​ Altruists are disproportionately likely to benefit from altruism. Slide 27-32 for example -​ Caller puts themself in danger by calling and warning about predator, actors fitness goes down -​ Recipient’s fitness goes up because they were warned about predator -​ Non-altruistic doesn’t know to call, their fitness goes up -​ Recipient’s fitness goes down, no one else saw the eagle -​ Altruistic action, actor gets cost, everyone else gets benefits -​ Non-altruistic action, actor gets benefits, everyone else gets cost  -​ -​ In non-altruistic group everyone dies, including actor because he can’t mob a predator by himself -​ Everyone in altruistic group lives -​ Assortment occurs → altruists find other altruists -​ Frequency of altruist increases because those who are cooperating survive Kinship is a mechanism for assortment -​ If animals live in a group full of sisters -​ From rules of meiosis: altruism is non-randomly distributed to other altruists Hamilton’s Rule -​ Relatives likely to share genes through common descent -​ If altruists aid kin, likely to help those who carry same gene for altruism -​ Altruism favored by kin selection when: ​ Benefits to recipient x relatedness (actor, recipient) > cost to actor ​ This is called Hamilton’s rule: br>c -​ Natural selection will favor traits that maximize inclusive fitness Grooming is altruism -​ If I’m gonna spend time grooming someone else, it’s less time to groom myself -​ Most instances are between mother and child -​ Occurs more often between kin than distant kin or nonkin Graph on 43, philopatric (whichever one stays in group) sex more closely related Kin Biases in behavior: Cooperative Breeding -​ Tamarins, marmosets -​ Honeybees -​ Meerkats -​ Naked mole rats -​ Humans? -​ Lack of available territories of suitable quality: best of bad situation (this is why kids stay with parents and help raise siblings) -​ Defense against predators  -​ Fun fact: callitrichid twins swap genetic info in utero and are chimeras of each other, with an average relatedness of 0.575 (they swap genes in utero) -​ Even their sperm is chimeric -​ So males can make sperm w/their sister’s genetic info Hamilton’s Rule: br > c -​ Estimate: ​ Fitness benefits to other ​ Fitness costs to self ​ Genetic relatedness How do animals recognize kin? -​ Kin recognition systems have evolved independently in many taxa -​ Kin recognition based on perception of cues that are used to assess relatedness -​ Mother’s don’t seem to recognize own infants at birth -​ Within a few weeks mothers discriminate between own infant and strange infant -​ Not clear whether mothers learn infants’ smell, appearance, or voice -​ Present mother w/’strange’ infant to care for and mother’s will accept and assume it’s theirs -​ Mothers and infants stay close together -​ Juveniles remain close to mothers after weaning -​ Infants become familiar w/older siblings because both are near mother -​ Mothers maintain ties to adult daughters, and become familiar w/grandchildren Primates may use age proximity as a cue for paternal kinship -​ If one male monopolizes matings → all infants born during his tenure will be paternal half siblings -​ If there is a turnover in identity of primary breeding male, then age similarity may be good proxy for paternal relatedness (who is my sibling → those closest in age to me) Could primates use facial cues to identify kin?  -​ -​ Primates highly visual -​ Kin resemblances are likely to exist Experimental design: -​ Look at example on slide 56 & 57 Non-kin Cooperation Look at game theory examples slides 61-67 How do individuals overcome the temptation to defect? -​ For humans: ​ Promise to cooperate ​ But, can you trust your partner? Bc best strategy is promise to remain silent and then confess ​ Talk is cheap ​ What would increase the credibility of a promise? → proving it over repeated interactions! -​ Cooperate only if partner cooperated before -​ Principle underlies theory of reciprocity Reciprocity = reciprocal altruism -​ Robert Trivers, 1971 -​ The immediate cost paid by altruist is repaid later by the recipient -​ Requirements: ​ Cost to donor < benefit to recipient → net benefit over time ​ Repeated interactions ​ Opportunities for role reversal Primates are good candidates for reciprocity -​ Individual recognition → identify those who helped them in the past -​ Good memories → remember previous interactions -​ Stable social groups → opportunities to interact again -​ Often have weak/moderate dominance hierarchies → role reversal Class 10  -​ October 16, 2024 Non-kin Cooperation ​ Reciprocal Altruism Evidence for reciprocity in animals -​ Vampire bats -​ Blood sharing with individuals that failed to feed -​ Most likely to blood barf with those who had blood barfed for them previously -​ More data suggested that blood barfing often occurred between child and mother NOT reciprocal altruism -​ Ask questions about slide 8 → don’t understand -​ Evidence for reciprocity in grooming in chimps -​ For kin reciprocity it’s more likely to occur even if there hasn’t been a prior altruistic action, for nonkin there’s more likely to be a response if there has been a previous action → altruistic reciprocity graph on slide 10 How do chimps identify who would be good cooperators? -​ Graph on slide 13: In the introduction phase the chimps are randomly gonna pick between mean and nice, it’s pretty 50/50. In the test phase they are much more likely to pick the nice chimp because they know they will cooperate. Class 10 Topics 1.​ Primate Life History 2.​ Uniquely Human Life History 3.​ Brain Size 4.​ Why have a large brain? 5.​ Cognition Primate Life History Life History is the timing of key events in a lifespan -​ Patterns of growth or development (when are you weaned, when do you stop reproducing, when do you die, etc.) -​ Natural selection alters the timing of these events to maximize reproductive success  -​ Real world Examples: -​ Possums reproduce early and a lot because they get eaten early on, need to reproduce quick to pass on genes before they die Life history is about trade-offs -​ Do you have a lot of offspring and split investment of energy between them or do you have one and invest all your energy? -​ Energy allocation is important: allocated to growth, maintenance, and reproduction. We think about how we allocate this energy because we have a finite amount of it. When young we invest all energy to growth. Then we invest energy into reproduction. Then after maintenance we invest in maintenance. Life History: correlated traits Fast life history Slow life history Reproduce early Reproduce late Small body Large body Small brain Large brain Short gestation Long gestation Large litters Small litters High mortality rate Low mortality rate Short life span Long life span Basic life history model: Imagine a fixed energy pool and you can either grow or reproduce but not both → when do you start reproducing? -​ If you wait too long you may die -​ Why shouldn’t every animal reproduce earlier? → there is an advantage -​ If you can grow to a larger body size, infant survival increases Graph on slide 29 -​ Dotted lines are mammals not primates  -​ -​ M ^-1 is average adult lifespan -​ Alpha symbol is average age at maturity -​ Primates mature more slowly than most mammals Primates: -​ Slow maturation -​ Large brains, long gestation, long lifespan, small litters -​ There’s variation within primates showed in graph on slide 29 Uniquely Human Life History -​ Large, fat, relatively undeveloped infants -​ Early weaning -​ Short interbirth intervals -​ Slow development, extended childhood -​ Menopause → most animals die when they stop reproducing -​ Long life Why would natural selection select for growing old and dying if it doesn’t increase fitness? -​ We favored genes that allocate energy to growth and reproduction earlier on in life but this takes away from genes that would go to maintenance