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Postdarwinism: the origin of fitness.
Jinnigan
Registered User regular
Registered User regular
I've been reading Out of Control, by Kevin Kelly, the the founding executive editor of Wired. It's a strange book about "self-sustaining systems, both living ones such as a tropical wetland, or an artificial one, such as a computer simulation of our planet."
More relevantly, at one point it talks about genetics, and the way that the popular method of thinking about DNA is wrong. DNA, Kevin claims, is not a linear flow of information that is read like computer code, but rather a complex geography where minor changes can cause huge changes in other spaces, and that many genes are often correlated with other genes. Thus, pigeons bred for white feathers also have a strong tendency to be near-sighted.
This may seem obvious, but it does have some interesting conclusions for evolution. He uses mutants as a clue as to what it might mean for evolution:
In essence, the idea is that Natural Selection and random minor mutation is not the only thing at play in evolution. Rather, the self-organizing behaviour of genes and growth is the important contributor of change, at least insofar as species-defining change is concerned.
Now, this book was written in 1994, so I'm very curious as to whether any new research, either in favor or disfavor of this theory, has surfaced.
More relevantly, at one point it talks about genetics, and the way that the popular method of thinking about DNA is wrong. DNA, Kevin claims, is not a linear flow of information that is read like computer code, but rather a complex geography where minor changes can cause huge changes in other spaces, and that many genes are often correlated with other genes. Thus, pigeons bred for white feathers also have a strong tendency to be near-sighted.
This may seem obvious, but it does have some interesting conclusions for evolution. He uses mutants as a clue as to what it might mean for evolution:
A small mutation can affect a suite of things in a single blow. An appropriate early tweak can invoke or erase ten million years of evolution. The famous Antennapedia mutant of the Drosophila fruitfly is an example. This single-point mutation engages the leg-making apparatus of the embryo fly to build a leg where its antenna should be. The afflicted fly is born with a fake foot sticking out of its forehead -- all triggered by one tiny alteration of code, which in turn triggers a suite of other genes. All kinds of monsters can be hatched this way. Which leads developmental biologists to wonder if the self-regulating genes of an organism might be able to tweak the genes governing these early suites into useful freaks, thus bypassing Darwin's incremental natural selection.
The curious thing about monsters, though, is that they seem to follow internal laws. While a two-headed calf may seem to us to be randomly defective, it isn't. When biologists studied freaks they found that the same type of monstrosities appeared in many species, and that their freakishness could even be categorized. For instance, a cyclops -- a relatively common freak in mammals, including humans-born with a single centrally positioned eye, will almost always have its nostrils located above its eye. This is true regardless of the species in which it appears. Similarly, two-headedness is much more common than three-headedness. Since neither mutation is a variation that offers reproductive advantage, as few of these freaks survive, natural selection cannot be selecting one over the other. This mutant order must be internally generated.
Thus we have two-headed freaks for perhaps the same reason we have bilateral arms; most likely neither is due to natural selection. Rather, internal structure, particularly the structure of the genome, and the accumulated morphogenesis of development, may be an equal or greater influence upon the variety of biological organizations possible.
[...]
Richard Goldschmidt spent a unrewarded lifetime showing that extrapolating the gradual transitions of microevolution (red rose to yellow rose) could not explain macroevolution (worm to snake). Instead, he postulated from his work on developing insects that evolution proceeded by jumps. A small change made early in development would lead to a large change -- a monster -- at the adult stage. Most radically altered forms would abort, but once in a while, large change would cohere and a hopeful monster would be born. The hopeful monster would have a full wing, say, instead of the half-winged intermediate form Darwinian theory demanded. Organisms could arrive fully formed in niches that a series of partially formed transitional species would never get to. The appearance of hopeful monsters would also explain the real absence of transitional forms in fossil lineages.
In essence, the idea is that Natural Selection and random minor mutation is not the only thing at play in evolution. Rather, the self-organizing behaviour of genes and growth is the important contributor of change, at least insofar as species-defining change is concerned.
Now, this book was written in 1994, so I'm very curious as to whether any new research, either in favor or disfavor of this theory, has surfaced.
Jinnigan on
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It's an interesting theory.
It's one of those things that are situational.
Take polydactyl cats, for instance. That's something I could see being a "useful monster" scenario.
But you're not going to develop a bat's wings that way.
Something like polydactyl cats or the flys with the legs for antenna, I'd assume it'd still take a bunch of generations for the mutation to be refined to a coherent organ.
New organs generally have to develop in increments, but old organs in new places? I'd find it odd for those to develop twice on their own.
That we see two-headed and not three-headed animals isn't surprising, as we have hox genes that code for bilateral symmetry, so if something's going to fuck up, it's probably going to fuck up bilaterally. If we were trimeric (is that the right word?) radial critters then I'd expect that we'd see three of any given fuck-up more often than two.
And, yeah, that does follow an internal logic, because bilateral symmetry offers some significant adaptive advantages over other forms of symmetry. Hox genes aren't magic, they're subject to the same evolutionary pressures as other genes, it's just that things like symmetry and four limbs branched off so long ago that they're so integral to functioning that they probably no longer evolve in any meaningful way, as any mutation in those genes (in higher animals at least) results in a non-viable birth, with some exceptions (artificial mutations in fruit flies, polydactylism, etc).
It's definitely an interesting and complicated set of relationships, but I'd hesitate to read any grand philosophical meaning into it. It's kind of like saying, "Hey, if we take this polynomial equation that defines this fractal function that looks like a coastline, and change one coefficient, the whole graph changes and it doesn't look like a coastline anymore!" Well, yeah, it does. That's not really all that surprising or meaningful.
the "no true scotch man" fallacy.
Most people think of it as the same thing, really. The psychic who can talk to a ghost isn't any different than someone who can make sense of a differential equation. And people are only as interested in either to the extent that it reassures them of their biases and comforts.