Constant, It's group selection because the individual is essentially making a sacrifice to reproduce less, to benefit the group. It happens blindly, through normal evolution of selecting the individual, but how else do you expect it to happen?

No group selection? I believe the math in Eliezer's post is wrong. Here is how a hypothetical fox/rabbit population could evolve restrained breeding through group selection.

Picture a geographically isolated fox/rabbit population. At some level, this is guaranteed, simply because there's not an infinite amount of land on this planet to inhabit. Even if the entire planet was one continent with just rabbits and foxes, then that's the isolation geography. So at some point there won't be other foxes getting to eat the un-eated rabbits from the restrained fox population.

Start with a balance of rabbits and foxes. Perhaps this is because foxes are newly migrated to the area. Whatever. The foxes feast on the rabbits, because they are so easy to catch. The rabbit population drops to something that can metabolically support only 5% of the current fox population. As the foxes die out, any fox that has genes to restrain its breeding, is going to do better than foxes that don't, because it will spend less energy developing fox fetuses that won't survive anyway because there isn't enough food to go around. THIS IS THE KEY. If we assume all foxes are roughly equal at catching prey, then any fox family with constrained breeding will have more viable offspring because their mothers didn't die out trying to give birth to 6 foxes with food for only 2. Or the baby foxes, will go up stronger because food for 2 foxes is spread for just those 2, and not 6.

Now after this initial die off of foxes, the rabbit population will rebound. So won't the non-restrained breeders just take over again? No. As soon as the non-restrained breeders get large enough to diminish the rabbit population, the restrained breeders will have the same advantage they had the last time around. And even MORE of the unstrained breeders will die out removing even more of their genes from the gene pool.

Eventually, the non-restrained breeding genes become so rare it's as if they never existed. Only when they randomly pop up due to mutations would the cycle start again.

And here's where something almost magical happens. Every time those unrestrained breeders go crazy and eat all the rabbits, it does, to a certain extent, harm the survivability of the restrained breeders. Not as much as the unrestrained foxes, but enough. That means that any gene that will suppress the initial growth of an unrestrained fox population, will spread itself throughout the fox population. Perhaps a gene will arise that builds multiple chemical/hormonal systems in the fox to specifically restrain breeding, making it exceedingly difficult for any one mutation that un-restrains breeding to actually CAUSE unrestrained breeding.

Group selection. Tada.

Eliezer, just because the raw mechanics of evolution are very simple, doesn't mean bizarre and conceptually complicated things can't happen in the real world mechanics of evolution. Even if they SEEM counter-intuitive to the principles of evolution.

Hi Erik,

It's not junk DNA, it merely has usefulness in many different configurations. Perhaps if the mutation would be to skip a base pair entirely, rather than just mis-copy it, it would be more likely to be detrimental.

OK, Let me make my point clearer, why we can't calculate the actual complexity limit of working DNA:

1.) Not all mutations are bad. Accepted knowledge: most are simply neutral, a few are bad, and even a fewer are good.
2.) If the mutations are good or neutral, they should effectivly be subtracted from the mutation rate, as they do not contribute to the "one mutation, one death" axiom because good/neutral mutations do not increase death probability.
3.) The mutations will not accumulate either, over many generations, if they are good/neutral. If a mutation really is good or neutral, that's EXACTLY what it is. It's like it never happened, it effectivly doesn't count in the "one mutation, one death" calculations.
4.) We do not know exactly how many mutations are good/bad/neutral. THUS we simply cannot come up with a specific upper boundary to the amount of working DNA in a genome.

Did Eliezer take this into account in the calculations in this article? Or am I missing something here?

Disagree. Any genome that has lower copy fidelity will only be removed from the gene pool if the errors in copy actually make the resultant organism unable to survive and reproduce, otherwise it's irrelevant how similar the copied genese are to the original. If the copy error rate produces detrimental genes at a rate that will not cause the species to go extinct, it will allow for any benificial mutations to arise and spread themselves throughout the gene pool at 'leisure'. As long as those positive genese are attached to a genome structure which produces mutations at a specific rate, that mutation rate genome will continue to exist because it's 'carried' by an otherwise healthy genome.

Sexual reproduction supports this concept very well. Fathers share only a portion of their actual genome with their offspring, (effectively a very low copy fidelity from parent to offspring.) And yet this is the most powerful type of reproduction because it allows for rapid adaptation to changing enviroments. However it arose, it's here to stay.