later on so we grow old and decrepit -​ These genes are pleiotropic – affect many traits -​ Selection can’t act against allele 2 because you’ve already passed on your genes through reproduction -​ Antagonistic Pleiotropy is a theory in evolutionary biology that suggests certain genes may confer beneficial effects early in an organism's life, enhancing  -​ reproductive success, while also causing detrimental effects later in life, contributing to the aging process. -​ Example: testosterone ​ Positive effect on fitness in males early in life; increase body mass and promotes aggressive behavior ​ Linked to prostate cancer and heart disease later in life Humans live a long time but stop reproducing at about the same age as chimpanzees -​ Grandmother hypothesis ​ There is a benefit to begin menopause and stop reproducing between age 45-55 but keep living because at this age it makes more sense to invest energy in current kids and grandkids than to continue investing in own reproduction ​ Grandma’s can improve reproductive success (and fitness) by helping their children raise their grandchildren and pass on their genes successfully ​ Graph on slide 39: dark black bar represents individuals who are over 50 in this population, women over 50 contribute a lot to food acquisition (for their kids and grandkids) ​ Top graph on slide 40: women who have a mother alive reproduce earlier, grandma’s increase reproduction in this way ​ Bottom graph on slide 40: grandma alive increases survival of first baby (grandchildren) Why do males also live long? → males long lifespan is a byproduct *Menopause occurs in killer whales too → hypothesis is that females have all the info about where the feeding grounds are so it's beneficial for them to stay alive Brain Size “Need to Learn” Hypothesis: Social and ecological complexity takes a long time to learn; juvenile period allows acquisition of adult competence. -​ Takes a long time to grow a brain, can’t do it too fast or you’ll use up too many calories. Brain structure  -​ -​ Hindbrain ​ Cerebellum ​ Brain stem ​ Basic life processes → functioning of your body -​ Midbrain ​ Senses -​ Forebrain or Cerebrum ​ 4 lobes (occipital, temporal, parietal, frontal) ​ Neocortex (outer covering) ​ Humans have more neocortex ​ Neocortex is decision making Intelligence and Brain Size -​ Graph on slide 52: chimpanzees have bigger brains than capuchins but capuchins have bigger brains relative than their body -​ Primates tend to have larger relative brains -​ Relative brain size is problematic because natural selection acts on bodies not brain size -​ Neocortex size relative to brain size is a good measure of intelligence Global Cognitive Ability -​ Experiment on slides 57 and 58: teach mammal that food is by the diamond, then switch it to the triangle and see how long it takes them to realize. -​ Result: Absolute brain size and neocortex size predict cognition well but relative brain size does NOT. Bigger brain → need more energy to run it The Expensive Tissue Hypothesis: You can’t grow expensive tissue unless you sacrifice other tissue. Energetic tradeoff with other expensive tissues like the gut. -​ Animals with bigger brains decrease the size of their guts. -​ Primates with better diets (smaller guts) have larger brains Why do primates have large brains?  -​ -​ Social brain hypothesis: large brains help us navigate social relationships, very socially complex world ​ Prediction: primates that live in larger social groups should have larger neocortex. ​ Graph not good because data was biased, he chose monkeys that prove his hypothesis -​ Ecological brain hypothesis: some type of foraging takes more brain power than others ​ Prediction: fruit eaters would have bigger brains than leaf eaters ​ More support from data -​ Behavioral flexibility hypothesis: learn new solutions to problems from others, cope with both social and ecological dilemmas, be innovative and flexible. ​ Primates with