Human Traits, Brain, Bipedalism & Selective Pressures

What is human taxonomy?

Classifying humans: hominins, apes, primates, mammals, vertebrates, etc.

What are hominin traits?

Traits like walking on two legs, small canines, tool use, bigger brains, complex culture, symbolic thought.

What is bipedalism?

Walking on two legs; key human adaptation.

What are the benefits of bipedalism?

Frees hands, better vision, uses less energy to move.

What are the drawbacks of bipedalism?

Harder childbirth, hernias, varicose veins, back problems, ankle injuries.

What is the obstetrical dilemma?

Pelvis adapted for walking vs. giving birth to big-brained babies.

What is human brain evolution influenced by?

Better diet, smaller gut, cooking, exploring new places, social complexity.

What is the cooking hypothesis?

Cooking made food easier to digest and gave energy for brain growth.

What is the trophic level effect on brain evolution?

Eating more animal foods gives energy for bigger brains.

What are innate human behaviors?

Behaviors humans are born with; universal.

What is the difference between proximate and ultimate causes of behavior?

Proximate = how it works; Ultimate = why it helps survival or reproduction.

What are social systems in primates?

Group size, mating patterns, and male/female differences shaped by environment.

What is inclusive fitness?

Your own reproductive success plus the success of relatives you help.

What is altruism?

Helping others even if it costs you; often helps relatives.

What is gene-culture co-evolution?

Genes and culture affect each other, e.g., lactose tolerance and amylase genes.

What is lactase persistence?

Ability to digest milk as an adult because of dairy culture.

What are amylase gene repeats?

More copies of amylase gene help digest starch; adaptation to high-starch diets.

How do UV and climate affect human evolution?

Skin color balances Vitamin D production and protects folate from UV.

What is central place foraging?

Bringing food to a central spot to share or store.

What is phenotypic plasticity?

One gene can create different traits depending on the environment.

What is convergence in evolution?

Unrelated species develop similar traits from similar environments.

What is the environment of evolutionary adaptedness?

Humans evolved ~200kya in Africa with small groups, seasonal diets, and foraging.

What are hominin anatomical traits?

Obligate biped, molar-like premolars, small canines, central foramen magnum, S-shaped spine, broad pelvis, valgus knee, double arch foot, flat face, adducted big toe, cooperative birth, pair-bonds.

What are hominin behavioral traits?

Slow maturation, central place foraging, tool use, culture, language, chin, high forehead.

What are costs of adaptations?

Trade-offs and harm if environment changes faster than evolution.

What is heterozygote advantage?

Two different alleles gives better survival than two identical alleles.

What is evolutionary disequilibrium?

Environment changes faster than population can adapt, making traits less useful.

What is selective pressure?

Anything in the environment that favors some traits over others.

What is inclusive fitness (professor’s flashcards)?

Success in passing on genes, including helping relatives reproduce.

What is kin selection?

Helping relatives can increase your own gene success even if it costs you.