by JOHN DERBYSHIRE
June 3, 2010
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. In both cases, there are occasional copying errors, which serve to make life (as it were) interesting.
The first genome story 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'sPhilosophy of Science course does its best to untie the knot.)
Sebastian Willnow/AFP/Getty Images
A photographer taking pictures of the Neanderthal man ancestor's reconstruction, displayed in a show of the Prehistoric Museum in Halle, eastern Germany.
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 with 1 to 4 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 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, and 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 rear-guard 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.
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Read more here/Leia mais aqui: National Review
