Evolution of Language Capacity

• Many species of animals communicate using signals and sounds, but humans have the most elaborate system
• Humans use bodies, hand gestures, symbols, and sounds to communicate through 7,000 different languages

Evolving a Capacity for Language

• Research examines whether animals other than humans share the ability to use language or its prerequisites
• In 1969, Beatrice and Alan Gardner taught American Sign Language ([ASL], or Ameslan) to a chimpanzee named Washoe
  • This showed that nonverbal language (body and hand gestures) may have evolved before verbal language
• Sue Savage-Rumbaugh taught a pygmy chimpanzee (bonobo) named Malatta the symbolic language Yerkish
  • Malatta's son, Kanzi, accompanied his mother to class and learned more Yerkish than his mother without special training
  • Kanzi can understand human speech
• Jared Taglialatela searched for elements of language in chimpanzees' spontaneous behavior, discovering that Kanzi makes sounds associated with meanings/semantic context such as – Peeps associated with food – Raspberry sounds/extended grunts to attract attention – These sounds are usually directed toward specific animals are frequently accompanied by gestures, learned from mothers

Brain Similarities

• "Chimpanzeeish" brains using MRI indicate that active regions during human language use are also active when chimpanzees use language
• Animal vocalizations, gestures, parent-child teaching are similar to human language and brain activity, and suggests that human language has antecedents in nonhuman animals

Origin of Primates

• The primate branch includes lemurs, tarsiers, monkeys, apes, and humans, branching from a cladogram showing the evolutionary history of closely related animal groups
• Figure 2.1 is the cladogram showing color vision, enhanced depth perception, and other traits, helped them guide guide hand movements
• Female primates produce only one infant per pregnancy and devote more time to caring for their young than most animals
• All primates diverged from a common ancestor, as shown by branching points distinguishing traits evolving before or after a time point
• Apes do not have tails and swing arms to brachiate, where preceding primates cannot

Hominins

• The human family, called hominins, includes modern humans, extinct species, and immediate ancestors
• Hominins are taller than predecessor apes, are bipedal, have long legs, traveled across continents
• Changes in hand/tooth structure and a reduced jaw size allowed for different diets and skilled tool use
• The family brain underwent an unmatched evolution, increasing to three times its original size

Human Evolution

• Human evolution from ancestral apes to modern Homo sapiens is not linear as numerous hominin species coexisted as recently as 20,000 to 40,000 years ago
• They included Neanderthals in Europe, Denisovans in Siberia, Homo floresiensis on Flores in Indonesia
• Present-day modern species is the sole survivor

Research on Human Evolution

• Scientists reconstruct human evolution using archeological, biochemical, genetic, and behavioral methods

Archeological Research

• Morphological reconstruction approximates a hominin body appearance, revealing similarities and differences from skeletal remains
• Neanderthals were discovered in Germany from the skulls
• Neanderthals' similarities accounted for their importance, and recent brutish reconstructions demonstrate their similarities
• Neanderthals used similar tools, lived in social groups, performed music, cared for elders, and buried their dead
• Neanderthals communicated using language and held religious beliefs
• Modern European humans interbred with Neanderthals, acquiring genes that influenced features like cold adaptation and vitamin D absorbance

Biochemical and Genetic Research

• Genes direct cells to produce protein molecules composed of amino acids and sequencing one species' cellular protein can be compared to that of another
• Amino acid sequences change about once every million years so different species' differences can estimate age
• There were 24 differences in the amino acids of albumin in Old/New World monkeys, which diverged 30 million years ago and changed about +1 amino acid every 1.25 million years
• This estimates that chimpanzees and humans diverged between 5 to 8 million years ago
• Species relatedness is determined by comparing DNA
  • Mutations can change genetic code sequences to a limited amount while still leaving the gene functional
  • Modern humans and chimpanzees share 99% of genes and are close living relatives
  • The 1% difference produces huge differences between the two species

Behavioral Research

• Comparative behavioral research informs on the origins of human behavioral traits
• Chimpanzees are similar to humans, defending territories as groups to invade others and kill neighbors to grow territory
• Chimps walk and omnivorously eat vegetation/fruit/insects, hunt cooperatively and live in complex social groups with rich communication methods
• Commonalities reinforce genetic evidence that chimps and humans share a common ancestor

Physical Similarities

• Humans, apes, and monkeys have similar physical brains and deal with fossil brains for hominin ancestors, gross size comparisons, and brain size relationships

