Human Evolution Essay
There is a theory that humans descended from an earlier, lower form of life. There is an assortment of evidence that shows that all living creatures on Earth descended from a common ancestry. Evolution doesnt discriminate against humans. It is believed that we too are a product of an earlier predecessor. The similarities in all life are evident if you consider that every form of life builds from the same building blocks–20 essential amino acids, four nitrogen bases, and simple sugars. Each of Earths past and present forms of life are, or were composed of a combination of those building blocks called RNA or DNA. In the very beginning of life on Earth, the genetic structure was very simple, but as time has gone by, the best combinations in the genetic sequence were individuals that reproduced.
Over the approximated 3.5 billion years that life has been in existence on Earth, there have been many mutations in the genetic codes of different forms of life. Only very few of the genetic mutations are indeed beneficial to the function of the species. Negative mutations give the life form a disadvantage for survival, thus reducing its chances for reproduction, but a positive mutation gives the species an advantage to survive and produce offspring. The offspring have a copy of the positive mutation now in their genetics to eventually pass down to their young and so on. Now you can see how the positive mutations have a way of piling up into different piles, which is why our result is a widely diverse life, which exists on Earth today. This theory of how evolution came to be is known as natural selection. It states that a weaker individual has a lesser chance for survival and reproduction than that of a stronger. Its natures way of weeding out the bad and seeding the good.
In the study of evolution, evolutionary scientists try to find the ancestry and genetic relations between organisms. They try to map out the path of the ancestry between organisms over the existence of the Earths history. Another essential part of the study of evolution is actually making educated predictions of the history of a species. The history of a species includes the geographical distributions and the species population over time.
All of the information that follows is valid in that it has genetic and fossilized evidence to prove its merit. Some of the most important aspects that make a human different from its ancestors are the development of communication, brain function, and the ability to walk upright, which frees up the hands to embark on other tasks. Language is considered by many to be the most unique of all the human attributes.
As strange as it may sound, genetically we are the most similar to that of primates as any other known living creature on Earth. The primate family includes chimpanzees, orangutans, gorillas and even humans. Other than genetic similarities, we can show other likenesses in the tissue physiology and also by comparing brains circuits in a brain analysis.
Humans are a prime example of natural selection. The domination of the world by the superior present day human is what ended all similar species. The species that we dominated were our greatest competition for food, intelligence, and essentially our very existence on this planet. When we beat our predecessor, we did it in a fight for our lives, not so much as an act of violence. In many cases, Humans may have killed our ancestors in a misunderstanding, not knowing why a similar being was so much more savage and violent. We may have protected our families by attacking these beastlike creatures.
The first things that we need to know are, Who were our first ancestors? Why did they evolve? What did they look like? And how did they live? Without this information, we will not know what we have arisen from.
The most likely place to look for our fossilized lineage is in the environment of our closest living relatives–Africa. This is the reason that most of our archeological digs have been occurring on this continent. Of the fossils found, the skulls have been the most important because by knowing the structure of the skull, we can see how distant their relations are to us. Since one of the most significant changes is brain size and function, the brain and brain cavities provide a lot of evidence for evolutionary change. We know about brain function from fossils because sometimes, even the brain is preserved inside the fossilized skulls.
Our most distant known lineage into the human path is very much similar to that of a chimpanzee. This creature was known as Australopithecus afarensis and can be dated back to 3.2 million years ago. A. afarensis was still very similar to a chimp. The brain size was no larger than ours. The finger bones were still curved, showing that it was still quite comfortable in the trees. Even though it was slightly similar, it was still very different. A. afarensis had smaller canines than a chimpanzees. The face structure was more vertical with less snout. The spinal column was more upright than that of a chimp. The hip bones also showed something unusual–this animal walked upright. This was the first step in our direction from that of our most distant living relative.
The famous Lucy fossil was the remains of an A. afarensis. This fossil showed that the A. afarensis, although different than chimps, still had a small rib cage and a large gut that was fit for digesting the large amount of vegetation that made up their diet. From the large gut, we can speculate that the diet of A. afarensis consisted of still mainly vegetation, and not yet much protein.
