How did Hominids evolve in Africa?

Answer 1

The frequently-heard answer is that we moved, or were driven, from the jungle to the grasslands, losing our ape-hair in response to the heat. However, baboons, who did this, have not lost their hair, nor have any of the other grassland animals. However, a recent hypothesis suggets we had an aquatic period (other animals who have streamlined, minimised, or total loss of, body hair had or have an aquatic period - otters, seals, hippos, etc). The suggestion is that our ancestors evolved the primary human characteristics (vertical posture, etc.) as a response to living in, or habitually frequenting, water - and the target place for this origin is the Danakil Horst, at the mouth of the Red Sea.

Another perspective:

In general terms Hominids split from living apes somewhere between 5 - 10 million years ago.

They evolved from being small brained, part-time bipedal/part-time quadrupedal with fingers and hands optimized for tree climbing and lacking fully developed language processing structures in the brain (e.g.: Australopithecus Afareneis);to large brained, full-time bipedal, with hands suited to manipulating object and fully developed language processing brains structures (e.g.: Homo Erectus -> Homo Sapien).

It is thought that rapid changes in climate and survival conditions provided selective pressure that gave an advantage to Hominids that were able to quickly adapt to a variety of conditions. This drove changes that favored intelligence, tool making and language.

Regarding body hair, later bipedal hominids were hunters that ran down their prey by outlasting them. Hominids could/can run much longer distances than other animals (although not typically as fast) because bipedal running, at a jogging pace, is more energy efficient than quadrupedal running and hominids could/can cool themselves by sweating. Most "Hairy" or fur-bearing animals don't have sweat glands and those that do (Horses etc) cannot cool themselves as effectively as hairless hominids can. Loss of body hair was an adaptation to promote cooling the body temperature.