Evolution without incest?

Yes, they do. In these species young males leave the group before they become reproductively active. They spend some time searching, and eventually find another group which they join, they attempt to breed with the females of that new group and may attempt to become the dominant male in that group.

Since the female offspring stay with the original group, and the male offspring set off to find a new group, this reduces the incidence of inbreeding.

Another mechanism used within these species to reduce inbreeding is found in the preferences of the females:

From: Krebs & Davies, 1993. An Introduction to Behavioral Ecology. Blackwell Scientific Pub. p. 241.

While I can’t possibly speak for most of the 2 million or so species on Earth, these anti-inbreeding mechanisms are very common. Many species even have multiple mechanisms that work to prevent inbreeding.

You seem to have missed my point here. The female offspring stay with the male (i.e. their father) dominated group. Thus, unless there’s a mechanism I don’t know about, they are most likely to mate with their own father. Is there a mechanism that reduces this kind of incest?

OK, perhaps I should introduce the concept of the founder effect.

If a population is founded by only a few individuals, the new gene pool will likely be very different from the parent population. This is thought to be an important part of speciation. Isolated populations are small enough that mutations can become fixed in them, where the new alleles would be lost (probably eliminated through genetic drift) in a larger one.

The isolated population is likely to change much more than a large population. A new species can be established much more rapidly this way.

Inbreeding is therefore though to be important for speciation, and hence for evolution. But it is generally bad for the individual. Suppose you have a recessive deleterious gene. Well, if you have a copy, your close relatives are much more likely to also have a copy. If you marry an unrelated person, your children are likely to carry the allele, but not express it. But if you reproduce with a close relative, your children are much more likely to get two copies of the gene, and express the trait.

One might argue that this would be good from an evolutionary standpoint, since then the deleterious allele could be selected against and eliminated. But we generally don’t think it’s good for children with genetic disorders to die, we try to save them, right? And we also have to realize that the genetic load of deleterious recessives is very very high. EVERYONE has many deleterious recessive genes. If we eliminated everyone with deleterious recessives, we’d have to eliminate 99% of the human race.

But then humanity would be stronger! Free of genetic defects! Sure, but we can acheive the same result with a little genetic counseling, and not have to eliminate 99% of humanity.

Fascinating! Might this phenomenon also help explain punctuated equilibrium? During times of increased environmental stress, you would see more small groups cut off from the parent population, with increased expression formerly masked recessive mutations. But in times of decreased stress, the anti-incest behaviors would tend to disperse recessive mutations, making their expression unlikely.

From what I’ve picked up on PE, the main factor is that in an unchanging environment, populations tend to stay the same as most mutations don’t match the environment. PE simply means that when the environment changes, the population does. This happens rapidly relative to the previous period of no change, but it does not happen at a faster rate then normal mutation. PE does not, I think, have any limit on population sizes. I’m drawing my claims about the rates of mutation under PE from River out of Eden.

Just to clear up some apparent misconceptions about PuncEq:

Punctuated Equilibrium is not an alternative form of speciation. Eldredge and Gould proposed the theory as an explanation that what we see in the fossil record (species appear rapidly, then remain ‘static’ throughout much of their history) is what we should expect to see based upon our understanding of speciation, not a result of inadequacies in said record. It attempts to explain the rate of speciation (specifically, that speciation is a geolgically rapid event, as opposed to the gradualistic view where species gradually transmute over great lengths of time), but says nothing about the mechanisms of speciation.

In a nutshell, E&G were arguing that what we see in the fossil record is real, and not an artifact of missing data (at least with regards to appearance of new species). This theory is what is known as Punctuated Equilibrium; no more, no less.

As was mentioned in the passage I quoted, females tend to avoid natal males (i.e. males that were around when they grew up). That includes males that were adults as they were growing up and males that were young as they were growing up. In addition, remember that lions, for example, don’t live as long as human beings. I don’t know how long the average dominant male in a lion pride remains the dominant male, but I suspect that the majority of the female’s reproductive life will be spent after the time her father has been replaced as the dominant male in the pride by a younger, unrelated male.

Actually, there’s more and more evidence that the majority are neutral, fewer are negative, and far fewer are positive. Think about it - with the degeneracy of the genetic code, you can get nucleotide mutations that code for the same amino acid. In addition, even if you do change the amino acid, there’s a pretty decent chance the new one will be similar enough to the old one so as not to make no nevermind. Even if there is a big change, it may be in an amino acid that’s not particularly important. It’s a subtle distinction, but one that could have some important ramifications.

And I quote Lemur866, “One might argue that this would be good from an evolutionary standpoint, since then the deleterious allele could be selected against and eliminated. But we generally don’t think it’s good for children with genetic disorders to die, we try to save them, right?”

or

If the “majority” of mutations are nefarious, or “the majority are neutral, fewer are negative, and far fewer are positive” (quoth Smeghead)

Couldn’t I assume that the positive ramifications of incestual mutations are eliminated due to:

The inability of modern man to allow the weak to die, and the morals of modern man which prevent inbreeding?

Just wondering :slight_smile:

Well, firstly, let me repeat: there is no connection between inbreeding and mutations. None whatsoever. Just wanted to make sure that was clear.

Now as to your question, which I interpret as “Are our modern technology and morals interfering with evolution?” To some extent, yes. Nearsightedness has become much more common over the last, say, hundred years because it no longer interferes with one’s ability to make a living and raise a family. OTOH, beneficial mutations will still be beneficial: if I’m born unusually good-looking by the current standards (I wasn’t), I’m more likely to find a mate and have children.

I would say that our evolution is being affected by our technology, but it’s a fallacy to think that we’re interfering with a predetermined pathway. It’s not like we were heading in one direction and now we’re headed in another. Evolution is just a natural consequence of our interaction with the environment. We’ve merely come up with some new ways to interact. Nothing wrong with that.

I want to second Smeghead on this. I don’t know where the idea that incest causes mutations comes from. Incest does not cause mutations. Errors in replication and exposure to radiation or mutagenic chemicals cause mutations.

Mutation is just one aspect (or “force”) of evolution. Some others are…
natural selection
sexual selection
genetic drift
recombination
gene flow

Also, I’ll third what Smeghead said…incest is not the cause of mutation. Mutation is caused by incorrectly copied DNA. Most mutations are not helpful. Some are harmful. Some, by luck, are beneficial.

Evolution will continue regardless of our morals.

I didn’t see anyone refute this…
There is no apex of evolution! Change happens. Evolution is simply change. There is no goal and no “best” evolutionary form. Some changes work, some don’t. The ones that work tend to survive and propogate better than the ones that don’t. Then the climate changes and new characteristics are better suited…the tables turn.
Lots of good info at…http://www.talkorigins.org/
(the website is working again!)