When you go to the movies, and there are mobs of people standing in line, spilling popcorn on your shoes, do you ever wonder where they all came from, and why they all seem to be at your movie? If you think about it, you're only at one theater, in one town, in one country, on this great big planet. Millions of people are rushing about at that same moment, on every continent, doing all kinds of things -- surfing the Internet, eating popsicles, strumming guitars. We are everywhere. Where did we all come from, what's it all about?
We're going to take you back, way back, 65 million years back. After all the dinosaurs had croaked, and before McDonalds ruled the planet, early primates developed from mammals in southern Africa through a natural process called evolution. Evolution is a theory first proposed in 1859 by Charles Darwin, who suggested that species evolve when the individuals best-suited to survival pass on their genetic traits. Today it's an idea some people still don't like because it can seem to clash with their religious beliefs. But the idea of evolution as the changing over time of different plant and animal populations to better suit their environment is now accepted just as much as the theory of gravity - and you're still sitting there, aren't you?
But back to that crowded theater. Using ancient fossils, scientists have been able to unearth the history of human beings and trace how we spread around the world. About 15 to 30 million years ago, groups of those early primates in Africa started to split up: some monkeyed around in the trees, while others ventured out and became "ground apes."
Through the process of evolution, "ground apes" began developing into early humans. They were short -- about 3 1/2 feet tall -- walked upright, and had teeth for munching on vegetables. You know the type. But, compared to the other primates, they had very big brains.
Researchers like to classify all the different types of early humans that evolved with complicated Latin words that are hard to pronounce. (They think this makes them look even smarter than they already are.) Some of these names are A. africanus, A. robustus, and A. boisei. The "A" stands for Australopithecus. These groups differed some in body size and teeth shape.
The next major step on the way to the popcorn line was the appearance of a new creature, Homo habilis. They are the earliest known members of the genus Homo, which is the gang that we all belong to. These guys invented stone tools, hunted animals, and wished they could order out for pizza. Something not all people know is that all these folks first hung out in Africa.
But people, being how they are, got antsy. A new people evolved: H. erectus, and they spread out into the cooler zones of Eurasia. This was about 1.75 million years ago. Homo erectus continued to develop the features that set Homo apart from Australopithecus: large brain and modern body size, and an increased cultural ability, as seen by their manufacturing of larger and more complex stone tools. They competed directly with A boisei for the first time, and wiped them out. Then, 1.25 millions years ago, H. erectus migrated into Asia and some of Europe, probably to follow animals that they ate -- and to see the sights.
About half a million years ago, a new form of human turned up in Europe and then Africa. These fossils look much like those of H. erectus, but differ from them in some ways, and more closely resemble our own species, H. sapiens. Some of the new features included larger brains, smaller teeth, the tendency to talk during movies, and massive facial sinuses, or air pockets in the skull. Doesn't sound pretty.
These early Homo sapiens coexisted with Homo erectus, but somehow, probably just through general rudeness, H. sapiens survived and H. erectus became extinct. By some 250,000 years ago, H. sapiens was the only human species left.
We're not home yet, young grasshopper: these archaic Homo sapiens had a couple of subspecies, the most well-known being Homo sapiens neanderthalensis. The Neanderthals lived at the same time as our direct ancestors: Homo sapiens sapiens. Neanderthals are generally misunderstood, thanks to cartoon and low-grade movie stereotypes of a shuffling, grunting savage dragging his mate by the hair and stopping only to fight the local dinosaurs. Today, even children realize that the dinosaurs died out over sixty million years before Neanderthals, or any human, walked the earth.
New evidence shows that in many ways, Neanderthals were not very different from us. They had a different skeletal structure, but nothing clothes wouldn't hide. Neanderthals had longer and lower skulls than living humans do, with larger faces and teeth. They had no chins, and massive brow ridges in front of a brain as large as our own, but differently shaped. Their bodies were stockier and more muscular than ours, which, combined with their facial features, gave them greater resistance to the fierce cold of glacial climate, and gave them a great chance to start as linebacker during their senior year of high school.
Neanderthals were also good at making tools. In contrast to the general-use tools of earlier humans, their stone tools were made in a variety of well-defined shapes, often for specific purposes. There is also clear evidence that they had control of fire, lived in caves or open-air structures, hunted large game from which they made clothing, cared for their sick or weak, and even buried their dead with some "religious" ceremonies.
Some scientists disagree, but most accept that the Neanderthals did not evolve directly into later Europeans or any other living people, but were instead replaced by modern humans. Nevertheless, Neanderthals interbred and mixed culturally with modern humans until around 30,000 years ago, when only Homo sapiens sapiens remained.
Now we're all in the same gang. During the next twenty thousand years, humans continued to get romantic, increase in number, and migrate, following herds of game animals. In this way, early northern Asian peoples crossed the Bering straits (over a frozen land bridge between what is now Russia and Alaska, but that you can't see anymore because ocean levels rose) to reach North America (between 30,000 and 13,000 years ago) and eventually wander on to Central and South America. Similarly, humans reached Australia by simple boats at least 30,000 years ago, and the less hospitable regions of Africa and Asia became inhabited as time passed.
Through the growth of human culture and the developments of tools and technology, modern humans spread everywhere and took all the good seats. Now you have people from all over the world sitting in the movie theater -- including that six-foot-six guy sitting in front of you. It's kind of a bum deal, but if Homo sapiens hadn't developed, wiped out the competition, and spread about the world, you wouldn't be here anyway. So, sit back and enjoy the movie.
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