By: Nick Babeaux
The Evolution of Humans has existed on the Earth for approximately 3.4 million years. At least, that's from when the oldest human ancestors have been found. The oldest known human is the fossil "Lucy," an Australopithecus, discovered by Donald Johnson and M. Taieb. Australopithecine's looked more like primates than modern-day Homo Sapiens; they walked semi-upright, they had low, sloping foreheads, protruding jaws, almost no facial expressions, thick body hair, and were about three feet tall. Over three and a half million years, humans have evolved greatly. We have grown from 3 to almost 6 feet, lost most of our body hair, become slender and adapted to walking, and grown brains over three times as large as the first Australopithecine's. Besides all this, humans (Homo Sapiens) have developed an advanced material culture. Now, instead of living in trees and digging food from the ground with sticks, we live in vast cities of millions and buy our food from the local grocery store with money (another recent development). Humans have come a long way, from Australopithecus to Homo Sapiens.
But we are also like the primates in many ways, too. We have the same basic body structure. Their hands are just like ours, except that they don't have opposable thumbs. Their feet are similar to ours, only with longer toes for gripping. And our faces are very similar as well. Nevertheless, we still have come a long way from living in trees to living in cities. Slowly, through hundreds of thousands of years, we mutated time and time again, natural selection ensuring that no harmful mutations continued. From the slow process of evolution, four distinct species emerged and died out, each giving way to its' successor: Homo Habilis, Homo Erectus, Homo sapiens Neanderthalesis, and finally, Homo sapiens Sapiens. We've come a long way over our brief (3.4 million years) existence on Earth. The first major step leading to Homo sapiens Sapiens was walking upright, or becoming bipedal. The Australopithecine's were the first to do this, actually rather clumsily. Their gait was, judging by their bone structure, was unsteady at best, and they probably mainly walked on all fours.
They also kept the ability to climb trees. The oldest Australopithecus fossil is Lucy, an Australopithecus Afarensis. Over 40% of her skeleton was found intact, making Lucy one of the most complete Australopithecus finds as well as the oldest. The Australopithecine's had a brain about the size of an orange (400-550cc), prominent cheekbones, and heavily enameled molars. They were about three feet tall, and had small, underdeveloped thumbs. Their toes were also shorter than other primates were. Australopithecine's, while definitely showing some human characteristics, were still much closer to the chimps and gorillas that we evolved from, so it is safe to say that they lived similar lives to other primates. They probably, judging from positioning of fossils at sites, lived in one place in small groups. It is thought that one male was in charge of an Australopithecine's group. We think this because of their sexual deformities. Sexual dimorphism is a noticeable difference in the sizes of males and females in a species. It is usually the males who are larger; in the case of Australopithecine's, the males were larger.
We know they lived in-groups because fossil groups of Australopithecine's are often found with more than 5 individuals in the same place. One site had 13 dead in the same place. While Australopithecine's are most likely direct ancestors of modern-day humans, they were still relatively unintelligent. Their tools, if any, were limited to sticks and rocks found on the ground. Australopithecines were vegetarians; even if they knew that animals were edible, they still had no reliable means of killing animals for food. That came with the evolution of Homo Habilis. About 2 million years ago, highly evolved Australopithecines made the realization that they can influence their environment, they made the first tools, began exploiting resources, and made the shift to Homo Habilis at the same time. Homo Habilis is the earliest known member of the Homo genus, and has been found only in Africa. Besides a brain size 50% larger than Australopithecus, Homo Habilis was taller, had an almost hairless face, and flatter nostrils. They were taller than Australopithecines, and were becoming omnivorous. Homo Habilis had, among other things, discovered that meat was edible.
They began scavenging dead meat, and added it to their normal vegetarian diets. We know this because of their teeth. Homo Habilis populated Africa until about 1.6 million years ago, when Homo Erectus emerged, causing their eventual extinction. Homo Erectus was the next step in human evolution, and had a much larger brain (1060 cc) than Homo Habilis. The name "Homo Erectus" means "Man who Walks Upright," which means practically nothing as all members of the Homo genus walked upright. They're not that many physical changes from Homo Habilis to Homo Erectus besides the larger brain; the most noticeable changes were a lighter, more delicate jaw and smaller teeth. The brow-ridge was also slightly larger than Homo Habilis. Homo Erectus lived until about 100,000 years ago, when Homo sapiens Neanderthalesis took their place. Homo sapiens Neanderthalesis commonly knows simply as Neanderthals, lived almost entirely during the most recent Ice Age. Evolution occurs in small, almost imperceptible steps. There are small mutations from one generation to the next. Anyone possessing a helpful mutation is more likely to reproduce, carrying on the good trait. Likewise, those with negative effects tend to die out. Pointing to the climate example: people living closer to the equator have dark skin to prevent severe burning and possible skin cancer, while people living closer to the poles have whiter skin because the high amounts of melanin are no longer needed for that particular climate. These physical differences, though, are just that: physical. The underlying bodily functions and intelligence that define humans remain the same.