Evolution and Evolutionary Psychology

Evolution and Evolutionary Psychology

• Unit Three focuses on the biological basis of behavior.

Topics Covered

• Evolution
• Relevance of evolution to psychology
• Evolutionary psychology and comparative psychology
• Human evolution
• Evolution of the nervous system
• Inheritance of learnt ability and sociability in animals

Physical Anthropology

• Study of human biological/physiological characteristics and their evolution.
• Focuses on human evolution and human variation.

Human Evolution vs Human Variation

• Human evolution refers to the evolution of Homo sapiens from their ancestors.
• Human variation refers to the differences that exist among individual populations.
• Anthropologists study both cultural and biological variation.

Hominin Evolution

• Australopithecus: Showed apelike and humanlike characteristics including bipedalism, a flat nose, protruding jaw, and curved fingers.
• H. Habilis: Larger braincase, smaller face and teeth, and referred to as "handy man".
• H. Erectus: More humanlike appearance, larger brains, broader set of tools, fire usage.
• H. Neanderthals: Adapted to colder atmospheres, larger nose, shorter and stockier, controlled fire, shelters, clothing, hunting and gathering and symbolic burial, tools for hunting and sewing, eyebrow ridge.
• H. Sapiens: Lighter skeletal build, bigger brains, complex language, specialized weaponry.

Evolutionary History

• Can be inferred from shared morphological and biochemical traits, including shared DNA sequences.
• Shared traits are more similar among species that share a more recent common ancestor. Phylogenetics, using existing species and the fossil record, can reconstruct a biological "tree of life".

Australopithecus afarensis Characteristics

• Had both ape and human characteristics, flat noses, strongly projecting lower jaws, small braincases (less than 500 cubic centimeters), long, strong arms and curved fingers for climbing.
• They had small canine teeth, walked upright on two legs, and adapted to living in trees and on the ground, surviving for approximately a million years due to their adaptability.

Homo Habilis Characteristics

Has a slightly larger braincase and smaller face and teeth.

• Retains some ape-like features and was named "handy man" in 1964, because this species was thought to represent the first maker of stone tools.

Homo Erectus

• Known to have modern human-like body proportions with elongated legs and shorter arms relative to torso size.
• Features adapted for ground life, losing tree-climbing adaptations, along with an expanded braincase.
• They required a lot of energy, and eating meat and other quickly digested protein helped them absorb nutrients better.

Campfires

• The earliest evidence of hearths occurs now, used for cooking and social interaction, warmth and protection from predators.
• The creation of tools like handaxes and cleavers for survival during changing climates.

Neanderthals

• Closest extinct human relative, with defining features of large middle face, angled cheekbones, and a large nose adapted to humidifying and warming cold, dry air.
• They were shorter, stockier, and adapted to living in cold environments, and their brains were equally large, proportional to their brawnier bodies.
• They had a diverse set of sophisticated tools, controlled fire, lived in shelters, wore clothing and were skilled hunters.
• There is evidence that they buried their dead with offerings

Anatomically Modern Humans

• Characterized by lighter skeletal builds compared to early humans.
• Big brains, averaging 1300 cubic centimeters, are housed in thin walled skulls with flat foreheads.
• Modern human faces show less heavy brow ridges and prognathism.
• Prehistoric Homo sapiens made specialized tools including composite stone tools, fishhooks, harpoons, bows and arrows, spear throwers, and sewing needles.

Human Development

• Humans controlled growth and breeding leading to farming and animal herding, and they learned to transform the worlds landscapes.
• As the environment got more unpredictable bigger brains became essential for survival.
• Early humans made specialized tools, controlled fire, lived in shelters, build broad social networks and exchanged resources.
• They created art, music, personal adornment, rituals, and complex symbolic systems.

Evolution Definition

• Evolutionary processes lead to diversity at every level of biological organization.
• Herbert Spencer first use "evolution" in 1852 to describe development of life.
• Microevolution refers to changes within an organism over time like mosquito resistance.
• Macroevolution refers to changes from one being to another i.e. transformation, tetrapods.

Organic Evolution

• Changes in living things.
• Charles Darwin described as "descent with modification”.
• Dodson and Dodson (1976), described as related populations diverging and giving rise to species.
• Dobzhansky, in 1951, stated evolution is development of dissimilarities between the ancestral and the descendant population".

Evolutionary Basis

• Before mid 1800s diversity of life was attributed to God's creation and remained unchanged. Fossil discoveries and geological sciences provided evidence to the contrary.
• Pre-Darwin biologists, and Darwin and Wallace (1858; 1859) proposed mechanisms for evolution.

Evolutionary Principles

• Speciation
• Irreversibility
• Parallelism and convergence
• Adaptive radiation
• Extinction

Irreversibility

• Louis Dollo, in 1893, proposed the Principle of Irreversibility or Dollo's Law; organisms can't return to a previous stage.
• Changed structure don't revert in evolution; once an animal passes stages return to ancestor can't occur.
• Flying reptiles adaptation to airborne life occurred in other distinct lineages the birds and mammals.

Speciation

• Orator F. Cook coined "speciation" in 1906 for splitting lineages.
• Speciation creates two+ species from one, or a related group that can make fertile offspring.
• 4 geographic modes are allopatric, parapatric, sympatric, and peripatric speciation.

Allopatric Speciation

• Allopatric (allos meaning other + patrâ means fatherland) speciation is geographic speciation.
• Population divides in two isolated groups by barriers, and they change genotypically and phenotypically.

Peripatric Speciation

• Members on border split and evolve into a new species.
• Difference is size of group; peripatric speciation has smaller groups.
• Unique traits get passed making new future groups distinct characteristics.

Parapatric Speciation

• Mode of event caused by smalls groups entering new habitats.
• Only partial area divides.

No Extrinsic barrier

• Species are separated by differences in same environment.
• Populations continuous, but mating not random.
• Individuals likely mate with those to their geographic range only.

Sympatric Speciation

• In this case, two+ species form from a single ancestor in the same place.
• Invertebrates, like insects dependent on host area, is a good example.
• Apple maggot lays eggs in apple fruits; after North American apples were introduced in the 19th century, a maggot specie developed.

Geographic Overlap

• Sympatric speciation is unique because it takes place while two subpopulations occupy same area.
• Organisms split in groups/ territory and become so different that can't reproduce.
• Parapatric speciation occurs with subpopulations in same species are isolated but have areas where ranges overlap.

This lesson covers evolution, its relevance to psychology, and evolutionary and comparative psychology. It also discusses human evolution, the evolution of the nervous system, and the inheritance of learned abilities and sociability in animals. Physical anthropology, hominin evolution, and human variation are highlighted.