Sunday, December 22, 2013

Nobody Here But Us Mongrels

(Picture from Io9's site here.)

I've been interested in Neanderthals for years.

The idea that there was a previous form of human being-- not quite like us but close enough to talk to-- that used to live essentially next door was irresistible.

My first accepted story involved a Neanderthal/Homo sapiens contact. And it came, as much of my fiction does, in retaliation.

I had just moved to Boston, fresh from the homogeneous midwest, and the amazing diversity stunned me. You could walk down a street in Boston and hear English in three different accents. Heck. You could walk down a street in Boston and hear three different languages. It was a different world.

Not surprisingly, I went to the science museum. At the time there was an exhibit on cave paintings. The docent was a well meaning old man who talked about the painters and how they couldn't possibly be painted by dumb old Neanderthals. This ticked me off and I went home and wrote a contact story from the Neanderthal point of view about encountering those smelly idiots, Homo sapiens. Asimov's bought it and I was off.

It turns out I was right.

Not about the cave paintings. Those are clearly dated and post-date when Neanderthals were in Europe. Not to say they didn't paint things or paint in caves. We don't know and, frankly, it's unlikely we ever will. But I was right in that Neanderthals were a whole lot smarter and like us than some thought way back in the Cretaceous-- that is, when I moved to Boston.

This idea that not only Neanderthals but most of our early relatives have been miscast has been growing over the years. A number of very important stories broke in just the last year.

The stuff that's mostly been in the news has been genetic in origin. One of the earliest discoveries was how some modern humans shared DNA with Neanderthals in such a way as to suggest cross breeding. What made it especially interesting was that the distribution of the Neanderthal DNA was not uniform. Some groups got more than others.

Then came the Denisovans, a group of fossils discovered in Siberia. Those fossils were about 41k years old Sequencing the Denisovan DNA suggested more interbreeding. More Europeans had Neanderthal than other groups. More Asian and folks from Oceania had Denisovan DNA. This suggested interbreeding might be a local affair. After all, Neanderthals were mostly in the mideast and up into Europe while Denisovans were more in Asia.

Then the Denisovans were compared with Neanderthals. Sure enough, there was interbreeding there, too. In point of fact, there was evidence that there was interbreeding between Denisovans and a potentially unknown hominin.

It shouldn't come as any surprise that humans will pretty much have sex with anything. Any perusal of a porn site will demonstrate that pretty adequately. Or you can read this in Scientific American. But go with an open mind.

That lack of surprise should therefore lead to a lack of surprise that we interbred with those previous cultures had considered, well, beasts. We're starting to look at our cousins as more and more like ourselves. Different, to be sure. There are a lot of differences, too. For one thing, your average run of the mill could toss your top star line backer over the goal posts. There appears to be a fairly vast difference in potential strength between our two groups. It also looks like Neanderthals had a different way of speaking and, potentially, seeing. They were different.

But not, apparently, different enough not to be taken seriously persons of affection.

This has caused several anthropologists and archaeology  to rethink the whole idea of what species we all might be to one another. There are species fundamentalists that believe that if two individuals can interbreed they are, by definition, the same species. By that definition, none of these folks are separate species at all.

But it gets even more interesting.

Let us travel to Dmanisi, Georgia.

The Dmanisi site is quite old-- 1.8 million years old. Five skulls have been found. All skulls have been dated to a similar time frame. All are quite different-- not different enough to be unrelated, mind you. The variation between the five skulls is similar to variation between random skulls of humans or chimps. But different enough that if they had not been found together they might have been considered different species. John Hawks has a good discussion of the Dmanisi skull here.

One of the interesting things Hawks mentions is that the most human like skulls were adolescents while the adult skulls in the same site had significantly reduced brain case sizes.

This is an interesting indicator to me. We know that we have bigger brains than our distant ancestors. That requires two things: variation in brain size and selection pressure in favor of larger brains. A mechanism might be nice. Possibly the mechanism for this is our lengthening childhood. We end up not selecting directly for big brains but for the variation in lengthening time as juveniles which give us the opportunity to develop sufficient brains to make a selective difference. Be interesting to see if that shows up in future science.

Be that as it may, it appears that diversity in the human species may well be the name of the game. Instead of differing species (Homo erectus, Homo neanderthalensis, Homo sapiens) there is one human species for the last ~2 million years with lots of variation. We're an experimental species. It's interesting to note a symmetry between our biological heritage and our proclivities.

One thing Hawks says and I believe it is true. He says that recent humans are not a good measure of our history. We're now pretty much the only game in town. All of our cousins are either dead or absorbed. We like to believe that we're still the same as we ever were: now, a hundred years ago, a thousand years ago. Maybe that's true. Or maybe that's just the conceited present thumbing its nose to the silent past.

A hundred thousand years ago we were not alone. There were other intelligent eyes peering out of big brained skulls seeing things differently from us.

I'd guess from the genetic evidence we found that pretty attractive.

Further links:
A. P. Van Arsdale
Early stone tipped projectiles, here and here
Mystery human species
Pushing back the clock on human finds

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