Most of us think of humans as being exceptional among Earth's organisms because, well, because we're the only ones that are so... human.
But that's not how it used to be. And some of this past year's discoveries in the world of paleo-anthropology really drive the point home.
Anatomically modern humans date back roughly 200,000 years, having arisen in Africa from "archaic" types who in turn probably arose from Homo erectus. Nowadays, we're the only living members of our genus and species, which makes it especially easy to focus on our uniqueness. Such alone-ness also feeds into mistaken ideas that evolution is a linear process with the singular aim of producing modern humans like ourselves.
But for most of our existence, we had company, and plenty of it.
Neanderthals split somewhat from our direct lineage about half a million years ago, but they continued to share Europe and the Middle East with our forebears until about 30,000 years ago, and according to DNA analyses published in 2010 by a team headed by Ed Green of UC Santa Cruz, they also shared in more intimate ways. As this web article explains, they also interbred with our ancestors. (http://news.nationalgeographic.com/news/2010/05/100506-science-neanderthals-humans-mated-interbred-dna-gene)
A Neanderthal-female reconstruction based on both fossil anatomy and DNA. Photograph by Joe McNally, National Geographic.
Strictly speaking, Neanderthals and our direct ancestors were therefore members of a single species, representing two slightly different branches of the same family tree. In other words, they were "people," too; or maybe "people-cousins" is a better term to use. Either way, we lost them about 30,000 years ago, for reasons that are as yet unknown.
And then there were the human-like, Neanderthal-like "Denisovans," whose DNA was recently coaxed from a 30-50,000 year old finger bone that was found along with a molar in Denisova cave, southern Siberia. We don't know much about them yet other than that they (or at least their fingers and molars) lived in southern Asia, and that much of their genetic heritage lives on among Papuans and Aboriginal Australians. ( http://www.scientificamerican.com/article.cfm?id=new-hominin-species )
Apparently, the ancestors of today's Melanesians interbred with Denisovan people-cousins in Asia on their way to New Guinea, Australia, and Pacific islands farther eastward. In other words, the Denisovans were enough like us to bear and/or produce viable human children. But now they're gone, too.
The following chart suggests that a walk in the woods or steppes of Europe or Asia 40,000 years ago could have been a wildly multicultural experience. Back then, you could have encountered all sorts of "regular" folks, plus Neanderthals and Denisovans (and, as noted on the chart, the pint-sized Homo floresiensis "hobbits," as well, though we don't have the full genetic scoop on them yet).
This is pretty cool stuff, prime material for daydreaming about stone artifacts and bones and digs and Indiana Jones hats.
But when I stop and really think about it, it's more than that.
Don't simply think of them as having disappeared tens of thousands of years ago, or you'll fall into the usual trap of assuming that they were just half-baked evolutionary dead-ends that are naturally "supposed" to be extinct. Think instead of the whole half-million-year span of our mutual co-existences, and you'll notice that they lasted quite a long time alongside us and then vanished relatively recently. If that time period were shrunk down to the span of a single day, our people-cousins would have disappeared just an hour or two ago after spending all day and most of the night with us.
From this paleo perspective, it's rather odd that we're now the only form of humanity on Earth. And that realization makes it easier to take the next step and ask: what would it be like if those people-cousins were still with us today?
Have you seen any of these "Geico cave man" ads (below) on TV or YouTube? If not, look some of them up on Google and check them out. They're hilarious, but also somehow oddly troubling, as well. Sometimes I think they make us laugh so hard because they also make us uncomfortable.
The main premise of these skits is that we try hard to avoid being "politically incorrect" when discussing different ethnic groups nowadays, but we still get away with speaking of cave people as dimwitted brutes. These characters bring cave men into the present day to confront us with those negative stereotypes, and we laugh to hear them chastise us for our modern-human-chauvinist-piggery.
Entertainment and marketing techniques aside, I think it's a fantastic way to force ourselves to think of these close relatives as being the real people that they actually were.
We normally tend to think of "cave men" as non-humans, as barbarian "others," as symbols of humankind's basest instincts and behaviors...just as people have so often done to members of other racial/cultural/religious/political groups throughout history. It happens most often when people don't know each other very well on a personal basis and, of course, it's particularly hard to get to know someone who has been dead for 40,000 years.
But even so, I sometimes wonder what the modern world might be like if, in addition to the many differences that so often seem to divide and trouble us, we also had to deal with the ethics and complexities of interacting with Neanderthals and Denisovans.
Would they be subject to the same rights and expectations as the rest of us, or would we treat them as we do chimps, which have only now become our closest living relatives?
What would religion be like with people-cousins still among us? Would some neo-evangelists claim that God actually created the world for Neanderthals to hold dominion over, and then point to the environmental damage that we "regular" humans cause as a sign that we're just the lowly spawn of Satan, sent to desecrate the Creation?
Are the widespread and diverse legends of "the little people," elves, dwarves, leprechauns, and such actually ancient folk memories of life among former relatives?
And the darkest question of all - did we kill them all off?
I don't have answers to these questions, though that's not surprising. It's tough to deal with them intellectually while navigating such great depths of time and mystery, and it's also difficult emotionally to fully acknowledge that we've lost entire branches of humanity in the not-so-distant past.
Sometimes when I do grasp that absence, the world suddenly seems emptier and un-naturally quiet, as if I've fallen asleep in the midst of a party and then woken up to find most of my friends gone. At other times, placing our people-cousins back onto the scale of human diversity where they belong seems to shrink the differences that we use to distinguish today's various ethnic/cultural groups from one another.
Above all, I just enjoying thinking about this stuff.
How about you, my fellow people-cousin?