杏吧原创

Our evolutionary history has important lessons for us 鈥� all of our closest relatives have gone extinct, leaving only more distant African apes

Set in Africa鈥檚 north-east corner, the Afar rift holds a unique record of hominid history. Seasonal floods have carried sediments into this basin, where they have been accumulating for millennia. It was there last February that our field camp was inundated. When the floodwaters evaporated, the millimetre of silt left behind became the youngest stratum in a succession of sediment layers that is today about 1.5 kilometres thick.

These layers have been accumulating for 6 million years as rivers and lakes came and went. Near the bottom of this succession of rocks is Ardipithecus 鈥� not a chimpanzee, and not a human 鈥� but from the earliest portion of our branch of the hominid family tree.

In 4.2 million-year-old strata we found the earliest Australopithecus, followed by remains of the 鈥淟ucy鈥� species in sandstones that are 3.4 million years old. Above this, in sediments 2.5 million years old, are traces of the butchery of large mammals accompanied by some of the earliest stone tools.

One million years ago, this valley was populated by hand-axe-making Homo erectus, which evolved into H. rhodesiensis and then into the nearly anatomically modern H. sapiens idaltu. In some of the youngest strata, we find fossils so anatomically modern that they could be lost among the 7 billion of us on Earth today. In these layered rocks we also find an unparalleled record of stone-tool technology.

As Darwin would surely appreciate, this evidence is overwhelming 鈥� the mammalian species we call H. sapiens has deep evolutionary roots in Africa.

Why does it matter? Human evolutionary history has important lessons for our species. We now know that all of our closest relatives have gone extinct, leaving only more distant African apes. The perspective that this knowledge provides is both timely and essential to the bipedal, large-brained, innovative, technological primate whose grasping hands now hold the power to determine our future on planet Earth.

Given the facts, it would not be wise to gamble on the widely held but risky notion that our future will be guided to good ends by divine intervention. Having evolved the capacity to influence the global future, it is high time the species begins to act sapiently.