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How Chimpanzees Evolved to Become Human Beings
How the chimps who wandered into Afar Triangle of Ethiopia could evolve to become human beings? This had to do with the geography of the area. The earliest early human skeleton fossil found was Lucy (https://en.wikipedia.org/wiki/Lucy_(Australopithecus) ) lived about 3.2 million years ago in Afar Triangle of Ethiopia. Lucy looked more like an ape but she had evidence that she could walk upright. Afar Triangle of Ethiopia was a semi-desert at that time as today. Chimps usually lived in the forest. Why they went to a semi-desert area? There must be some food source that attracted them. What was the food source then? I believe it was the clams. This situation was similar to why a group of brown bears went to the northern territory for seals. Eventually they became Polar bear. Chimps were known to be able to crack a nut by hitting it with a rock. So they would be able to crack clams by using a rock.
In the semi-desert area there were open patches of grassland separated by sand one or two miles apart. Animal density was low. Therefore it could not support large predators like the lions which hunted in a group. There were rarely any lions. Smaller size predators like hyenas, leopards, cheetahs and wolves …etc were present. Chimps were pretty strong and they were about the size of hyenas. Chimps were known to use a stick as weapon. Since there were no or few lions, their main predators were the leopards and hyenas. Defending as a group and using the stick as a weapon, they could fight off those predators. So they always carried a stick.
At first they searched for clams in the beach areas when the tide was low, using the stick to dig them up. Later they found there were much more clams under the seabed near the shore area. They began to dive down to search for clams. They might also hunt for other slow moving shellfish such as sea-urchins, snails, sea cucumbers, abalones, crabs, shrimps…etc. When they came up to the surface they could use the stick as a floater. Swimming could help to straighten the body. After many many generations, their body evolved to become a straight line. Their arms became shorter. All swimming mammals have shortened limbs. But their legs were not be shortened because they swam liked a frog. Thus they could not do knuckle walking anymore. They had to walk upright. At first they needed the help of the stick as the third leg. Later their leg muscles were developed and they could walk bipedal. They walked to the safe place of a cave or a tree top to sleep at night.
They became bigger in size and stronger from the nutritious food and swimming. However after the chimps’ population had reached a certain level, the amount of shellfish in the area could not support the population. They needed to find new resources. Some of the chimps became land hunters. One important factor on staying under the sun was the body water evaporating rate. If the chimps stood up right, they had a smaller area under the sun, resulting in less body water evaporation. Water was precious in a semi-desert. Standing upright and holding a stick also helped to defend against a sudden ambush attack by a predator. First they could check over the tall grass to see if any predator was hiding there. Second the predator would not able to jump on his back comparing to if he did knuckle walking.
They could also use the stick as a hunting tool. There were many small animals in the semi-desert, snakes, spiders, lizards, centipede, chipmunks etc. Some of those animals were poisonous. They could use the stick to find those animals hiding under a rock. A swing of the stick could kill the small animals and avoided being beaten. They could throw a stone to knock down a bird, or to scare away a predator.
Then they made many innovations. They could sharpen the stick by robbing it against a rock to a very sharp point. This could pierce through an animal’s skin and kill the animal. Although they could not run as fast as antelopes, they learned group hunting and could corner the antelope. They could steal food of animals hunted down by predators. With a stick as weapon, they could fight off any predators in the semi-desert area. Actually they could follow the predators and took over the kill as soon as the predators made a hunt. They used sharp stones to cut open the animal body, another innovation. They ate booth plant matter and animal meat. After many many generations, they developed new muscle which allowed them to throw a rock at speed of 106mph, the speed that a base ball pitcher can throw. This could knock an animal unconscious. Humans are the only animal that have developed such ability.
Then they invented two more important weapons, the spear and the axe by tying a sharp stone to the stick end. An overhead swing of the axe could kill or wounded a predator. By this time they were big and strong enough that they could compete with any predators including lions. Then they moved out of the semi-desert area into the fertile land where food was much more abundant. Eventually they spread all over the world.
