Tuesday, March 20, 2007

A death in the family

It's an odd sensation to pick up the newspaper or, in my case, a magazine, and find out for the first time about the death of a family member. Not that it was a close family member, nor that I was unaware of the fact that they were dead. Actually, the real news was the former: the fact that they were not as close a relation as I had been led to believe.

Of course, as I'm sure you realized the instant you began reading this that the relative I was talking about was homo erectus, who apparently died, oh, tens of thousands of years ago, I guess, I don't know the specifics. I was reading a fascinating article in Newsweek on a number of interesting developments in the study of human evolution, and I marveled, not at the information, but at the manner of presentation of the information, and the implications it might have for both those who put their trust in fundamentalist Christian dogma about the origins of man and those who put their faith in Darwin, or whatever, I think you know what I mean, although I am here and no doubt throughout this writing going to be far less than scientifically precise. Here I present another meandering musing on evolutionary theory that may be almost as random and aimless as the supposed forces of natural selection themselves.

So anyway, it turns out that the paternity test came back, and erectus is not the baby's father. The article itself is vague on exactly when the test was performed, but really, when erectus has been gone for thousands of years, it's not clear exactly how much it matters; suffice it to say that the suspected connection was never there, at least not in the way many scientists suspected. Rather than being our father, the family tree of the hominids that is now considered more accurate shows erectus as a sort of "first cousin twice removed" or grand-uncle, something of the sort. I don't know whether this came as a surprise to evolutionary scientists, but it sure does seem to have come as a surprise to the author of the article. Homo erectus was a species that, according to what is known about it, managed to thrive for around two million years and spread across various parts of three continents. They didn't make tools, or at least not more than very crude ones, but they walked upright, looked a lot like modern humans and are believed to have had a pretty good cognitive ability, based on what appears to be the structures of the brain. Still, they died out, and--along with homo neanderthalensis--seem to have not been our ancestors, nor the ancestors of any living species.

The author of the article seems to be very surprised to find that such seemingly advanced species of hominids could have lived and yet not been our ancestors. "More than once in human prehistory, evolution created a modern trait such as a face without jutting, apelike brows and jaws, only to let it go extinct, before trying again a few million years later." The author's view of evolution is interesting to me, both because many of the things they seem to find surprising seem obvious to me, and because it's the sort of surprise that I think for some people may be based on commonly-accepted ideas of evolutionary theory. If evolution is indeed an unguided force of nature (more or less, "force" may be a poor choice of words) then why not create something randomly that turns out not to be useful at the time it's created? Heck, species die out all the time, so why should it be so unusual that hominid species have also done so, even if they were similar to other ones that did survive?

For that matter, does the author really think of evolution as an unguided force? Would one say of an impersonal force, "evolution created", or "let it go", or "trying again"? It sounds more like the description of a cosmic tinkerer or scientist, trying little experiments to see what happens. Of course, that's hardly the view of any world religions I know, either, which is why this evidence, while it "upended traditional ideas" about evolutionary theory hardly gives weight to creationism. Certainly the God of the Bible isn't the sort of being that would have created numerous nearly-human species just to let them die out, right?

Both the author's view of an age-old understanding of evolution and the implications of a theory of theistic evolution favor the idea that human descent is a matter of a straightforward, linear progression of "{Sahelanthropus tchadensis} begat Australopithecus who begat Homo habilis who begat Homo erectus who begat Homo sapiens." Of course now it would seem that few if any of these ancient hominids are direct descendants of our modern species. There are two mistaken assumptions here, firstly that evolution is linear, and second that the whole point of evolution is to yield an end product of homo sapiens. Both of these concepts are worth exploring, though.

The author says about these dead-end branches that "It's like discovering that your great-great-grandfather was not an only child as you'd thought, but had a number of siblings who, for unknown reasons, left no descendants." I say, is that so momentous? My grandfather was into genealogy, and it's interesting to me to note that while scientific studies of genealogy like to focus on the Y-chromosome as a pointer to study lineage, my grandfather has left behind no descendants with his Y-chromosome. On that side of my family, I have only one male cousin, and he, like me, was born of one of our grandfather's daughters, while my grandfather's only son has only daughters himself. Now that Y-chromosome may exist in a distant relative somewhere--and probably does, actually--but if by odd chance there was a genetic mutation in my grandfather's Y-chromosome that might have been significant in some way, the world will never know. If it happens on a small scale with my own maternal family (and possibly paternal family, as I have no sons or brothers), then why not on a larger scale? That being said, while those branches seem obviously likely to exist to me, it's not completely wrong to look at evolution as a linear process in one sense, because my own Y-chromosome came from a direct line of male descendants before me, obviously, and if you wanted to track its origin, my lack of genetically significant male cousins doesn't matter at all. Homo erectus may be interesting biologically, but only tells us things about who we are indirectly.

