Question

Outline three reasons natural selection may have favored bipedal locomotion in the hominin lineage. In each case, explain why hominins became bipedal but other terrestrial primates, such as baboons, did not.

Answer 1

Bipedal locomotion may have been an adaptation to living in a mixed woodland and grassland environment.The three reasons for the bipedial locomotion natural selection -

1. An upright posture also potentially helps to dissipate excess body heat and reduces the absorption of heat from the sun because less skin has a direct exposure to ultra violet radiation during the hottest times of the day.
2. It made it easier to see long distances when moving over areas covered with tall grasses.
3. Improved thermoregulation - Air temperature is warmer closer to the ground beacuse the sun heats up the soil and then the soil radiates that heat, so natural selection favored animals who walk upright

The postural feeding hypothesis (reaching for food/balancing) provides an explanation for the partial bipedalism of the earliest hominins. The savannah-based theory describes how the largely bipedal hominins that started to settle on the ground became increasingly bipedal. Hypothesis for the evolution of bipedialism in hominins -

• To be successful providers, males needed their arms and hands free to carry food, and thus bipedalism evolved.
• Hominids evolved to walk upright in response to climate change. As forests shrank, hominid ancestors found themselves descending from the trees to walk across stretches of grassland that separated forest patches. The most energetically efficient way to walk on the ground was bipedally