While the Australopithecus afarensis existed, there was a great climate change in Africa. The once tropical African continent warmed and the main portion of the continent closest to the equator turned to dry grassland. The food that A. afarensis was accustomed to eating, had disappeared. Many of the chimps, like other animals, migrated south to the bottom tip of Africa. There in the forest, this upright primate had a disadvantage to the chimps, so it quickly died off in the forests. The Australopithecus that stayed had to adapt to survive. There was very limited food that these creatures could digest; they could not process the fibrous grasses that covered the plains. The Australopithecus split into two different forms of the species–a robust more animal-like version and a graceful more human-like model. The robust version adapted to eat the roots of plants. The tough root and difficult dig to obtain the meal resulted in a large-jawed, thick-skulled, digging creature.
The smaller, more graceful was the one humans are in closest relation to. We find it evident in the size and shape of the brain found in fossils. These are the first of our ancestors that used stone tools. These stone tools were the adaptation that fueled their kind. The stone tools at the time and great intelligence were what allowed them to obtain food. When scavenging for food, they would take a completely cleaned animal carcass and using their simple stone sledges, smash open bones and eat the protein rich marrow from within. They would also use their hammers to crack open the skull to obtain the brain, which was also rich in protein. The advantage here is that they had no competition for their newly found food because no other creature could access these meat reserves.
The protein they were ingesting was food that was high in energy and much easier to digest than plant material. After generations went by, the large digestive track was slowly shortened because it was no longer needed. As the size of the animal lessened, the ratio between weight and energy rose. This gave room for the brain of these graced Australopithecus to adapt to the environment, and since intelligence is what kept this branch alive, their intellect developed more. The individuals who where the most intelligent made the best tools, and thus had a better chance for survival and reproduction. Tools, meat, and larger brains were the reasons that this species strived, but if you take out any of these vital parts, the others couldnt develop.
Homo erectus is the next known ancestor down the branch to humanity. He dates back to 1.8 million years. H. erectus looked much like human, but still had a mind no more complex than a chimps. The brain of H. erectus was still 30% smaller than our own.
Homo heidelbergensis shows much more human-like characteristics than its predecessor, Homo erectus. The first evidence of H. heidelbergensis in Europe dates back to .5 million years ago. There have been 5 tons of remains found in circle patterns in a small area. The circle patterns are evidence that they were living in round, maybe hut-like enclosures. When you consider the small area in which they were found, you can see that possibly they lived in a small community. Now living in Europe, having shelter was essential because Europe was a great deal cooler than their arid grasslands in Africa. Shelter is probably what allowed them to venture out of Africa for the first time, because without that support, they would surely freeze in the cold season.
In a cave in Italy, scientists have found the skeletal remains of one of these male creatures and the skeleton was preserved quite well. Deep in this cave, it has been partially covered by crystals that the cave has formed. By measuring the size of these bones, we know the size of this creatures male gender. This Creature used stone tools, but they used better stone like flint. Their tools were much sharper and lighter. They have found that they chipped hand axes out of flint that are much more complex than that of the previous. They also showed that they had many of the flint remains in one area, signifying that they used mass production to obtain their tools.
They used theses sharp tools to butcher animals, meaning they had made the kill and no longer were only scavenging meat. At this time in history, animals, such as rhinoceros, elephants, lions and the largely extinct cave bear existed in Europe. H. heidelbergensis had a brain size very close to the size of a present day human. They used different tools when disassembling these large animals. They used large rocks for smashing bones, which enabled them to retrieve marrow from their thick bones. They harvested some of the bones from these creatures for tools in various activities. Their sharp flint tools were used to remove the meat from the bone. They also used antlers to dig and punch an initial hole in the carcass before butchering it.
There is evidence that .5 million years ago when we know they had inhabited Europe, they not only were living there, but were also flourishing. This shows that they may have been there for many years prior. It isnt fully understood about why they migrated out of Africa and into Europe.
In the new cooler climate, their edible vegetation was scarce; therefore there were less food options. The only two options were to scavenge or adapt. Our ancestors, like before, rose to the occasion and adapted to become hunters. They became hunters to eliminate scavenging against the ravage carnivores of their day. In Europe H. heidelbergensis was more advanced than the H. heidelbergensis of other areas. The advancements in the H. heidelbergensis of this area are evident in their tools.
It is believed that the Europeans used language. This is proven by their methods of passing down knowledge. This much larger axe head was too large for actual function. It was probably used as a model to show the detail of the axe head. Their scale model was proof that they must be teaching the art of tool making and in the process, using complex communication. This language was likely to be very simple to the language we know today, but it allowed them reflect on the past and to teach more efficiently.
