Please clear up something for me about evolution theory

I’ve heard things before along these lines:

The female selects her mate based on how much she believes he will contribute to the gene pool and the successful survival of her progeny.

Unless I misunderstand, that sort of thing seems to be saying that animals have an instinctive desire that their gene pool survive, and I have two problems with that.

(1) I don’t think it’s necessarily true. I think that animals (including humans) are primarily hedonistic, and are not very motivated by what might happen to generations yet unborn.


(2) There are many organisms, including some animals, who simply lack the cognitive ability to make the kind of induction required to perceive any advantages from selective procreation.

Can someone help me, please? What have I misunderstood?

The urge to procreate is INSTINCTIVE, logic has no bearing on it.

Actually, sexual selection is different from natural selection.

Sexual selection generally modifies only the males (occasionally the females by analogy), based on characteristics the females “like.”

Natural selection simply works on the fact that all of the unfit animals (both male and female) won’t be around to mate and pass on their genes - nothing logical about it.

Right, but that’s not what I’m asking about. I’m asking about the urge to selectively procreate based on which mate will contribute the best genes.

I’ve heard from Darwin’s Finch and others that it is a mistake to equate natural selection with the notion of survival of the fittest. Sorry to be so dense, but I am fairly confused on this.

It is how you are programmed to find whatever attractive.

The female gets the hots for the studly (whatever) male rather than the weak male.

Of course not all females (of every different species) have a choice and go with whatever male is available. Often in these cases the male does the work of getting rid of rivals. Last male left standing gets the action.

In other cases (like salmon) only the strongest males and females make it all the way back upstream. At that point its orgy time.

In yet other cases it is more of a shotgun approach…jillions of eggs with sperm everywhere and mother nature will weed out the vast proportion of the population (you see this with a lot of aquatic life). Only the strong (or lucky) survive long enough to reproduce. The shotgun approach is also used by some insects. IIRC Cecil once answered a question about how many flies there would be if every fly lived and every fly reproduced at maximum output. I think inside of a year flies would fill our solar system. In this case they do indeed go for massive numbers expecting only a very few to survive and attraction has little to do with it.

Humans are somewhat different as we aren’t as completely governed by instinct as most other species (although the instinct is still there).

Well, I just finished “Origin of Species” and Darwin himself mentions several time the “doctrine of natural selection, or The Survival of The Fittest.”

Maybe Finch can explain it to me, since I know that many advances have been made in our knowledge of biology since Darwin.

Actually, Darwin proposed the idea of sexual selection.

The idea works indirectly, Lib. Some females find a certain trait more attractive than others. Sometimes those triats correlate to how “good” the males genes are. Those “good” genes cause the offspring of those particular female to have a better change at survival. The process repeats and becomes a feedback loop. The female is not doing this consciously, but the result is almost the same as if she were-- it just takes a lot longer.

“better chance at survival”

Yes and no; the ‘desire’ is programmed; consider the following dumb hypothetical…

A population of birds in which the males have a tuft of black feathers on the top of their heads.

A mutation occurs that, due to a convenient conjunction of enzymes during development, causes a number of effects; males with the mutation display the following characteristics:
The tuft of feathers is white.
The viability of sperm is enhanced.

Less significant mutations in the population happen to result in some females having an innate preference for black tufts and others having a preference for white ones (this isn’t a conscious or intellectual preference - it just happens that white tufts ‘push all the right buttons’ for some of the females)

The females with the preference for white tufts end up selecting mates who happen to be better breeders; this not only introduces selective pressure in favour of the white tufted males, but because the females contribute to the genetics of the opffspring, their innate preference for white tufts also enjoys favourable weighting. - The result is that, because the white-tufted birds happened to be better breeders, the proportion of offspring with white tufts will increase, but so will the population of white-tuft-preferring females, since they are the ones that are ‘choosing’ to mate with the better breeders.

Hope that made some sense - in reality, it could just as easily be the other way around with the genders, or a whole llot more complex due to multiple factors all at the same time.

Here’s another example:

Experiments have shown that humans consider facial symmetry to be a desireable trait in a prospective mate. This instinctive preference is a genetic trait. This is not a conscious decision that the subject thinks about. This is a genetic trait that is probably common to all modern humans. How did this come about? At some time in the past, some human (or some mammalian anscestor of humans) was born with a random genetic mutation that carried this trait. Since this was a random mutation, this could have been either something good or something bad. As it turned out, this preference for facial symmetry made it more likely that this ancestor would pick a healthy mate. For a variety of reasons, picking a healthy mate makes it more likely that any children produced will be healthy and well cared for. If this human actually survived long enough to find a healthy mate and produce children, they would probably pass the trait on to the next generation. And since this trait gave individuals a competitive advantage over individuals who didn’t have this trait, their descendents would gradually become a larger and larger portion of the gene pool of the species.

