Comment by upquark | Hacker News Reader

Comment by upquark | Hacker News Reader

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Awesome post. About the "fantastic two-gene change": can't there ever be a force pushing for a species to obtain two independent mutations more or less simultaneously? What I mean by that is pressure on a species to maintain / promote a few existing mutations in the population (each individual may carry one, or the other, or none, but the offspring of carriers is likely to end up with more than one). I imagine in very narrow bottlenecks this could be the case, e.g. tough ecosystem forcing early humans to a. become bipedal and b. think/plan better. Such bottlenecks could also be caused by inter-species dynamics, climate change, etc.

Actually the more I think about it, the more I am convinced that multiple interacting species introduce a serious argument against the blind hill-climbing view of evolution. Essentially what you have is not a single point on a landscape blindly climbing in the direction of the gradient, but a probability distribution with a given mean point that could jump to another mean currently at its periphery given enough pressure / interference. E.g. a newly migrated predator eating away 90% of variance of the distribution of some existing sheep-like species, leaving only its tough "tail", thus severely relocating the centroid. Maybe this is something trivial I'm just realizing, I'm not a biologist.

Kevin Kelly wrote about "co-evolution" in his book [0] Out of Control. Great book, by the way. I don't think he coined the term, but co-evolution regards how relationships between different kinds of species can effect the adaptations that each species undergo. So in your example, wolves have a definite effect on the sheep population's genepool, but the truth is the sheep have a similar effect on the wolves.

[0] http://www.kk.org/outofcontrol/

Cool, thanks for the link.

I wanted to keep it simple. All the details do get complicated, beyond even my comprehension (beyond anybody's, as far as I know, genetic science continues to find surprising things on a regular basis). Another semi-sort-of exception is bacteria, which can for instance trade large chunks of genes directly, though, again, not in a very directed manner. There's also quite a few "control" genes that exist where it may be a relatively simple mutation to change the length of an arm, or finger, or even just turn something off entirely, which can cause huge visible changes even though it was just one gene change.

However, in your first case, it sounds to me like you're talking about two changes, each of which are beneficial, or at least neutral. That wasn't what I was talking about, that happens all the time. I'm talking about changing two or three or four (or more) genes simultaneously in a way that each individual change, if applied on its own, would be detrimental, but the whole is an improvement.

I don't remember too much from my college genetics, but I recall that since so much of our DNA isn't actively used it can evolve much further away than would otherwise be possible if every base pair was actively used. As soon as the proper start and stop codons are mutated back in (I'm simplifying), bam, you have a new active gene which could result in much more drastic change than any single mutation would provide.

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