larger brains tend to be more innovative Cognition Cognition: the processing of information that animals have and how they apply that knowledge -​ What do animals understand about themselves and the world around them? -​ How do we figure out what animals are thinking? The Mark Test (Mirror Self Recognition Test) -​ Do animals when looking in a mirror know they are looking at themself? -​ You put a mark on their forehead, if a chimp looks in the mirror and tries to rub off the mark they know they are looking at themself. -​ Mirror self recognition is only seen in apes -​ Dolphins and elephants also pass the mark test Theory of mind Whether or not you can understand the thoughts of others. -​ Test in monkeys: observer looking away, observer looking at food, monkey will steal food from the observer who is looking away -​ Chimps tested against other chimps: dominant on one side, subordinate on the other, in which cases does the subordinate go after the food? -​ Subordinate more likely to refuse food if dominant knows where it is, chimps know what other chimps know about the world  -​ Physical Cognition How objects work -​ Chimps have good physical cognition Social Cognition -​ Humans outperform chimps and monkeys in this way Unit 3 Class 11 October 21, 2024 1.​ Reconstructing the past 2.​ Evolution of primates 3.​ Evolution of bipedalism 4.​ Earliest hominins Reconstructing the past *Earth has changed over time Ex: continental drift -​ Barriers lead to speciation -​ Continental positions change ocean currents, which changes climates Global Climate Change -​ Lots of fluctuation during primate evolution -​ Cooling trend overall in last 65 million years -​ Warmer in every Eocene and early Miocene -​ Cooler and more variable in Pleistocene -​ Primates evolve in the paleocene  -​ -​ Need to know the names of these phases -​ During pliocene phase, rainforests are turning into savannahs Fossilization -​ Those working specifically with fossils of primates, apes, and humans are known as paleoanthropologists -​ These bones and teeth can tell us how our ancestors moved, how big they were, what they ate, and what their mating and social structure may have been. -​ The plant and animal fossils found in the vicinity can be used to reconstruct the environments inhabited by our ancestors. -​ Burial is the key -​ Absorption of minerals and replacement of organic compounds -​ Hard materials fossilize more often (bone and ESPECIALLY teeth) -​ Soft tissues and behaviors rarely fossilize -​ There is an overestimate of the time of first appearance and an underestimate of the time of extinction -​ -​ Oversimplify the relationship between fossil taxa -​ Underestimate divergence times -​ We’ve only found 3% of all species’ fossils  -​ The Principle of Superposition: If a rock strata has not been disturbed the lowest stratum was formed before the strata above it. (The bottom layer of rock is older than the layer on top of it.) Potassium-argon dating -​ 1.25 billion year half-life → we can look at the ratio of radioactive potassium to argon and give this rock a date if it’s younger than 1.25 billion years ​ Useful for older than 500,000 years -​ Volcanic rocks -​ Fossils not directly dated -​ Can date fossils millions of years old Biostratigraphy -​ We can look at multiple sites, if we know the ages of the layers of rocks in one site we can date the other sites’ rocks by associating them with the fossils of species we find in the rocks. Fossil record is biased… -​ Not everything fossilizes -​ Small animals are less likely to fossilize -​ Some habitats are less likely to create fossils -​ Savannahs are good for fossilization -​ Tropical rainforests are not because the soil is acidic and it breaks up organic material. -​ Primate fossil record is sparse because most live in tropical rainforests Evolution of primates  -​ Primate Characteristics to identify a fossil primate -​ Grasping hands and feet -​ Nails instead of claws -​ Forward-facing eyes encased in bone -​ Hind limb-dominated locomotion -​ Relatively large brain -​ Generalized teeth Evolution of early primates: Plesiadapiforms -​ Maybe not primates -​ No binocular vision -​ Small brain -​ Some nails, some claws -​ Grasping hands and feet in some -​ 65-54 mya (Paleocene epoch) Eocene: 40-50 mya: Origin of “true” primates Eocene Primates: Adapids and Omomyids -​ Earth warm and wet ​ Tropical forest spread into North America and Europe -​ Primates have evolved ​ Full suite of characteristics ​ Two families: adapids - like lemurs & omomyids - like lorises Late Eocene-Oligocene: 30-45 mya. Origin of Anthropoids  -​ -​ African origin -​ New world & old world monkeys, apes and humans -​ Early anthropoids have been discovered in the Fayum of Egypt, Oman and Algeria and date from the Oligocene. -​ They were tiny How did monkeys get from Africa to South America? -​ Africa and South America were not connected 45 mya -​ Most likely hypothesis: animals traveled from Africa across the Atlantic Ocean into South America by rafting (giant chunks of land that break off and float across to South America) Miocene: 5 to 23 mya. Planet of the Apes -​ Warm and wet, became cool and dry overtime -​ In the early Miocene (22-17 mya) there was great diversity of fossil apes – more than 10 genera and 15 species known -​ Apes versus monkeys ​ Apes have no tail ​ Forelimb suspension ​ Short, stiff lower back ​ Mobile joints ​ Long arms and fingers Proconsul and Friends -​ Africa: 17-23 mya -​ Frugivorous -​ Forest environments -​ Apelike skull and teeth -​ Monkey-like postcrania ​ Quadrupedal, non-suspensory ​ But no tail -​ First feature that evolves for apes is probably the head Middle Miocene (10-15 mya) -​ Africa: Nacholapithecus and Kenyapithecus  -​ -​ Asia: Sivapithecus -​ Europe: Dyropithecus, Pierolapithecus, Oreopithecus -​ Pithecus means ape -​ Don’t need to know these names ^ Oreopithecus aka Cookie Monster -​ 7-8 mya -​ Northern Italy in coal mine -​ Swamp habitat -​ Folivore; teeth different from any other ape -​ Need to know this name Sivapithecus -​ Looks like an orangutan -​ Dish face -​ Tall narrow orbits Gigantopithecus: really great ape! -​ China -​ Gigantopithecus giganteus/blacki: 300+ kg - bigger than gorillas! -​ Ate bamboo, like pandas? Apes disappear in Europe about 8 mya only apes left are in Asia and Africa Evolution of bipedalism -​ Belonging to subtribe Hominina i.e. creatures more closely related to humans than to chimps -​ Not to be confused w/hominids (African apes) What is unique about us? -​ We walk on two legs (bipedalism) -​ We have small canines and large molars with thick enamel -​ We have large brains -​ Very slow life histories and long juvenile periods -​ Overlapping offspring and cooperative breeding  -​ -​ Talk and have elaborate symbolic culture Types of Bipedalism -​ Obligate: MUST do it; no other efficient choice -​ Habitual: can do it efficiently and ‘make a habit of it’ most of the time -​ Facultative: can do it if they have to What it takes to be a Biped: skull Foramen magnum placement is shifted, as a biped, head needs to be on top of the body so the foramen magnum comes from the bottom center of skull, not the back Spine -​ Lumbar lordosis: S-shaped curve in spine, allows the head, neck, pelvis, and knees to be aligned Pelvis Bipeds have a short, stout pelvis and the iliac blades face to the side * When we have a flat piece of bone, there is a muscle attached to it  -​ -​ We have abductor muscles that join the femur to the wide flaring ilia -​ Stabilize the body when your weight is on one leg (like when walking) *Should be able to explain this on an exam Femoral Neck -​ Uneven thickness of dense cortical bone in the neck of the femur prevents stress on the femoral neck -​ Longer femoral neck is for abductor muscle attachment. -​ Top weight is pressing down on femur but we have this extra bone to support the extra weight Femur -​ Our legs (femoral