In this short film, the main focuses are on why and how we became human over millions of years. The Afar in North Eastern Ethiopia, part of The Great Rift Valley, is the location of the first steps in discovering the answers. Archeologist, Zeresenay Alemseged had made a remarkable discovery. He found a cheek bone of a small face that more than likely was from a baby embedded into sandstone. It was found on top of volcanic ash that was dated to be about 3. 4 million years old. The fossil was from the dawn of human evolution. The archaeologist named the fossil Selam, which meant, peace.
Selam was actually the same species as Lucy, another fossil founded by Don Johansen in the 1970’s. The key reason to why these fossils were quite important is that they were both bipedalist species. Millions of years ago in Kenya, Africa, the climate was dramatically different from what it is presently. Instead of an extremely dry hot desert, it was covered with wet and tropical rainforests and included a massive lake larger than any of The Great Lakes. This is where the ancestors of Selam and Lucy lived, but as the environment dried up and the rainforests shrunk, that is when theses species developed the trait known as bipedalism.
There are a couple theories on why this happened, one being that they had to stand up to see over tall grass, another being that they had to stand up to reach fruits, another states that they stood up to cool down more efficiently. It is also believed that the most compelling theory is that they stood up to save energy. About 1600 miles west of the Great Rift Valley in the Sahara Desert, known as Northern Chad is where they decided to explore next. After 25 expeditions of coming up with zero results, finally on the 26th expedition they made a shocking discovery.
The found a smashed misshaped skull dated to be about 6 million years old, it was so deformed that it was hard to determine exactly what it was from. The fossil which was called Tumai, had been taken to a particle accelerator to build a 3 dimensional image of the crushed skull. The real question to be answered was, did this species walk on two legs millions of years before Lucy and Selam? The way that is answered is, by understanding what way the skull was connected to the spine and the examining the shape of the skull.
They had noticed that if the skull was set on top of an ape’s skeleton the eyes were aimed down at the ground which wasn’t sensible. Then it was set on top of a human’s skeleton and the eyes were normally aimed straight forward. The difference in childhood between chimpanzees and humans differ drastically. A Chimpanzee’s brain is fully developed in about 3 years; meanwhile a human’s brain takes about 2 decades to fully develop. Selam was about 3 years old and her brain was only 75% developed which had suggested that her brain growth was slower.
In 2. 5 million year old rock layers there has been a discovery of rocks that at first sight appear to be ordinary, but are most definitely a specific tool shaped by a certain species. This species is classified as a Homo Habilis, drawing conclusions from the tool making it is suggested that this new species marked the new era of meat eating bipedalists. The Homo Habilis possessed a forehead to accommodate the nearly doubled expansion of brain size, while Australopithecus had no fore head it also had a much smaller frontal lobe.
Australopithecus’s brain size was measured at 400cc’s and Homo Habilis was measured at over 700 cc’s which does justify a significant increase in cognitive capabilities. The need to survive violent swings in climate is the key reason why our ancestors had become more adaptable. Africa was periodically pulsing with climate change going back and forth between wet and dry. These changes could occur with a time period as short as 1,000 years. Layers of deep sea sediment were drilled from the bottom of the sea floor, and then tiny sea shells of organisms were dated to figure out when these climate changes occurred.
So, during the 3 million years between Tumai and Salem, when the brain size was not growing at all, was when the climate was stable with no radical changes. With that being said, the climate changes and variability itself was the sole reason for human evolution. In the film it says “Human evolution is nature’s experience with versatility, we are not adapted to any one climate, we creatures of climate change”. The variations of nature’s climates propelled our ancestors to become the most intelligent species of all time, Humans.