Sexual Selection, Stasis, Runaway Selection, Dimorphism, & Human Evolution

Just to throw an idea out there, some time ago I read an interesting paper on the the hypothesis that hairlessness is a side-effect of increased testosterone.... in human females. In other words, increased female sexual agressiveness (which would tie in to the relative lack of sexual dimorphism in humans, perhaps) led to hairlessness, rather than it being a selected trait.

Interesting hypothesis, and it relates to the male-pattern hairiness in women (see Message 41) being caused by androgens (going the other way). Here I disagree. It may be the mechanism for the feature that was selected, or there may be some other mechanism, but the fact remains that the feature was selected.When there are genetic anomalies in individuals, the survival of the anomaly in the genome relies on the individuals being selected for (1) survival (2) breeding.And in this case we still see a marked preference for more "bare-appearing" women. Otherwise depilatories, razors, waxing and other removal systems would not be necessary.I do not see a mechanism selecting for more testosterone in females, and would expect rather that this would be counter-selected by the impact on reproduction ability. Rather I would expect this trend to be tolerated to produce the desired result.Thanks

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we are limited in our ability to understand
by our ability to understand

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RebelAAmerican.Zen[Deist
... to learn ... to think ... to live ... to laugh ...
to share.

from {Criticizing neo-Darwinism} thread
EvC Forum: Criticizing neo-DarwinismIf we need to segregate sexual selection from the discussion.

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Yes, the difference between male combat and female choice (the 'old' terminology) is the same as the difference between intra- and inter-sexual selection. Sorry for not noting your recognition of this.

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IS IT?Does anyone in this thread have an opinion on
Science and Politics
? or did I just miss reading about it here on EVC?This seems to have been what was on reply as to if Darwin was maligned or not but the response to that was a, "I know but..",there is another quote where the difference in this trait is ...(current issue of SCIENCE).other links
Page Not FoundRochester Review • University of Rochester

Good find Brad.
I am going to have to spend some time on this and put together a cogent analysis once I get the time to read everything you linked - hopefully this weekend.I once did an independent studies project on Sexual Selection back in the 70's and it still tickles my interest.EZ

Great,because I have started to make up my mind!!It has always been curious to me why "emlenisms"
Page not found | Department of Neurobiology and Behavior
held so much weight at Cornell. I also have my human personal experience which definitely tends towards investment prior to conflict but I will have to WORK to keep my personal bias out of it. In any effect I will guess that game theory *can* get around some "older" visions of the subject. I can not see how it matters whether Darwin was misinterpreted or not.This is what Bruce Wallace had to say about it in 72 from Prentice Hall
The titles to these volumes are listed on the third thumbnail. Wallace's discussion is relevant to the comments in SCIENCE this week on a "within generation 'integral'." The area I boxed in, is likely the reason that Sheldrake finds Gould's writing as coming to a boring point. Gould is constantly transitioning through this phrase of Wallaces'. Daphina may be "brinksman" but a decision really is not.This message has been edited by Brad McFall, 05-11-2006 04:43 PM

I can see the "need" to branch off "criticizing" neo-d into a particular discussion of sex selection because in the book by Stove, I cited in that (other) thread, Stove speaks of a category of organisms that are baby snatchers/mother's with snatched babies. In my personal case it was one of sperm sneaking etc and this seems to fall within Roughgarden's notion of investment prior to conflict (no one sperm CELL can be in conflict principle of BSM)which IS NOT sexual selection. So I can see a challenge to sexual selection that is independent somewhat of my challenge to neo-darwinism in general which is rather about "general welfare" vs the economics of biological change etc.So in this particular context I would like to add what Bruce Wallace %reall% means as far as I can DELIMIT and FOLLOW it. I have posted the last few pages in his first volume above and now I would like to add the last paragraph before that section. It reads,

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"Because decisions, even when properly made, can err, the routine decision-making process outlined here is most useful in arriving at trivial decisions, which if wrong lead to remediable, not irreparable, consequences. Decisions that may lead to irreparable harm, such as a decision to play Russian roulette, as the following essay emphasizes, must be made by extraordinarily thoughtful, not routine, procedures."