shafts) are really long -​ Femur = thigh bone -​ We can take longer steps Knees and Feet -​ Knee ​ Bicondylar angle -​ Foot and ankle ​ Non-grasping big toe, we put pressure on our toes to push us forward ​ Arches Why bipedal? -​ We shifted from rainforest environment to woodland -​ In rainforest food is abundant  -​ -​ Not in the savannah, have to travel for food Okay observations about why bipedal: -​ Feeding adaptation ​ Arboreal bipedalism, have to stand up and reach things ​ Ground feeding -​ Carrying and provisioning, have to carry a lot of food to feed babies Better observations: -​ Thermoregulation ​ Less solar radiation ​ Standing upright helps us regulate temp and not overheat because we have more wind hitting our body when we walk upright -​ Energetics ​ Bipedalism saves energy (calories) ​ It costs more energy to move your body around walking on all fours ​ Calories turn into babies → bipedalism favored by natural selection *chimps need to climb trees, this is why they don’t walk bipedally Earliest Hominins -​ 6-8 mya -​ Last common ancestor of chimps and humans 6-8 mya Sahelanthropus tchadensis -​ Chad, Africa -​ 6-7 mya -​ Hominin → we don’t know if it is an ape or hominin ​ Foramen magnum suggests bipedality ​ Chimp-sized brain ​ Small canines ​ Flat face; large brow ridge ​ Paper from 2022 suggests femur is more human-like and indicated bipedalism Orrorin tugenensis  -​ -​ Kenya, Africa -​ 6 mya -​ Mix of woodland and savanna -​ Curved fingers suggest tree living -​ Hominin? ​ Femur suggests bipedality ​ Teeth chimp-like ​ Transition fossil between chimp-like ancestor and hominin Ardipithecus kadabba -​ Ethiopia, Africa -​ 5.2 - 5.8 mya -​ Hominin? ​ Toe bone suggests bipedality ​ Canine sharpens against lower premolar Ardipithecus ramidus -​ Ethiopia, Africa -​ 4.4 mya -​ Woodland habitat -​ Hominin? ​ Bipedal based on skull, pelvis, and foot ​ Climbing based on hand, foot, and pelvis ​ Small brain ​ Small canines ​ Short arms? Ardipithecus ramidus: Teeth -​ Incisors ​ Smaller than frugivore chimps -​ Molars ​ Thicker enamel than African apes; thinner than humans -​ Canines ​ Not sharpened ​ Not dimorphic  -​ Ardipithecus ramidus: hands -​ Hand: not knuckle walking -​ Foot ​ Grasping toe ​ Stiff foot for bipedalism -​ pelvis ​ Ilium adapted for bipedalism ​ Lower part apelike Class 12 October 23rd, 2024 1.​ Australopithecines 2.​ Early Homo and the first tool-makers 3.​ Homo ergaster and friends Early Hominins Sehalanthropus tchadensis Orrorin tugenesis Ardipithecus ramidus Chad, Africa Kenya, Africa Ethiopia, Africa 6-7 million years old 6 million years old 4.4 million years old All likely bipedal! Hominin Diversification Australopith Radiation -​ Small brains -​ Skilled upright walking, this tells us that we walked before our brains got big -​ Retain tree-climbing ability -​ Chimpanzee-sized with pronounced body dimorphism → males 2x as big as females -​ Reduced canine dimorphism -​ Large molars  -​ Australopithecus anamensis -​ Kenya and Ethiopia -​ 3.9-4.2 million years old -​ Grassy woodland environment -​ Bipedal: tibia (shin bone) → bipeds have a flat and wide top of the tibia -​ Long arms, shorter legs and curved fingers -​ Canines smaller than modern apes -​ Thick enamel on molars → enamel protects tooth from getting cracked Australopithecus afarensis -​ Ethiopia and Tanzania -​ 3-3.6 million years old -​ Woody grassland -​ Smaller canines, larger molars than Au. Anamensis -​ Slightly larger brain than a chimp (450 cc) -​ Bipedal -​ Body size dimorphism -​ Skull and teeth ​ More U-shaped dental arcade than humans ​ A smaller diastema compared to chimps  -​ ​ Some dimorphism in canines ​ Molars more like chimps -​ Locomotion ​ Some tree climbing, based on scapula, fingers ​ Curved finger bones like chimps -​ Bipedal based on pelvis, footprints and feet (Lucy is Au. afarensis)  -​ -​ Big toes of A. afarensis are more like humans than chimps (slide 13) -​ Dikika Child ​ “Selam” ​ Dikika, Ethiopia ​ 3.3 myo ​ 3 yr old female fossil found ​ Bipedal; tree climbing? ​ Hyoid: no language → bone in throat found called a “hyoid”, shape of hyoid bone is due to human language, the hyoid in this fossil is shaped in a way that proves it didn’t talk ​ Slower brain maturation (more human-like) → only about 75% of its brain was grown at 3 yrs old. Australopithecus garhi (garhi means surprise) -​ East africa -​ 2.5 myo -​ Cranial features: ​ Small brain (450 cc) ​ Sagittal crest ​ Large teeth -​ Postcrania: longer legs? -​ Stone tools? → only species associated with stone tools were genus homo Australopithecus africanus -​ South africa -​ Taung child  -​ ​ Found in 1985 ​ Foramen magnum = bipedal ​ Small brain ​ Small canines ​ Challenged large brain first idea ​ This fossil was in the hominin line -​ Sterkfontein cave ​ First fossil named Mrs. Ples ​ Hundreds of fossils in this cave ​ Limestone cave formed close to a predator site, leopards make a kill and then drag it up a tree, bones fall from the tree ​ Lots of the fossils have canine marks on the skull, suggesting that they were food for various predators -​ More info about Au. africanus ​ 2.2-3 myo ​ Woody grassland ​ Cranially like Au. afarensis – bigger molars, smaller canines ​ Brains: ~460cc ​ Bipedal ​ Large size dimorphism (males 50% bigger than females) ​ Rapid tooth development ​ Teeth growing faster than brains ​ Large molars suggest crappy diet ​ Might need to grow teeth faster because once weaned off mother, need those teeth to eat food Austrolapithecus sediba -​ Malapa Cave, South Africa -​ 1.98 myo -​ Cranial ​ Small brain (420 cc); small teeth ​ Reduced musculature for chewing -​ Diet ​ Phytoliths: fruit, leaves, bark -​ Hand humanlike -​ Pelvis humanlike  -​ -​ Arms relatively long -​ Thorax apelike -​ Foot primitive: suggests a unique form of bipedal walking (hyperpronation, walked on outer edge of its feet) Paranthropus: The Robust Australopiths Paranthropus aethiopicus -​ Kenya -​ 2.5 myo Paranthropus boisei -​ Hyperrobust -​ 1.3 myo -​ Kenya, Tanzania (Olduvai Gorge), Ethiopia -​ Ate seeds, tubers, roots -​ Nutcracker Man → had massive teeth and jaws for biting really hard food Cranial adaptations to nutcracker diet -​ Enormous back teeth -​ Sagittal crests ​ Large temporalis muscles -​ Huge cheek bones (zygomatic arches) -​ Postcranial: bipedal ^ Face designed like this so it doesn’t break when you chomp down on something hard  -​ -​ Large temporal fossa creates postorbital construction -​ Not room for a big brain Robust vs. Gracile Australopiths -​ Robust premolars look like molars -​ Hugely expanded surface area of molars Paranthropus robustus -​ South Africa -​ 1-1.8 myo -​ Brain: 530 cc (getting bigger) -​ Cranial and dental adaptations for heavy chewing -​ Bipedal -​ Extended growth? → males kept growing through adult lives  -​ ^ Both trees are equally likely based on fossil evidence we have, we don’t know if afarensis or africanus is in direct line of homosapiens Early homo and the first tool-makers ​ Entering a cooling period about 1 myo, and we start to see periodic Ice Ages. Origins of Homo -​ 2.3 mya -​ Africa -​ Larger brains -​ Smaller teeth (molars) -​ Australopithecus limb proportions -​ Rapid development Homo habilis -​ 1.4-2.3 mya -​ East and South Africa -​ Brains ~600 cc -​ More rounded skull -​ Less prognathic face  -​ Taxonomic diversity or sex differences? -​ KNM-ER 1470 = Homo rudolfensis -​ Slightly larger brains The Origins of Tool Use -​ Tool use probably quite ancient -​ Apes use tools ​ Sticks to extract insects ​ Stone to crack open nuts ​ Sticks to test water depth -​ Homo uses tools often and begins making stone tools The Oldowan Tool Industry Mode 1. -​ Flakes, hammer, stones, cores -​ Simple tools associated with Homo habilis -​ Bang rocks together to make them Earliest evidence for stone tools -​ Old theory was it was only Homo habilis -​ Dikika (3.4 mya) - cut marks