As for the concept of evolution being directed at the creation of modern humans, oddly this is a sort of yes and no, and it's only yes due to random chance, one might suppose. It seems sometimes like humans are the pinnacle of life on this planet, but that's only out of an anthropocentrist sort of view. Evolution seems to focus on humanity because the study of evolution largely focuses on human evolution. Biological science will no doubt study all life, but put its primary focus on our own life because, despite occasional claims to the contrary, we as a society do try to use science to answer the same questions we struggle with in religion. We want to know how we got here, and what possible purpose we may have in being here. Sometimes it may make us forget that science does try to be dispassionate and unbiased as much as it can be. It makes sense to want to study ourselves, but in doing so, we inflate our own abstract sense of self-worth sometimes, and pure science doesn't give us that. To the undirected force of evolution, while today we may be the dominant species, thousands of years from now we may be another homo heidelbergensis: a stepping stone to a new, more advanced species, or tomorrow's homo erectus: just another evolutionary dead-end. That being said, while in a grander scale our place in the order of things may be temporary, at the moment we may indeed stand at the apex of the animal kingdom.

But as we stand at the summit and view those others that fell off of cliffs along the climb here, the surprise at what we see is interesting. While I strongly suspect the author is perhaps somewhat clumsily presenting information in a newsweekly that's not really "news" (I mean, aside from the fact that this is all stuff that happened hundreds of thousands to millions of years ago), there was a time not too long ago when this information was being newly processed by scientists and shaking up their own more sophisticated assumptions of hominid descent. After all, it's only been a little over 150 years since the first skull of a neanderthal was discovered, making scientists start to think more deeply about our biological place in the world, but every time a discovery is made, claims are made about what significance such and such fossil has, charts are rearranged to reflect new thinking, and human evolution is turned upside down, shaken out of its box and put back together.

Even now that we have begun to use more sophisticated methods of examining fossils, including DNA analysis (although I don't understand how one gets DNA from a fossil, but no matter) there seems to be a lot of assuming going on. In the opening of the article, we are assured that "...DNA...accumulates changes at a regular rate." Later, we are told that (my emphasis) "...DNA changes at a fairly regular rate." Technicality, right? Molecular biologists supposedly can use this rate of change like a clock, which is why we are told about it, but then about halfway through the article we are told of a specific gene:

It had changed in only two of its 118 chemical "letters" from 310 million years ago (when the lineages of chickens and chimps split) to 5 million years ago. But 18 letters changed in the (relative) blink of an eye since the human lineage split from chimps'...
How's that? We know that the change is regular, except when it's not regular? It seems that in these huge time scales of millions of years, so much is assumed. The article tells an interesting tale of how DNA of body lice tells us that they evolved about 114,000 years ago, and since they live in the habitat of human clothing, that must be when we evolved to lose most of our body hair. Oh, it's a fascinating theory, no doubt, but then, does it really make sense?

Why evolve to lose our body hair if it's just going to force us to invent clothing to keep ourselves warm? Why not invent clothing, which leads to the evolution of body lice, which between the two leads us to evolve to lose body hair, since clothing means it is no longer needed, and it's easier to delouse if you have less hair? Could we have the cause and effect backwards? Not to mention the fact that there are plenty people alive today that still have lots and lots of body hair, so it's not quite a common trait of the whole species.

And how do we really know what is a common trait of a whole species? The briefly-mentioned sahelanthropus tchadensis had a big part to play in rearranging the diagrams of hominid descent with its discovery, but then it's only a single fossil! Using the family tree metaphor again, it seems sort of like finding a single picture of a man in an old family photo album who looks sort of Italian, and dumping out all the pictures in your (non-Italian) family's album to rearrange the lot of them. Surely there must be a more rational approach, but then I'm not a photo album arranger, nor am I a biologist. Still, if a person who's never been to the U.S. saw a broadcast of a basketball game from Houston, would they be fair to assume that there exists in the U.S. a race of seven-foot-tall Chinese men?

My personal observation on all of this? There are far too many fossils of our ancient, branching family tree to deny that there is something to the theory of human evolution, but at the same time, there seem to be far too few fossils to say anything about it with definitive surety. Maybe in the end I will be proven wrong, but it seems to me that the science of evolution, in studying things that happened millions of years ago that left behind scant evidence, we operate far more on speculation than anything else.

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