Ch. 15 Comparing Primates

Anthro317 Final

What is the definition of a “comparative study” according to Nunn and Barton (2001)?

An analysis of trait variation across species (rather than within species) with the aim of testing hypotheses or generating new ones.

Why is the comparative approach useful in primatology?

1. To test hypotheses explaining broad patterns of variation

2. To infer adaptation (especially when convergent evolution is seen)

3. To conduct “natural experiments” when experimental manipulation is impossible (e.g., you can’t easily change the body size of wild primates)

What are some examples of traits examined using the comparative method?

• Morphology: Body size, brain size, sexual swellings

• Behavior/Ecology: Group size, diet, extinction risk

• Culture: Language, tool use

What is the predicted relationship between body size and home range?

Larger animals generally require more space (larger home range)

What does comparative data (Milton and May 1976) show regarding primate body weight and home range?

There is a positive correlation; as body weight increases, home range size (HR) generally increases. The data points form a linear trend when plotted on a log-log scale.

Why are species not considerd “independent” data points in comparative studies?

Because all species are related. Closely related species share similar traits due to common ancestry, not necessarily because they independently evolved those traits for the same reason (adaptation)

If distantly related species have similar traits, what is this likely due to?

• Convergent Evolution: Adaptation to similar selective environments

• Constraint: Strong genetic or physiological constraints (e.g., all mammals having four limbs)

If closely related species have different traits, what is this likely due to?

Evolution, possibly natural selection driving them apart

Which ape species is most closely related to humans?

Chimpanzees and Bonobos (they share a common ancestor approximately 7 million years ago).

Which group forms a “clade” (a group with a specific common ancestor) separate from humans and African apes?

Orangutans

Why are Chimpanzees often used as models for human evolution?

Because of their tool-making, hunting/meat-sharing behaviors, and complex social relationships (including lethal aggression/territoriality) observed by Jane Goodall

Why are Baboons considered ecologically relevant models for early hominins?

1. They occupy savanna/grassland habitats similar to early hominins

2. They have diets that include seeds and meat

3. Some form multi-level social structures

What is specific about Kinda baboons that make them interesting for human evolution comparisons?

They have low levels of sexual dimorphism and physical aggression, and they maintain relatively strong male-female social relationships even when females are not in estrus.