Mutation

But the statment:
"Most mutations are harmful or neutral" can be true
AND at the same time
"Most mutations are harmful" can be false.If 1% of mutations are beneficial, 25% are harmful and 74% are neutral then that is the case.I don't even know if we actually no what the real proportions are. It may well be that we see "most" mutations (well over half) as being neutral because we don't count all the non-viable fetuses that never make it beyond very early stages of gestation.Let's say in everything that lives to birth it is probably true that the majority of mutations are neutral since all of us, for example, have several.

Don't be so sure of this. Just because we don't have lions chasing us doesn't mean that we aren't being selected.Right now it is possible that addictive physiologies and personalities are being selected against for example. A tendancy to get angry too fast might be selected against (where it may have been selected for in a physically competitive environment. Good parenting instincts for teaching and socializing children may be selected for over the ability to hunt for food.You are forgetting how very fine the filter is and how subtlely it may act. We don't know what selective pressures we are under.

You know, I can understand that it is hard to grasp what is possible. It is made harder when there are so many misconceptions.One thing you should note is that each and every individual organisms is an little experiment. Each one contains some mutations. There are, at each moment on the planet, how many individuals?I don't know but even just taking multicellular life it must be around the trillions mark. Potentially benefical mutations are only rare in that a specific indivdual has a smallish chance of having one. However, they are in absolute numbers very very common.Also the split between beneficial and neutral may be a bit too sharpe. It is clear that mutations are not, by themselves, either of those. It waits on the environment to sort out which are and are not beneficial.Another problem is the idea that the mutation has to be somehow spectaculary beneficial. It doesn't. The whole process of selection is statistical. As you point out even beneficial mutations could, by pure bad luck, not make it. But the slightest extra edge could also make the difference between more and fewer offspring too. One could claim, without good evidence, that every surviving individual has shown their specific genome to be somehow beneficial. How can you discount that?There are trillions of experiments a year. These can add up to real change pretty quickly. We see how rapidly organisms can change in a very short time in the lab. The world around us is an very large, very long running experiment.It may be difficult for you to accept what can arise out of this stew of every changing organisms but simple incredulity isn't enough to refute it. All the evidence we have says that it can and more, has happened.

Can you tell me the percentage of mutations that are, in any way, beneficial? I can't calculate the odds until I know this.

There are a couple of threads on this whole topic. Behe's Irreducible Complexity Is Refuted
and
Defence of Intelligent DesignThere are others of course.To summarize, the irreducible complexity argument seems to boil down to one of incredulity. That is, since the person suggesting IC can't imagine how something could evolve then it could not have.In all cases that I know of the examples have been shown to not be IC. Both the eye and the flaggelum have reasonable possible evolutionary pathways. He never shows this. He simply says they couldn't have, he doesn't show that they can't. Then others can show ways they could have.[This message has been edited by NosyNed, 04-13-2004]

You understand that there are other ways of introducing variety of course.Secondly why do you think that once in a thousand cell divisions is an "only"? That means that mutations are happening at an enormous rate. (I think you're number might actually be over estimating the rate of occurance but I'm too lazy to try to find that out).Let's go with your number. And let's restrict this to only in the sex cells (not somatic where it doesn't get passed on). Let's be even more restritive and say is it only 1 in a 1,000 individuals that has a mutation (this is hugely wrong since you and I probably have several each as do all of us). How many mutated individuals are being born every single second? Can you guess? To stop this from being in the trillions let's only pick multicellular organisms. Now how many? My wild assed guess is that it will come out to some millions a second. Mutations are common. How many are harmful (I'd guess half based on humans). How many are waiting in the wings for the right selective pressue -- the other half.How can it not be?In some research work it is a problem to stop the subjects from evolving under inadvertant selective pressures.This message has been edited by NosyNed, 05-10-2004 02:11 PM

I deliberately chose to avoid the words neutral or beneficial. It is probably not to difficult to tag a mutation as harmfull. Certainly if it kills the individual before birth it is.However, in the bigger picture, I don't think that one can be so sure about beneficial or neutral. Sure, it may be clear that a mutaion helps an individual and maybe that it doesn't. But from an evolutionary standpoint any of the so-called neutral mutations could be beneficial. It is just a matter of them hanging around in the population till the "right" conditions arise. It would seem to me that just having genetic variability is a darn good thing in itself.

Agreed. I wasn't thinking it through carefully enough. So in the mix of changes we have those which are clearly detrimental (the organism spontaneously aborts), those which are clearly neutral (not expressed as far as we know), those which appear to be beneficial (but it's hard to be sure over the short terem), those which appear to be neutral (but could be beneficial or harmful as the selective pressures change) and those which appear to be harmful but might be reevaluated with selective changes.It seems that we end up with a lot which are neutral, a significant number which are harmful and another bunch which come down to
"dunno for sure".