The reason why the group of chimps wandered into the semi-desert of Ethiopia could evolve to become human beings was because the new living environment had force them to apply innovations in order to survive. 4 million years ago the chimps’ intelligence had advanced to the level that they could make innovations. But living in the forest did not encourage them to apply such ability. So they stayed unchanged for 4 million years. They do not want to come out of the forest because of the presence of large predators like the lions. After the chimps that developed bipedal walking by staying in the water and then forced to come back to the land, the new living environment encouraged them to make more innovations. The more they practice, the more excel they become. Eventually they become human beings like us today.
Chimps had to go through an aquatic stage to be able to walk bipedally. Even by chance if they lived in a semi-desert area where there had no large predators, still they could not develop bipedal walking. They had to stay low to look for food on the ground. They could not run fast bipedally to hunt. They had to do knuckle running. With their long and heavy arms and bended body, it would be too tiresome to stand up for a longer period of time. It was only after staying in the water for many many generations that their arms were shortened, their body straightened, their main muscles shifted from the arms to the legs, and then they could develop bipedal walking. In the water both diving and standing straightened the chimps' body. To understand how difficult this transformation would be, imagine a group of human beings want to develop knuckle walking instead of bipedal walking. To achieve that, they have to do knuckle walking at least more than 50% in their daily walking activity. This is because the body has to know that knuckle walking is the main method of locomotion. The higher the precentage, the faster the transformation. But knuckle walking for this group of human beings will be so tiresome that nobody will be willing to do it. However, if something have happened that the only way for this group of human beings to survive is to do knuckle walking, then they will be forced to do so. At first they will be walking/running slower than doing bipedally. Only after many many generations, their arms will be elongated, their body bended, their legs shortened, their muscles shifted to the arms from the legs, and then they can do knuck walking with ease and can run faster than running bipedally previously. It takes a very long time to achieve that. This situation would also be true with the chimps coming down the tree. If they could survive with knuckle walking. Why they wanted to develop bipedal walking which is slower? Baboons came down the tree and stay in the open area for millions of years. They have never developed bipedal walking. This is because their daily activities do not require them to develop bipedal walking. They search for food on the ground and they need to run away quickly from predators. If they develop bipedal walking, there would only be disadvantage and no advantage to their daily activities. In order to develop bipedal walking, it has to be advantageous to their daily activity.
On the contrary, after the above chimps went through an aquatic stage, their arms were shortened and their body was straightened. They could not do knuckle walking any more. They could only walk bipedally. Judging from Lucy's body features, she had to walk bipedally (http://efossils.org/book/limb-proportions). Now they were forced to return back to the land. Although they could still climb trees, though not as easy as before, but there were not much trees in the semi-desert area to support them for a living. In order to survive, they made innovations in hunting techniques. By doing so, not only they survived, they even became prosperous. This is my view of how chimpanzees evolved to become human beings from a "making innovations" point of view. I therefore believe chimps did go through an aquatic stage to evolve to become human beings and the Aquatic Ape Hypothesis (http://rationalwiki.org/wiki/Aquatic_ape_hypothesis) is true.
The Aquatic Ape Hypothesis has been debated by scholars for more than eighty years to decide if the hypothesis is true or not. Most of the discussions concentrate on the body feature differences between humans and chimps, such as why humans lost most of their hair and why humans' nose is pointing downward while chimps' nose is flat. The debate leads to no conclusion. I come up with a "critical thinking" solution for this hypothesis. A critical thinking solution requires one to do some thinking. My solution emphasizes on logic. It bases on the conditions that a transformation can take place. Therefore there will be less uncertainty. My solution shows it is illogical for the chimps just came down the tree and be able to develop bipedal walking directly. Chimps had to go through an aquatic stage to achieve that transformation.
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Stephen Cheng