If mutation is the catalyst of evolution, doesn’t it follow that mutations attributable to incest are a missing link in modern human evolution? Have we allowed our morals to extinguish any hopes of evolving further? I am not trying to justify the actions of people who pumpkin, I am just wondering if we have squashed any hopes of becoming amphibious, super-intelligent, or perhaps winged.
Too small a group is unable to give any useful mutations a chance because the harmful ones build up too quickly.
(I really need an IANAB for these biology type threads…)
“Mutatiom” comes from adaptation. It happens on its own without resorting to jumping your sister. Theory of survival of the fittest and all.
Don’t expect to see “evolution” in your lifetime either (at least in humans). It took x number of thousands of years to get this far. Don’t expect babies with 3 times the brain capacity to start popping out tomorrow.
Incest does not cause more mutations to occur, it merely makes the expression of recessive genetic disorders more likely, which is almost always a bad thing.
Reminds me of a quote in Maxim, or Stuff…can’t remember it exactly.
“People born with mutations usually have hideous defects, not superpowers with hot, hot bodies”.
So what we have learned so far is: All mutations are bad, I find this hard to believe.
Survival of the fittest can’t be all there is to evolution. If so, we would either regress/devolve or remain the same, I am sure this is not true.
IBBen, you’re not paying attention. Incest does not cause mutations to occur (no more than they occur naturally.) It makes it more probable for recessive genetic defects to occur, since family members are more likely to carry the same recessive genes. A genetic disorder (such as anemia) is NOT a mutation. Genetic disorders are usually recessive (meaning you need the gene from EACH parent to get it, meaning if EACH parent carries the gene, there is a 25% chance of getting it. This is covered in 9th grade biology.) A mutation occurs when an amino acid sequence CHANGES. Mutations occur as part of the fertilization process, and can also be caused by radiation, and other things.
Evolution works through mutations. Incest does not affect the rate of mutation.
IBBen: I don’t think anyone has said this. I’m pretty sure Lord Davidson is joking. He quoted Maxim or Stuff for God’s sake. 
Not all mutations are bad. The vast majority are bad, a small number confer no special survial ability, and a small number increase a population’s ability to survive.
Humans have reached the apex of their natural evolution. By the time some adaptive evolution takes place, either Humans won’t exist anymore, either we will have perfect control over our genes and population…
I don’t think anyone said that mutations are bad. The word “mutation” has gotten a bad rap today. Say “mutation” and people start thinking a Swamp Thing type creature due to nuclear testing or what not.
Evolution is practically a synonym of mutation. It would be lost without it. But mutation happens in more ways than incest (thankfully).
But if there is an advantageous, but recessive mutation, incest would make its expression more likely as well. Admittedly, advantageous mutations are just a small minority of all mutations, but they do happen and are not always dominant.
Right, but MOST recessive traits are bad. Again, the expression of a recessive gene is NOT a mutation, since no genes have changed. Apples and oranges here.
Another way of thinking about this is the following: our genes “want” to spread themselves. Keeping them within the local pool, so to speak, does not advance them any farther than they are already, or at least no where nearly as far as they can go if they can go outside the local family. I’d recommend, for your edification, chapter 3 in Steven Pinker’s book, How the Mind Works. It lays out some of the current ideas in evolutionary thinking and may explain some of the more complex notions that may illuminate your thinking on the topic.
If it’s an advantageous mutation, it will diffuse through the population. Eventually, some folks will wind up with the mutation for both copies of that gene, and, through the advantage have better breeding chances than had they not had the mutation. If it’s enough of an advantage, eventually the mutated gene will outbreed the non-mutated gene to the point where almost no one in the gene pool has the non-mutated gene.
Incest restricts the flow of genes from diffusing as fast through the pool. It hinders good genes from separating from bad genes. “Yeah, she’s got a beautiful face. Too bad she has the intelligence of a gibbon.” I’d venture as far to say that populations where incest is taboo are healthier than those where it isn’t.
But if it’s recessive, it will not be expressed, and so give no advantage to its owners. So there’s no guarantee that it will diffuse through the population. It could just as easily disappear from the gene pool. Incest causes recessives to be expressed more, thereby bringing out any advantageous recessives. Yes, it also brings out disadvantageous recessives which seems wasteful, since there are far more disadvantageous mutations. But somehow I have the feeling that in the long run, it’s better for species to have recessives expressed than not.
Incest is very common in the natural world. It’s not just a technique used by animal breeders, although they take it to an extreme not usually found in nature. If it was as disadvantageous as you seems to indicate, why haven’t most species evolved a mechanism that would minimize it?
Don’t confuse recessive genes with evolution. They are separate entities. If two cousins who married both carried the gene for XYZ condition recessively and had kids, that is NOT evolution.
Whether incest is common or not depends on your definition of common, but I wouldn’t have used the term. Many species, from birds to squirrels to fungi, do have sexual recognition adaptations that reduce incest. For example, two genetically identical strains of Fusarium, a fungus I worked with a few years ago, will set up an interference zone to prevent mating, repelled by their identical chemical products.
There are many, many examples of this in nature. I can’t possibly speak for most species, but it is common for organisms to have features that reduce the incidence of incest or make incest impossible.
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Incest is bad, in general, for the genetic health of a population.
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Evolution is good for the survival of a population.
The previous statements are not in conflict. Incest is not the only way to increase the number of advantagous genes in a population. Any sort of non-random mating which occurs between two organisms which share the advantagous genes, increases the genes in the population. Incest is an extreme example of such non-random mating, but not the only example.
Don’t you see? In the long run it does. The harm done by undirected inbreeding far overshadows the chance that a wonderful mutation will be cut off from being passed on, and will never return again.
Name 3 species that inbreed as a practice.
Most have. Many, many species select for mates that are different from themselves. Many, many social animals have intergroup migration to prevent brothers and sisters from mating.
Well, maybe I’m wrong. But I wasn’t thinking of brother-sister incest. I would imagine father-daughter is more common. If nowhere else, in lions, gorillas and other species that have dominate males with harems. Do these kinds of species have mechanisms that work against incest?