THE HISTORY OF PEOPLE, PART 1

 

What does it mean to be human? This is one of the big philosophical question, however I’m asking this as much as a biological question as a philosophical one. If we could trace yours, mine or anyone’s family tree back far enough, over millions of generations we’d arrive at some apes living in the jungles of Africa roughly seven million years ago. The story of how we went from apes living in trees to forming complex civilizations is fascinating and often misunderstood. 

Some of the details of this great drama are educated guesses made by people who have spent their careers studying the topic, but the basic facts are supported through conclusive archaeological, geological and genetic evidence. Over the course of several short articles I hope to give an overview of the human evolution, culminating in the first human civilizations roughly 5,000 years ago. My goal is to give the big picture without getting too bogged down in the details that, while interesting, aren’t crucial to understanding how we’ve come to live in this modern world.

The point at which early primates are thought to have broken ow from other primates is between 6 and 7 million years ago. It’s believed that some of these primates migrated out of the jungles into open savannahs in Africa. It’s not known why this happened, but it generally seems to line up with a period of cooler and less stable global temperatures suggesting habitat loss due to a changing climate. In this environment, standing upright was a distinct advantage because they could see predators and potential sources of food from a greater distance. Also, the available sources of food tended to be more spread out and walking upright is more efficient than walking on all fours. These first upright primates were much smaller than modern humans and still had more in common with earlier apes than us.

The process of evolution continued for millions of years; useful mutations were replicated through reproduction while detrimental mutations weren’t. People often imagine a single genetic line leading to the inevitable modern humans but in reality, the picture is much muddier. Innumerable branches split ow from those first primates that wondered onto the African plains, some went extinct, but others formed new species that survived for long periods of time and some, who were genetically similar enough to breed, may have merged back together. In other words, there’s likely no single line that leads back to those first early primates that stood upright.

Still these various groups of early erect walking primates continued to evolve and take on more characteristics of modern people. In 1974 anthropologist working in Ethiopia discovered what many at the time proclaimed as the evolutionary “missing link.” The anthropologist themselves discouraged that term because it implies a single evolutionary chain rather than the more complex reality. Still the unearthed skeleton, officially proclaimed the species Australopithecus afarensis but popularly known as “Lucy,” demonstrated a tantalizing mix of characteristics of earlier primates and modern humans. 

The find, which was dated to 3.2 million years old, was clear evidence of the evolution of early humanlike primates, although it’s impossible to say with certainty if Lucy was a direct ancestor of modern humans. Lucy (and the dozens of other similar skeletal remains that were later found in the same region) was an important discovery in showing the evolutionary relationship between earlier primates and modern people, yet Lucy was clearly very different from us. She was much shorter, under 4 feet, and had a brain size closer to that of a chimpanzee than a modern human.

When we skip forward roughly another million years, we start to see several species of human-like primates that are much more closely related to modern people. This new group is the genus Homo, probably the most famous of the early members of this genus are Homo habilis and Homo erectus. For those of you who it’s been a while since you had biology class, our scientific name in the animal kingdom is Homo sapien, so we’re now dealing with our own genus. 

In fact, it’s with the genus Homo that we start seeing scientist referring to members of the species as humans and people, but there’s not universal agreement on this point. This is when we start seeing stone tools being created and there is evidence that these early humans could make fire and cooked meat, but again there is disagreement among scientist on this last point. Still, these were not fully anatomically modern people. They were still relatively short, under 5 feet tall and had considerably smaller brains, probably half to 2/3 the size of modern people.

This brings us to the most recent and most similar species to us, Homo heidelbergensis and Homo neanderthalensis who first appeared about 700,000 and 500,000 years ago respectively. These early people were similar in size and brain mass to us. Of the two, we know more about neanderthalensis, commonly referred as Neanderthal. This is because they only went extinct roughly 40,000 years ago, as opposed to 200,000 years ago with heidelbergensis. It’s also known that we co-existed with Neanderthal in southern Europe and western Asia. It’s with these last two species that there is wide agreement that they were early humans as opposed to merely human-like primates.

Looking at the evidence of how Neanderthals lived it would be difficult to differentiate between their lifestyles and that of the Homo sapiens who lived at the same time, although there were physical differences between them. Neanderthals buried their dead, created art, and made compound tools by fastening stone tips to wood spears. These are all activities that earlier human-like primates never engaged in. One thing we don’t know about the Neanderthals is why they went extinct. Competition for resources or possible direct conflict with Homo sapiens is a possibility. Inability to adapt to the coldest part of the last ice age is another possibility, we simply don’t know.

The story of the Homo sapiens will have to wait until the next installment. Over the course of the last 50 years our knowledge of the evolution of primates from ape to modern human has grown exponentially but there is still much we don’t know. Most importantly, how these earlier species interacted with each other and which combination of species are our direct ancestors. Still we have a good idea of the timeline and progress of early human and human-like primates which will gives us the context to understand the rise of our own species.