There is no intelligent decision-making behind this process. The only reason this quirk in mate selection is a survival trait is because it turns out that facial symmetry indicates that the prospective mate is more likely to be physically and genetically healthy than a mate with an unsymmetrical face. If this quirk was not an advantage, it would not have been propogated throughout our gene pool.

It wasn’t that some genetic ancestor figured this out and decided to act that way, and it’s not your DNA making a decision, it’s simply a case of a random genetic mutation providing a some ancestor with a better chance to produce successful offspring.

Don’t think of “fitness” as being strong, or tough, or anything like that. Those things can be part of fitness, but what fitness really is is the ability to have kids. And part of the ability to have kids is the ability to convince a member of the opposite sex to mate with you.

Take a peacock’s tail, for instance. A peacock’s tail is an advantage to him not because it helps him deal with predators, or because it’s correlated to some other trait. A peacock’s tail is an advantage to him because peahens think that a big, flashy tail is sexy. No other reason.

Now, why do peahens think that big tails are sexy? Well, suppose we had a mutant peahen who liked small, subdued tails. She mates with the most subdued peacock she can find, and the peachicks are disproportionately subdued, compared to the peacock norm. When the males grow up, they have subdued tails, and since most peahens like flashy tails, they have a harder time getting mates. So our mutant peahen has fewer than normal grandchicks, and her mutant gene for preferring subdued males eventually fades out of the gene pool. So we’re left with most peahens still preferring big tails.

Notice that the sexually-selected trait didn’t have to be a big, colorful tail. It could be anything perceptible to the females. Once sexual selection takes hold, it tends to run away to extremes. The initial impetus that started the runaway sexual selection could just be random genetic drift, which could affect any trait.

Your basic problem here is teleological thinking - that animal behavior is directed toward some goal. Instead, the evolution of animal behavior is the result of a process. Those animals that are genetically programmed to behave in a certain way - in this case, to be attracted to mates that happen to have good survival characteristics - are more likely to leave offspring, resulting in this behavior spreading through the population.
Rather than mating behavior, think of migratory behavior (as one example). A young bird that has never migrated before doesn’t undertake the journey because of hedonistic enjoyment, nor because it understands a warm climate and plentiful food will be its reward. It migrates because its ancestors that had this behavior survived, and because individuals that did not have this behavior died. This behavior has become programmed in by natural selection; the bird has absolutely no knowledge of any immediate goal (the tropics) or ultimate goal (survival).

See here for a discussion of teleological thinking in relation to evolution.

Well, most of the remaining members of a species would tend to have at least a subconcious worry about procreating. I mean, if a species had very little worry about perpetuating itself, the likelyhood of it being around still are very small.

This is classical sexual selection. The trait is selected for purely because it is attractive, not because it has any adaptive/survival value at all.

It might also be mentioned, however, that some theorists postulate that characteristics such as the peacock’s tail may evolve through what is known as the “handicap principal.” They are actually so elaborate that they are detrimental to male survival. Males that have very large tails thereby demonstrate that they are capable of surviving despite this handicap - that they must be super-good at finding food, resistant to disease, etc. And females select (not consciously, of course) these super-survivors.

Hmmm, makes you wonder that perhaps if these chicks liked small-tailed birds instead of mutant-tailed, maybe peacocks would be a whole lot more numerous/succesful than they are today? Evolution doesn’t always choose* the absolute best path for making the mostest and bestest babies, just whatever happens to be good enough at the time.

  • I know, I know - there’s no choice about it.

That should be a fairly good indicator that on the individual level, there’s little to no (and I lean towards the latter) logic devoted to choosing who to hit the sheets with or how to go about it. Logically you should drop that ridiculous predator magnet off your ass, not spend weeks on end smashing skulls with other guys on cliffs, or wasting 1/2 your time singing and doing some silly dance that will just as likely get you spotted & eaten than impress a chick.

I know it’s not a popular thought, but I just now wondered if perhaps the only examples of “conscious” breeding for specific traits (within your own species) on any kind of level might be the various attempts at human eugenics programs throughout history… none of which were very succesful.