If a species can deal with detrimental mutations for several generations, then that simply means that the species has more time to weed out those really bad mutations, making the "one mutation, one death" equation inadequate to describe the die off rate based purely on the mutation rate. Yes, new mutations pop up all the time, but unless those mutations directly add on to the detrimental effects of previous mutations, the species still will survive another generation.

To add on to my other argument that we "know too little" to make hard mathamatical calculations on how big a functional genome can be, we also shouldn't work under the assumption that mutation rates are static. Wikipedia's "Mutation rate" article states the rate varies from species to species, and there is even some disagreement as to what the human rate is. There is NO REASON why a species can't evolve redudent, error correction copy mechanisms so the mutation rate is right at the sweetspot, providing variation but not so much as to cause extinction.

AGAIN, I still advocate that the original point Eliezer made can't be proven untill we know exactly how many mutations are detrimental. As a neutral mutation simply doesn't count, no matter how many generations you look forward, and benificial mutations can counter detrimental ones.

Scott A. I wasn't suggesting DNA would magically *not* mutate after it had evolved towards sophistication, only that the system of genes/DNA that govern a system would become robust enough so it would be immune to the effects of the mutations.

Anway, evolution does not have to "correct" these mutations, as long as the organism can survive with them, they have as much a chance of mutating to a neutral, positive, or other equally detremental state as it has of becoming worse. As a genome becomes larger and larger, it can cope with the same ratio of mutations it always has. The effects of the mutations don't "add up" as is assumed by Eliezer, they effect the local region of DNA and its related function, and that's it. If an organism happens to have a synergetically enhanced group of detrimental mutations, then yes that one will die, but showing empirically that that would happen more often than not, I thin, would be very difficult.

In any case, I still don't see where the ~25 megabyte number comes from. Wouldn't you need to know precisely how many mutations were detrimental to work that number out? And I'm assuming it's reasonable to say we don't have that information?

Actually, Scott Aaronson, something you said in your second to last post made me think of another reason why the axiom "one mutation, one death" may not be true. Actually, it's just an elaberation of the point I made earlier but I thought I'd flesh it out a bit more.

The idea is that the more physically and mentally complex, and physically larger, a species gets, the more capable is it is of coping with detrimental genes and still surviving to reproduce. When you're physically bigger, and smarter, there's more 'surplus' resources to draw upon to help in survivial. Example: There is a rare genetic disorder that causes some people to have no finger prints. This mean's that their manual dexterity is greatly reduced because of lack of friction in the fingers. And while detrimental, this is a historicaly prevelant case that has not gone away just because it's bad for an individual. You can learn to avoid situations where failure in manual dexterity could be fatal, etc.

I also believe it's possible for long standing sections of DNA to evolve and become more robust to mutation once they have "proven themselves". Meaning if a certain series of genes/DNA that serve a benificial function are around long enough, they will become more refined and effective, and especially robust. However this is accomplished specifically, which of course I don't know, I don't see why it's mechanically impossible. Thus, large sections of DNA could essentially be "subtracted" from amount of DNA to be mutated per generation.

Any flaws in this logic?

Eliezer, I see two potential flaws in your argument, let me try and explain:

1.) The copy error rate can't directly translate mathematically into how often individuals in a species die out due to the copy error rate. We simply can't know how often a mutation is neutral, good, or detrimental, in part because that depends on the specific genome involved. I imagine some genomes are simply more robust than others. But I believe the prevailing wisdom is that most mutations are neutral, simply because proteins are too physically big to be effected by small changes. Either way, I can't see how anyone knows enough about this to be confident in coming up with specific mathematically calculated numbers.

2.) One bad mutation does NOT equal one death, as far as I see it. Greater intelligence leads to greater capability to cope with detrimental circumstances. Sickle-Cell-Anemia is detrimental, but people live and reproduce with it, and have for generations. But it's almost entirely detrimental, especially if your risk of Malaria is low. It's true, organisms with non-detrimental versions of the genes will gradually take over, but that doesn't mean the detrimental versions can't survive on their own and with just a lower population cap.

And not referring to you in saying this Eliezer, but this whole “Most of the DNA is junk” mantra reeks of conventionalist thinking, a classic form of bias, and has always annoyed me when I saw it in science programs and news articles. Current scientific knowledge knows more about proteins than any other aspect of the function of DNA, so it follows that people will focus on this and gloss over the importance of the other functions of DNA. If you know something very concrete about DNA: proteins, that are amazing enough in themselves, it's very easy to justify the case that the rest is simply junk DNA. I doubt that, I think we just do know what it does yet on a mechanical level.