So how did humans become bipedal? As we have seen, if a species obtains a niche in its environment that has a constant supply of food there is not any need to migrate unless it is invaded by a more aggressive species. However, if a species has to migrate the creature will have to adapt to its new environment. Occasional mutations are happening to all creatures and if they are harmful that creature will become extinct, usually in one generation, but if the mutation is helpful the creature will prosper as a sub species like giraffes and okapis or sea otters and river otters.
Sub species are also formed by separation due to changes in the environment such as deserts, mountains, lakes or rivers. After hominins mutated from the last common ancestor of chimpanzees, chimps had another mutation about two million years ago when communities of chimpanzees lived around the Congo River, formally the Zaire River. However around about the period of the mutation south of the River Congo suffered from a lengthy drought which wiped out the preferred food of resident creatures. When there is limited supply of food larger animals will move out or die out. This what happened to Zaires chimpanzees, but fortunately some learnt and mutated/evolved to be able to survive with less food, the side effect was their bodies became smaller until they became a sub species of chimpanzee… Bonobos.
The reduction of size in isolated creatures is a process in which a breed of animals or plants is changed to become significantly smaller than standard members of their interest species. The effect can be induced through human intervention or non-human processes, and can include genetic, nutritional or hormonal means. Hominins isolated on the island of Flores were so much reduced in size that when they were discovered they were nicknamed “The Hobbits”. The thing about Bonobos was not only were they smaller and slimmer but their legs were longer, this could indicate that certain parts of their skeleton, muscles, tendons and body tissue and were prone to mutation. Whats more. you will rarely see chimps in deeper water, they hate water, they don’t swim. Their low body fat ratio causes them to sink and their top heavy body composition makes it difficult for them to keep their heads above water. However, some chimpanzees do enjoy a good splash around in shallow water. Bonobos are more comfortable in water and have often been observed in deep water.
So far, at over 7 million years old the fossils of S. Tchadensis are the oldest hominins that were bipedal. S. Tchadensis’s fossil is so far advanced in bipedalism that the mutations that led to walking on two legs must have started well before 7 million years ago. What caused one of the primates to develop a mutation that caused it to adopt a two legged gait? We have to go back further in time than homo Sapiens and apes to the common ancestor of both. We discussed how the weaker family, clan or tribe of early primates had to move on to other feeding localities when more powerful primates moved into their territory. Migration would have to be in the vicinity of water eventually, over aeons of time arriving at the source or the sea. Once these photo hominids arrived at the sea shore a whole new world opened up to them. Along the shoreline and shallows was an abundance of food for omnivores, and by wading a little deeper slow moving aquatic creatures were available, wadding would encourage bipedalism to keep your head out of water. There is plenty of evidence that our early hominoids spent time on shores from their earliest settlements being packed full of discarded seashells, suggesting our ancestors had a high-protein diet that might have helped brain development.