The Origins of Humans - Homo Sapiens

9(6) Kevin Bao

History 9H

2015.09.01

Homo Sapiens

        Humans are one of the most successful species on planet Earth, populating the landscape and dominating the resources. However, just four million years ago, we evolved from apes into Homo Sapiens in the most remote parts of the Great Rift Valley near the Omo River. Thanks to our abilities to evolve and adapt, we as Homo Sapiens survived, as the fittest among all, and flourished. While we did, we began to do something else—spread out. Numerous individuals tried to unearth the origins of humans, either using science or religion.

        The current theory commonly agreed by scientists, archaeologists, and anthropologists is supported by an abundance of fossils accumulated over the years. Equipped with language, hunting skills, adapted sweat glands, endurance, and the larger brains we had developed, our earliest ancestors seem to have already colonized much of Africa by 160,000 years ago. There have been theories where humans evolved on different continents, nonetheless, through DNA research, geneticists across the world have come to the same conclusion that everyone outside Africa does indeed descend from one tiny group of pioneers that ventured out of Africa. Around 125,000 years ago, the arid area around the Sahara got greener due to climate change, this opened up multiple routes for early humans to spread out. For just a few thousand years, the deserts were lush and green. Now we know that some did try to travel out of Africa during this short gap. For example, human burials were found in Israel dating back to the period of the climate change. However, the Sahara once again closed the door on any migration route north, except for one—the Gate of Grief across the Red Sea. Nevertheless, 30 kilometers was still a lot without a vessel. How did they get across? It turns out, 90,000 years ago, the same climate that changed the Sahara back to a desert did something else—it dropped the sea level, which made the gap much smaller between Africa and Arabia. So it would be very likely for our early ancestors to travel out of Africa, possibly in search of more food. Continuing on the journey, archaeologists excavated lots of stone tools in Arabia dating back to 70,000 years ago. Yes, there were deserts scattered around the Arabian Peninsula, but parts of oasis were still lush and green along the coast line. Evidence even suggests there were springs of fresh water. These pioneers traveled through the Persian Gulf which was a great fertile plain and eventually out of Africa. This was a massive leap for humanity. They were brave enough risk everything, and took a step into the unknown. Geneticists estimated just a few hundred people in that tiny group of volunteers. The rate of spreading across the remaining continents was phenomenal. By 60,000 years ago, they already reached Australia by seafaring; by 40,000 years ago, they arrived in Europe and Asia, driving out the Neanderthals while inventing sewing needles to keep warm; and by 14,000 years ago, they eventually put their feet on the soil of the Americas. It’s quite amazing to imagine how those few people turned into the 7 billion population today.

        Since the birth of our species in Africa, our skin had been dark and our facial features had been identical. Traveling across the continents and experiencing different environments, and for the first time in the history of mankind, gave us a new look. While we were colonizing the world, we also hunted animals and other species to extinction. Just like Darwin suggested a plausible mechanism called Natural Selection, where it acts to preserve and accumulate minor advantageous genetic mutations. Suppose a member of a species developed a functional advantage. Its offspring would inherit that advantage and pass it on to their offspring. The inferior members of the same species, which are disadvantaged, would gradually die out, leaving only the superior members of the species. He also proposed that humans, over the centuries, had produced dramatic changes to the animal populations. Moreover, Darwin’s theory is also a slow process, as he wrote, “Natural selection acts only by taking advantage of slight successive variations; she can never take a great and sudden leap, but must advance by short and sure, though slow steps.” Using this theory, anthropologists proved many changes to our bodies and the animal population. For example, our skin had always contained pigments to protect as from the sun—an adaptation in Africa. Vitamin D is vital to our bodies, especially our bones, we make it in our skin the presence of the sunlight, but dark skins block it out. This was a problem to early ancestors because of the weak sun in Europe during the Ice Age. That’s why archaeologists excavated many skeletons with the symptoms of rickets. Humans possessing this disease usually had misshapen or curved bones, making it really hard for them to reproduce, even survive. On the other side, those humans who had already evolved lighter skins could produce more Vitamin D, thus producing more offspring and passing on the genes. It was at the same time when the facial characteristics of Asians changed in Siberia and East Asia. Although there is no evidence, it is very likely that these characteristics were adaptations for cold, protecting the eyes and reducing heat loss. Also, they were considered attractive in ancient times by culture, therefore passing on their genes. Furthermore, while humans thrived, many other species of animals such as mammoth were driven to extinction because they were not able to adapt to the new threat. Likewise, Neanderthals were also driven to extinction as Homo Sapiens had better communication, social network, and even artistic talents. They were held together by a strong shared identity.