Genesis - The Human Race Arrives

Standing on the Serengeti plains of East Africa, you can’t help but feel small. Mostly this is because, in the face of so much of the world all around you, you become acutely aware of your mortal insignificance. Everywhere you look there is no end to the grasslands and scattered shrub and baobab trees that sweep out to the horizon. Everything – mountains, gorges, clouds – shrinks. Smaller objects, like lions and wildebeests and zebra, can disappear altogether in the heat and the piddling ability of your eyes to pick out details in the things around you, even moving things.

It is all so vast that it feels otherworldly, except that it is not. In fact this is home. Because it was in a place something like this that our kind got its start. And maybe that’s why it also feels timeless, as if it has always been there, and always will be.

But Africa’s savannas have not always been here. Six million years ago, about a million years before the creatures that would someday evolve into us, split off from those that would later lead to chimpanzees and gorillas, Africa was a much more tropical place. In fact the whole world was. Rain forests rose to latitudes as far north as London. Areas that are dry grasslands, even deserts, today were cool, wet jungles where species of apes lived an Edenlike existence. The environment was warm and sheltered; the food was plentiful and predators, relatively speaking, few. Life was good.

If the behavior of today’s gorilla’s and chimpanzees are any indication, troops of them, maybe 20 or 30 at a time, lived and roamed the forests, knuckle walking on all fours for short jaunts, and swinging from tree to tree if they wanted to cover more territory with greater speed. Long- armed and bow-legged, their bodies were built for the jungle. Their feet, like their hands, were designed for gripping branches, with four, long finger-like toes and a fifth inner toe that acted like a thumb as they grasped and swayed gracefully from tree to tree.

There are almost no fossils of the tree-dwellers who preceded us. The moisture and bacteria that make jungles jungle-like aren’t generally kind to bones left behind. But we know these creatures had no cities or weapons and hadn’t managed much in the way of invention. Like today’s gorillas and chimps, they very likely communicated with a limited number of calls, hoots and grunts. Occasionally a little chest banging might have been in order, or some fang bearing, to clarify a particular point. Nevertheless, these apes were the smartest animals on the planet. Of course, from our vantage point -- had we been there to watch -- their day-to-day life would have seemed tremendously simple. Some foraging, some sleeping, some copulating when the times were right. There was child-rearing, of course, and, undoubtedly, a family spat from time to time. There would have been no human sounds or signs. No distant, rumbling of jets flying 30,000 feet overhead. No honking horns or passing cars. Not even a murmured conversation.  The nights would have been utterly black and unlit except for the ever-changing moon and the brilliant stardust of the Milky Way tossed by the big bang across the dark blanket of the sky.

The world was devoid of humanity. But it would not remain that way.

Humanity was coming.

Genesis

We are descended from a branch of the ape family that was geologically orphaned. Though anthropologists verbally brawl over the details, the creatures from which we evolved seem to have been a breed of ape that was caught around five million years ago on the drier, eastern side of Africa’s Rift Valley when it began to form.

Some primates followed the retreating forests to south and central Africa beyond the western rim of the rift mountains, but our progenitors were left to cluster around what shrinking forests remained in the east. Those that followed the jungles southward evolved into today’s three subspecies of gorillas and two subspecies of chimpanzees – pan troglodytes, the chimps you see at the circus, and bonobo monkeys, very likely our closest relatives. They still live there today though their days may be numbered.

Five million years ago you wouldn’t have been out of line if you had concluded that the other apes, those caught on the eastern side of the rift, were the ones marked for extinction. But they hung in, and in time they even split into several families of their own. We didn’t think this was true even a few decades ago. We once assumed that our kind marched cleanly from a single line of protohumans into the present, each model an improvement over the previous one. But now we know better.

In recent years a bewildering amount of new evidence has surfaced about various early versions of us. Some tribes might have evolved in Chad, much fart her west than scientists once thought. Most seemed to have settled in the east.  A handful may even have met up and interbred as they wandered the drying, broken landscape. Others may simply have gone the way of the dinosaur, leaving behind no descendants, not a single gene, just a few petrified scraps of bone -- muddled messages from the past that we haven’t yet deciphered. Our emergence was a far messier evolutionary business than many paleoanthropologists suspected as recently as the 1990s.

Whatever the exact details, it’s clear that when our progenitors were orphaned and split off from the common ancestor we share with chimps, we were cast out of Eden. No longer able to lounge in the sheltered environments of a tropical forest, we were forced to adapt to a life where there were increasingly fewer trees to swing among or climb up into for protection. There was less low hanging fruit, more predators and fewer places to hide. Life became more complex and  more dangerous. If you were unfortunate enough to find yourself lost in the open savanna away from any trees, you were exposed and vulnerable, and far more likely to become dinner for the prides of big cats that roamed the grasslands carrying their big cat appetites with them.

Apes that could survive here would have to become smarter, faster, taller, more cooperative, better communicators and, to ensure the species survived, more sexually active. Such apes did evolve. They morphed from jungle apes into savanna apes, and their kind would lead to the human race -- all 7.2 billion of us.

This is an excerpt from Chip Walter’s book Thumbs, Toes and Tears (And Other Traits That Make Us Human). Visit www.vagabond-adventure.com/books for all of Chip’s other works. A limited number of signed copies are available here.