Comment by jerf | Hacker News Reader

Comment by jerf | Hacker News Reader

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Evolution works by incremental changes, each of which to a first approximation must be at least neutral and preferably advantageous to producing offspring. In order for evolution to get from A to B, there must be a path of incremental advantageous changes to get from here to there. It can't magically leap from one optimum to another. So you see things like the way the same basic body plan is reused endlessly in the natural world; with only incremental changes available to create the next species, you can't create a whole new body plan from scratch, even if it would be completely appropriate due to, say, transitioning from land to water. It is also completely goalless; if there is a fantastic two-gene change that a species could make, even if both are individually advantageous, there's no particular force that will cause them to occur [1].

Evolution is both very powerful, with many people underestimating it, and profoundly stupid, with many people also overestimating it. Once humans really get cracking with the gene engineering (which has proved harder than we had initially hoped, but I'm still confident we'll get there), I'm sure we'll find a plethora of relatively simple changes we can make to natural organisms that may involve changing three or four genes simultaneously where no single change is advantageous, which is a thing that evolution essentially can't do.

[1]: Or at least, not yet... one bizarre-ish, "Selfish Gene" way of looking at human gene engineering is evolution evolving itself a way to make those multi-gene changes. Still not in a directed fashion, of course. But evolution will still apply to our own gene engineered creations, just possibly with a very different set of constraints, such as potentially severing the billion-year-old connection between fitness and direct biological reproduction... as I've said on HN before, you don't have to be a full-on "Rapture of the Nerds"-style Singulatarian to see that the future may get very weird....

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.

Regarding your footnote, there are already several examples of evolution evolving itself more efficient ways to evolve. The first example that comes to mind is sex, then passing knowledge between generations through non genetic means (IE a parent teaches its offspring).

Whoa. That blew my mind.

So we're evolving in such a way to be able to make combinatorial multi-gene changes- by evolving brains big enough to be able to develop gene engineering?

There's another term from the mentioned "Selfish Gene" (which is a book by the same title): https://en.wikipedia.org/wiki/Memetics

It's a view on how ideas spread and use hosts (e.g., human brains) as carriers. They mutate, they're selected, they compete for "brain space". One funny perspective is that we're the slaves to genes and memes, both using us to survive. We're just carrying out their orders. :)

(In the end it's just a way to look at information diffusion with focus on the way how ideas replicate and the condition of their success or failure over time, abstracting away from social/cultural context and other hard to grasp things.)

Wouldn't it be in the best interest of memes to never let us figure them out though? To never obtain this view of the world where memes are exposed for the parasites that they are? Maybe "theory of memetics" is a next-generation meme that took over our collective consciousness to exterminate all the other primitive memes and gain world domination :)

They are only parasites only if you also think that genes are parasites too.

Remember, it's not directed. Evolution qua evolution hasn't got a problem going to the brink, then watching humanity wipe out, then never building another intelligent species on Earth again... of course it doesn't have a problem, since it isn't a human or even a living thing that could have a problem, or indeed have anything.

But observationally, humanity is currently in a place where that level of gene engineering is a decent bet, yes.

I had this cool idea for a sci-fi book (I may one day write), set long after modern civilisation collapses. Humans survive but with all the readily available iron ore used up, we are perpetually stuck in a pre-industrial revolution world. Hundreds of thousands of years pass and we evolve. At this level of technology we can farm, so we're still very successful, and the biggest threats to us are diseases rather than predators. So we evolve towards having much greater conscious control over our bodies and health. Incremental changes happen, starting from an expansion of the existing placebo effect, towards a conscious ability to manage immune responses, and then further into being able to affect cell chemistry in different areas of the body. The book would follow what happens when humans evolve the ability to do genetic engineering on themselves, and the following completely organic technological revolution. (Probably ending with some gene hackers growing diamond hulled space craft and leaving to explore the galaxy.)

But the jury is still out on whether that ability is a net positive for our survival in evolutionary terms. And if it isn't, well, natural selection is quite merciless.

Mutation forces organisms to explore evolutive paths quite astray and I'd expect it happens quite often that a 2 gene mutation propagates into the "global pool" for being very advantageous. Of course, specific or optimal 2 gene mutations are wildly unlikely to be found.

What I mean is, a more adequate picture of the process is not a simple "path" analogy. It's more like you have a high dimensional optimization space and a wildly varying survival function, and the organisms are bouncing around this space in a random motion. This allows them to occasionally cross valleys and take very distinct paths to each far away maxima, specially if there are a few minor maxima along the way.

My point being organisms have a given capability to bounce around: they don't have to take a monotonically improving path, although this capability is limited because otherwise (if the mutation rate is too fast) the results are too chaotic.

They're somewhere in the middle of monotonically improving, guaranteed optimization (low mutation; gets stuck at local maxima) and completely random (high mutation; does not retain advantages well and leads to many deleterious results).

One interesting way to look at/remember this it is through history. Evolution by some early thinkers was thought of often as Ernst Haekel's tree of life[1].

In this representation of life it is directed and goal based. This is a misunderstanding of evolution that was common in a world that saw humanity as the peak of the process of evolution. For this reason Darwin perferred to think of it as a directionless bush rather than a directed tree.

1: http://en.wikipedia.org/wiki/File:Tree_of_life_by_Haeckel.jp...

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