Man the Wanderer

One of the most distinctive things about humans is how widely spread our species is. Few species that have not hitched a ride with us have managed to spread so far and wide.  Men armed with stone tools built boats and settled the furthest islands, from Hawaii to New Zealand; men sewed hides of mammoth skin and built shelters out of snow to survive in the arctic. We live in deserts and swamps, mountains and valleys, and have thrived nearly everywhere we’ve gone.

And–until recently–our ability to travel far and wide resulted in a plethora of human species. Homo Erectus, Neanderthals, and Denisovans all lived around the same time, alongside Homo naledi (South Africa), Homo heidelbergensis (Africa), H. Floresiensis (Island of Flores, Indonesia), and H. luzonensis (from the island of Luzon, Philippines.)

Those aren’t even all the varieties of human that have existed, people who looked and behaved much like us. There were others, some older, some whose bones we haven’t found, yet, but whose DNA shows up in modern humans.

Map of the distribution of Middle Pleistocene (Acheulean) cleaver finds (Wikipedia)

The first out of Africa event occurred about 1.8 million years ago, when Homo erectus hefted his achulean handaxe and headed north. He seems to have thrived in Asia, arriving in China a mere 100,000 years later, and Indonesia 50,000 years after that. It took a fair bit longer–another 250,000 years–for erectus to arrive in Spain, and he had trouble crossing the mountains into the rest of Europe (it was probably too cold for him.)

This was before widespread use of fire (about one million years ago) and clothes (about 170,000 years ago) allowed humans to spread much further–one of the oldest known sewing needles was wielded not by Homo sapiens, but by our cousins the Denisovans, in Siberia.

But what motivated us? Why did we spread so far?

Before the invention of agriculture, most humans must have been nomadic, at least part of the year. Our stone tools let us be hunters–despite our puny size–and we probably followed our prey, and when we ran out or couldn’t find the animals we sought, we moved on in search of more.

Did being smart let us expand our initial range out of Africa, or did expanding our range as we followed game make us smarter? Probably both; early Homo erectuses skulls had volumes around 850 cubic centimeters, but by the time erectus reached Indonesia, his skull had grown to 1,100 CCs. But erectus did not persist–he was replaced by later waves of humans who emerged from Africa with much more advanced tools.

Settling down must have been quite the change–we moderns find moving stressful, but our ancestors probably found staying put strange and difficult. Perhaps they planted, then wandered off for a few months until their crops ripened.

Even today, I think there’s still some urge to wander left in us. Somewhere between 15 and 25 we get the urge to get out of Dodge, to seek our fortunes (and spouses) somewhere far from home.

We gotta roam.