Humanity's Past, Humanity's Future
The science news this month was dominated by two genome stories. An organism's genome is the sum total of all its genetic information — its DNA. In sexually reproducing species, a child gets half its genome from one parent, half from the other. Asexual organisms like bacteria just copy DNA from one generation to the next. There are occasional copying errors in both cases to make life (as it were) interesting.
The first genome story of the month concerned one of those sexually reproducing species. Well, one or two, depending on who's counting. "Species" is a knotty concept. (Lecture 34 in Jeffrey Kasser's Philosophy of Science course does its best to untie the knot.)
In the few millennia prior to 30,000 b.c. our own remote ancestors in Europe and the Middle East, whither they had spread after leaving Africa, were sharing those territories with an older stock, the Neanderthals. Around 30,000 b.c. the Neanderthals disappear from the archeological record, leaving our ancestors in sole possession of the turf (tundra, whatever). Were we and they separate species — Homo sapiens and Homo neanderthalensis? Or two distant breeds of the same species — Homo sapiens sapiens and Homo sapiens neanderthalensis? A closely related issue is: Could the two stocks cross-mate, producing fertile offspring?
Apparently they could, and did. That's what we learned this month. A team of biologists in Germany has for several years been working to figure out from fragments of bone what the DNA of Neanderthals looked like. We already know what modern Homo sap. DNA looks like. (There's a specimen here.) The researchers now have enough Neanderthal DNA to be able to declare that yes, there was successful cross-mating. The base populations of Homo sap. outside Africa have genomes made up with one to four percent of Neanderthal genes.
These are early results, and there are problems to be resolved. So far the archeological timeline seems not to match the genetic timeline (which can be estimated from known rates of genetic change.) We also don't know much about what, if anything, the Neanderthal genes do. "Some of the genes seem to be involved in cognitive function and others in bone structure," says the New York Times report vaguely. And of course we know nothing about the intimate encounters that must have occurred to produce the gene-mixing, whether they were peaceable or violent. We only know they occurred, between creatures not much different from ourselves, in the unimaginably remote past.
This month's other genome story concerned the opposite end of the complexity scale, and points us to the future rather than the past. Craig Venter and his colleagues put together a genome from scratch, using off-the-shelf chemicals. They swapped it for the genome of a living organism, a wee one-celled asexual critter named Mycoplasma capricolum (which, as its name suggests, causes goats to feel unwell). Then they put the transformed cells on dishes of jelly and waited for them to reproduce. The cells did so, very happily, and there are now several billion individuals of this new organism with its made-up genome. (A cell contains much more than a genome; but all the other bits are templated in the genome, and after a few dozen generations Dr. Venter's invented genome was calling the cell-construction shots.)
There has been much quibbling about whether Venter and Co. have actually "created life." The quibblers are fighting a rearguard action, though — one they actually began fighting eight years ago, when a different group synthesized a virus. The quibblers had a good case then — viruses are more like non-life than life — but they have a much weaker case now, and after another milestone or two along this path, they will have no case at all.
And quibbles aside, this is a real milestone. As The Economist put it:
Life's essence is information. Heretofore that information has been passed from one living thing to another. Now it does not have to be.
Dr. Venter's new organism, whatever they decide to call it (may I register a vote against the proposed Mycoplasma laboratorium?) has no ancestors. Of no living — energy-processing, spontaneously-reproducing — thing has that been true for three or four billion years on our planet, so far as we know.
The first of these stories addresses humanity's past; the second, our future. Both constitute further dethronements of our species. Small, incremental dethronements in both cases; but we can expect many more of the same. Before a few more years have passed, the "folk metaphysics" that most of us carry around in our minds, as our ancestors have done for centuries, will be completely untenable.
Following the discovery of our Neanderthal admixture, it is clear that we are even more of a kluge than we thought. What evolution generally delivers is a terrible mess. Here's anthropologist Melvin Konner on the human brain:
If you insist on the computer model, think … of a late-1970s Tandy desktop computer somehow hopelessly yoked to a Cray supercomputer, an early Macintosh, a Pentium multimedia-based system, an old mechanical calculator, an abacus … Aging, rusted, rudimentary, even broken components stay and play their roles …
Biologists have known this stuff for a long time, but most nonspecialists have been reading only the first bit of Hamlet's address: "What a piece of work is a man!" A few more revelations about our species' jumbled, chaotic deep history, and we shall be in the "quintessence of dust" camp, where man delights not us.
Craig Venter's result knocks away another prop from under our folk metaphysics, by killing vitalism once and for all. Living processes, presumably including those that comprise human thought and feeling, are complicated chemical reactions. Sure, you can still think up arguments for vitalism, ensoulment, and human exceptionalism; but those arguments are, by some small degree, a harder sell this month than they were last month, and they will get harder yet.
The consequences, it seems to me, will not be good. Our folk metaphysics is false; the facts uncovered by science are true. Can we live without comforting falsehoods, though? Or rather: How many of us can?
There is a line of thought going back at least as far as William James, and most lucidly expressed, to my knowledge, in Lionel Tiger's 1979 book Optimism: The Biology of Hope, which argues that life is insupportable without self-deception. Once human beings evolved to the point where an individual could reflect on his own mortality, the toil and pain and disappointment of ordinary life, and the knowledge of its inevitable conclusion, could not be borne without sedation, either via opiates (internally generated or self-administered) or via hopeful, optimistic habits of thought, however much at variance with cold reality. To quote myself:
The overall picture that emerges from the cognitive science researches of the last half century is one of a brain that struggles to cope with reality, and rarely does very well at it.
Worse yet: its not doing very well may be adaptive. That's a term of art in biology. A trait is adaptive if an organism that possesses this trait gets a reproductive edge thereby over an organism that doesn't.
Researchers like S. Taylor and J. Brown (Illusion and Well-Being, 1988) have found that a moderate degree of self-deception is normal in mentally healthy people, and is likely adaptive.
If self-deception gets more difficult, so will happiness. Unless, perhaps, Craig Venter and his successors can come up with a genetic fix.