on bones that may be associated with the tools -​ Gona (2.5 mya) - first modified rocks (Au. garhi?) Oldowan toolmakers -​ Right handed -​ Suggests that they were engaged in hand-to-hand combat where right handed beings have an advantage Dikika cut marks ~ 3.4 mya -​ Cut marks made before the animal was fossilized -​ No stone tools found at this site Complex Foraging -​ Mode 1 stone tool technology ​ Carcass butchering  -​ ​ Digging sticks -​ Swartkrans. South Africa bone tools ​ Termite, extractive foraging Meat Eating -​ Evidence for meat eating ​ Concentrations of butchered bones and tools ​ Bovid concentrations outnumber all others -​ Taphonomy: a study of what happens to bone after death ​ Tooths make broad smooth grooves and stone tools make sharp parallel grooves. -​ Olduvai ​ Not water accumulated ​ Some hyena dens ​ Hominins- cut marks *Cut marks do not necessarily mean hunting -​ Hominins too small and too poorly encephalized to hunt – a claim that Zarin doesn’t 100% buy because chimps hunted -​ Scavenging scraps from hyenas’ kills? -​ Probably both -​ Evidence that they might be both because some cut marks are on bones that hyenas would’ve eaten first had they killed that prey, other marks are on bones they would leave behind Central place foraging -​ Human universal, not found in primates -​ When did this begin in hominins? -​ Olduvai – 1.9 mya?  -​ -​ Circle of stones → could this be a shelter? We don’t really know Home Life -​ Olduvai stone circle unlikely to be a home base -​ Carnivore activity -​ Limited processing of bone -​ Weathering of bone -​ Processing site for stone tools, this is where you go to butcher animals but don’t live there Homo ergaster and friends -​ Evolved from early Homo -​ 1.8 mya to 600 kya -​ Africa -​ Early Homo erectus (Asia not Africa) Skull -​ Primitive: postorbital constriction, no chin, receding forehead -​ Derived: taller skull, less prognathic, larger brain (900 cc - cubic centimeters), smaller jaws and teeth -​ Unique: brow ridge, occipital torus H. ergasters (Africa)/erectus (Asia) -​ More angular shape -​ Max breadth low H. Sapiens -​ More rounded shape -​ Max breadth high Postcrania -​ Long legs, narrow hips, barrel chest -​ Much taller than humans -​ Modern human body proportions -​ Reduced sexual dimorphism  -​ -​ Language limited? -​ Terrestrial biped; runner? Tools and Diet -​ Acheulean industry ​ Mode 2 ​ ~1.5 mya ​ Biface (hand ax) ​ Specifically designed → carcass processing? ​ No change in tool technology for 1 million years, not an innovative species Meat Eating -​ KNM-ER 1808 (Kenya): Vitamin A poisoning from eating liver of animals -​ 1.6 mya -​ Hand axes plentiful -​ Cut marks on animal bones -​ Tooth anatomy -​ Had tapeworms → evidence of meat eating Questions about Homo ergaster -​ Language? -​ Hunting or scavenging? -​ Fire? -​ Cooking food? Class 13 October 30, 2024 1.​ Homo floresiensis 2.​ Homo heidelbergensis 3.​ Homo neanderthalensis 4.​ Homo sapiens ​ Fossil data ​ Genetic data  -​ The Australopithecines -​ Small brains -​ Skilled upright walking with a retention of tree-climbing ability -​ Pronounced body size dimorphism, reduced canine dimorphism -​ Reduced canine size, increased molar size -​ 42. Mya to 1.98 mya The Paranthropines -​ Skilled upright walking with a retention of tree-climbing ability -​ Robust face/skull with massive teeth for chewing -​ 2.5 to 1 mya Homo habilis/rudolfensis -​ Larger brain -​ Smaller molars -​ First habitual tool user -​ 2.3 to 1.4 mya Homo ergaster and friends -​ Evolved from early Homo -​ 1.8 may to 600 kya -​ Early Homo erectus  -​ -​ Africa: Homo ergaster, Asia: Homo erectus Dispersal out of Africa -​ Dmanisi, Georgia -​ 1.8 mya ​ 5 skulls (brain 546-777 cc) ​ Could be an earlier hominin species? ​ Postcrania Homo-like ​ Oldowan stone tools ​ First evidence of hominins out of Africa Found skulls: Homo erectus -​ Discovered in 1891 by Eugene Dubois in Indonesia - called “Java Man” -​ 1.6