The Evolution of Humans

Some 75000000 years ago our possible ancestor was a tree shrew. Even though there is little to no similarities between modern day humans and tree shrews, most scientist's believe that this rat-like creature is our ancestor. The five main characteristics that distinguish humans are erect posture, well-developed brains, opposable thumbs, binocular and color vision, and speech which the tree shrew had none of.

The first critical step was getting into the trees away from fierce competition on the ground. The three-dimensional world of the trees required a better sight, so binocular vision evolved. The three-dimensional world also needed awareness of everything all around, thus, a better(Key word; not perfect, only better) developed brain came to be. To keep from falling out of the trees, primitve grasping hands evolved.

Some 25000000 years later, prosimians evolved from some of the tree shrews. These included the tarsier and ring-tailed lemur which most people confuse as monkeys. Prosimians resembled humans more than the tree shrew with a shorter snout, better hands and eyes, and better developed brain but still lacked erect posture, and speech. Despite the improvements, all the characteristics fell far short from that of a modern human. 40000000 years ago monkeys evolved from the prosimians having no obvious differences but had better developed hands and eyes and were more intelligent than the prosimians.

Next are the Apes, our closest cousins. The main game changing activity they practiced was tree swinging. First since tree swinging made the apes's body in an upright position its head had to be able to switch positions in order to see where they were going. This would lead the way for erect posture which would free its hands for tool use. The tree swinging would also increase the apes hand dexterity, which would lead to a better developed brain.

You might be thinking, why did all monkeys not evolve into humans? One might say evolution and natural selection are conservative and don't favor changes unless forced by circumstances. An example are the chimps, who had a niche in nature and felt no need to evolve. The gorillas's great size made it easy for survival so had no need to evolve. The gibbons and orangutans had stayed in the trees too long and over specialized their tree swinging skills and did not evolve on the ground where our ancestors did. The baboons came out of the trees too early and did not fully specialize their hand skills and upright posture.

Some apes did come out of the trees in the African Savannah to get food. We know this by examining their jawbones and teeth. They were much bigger then, which suggests they were eating lots of seeds and grains, which required massive jaws and molars to grind up. This meant that there canine teeth were lost because they would get in the way of chewing and nature chose eating over defense.

Now without any main defense system the evolving apes needed some form of weapon. The earliest weapons were either a stick, or large rock or bone. This was one of the first technologies made, and was the dawn of the hominids

The term hominids refers to "modern humans." Hominids had many collateral branches which came to an abrupt end such as the Neanderthals. The earliest of these hominids were the Australopithecines. They were somewhat human in that they had more evolved characteristics than the apes, however, most scientists do not generally think of them as humans because ther brains were much smaller (450cc compared to modern day 1400cc) and their hands had little or no precision grip and probably couldn't talk.

Australopithecus Afarensis was likely the ancestor of two branches of Australopithecines. One of the branches, the larger in size, was vegetarian. The other was an omnivore. The importance of this is that hunting required more inventiveness than did collecting plants. As a result, the meat eaters developed better tools, such as containers for storing the meat and better weapons for hunting, much more than the vegetarians did.

Eventually the meat eaters evolved into what most scientists call the first true human, Homo Habilis, ("Handy Man") with a brain capacity of 650cc. They made very crude weapons but could not speak. That is why other scientists reserve the spot of the first humans as Homo Erectus which had a brain capacity of 750cc and the abilty to speak.

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