This post was originally published on December 16, 2012 on a previous version of ChipWalter.com.

From the Introduction of Last Ape Standing

Over the past 180 years we have so far managed to stumble across, unearth and otherwise bring to light evidence that 26 separate human (hominin, to use the up-to-date scientific term) species have evolved on planet Earth. As you may have noticed, twenty-five of them are now no longer with us, done in by their environments, predators, disease, or the unfortunate shortcomings of their DNA. The lone survivor is a peculiar, and peculiarly successful, upright walking primate that calls itself, a little self-importantly, Homo sapiens sapiens, the wise, wise one. In most circles, we simply call them you and me.

Of all the varieties of humans who have come and struggled and wandered and evolved, why are we the only one still standing? Couldn’t more than one version have survived and coexisted with us in a world as big as ours? Lions and tigers, panthers and mountain lions co-exist. Gorillas, orangutans, bonobos and chimpanzees do as well (if barely). Two kinds of elephants and multiple versions of dolphins, finches, sharks, bears and beetles inhabit the planet. Yet only one kind of human. Why?

A common belief is that we stand-alone now because we never really had any company in the first place. We evolved serially; this thinking goes, from a single procession of gifted ancestors, each replacing the previous model once evolution had gotten around to getting it right. And so we moved step by step (Aristotle called this the “Great Chain of Being”), improving from the primal and incompetent to the modern and perfectly honed.  Given that view, it would be impossible for us to have any contemporaries. Who else could have existed, except our direct, and extinguished, antecedents? And where else could it all lead, except to us, the final, perfect result?

This turns out to be entirely wrong.  Many of the 26 human species that have so far been discovered (and there are very likely far more that we have yet to discover), a considerable number of them lived side by side at one time or another. They competed, sometimes they may have mated, more than once one variety likely did others in either by murdering them outright or simply outcompeting them for limited resources. We are still scrounging and scraping for the answers, but learning more all the time.

If we hope to place our arrival on the scene in any sort of perspective, it’s a good idea to remember that every species on Earth, and every species that has ever lived on Earth (by some estimates 30 billion of them), enjoyed a long and checkered past.  Each came from somewhere quite different from where it ended up, usually by a circuitous, and startling, route. It’s difficult to imagine, for example, that the blue whales that now swim the world’s oceans, great leviathan submarines that they are, were once furry, hoofed animals that roamed the plains south of the Himalayas 53 million years ago. Or that chickens and ostriches are the improbable descendants of dinosaurs. Or that horses were once small-brained little mammals not much taller than your average cat with a long tail to match. And the Pekinese lap dogs that grace the couches of so many homes around the world can trace their beginnings to the lithe and lethal grey wolves of northern Eurasia.

The point is, behind every living thing lies a captivating tale of how the forces of nature and chance transformed them, step by genetic step, into the creatures they are today. We are no exception. You and I have also come to the present by a circuitous and startling route, and once we were quite different from the way we are now.

Theories about our ancestry have been amended often because new discoveries about how we came into existence keep emerging; several times, in fact, while this book was being written.  However it played out in the details, we know this: for every variety of human that has come and gone, including those we think we have identified as our direct predecessors, it has been a punishing seven million years. Survival has always been a full-time job, and the slipperiest of goals. (It still is for most humans on the planet. More than 4 billion people — nearly two-thirds of the human race–subsist each day on less than $2). But luckily, for you and me at least, while evolution’s turbulent dance rendered the last line of non-Homo sapiensDNA obsolete 11,000 years ago, it allowed ours to continue until finally, of all the many human species that had once existed, we found ourselves the last ape standing…