Why evolve to bipedalism

Question 1

Energetic efficiency

Answer 1

If one compares human walking to chimpanzee, it’s clear its more efficient to walk on to legs instead of four, at least over knuckle walking apes. The way a biped disperses heat is also more efficient than quadrupeds as bipeds stand slightly taller off the ground and during midday sun they have less surface area to be heated, mainly in savannah environments.

Question 2

Ecological influences- How they came about.

Answer 2

This focus’ on the role of the changing environment of East Africa between 5 and 8 million years ago. In the late Miocene of Africa the grasslands expanded and and forests decreased as a result of global warming and drying- This resulted in widespread Savannahs.

Question 3

Ecological influences and the result

Answer 3

Savannahs mean greater distance between food sources,, therefore individuals had to forage longer distances across open land. This resulted in natural selection favouring bipedalism as a more efficient mode on transport. Standing upright would’ve allowed one to see over tall grass and scan for predators- a selective advantage.

Question 4

Dietary influences

Answer 4

There may be some dietary rewards of bipedalism. Standing upright for the benefit for feeding in fruit, both in the trees and on the ground, they’re able to pluck. Bipedality, group size and body size may’ve adapted in response to greater patchiness of food sources but also led to greater risk of being eaten travelling between these areas, leading to social groups.

Question 5

Mating influences

Answer 5

Could benefit males engage in social displays, in chimpanzees for example stand upright for short periods of time in order to assert dominance over other males. Habitually walking upright may’ve made males look more imposing resulting in more mating opportunities. However, why this would result in habitual bipedalism and not a temporary behavioural tactic is still unclear.