Evolutionary Biology & Primate Adaptations: Natural & Sexual Selection, Hypotheses, and Social Behaviors

Natural Selection

Process where traits that enhance survival and reproduction become more common. → Example: better-camouflaged animals survive predators.

Sexual Selection

Type of natural selection focused on traits improving mating success. → Bright colors or large size that attract mates.

Intrasexual Selection

Competition within a sex (usually males) for access to mates. → Male gorillas fight for harems.

Intersexual Selection

Mate choice between sexes (often female choice). → Female peacocks prefer males with larger tails.

Arboreal Hypothesis

Primate traits evolved for tree living. → Grasping hands/feet and depth perception for branch movement.

Visual Predation Hypothesis

Forward-facing eyes evolved to catch insects. → Tarsier-like primates hunting at night.

Angiosperm Co-evolution Hypothesis

Primate vision and grasping evolved to exploit flowering plants. → Color vision helped spot ripe fruit.

Social Intelligence Hypothesis

Big brains evolved to manage complex social networks. → Chimps remember allies and rivals.

Fitness

Reproductive success; ability to pass on genes. → More surviving offspring = higher fitness.

Adaptation

Trait shaped by natural selection to solve environmental challenges. → Prehensile tail in monkeys for arboreal balance.

Adaptive Radiation

Rapid diversification when new ecological niches appear. → Early primates spreading into different habitats.

Kin Selection

Helping relatives to increase shared genetic success. → Grooming kin in a troop.

Altruism

Costly behavior that benefits another, often kin. → Warning calls that expose caller to danger.