Even though their tools couldnt take down some of the larger prey, their intelligence proved itself again. They used swamps as traps, and would drive a large animal into a corner, where it would then have to retreat into the swamps. Once they entered, they couldnt escape the quicksand-like substrate. There is also evidence of the use wooden tools. Archeologists have found perfectly preserved wooden spears in the prehistoric swamps. When they examined the spears, they found that the tip was on the toughest part of the wood–the base. These spears were also found to be perfectly balanced, so they could be used as javelins. This was another step into humanity. They now had more food for themselves, their mate and their offspring.
Neanderthals had a very robust build; they were short and very strong unlike anyone today. It is known from fossil records that Neanderthals disappeared at almost the exact time that that humans arrived. It has been widely believed for years that Neanderthals were our predecessors, but today we can tell that Neanderthals were a completely different, but almost parallel evolutionary relative. This is known by genetics. The last known Neanderthal fossil dates back to 28 thousand years ago. Before the humans invaded the land, the territory belonged to the Neanderthals. Their brains had completely different evolutionary paths than us; they may have appeared very similar to us, but were, in actuality, quite different.
The brain of the Neanderthal evolved differently and not as drastically as that of the human brain. The evolution of the Neanderthals mind hit a plateau, and it is seen in the fossil records that the tools of the Neanderthals remained unchanged for a quarter million years before their extinction. Other than human competition, the main reason for the disappearance of the Neanderthals was a change in climate and landscape. They couldnt survive in an area with a disappearing habitat. They were so dependent on what they were accustomed to, that the transition couldnt be made and the result was an eventual extinction of their species. In the rapidly cooling European areas, humans used their intelligence to adapt, but Neanderthals were isolated to pockets of still wooded areas. One by one, the Neanderthals died off.
Homo sapiens date back to over 100,000 years ago, as the skull fossils found in Africa show. These humans were still quite primitive, but the bone structure was that of a present day human.
Now that Neanderthals had disappeared, this meant less competition for our human ancestors. This is a perfect example of Charles Darwins theory of survival of the fittest. They couldnt adapt and died, and could no longer pass on their genes. We survived and we continue to procreate.
Using decorative beads is one of the first examples of art in our species. One of the beads found was made of shell. The strange thing about this shell bead was that it was found hundreds of miles away from where it first lied. This is evidence that humans may have been trading with neighboring tribes. Another possibility is that they traveled the distance to retrieve the shell, but this proves that they were traveling into a much cooler climate. If they were able to survive in this cooler area, then they must have also been wearing warm clothing and building sturdy shelters.
We have found decorative beads with the remains of Neanderthal bones. Not many of the recorded Neanderthals, in fact, used beads. Some consider that to show they used art also, but others believe it was simply them mimicking what they had seen their human counter parts doing. The Neanderthals beads were much more primitive, but that may be partially due to them being unable to grasp the function of the decoration as a form of self expression. This is a prime example of the similarities and differences in the minds of the two creatures.
There is a theory that the last few Neanderthals had to interact with humans. In this theory, there is a possibility that some Neanderthals breed in hybridization between the two. If this were the case, then most of us would have traces of Neanderthal genes hidden in our genetic sequences.
Humans used beads as barter and it aided in the process of large alliances and community. In their trades, they thought it was necessary for them to be civilized, which would also help shape, what we have become today.
After they had migrated out of Africa, it was first believed that humans quickly inhabited Europe. Now, contrary to that belief, there is evidence that we slowly moved into Europe and had inhabited the new continent for quite some time.
Humans were the most dominate of the two, taking over the food and habitat of the last living Neanderthals. Humans are the present day victors. We have shown our capabilities and superiority and only time will tell where we evolve from here.
Anthony M AikinWork CitedDoolittle, Russell. “Evolution.” McGraw-Hill (2000): 4.
Futuyma, Douglas. “Organic evolution.” McGraw-Hill (2004): 11.
Rightmire, G. Philip. “Human evolution in Eurasia.” McGraw-Hill (2004): 4.
Wilson, Edward. From So Simple A Beginning. New York City: W. W. Norton & Company Inc., 2006.
Dawn of man Vol. 1. Dir. John Lynch. Videocassette. British Broadcasting Corporation, 2000.
Dawn of man Vol. 2. Dir. John Lynch. Videocassette. British Broadcasting Corporation, 2000.
Dawn of man Vol. 3. Dir. John Lynch. Videocassette. British Broadcasting Corporation, 2000.