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The problem of sexual selection as primative or derived IS one of possible "irreparble harm" NO MATTER HOW MUCH ADAM SMITH one finds in the base of evolutionary thought. Having been in psyche hospital, jail for state charges in Lousinana, rejected by Cornell, lover, and family, I have given more thought to this decision about the sky over Ithaca than Wallace. But it is a decision that must be made in real time every time nonetheless.

Regarding this book by Joan Roughgarden, Evolution's Rainbow.
I think it falls very short of a credible attack on sexual selection theory.Does sex role reversal occur in the animal kingdom? Of course, but it has specific ecological correlates that result in a reversal of the asymmetries between male and female. Females become larger than males and take on the aggressive behaviors. Males become specialized in parental care. We see this in the polyandrous jacanas and pharalopes. This does not mean that the ”normal’ asymmetries reflected in conventional sex roles are not important forces in shaping male and female behaviors.Is the term ”gender’ useful or merely anthropomorphic as the author claims? I say the former. It is valuable to distinguish between ”sex’, meaning ”gender alignment’ and ”sex’ meaning meiosis plus recombination followed by fertilization. Gender has consistent morphological and phsyiological implications across taxa. It is not a useless anthropocentric term as the author wishes to contend.Are same-gender sexual interactions ”normal’ in many animals? Yes. Does this type of interaction have social functions and value in reducing aggressive interactions? Yes. Does that in any way negate the validity of sexual selection as a powerful force shaping behavior and physiology? I think not.The asymmetries between the sexes, starting with the differential investment in gametes (anisogamy), and ending with differential investment in parental care, create many incontrovertable conflicts between the sexes that are resolved in different ways in different species. The author attempts to dismiss the significance of these differences in a very unconvincing manner.Why did internal fertilization evolve? To give the female greater control over the fertilization process.
Why are >90% birds monogamous?
Because of the energetic constraints of bird parental care that reduce brood survival dramatically if both parents do not invest in rearing.
Whay are >90% of mammals polygynous?
Because the female’s mammary glands represent a specialization for rearing altricial young that facilitates her early abandonment by the male.This author clearly has a political axe to grind because of her own gender reversal. She has provided no credible argument against the importance of sexual assymetries and sexual selection in evolution, only decided quite subjectively to devalue them in favor of vague ecological alternatives.Sperm ARE cheaper than eggs - if they weren’t, polyandry would be just as frequently observed a mating strategy as polygyny - but it is very, very rare indeed.
Females ARE more choosy about mates than males, because of their greater investment in oogamous reproduction.
Males ONLY start becoming choosy in *monogamous* mating systems when they are required to make comparable or greater investment in parental care to ensure offspring survival.
Males ARE larger and more aggressive in polygynous systems because of having to compete for females and defend them or their resources.
All these trends are undeniable to anyone who has studied mating systems across a broad number of taxa.Sexual selection remains without parallel as the most convincing and consistently effective mechanism for explaining sexual dimorphism and gender-sepecific behavioral differences in nature.Finally, the press articles you linked popularizing this book are among the worst lolly-gagging, insipid, non-critical, ”awestruck by ignorance’ tripe that can pass for coverage of science in the press.Just my (not so humble) opinion - you asked for it This message has been edited by EZscience, 05-12-2006 10:05 AM

Is there a credible difference of social selection and sexual selection within a nexus of artifical and natural selection?That seems to me to be the question.In trying to make a case of the interactions that *might* occur in species selection Gould relates (SETH p 732)

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This crucial condition can be validated at the organismic level- not because mutation represents a process so differnt from natural selection, and operating on material (the structure of DNA)so disparate from the bodies of organisms (integrated tissues and organs), that we cannot postulate a reason why favored directions of mutation should correspond in anyway to the needs of organisms.