Australopithecus

• Hominin evolution studies dismiss the old views that walking upright led to skilled hands and bigger minds
• The Australopithecus ancestor walked upright, had similar hands for use, and used some tools
• Scientists deduced upright posture from back, pelvis, knee, and foot bones, where australopiths left footprints in volcanic ash 3.8 million years ago
  • Impressions featured well-developed arches, with an unrotated big toe, more like human feet, yet similar brain sizes to chimpanzees

The First Humans

• The oldest fossils of genus Homo (human) came from Mary and Louis Leakey in Tanzania in 1964 and dated to 2 million years ago
• The primates resembled Australopithecus but resembled larger brains (the Leakeys named it Homo habilis (handy human" for mistakenly believing the species members were the first makers)
• The first humans widely migrated from Africa to Europe and Asia was Homo erectus whose (mistaken) predecessor was H. habilis had a stooped posture
• The brain was bigger than any previous hominins species, overlapping current human brain size records

Modern Humans

• Modern humans (Homo sapiens) appeared in Africa about 200,000 years prior, coexisting/interbreeding with other hominin species until 30,000 years ago in Europe and 18,000 years ago in Asia
• Toolmaking, language use, or social organization may have led to the replacement of other human species

Relating Brain Size and Behavior

• Scientists propose that brain complexity and size enable behavior evolution and adaptive large sizes are adaptive for animals such as humans

• Gross brain sizes larger than humans' exist

• Estimated relative brain size estimates size by comparing brain size to body size and by counting brain cells

• A small roundworm (Caenorhabditis elegans) has 959 cells and 302 are neurons, where blue whales have 15,000 grams brains

• 30% of C. elegans are nervous system, whereas in terms of body weight, less than 0.01% of the blue whale is nervous system - no one thinks complexity in a roundworm's nervous is equivalent to that of a whale

Brain Size vs. Body Size vs. Counting Brain Cells

• Larger species have larger brains than less complex species for behavior (Jerison's index of brain size), comparing the brains of species relative to different body sizes
• As body size increases, brain size rises as about ⅔ total
• Ratio actual brain to expected brain sizes can quantitatively measure the encephalization quotient (EQ). The animal to the right of the trendline has a smaller EQ and opposite for large EQs on the left
• Cat have Average EQ and bats the opposite
• Modern human brains have the highest EQs
• Dolphins have almost as high EQs as humans

Brain Sizes of Species

• Species brain size and EQ include monkeys, apes, humans
• Threefold increase in brain size (EQ 2.5 chimpanzees to 7.3 moderm humans) is dramatic
• Cell number counting with estimate, body/brain size can evolve independently
• Gorilla are large as humans, but have small brains while humans have large bodies and brains
• Australopithecus ≈ 50–60 billion neurons, Homo habilis≈ 60 billion, Homo erectus ≈ 75–90 billion
• Modern humans ≈ 86 billion
• Large but similar QEs show less neuron concentration: Cortex neurons are similar in chimp-dolphin and humans
• Higher number makes humans specialized

Hominin Brains

• Requires understanding adaptive advantages with more neurons and metabolic support advantages and hypotheses as the human brain rapidly grew
• First, the hypothesis is adapting to drastically climate forces made hominins adapt increasing food complexity
• Primate lifestyles also favor systems for brain growth
• Cooling/metabolic processes are linked to better brain growth and smaller bones allowing dietary selectivity
• Slow maturation favors development due to retention of primate behavior with large degree if cooperation, so more time to increase and enrich themselves

Climate

• Climate drives the increase in size (including culture changes) ,Wherein New species emerged after new climate in that new place
• 8 million years ago: deformation of earth forms Great Rift leaving jungle climate west, savannah east in which the fossil evolution shows to hominin (bipedalism,increased body, brain size)
• Drying 2 million years ago forced adaption with new food so H. Habilis appeared
• 1 million (eructus) cooling sea bridges for tools(hunters) that ended disappear Other in Eu rope
• 30,000 Potts notes adaptability has been good so far while still short compared total

Primate life

• Robin Dunbar social:primate lifestyle and group (150) correlates explains Brain by how it Enhance
• Eat grass no brain growth but fruiting can

Fruit

• Katharine relation fruits, larger brains: finding Requires vision, motor skills, spatial skills, remember trees, competitor readiness (with friends helping parent)
• Yield Nutirents energy then humans had other scavengeing needs needing distances and cutting and fire usage