Humans may have left Africa sooner than once thought

I said my views on evolution are always evolving. This is a good example of that.

Modern humans may have left Africa thousands of years earlier than previously thought, turning right and heading across the Red Sea into Arabia rather than following the Nile to a northern exit, an international team of researchers says.

Stone tools discovered in the United Arab Emirates indicate the presence of modern humans between 100,000 and 125,000 years ago, the researchers report in Friday’s edition of the journal Science.

While science has generally accepted an African origin for humans, anthropologists have long sought to understand the route taken as these populations spread into Asia, the Far East and Europe. Previously, most evidence has suggested humans spread along the Nile River valley and into the Middle East about 60,000 years ago.

“There are not many exits from Africa. You can either exit” through Sinai north of the Red Sea or across the straits at the south end of the Red Sea, explained Hans-Peter Uerpmann of the Center for Scientific Archaeology of Eberhard-Karls University in Tuebingen, Germany.

“Our findings open a second way which, in my opinion, is more plausible for a massive movement than the northern route,” he said in a telephone briefing.

These findings are always interesting, but it takes so much evidence to come to any sort of conclusion that the theories put forth are always so tentative. We can say humans probably left Africa earlier than previously thought, but speculation on a new route is less solid.

One recent theory I recall hearing is that humans and Neanderthals once interbred. There is some evidence for it, and just last year some good DNA evidence was uncovered showing as much. In fact, I would go so far as to confidently proclaim that the evidence solidly shows humans interbred with Neanderthals very early in the human exit from Africa. Beyond that, I very much doubt there was interbreeding; the Neanderthals in all probability died out as a unique species, unable to breed with H. sapiens.

I mention this theory because the first thing that popped into my mind upon reading the first few paragraphs of the article was how long it would take until someone suggested Neanderthals may have been responsible for the toolmaking.

The techniques used to make the hand axes, scrapers and other tools found at Jebel Faya in Sharjah Emirate suggest they were produced by people coming from somewhere else, said Anthony E. Marks of Southern Methodist University in Dallas, adding that there are similar tools made about that time in East Africa.

“If these tools were not made by modern man, who might have made them?,” Marks asked. “Could Neanderthals have made them?”

Neanderthals were mainly in Europe and migrated into Russia but “there is no evidence for any Neanderthals south of that” zone at that time, he said. “To suggest one group of Neanderthals took a turn south and went several thousand kilometers … seems to me a very difficult explanation and one that doesn’t follow any reasonable logic.”

I have to agree with that assessment of the data. Humans moved towards Neanderthals, plausibly going through the areas of this recent discovery, not the other way around. Now that we have evidence left by our ancestors, this adds a new route humans took when leaving Africa. I find the scenario plausible, even likely. It still isn’t certain, but there is now some good evidence for it.

Are humans “more advanced” than other organisms?

I recently had a discussion with a friend where he asserted that he was more advanced than, say, a plant. By the common connotations that come from the word “advanced”, we would have to agree that his statement was true. But it asks an interesting question: What do we really mean when we say we’re advanced?

To put the discussion in a proper framework, think in evolutionary terms. That means we can’t compare Albert Einstein to Sarah Palin and say, “Why, yes, he was more intellectually advanced than she is.” Of course that is true, but if we’re going to discuss evolution and what it means to be advanced, we’re necessarily comparing species, not individuals. That is what makes my friend’s initial comparison to plants a reasonable starting point.

But it is only a starting point. Because what are we comparing exactly? In terms of brain development, yes, he beats that plant handily. But what about in terms of ability to photosynthesize? Well, the plant just got a knockout in that round. Clearly there is a difficulty in making useful (and, in my view for this discussion, any) comparisons between species. Maybe we need to find a species that is closer in relation to humans. (It certainly would help for it to have a brain in the first place.) The animal I chose for the discussion and the one I am choosing for this discussion is the skunk. Jerry Coyne is the inspiration.

It does not always [evolutionarily] pay to be smarter, either. For some years I had a pet skunk, who was lovable but dim. I mentioned this to my vet, who put me in my place: “Stupid? Hell, he’s perfectly adapted for being a skunk!” Intelligence comes with a cost: you need to produce and to carry that extra brain matter, and to crank up your metabolism to support it. And sometimes this cost exceeds the genetic payoff. A smarter skunk might not be a fitter skunk.

A skunk is vastly more well adapted to life as a skunk than any human ever could be. All the things it takes to be a skunk? A skunk has them nailed down pretty well. The counter to this point was to say that if humans decided to destroy all skunks, we could. True enough. But does that make us more advanced? Of course our intelligence allows us to wipe out many other species, but the whole point of bringing up a skunk and its adaptation is to say that a comparison of intelligence is not valid for purposes of this discussion in the first place! (As always, you know I mean it when I use the lazy-man’s exclamation point.)

When we choose to compare intelligence in order to define what it means to be advanced, we have two massive assumptions going on. First, we’re assuming that intelligence is better than toothiness or having sharp claws or any other characteristic we see in nature. This assumption is untenable because some environments might call for all or any of those characteristics over intelligence. To put things in perspective, try thinking on an evolutionary timescale. So far I have only been comparing humans to other extant organisms (plants and skunks). But what if we go back 100 million years? 200 million? 500? 600? Any human put into an ancient enough environment would die. We know this because the right foods would not be available or because there would be no proper shelter or because the atmosphere would be poisonous or because our immune systems would not be evolved to cope with the bacteria and viruses present at the time or because…and so on. The assumption that intelligence is better than anything else is clearly wrong once we recognize that evolution and the ability of a species to survive depends largely upon environment.

The second assumption in this whole discussion is that we can even say something in evolution is “advanced”. We can say more complex or better suited to a particular environment, but “advanced”? That implies evolution is on the march towards some goal, to some end. That is not true. Science has demonstrated this again and again by showing what a contingent process evolution is. Take the Lenski experiments, for example. (I’m rather disappointed I never wrote about them here.) Richard Lenski and his researchers followed several lineages of E. coli for 20 years (in fact, they’re still following them). They would freeze samples every 500 generations so they could go back and re-run the tape of evolution should some fundamental change occur. And, eventually, such change did occur. Some E. coli were able to consume a natural by-product of their environment after nearly 30,000 generations. Lenski et al. unfroze the old generations to see just what enabled the bacteria to obtain their new found skill. As it turned out, they had to go back many thousands of generations; it wasn’t just one mutation, but at least three. The first two were effectively random. But they were necessary in order to get to the third mutation – the one that opened up a new food product for the colonies. But in the re-running of the tape, not all lineages re-evolved the new mutations. The chance involved in the process was too great to be inevitable; evolution is contingent.

So my answer to the question, Are humans “more advanced” than other organisms?, is to say it is an inappropriate question in the first place. There are several things we should not be assuming:

  • Intelligence is the best trait (whether to this point or in terms of possibility)
  • Evolution is goal oriented
  • The ability to destroy other species and still survive is a mark of advancement

I mentioned the argument for point three, but I have yet to address it. This one is pretty straight-forward, I think: We may be able to destroy many species, but that really only applies for large organisms. The vast majority of life is microbial. Since we would never be able to destroy it all (or even a minute fraction of it), does that mean it is more advanced than we are? What about all the bacteria we need to keep us alive? We certainly could not destroy all the mitochondria of the world and still survive.

Evolution is a contingent process that has no march towards any end. It is about the ability to survive. Our genes are interested in propagating themselves and that is why we are here. Life may mostly (though not entirely) be more complex since it first sprung forth nearly 4 billion years ago, but it always depends upon its environment – and that makes some characteristics more valuable than others. Sometimes.