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I have no way of juding the gender role reversal of the author just as I can have no expectation that you or anyone else %should% believe me that I am inclined to social selection particularly because the conflict in my own reproductive effort happened AFTER not before agreeable sex. I do not know for sure how it happened in my lovers' mind but that is never what I have access to anyway.So now to your observation.Perhaps I should not have directed EVC to the links but should have copied some of this:
SCIENCE(see below)What I was trying to ask you when you related

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male combat and female choice (the 'old' terminology)

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intra- and inter-sexual selection

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was the difference of social and sexual selection.It seemed to me that a priori one might consider male combat and female choice as not only intra-sexual selection and that inter- sexual selection, (perhaps you can say again what you meant by that ( that might be my only issue here, I dont know) if it did not consider social selection of Roughgarden et al, can not accomodate any reverse asymmetry (your word) capability of +> and 0+ no matter what the origin of sex itself was. Thus I do not think that I am disputing the notion of "gender."

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Published this May by UC Press, Evolution’s Rainbow calls for the “outright abandonment of Darwin’s sexual selection theory” and posits a new theory of “social selection” to take its place.

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Page Not FoundI do not see the real issue as being about role reversal. Correct me if I am wrong or have misread what your are writing. It seems to me that what is at issue is if something we might only be thinking about as artifical selection is an "aspect" of natural selection due to 'social' aspects AFTER the arrival of the molecular existence of sex (thus why it matters if sexual selection is primative rather than derivative (if "yes" than Roughgarden and I would be wrong (as argued in this thread) but if "no" then... well...))which would ipso facto then imply a different ESS (evolutionary stable strategy decided) division.This came out by Roughgarden et al explaining to the letters to SCIENCE in VOL312 p 694(see tumbnail below) where they named "old fashioned" ESS and their version, which includes "strategies developed in behavioral time". So when you say,

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it has specific ecological correlates that result in a reversal of the asymmetries between male and female.

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is the "ecology" meant in the 'old' fashioned of Roughgarden sense?You also said,

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The asymmetries between the sexes, starting with the differential investment in gametes (anisogamy), and ending with differential investment in parental care, create many incontrovertable conflicts between the sexes that are resolved in different ways in different species. The author attempts to dismiss the significance of these differences in a very unconvincing manner.

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The only way right now that I can start to figure out what you mean is if Gould is wrong and that I am free to explain how favored mutation directions correspond with organismal needs, which I am tempted to do but is not due if I have misread you. This message has been edited by Brad McFall, 05-12-2006 03:15 PM

I am not sure I can respond adequately to all your points here, but I will start with what I feel I understand. I think these dichotomies are worthy of some consideration.I see social selection as a force imposed by advantages/disadvantages mediated by the social structure specifically. I am in favor of a narrow definition, but I see social selection as acting on behavior that is both dependent and independent of gender. In contrast, all sexual selection is gender dependent and it can occur independent of any social structure at all.The next dichotomy is a little more ambiguous, simply because by ”artificial’ we imply a ”human-mediated’ effect. Since our social environment is mediated ONLY by human interactions, it is hard to classify ”social selection’ as anything but a form of (unintentional?) artificial selection. That’s pretty typical, from my experience I am not sure I follow this, but let me clarify.By ”intrasexual selection’ I am refering specifically to conflicts within one gender that influence their access to, or mating success with, the other gender. So its pretty much always based on competition or conflict, direct or indirect, between members of the same sex.By ”intersexual selection’, I mean active choice of mates, normally the female being the choosy one, but not always. One sex selectively influencing mating opportunities, and hence genetic fitness, in the other. In monogamous systems it becomes reciprocal once repoductive investment is equalized by male parental care. The landmark experiments by Anderson on the widow birds in Africa showed beautifully how this type of sexual selection can produce to the runaway effect hypothesized by Fisher and lead to exaggeration of a ”favored’ trait in the selected sex, in this case tail length.I think these are valuable concepts with great explanatory power that are consistent with a lot of observation and evidence and they certainly haven’t been debunked by M(r/s) Roughgarden who wants to replace them with her concept of ”social selection’. The traditional sense, as in the Orians-Vernier polygyny threshold model. For example, polyandry is strongly correlated with inhabiting very poor habitats. A female needs to enlist the help of many males to successfully rear a brood, or must defend such a large territory to have sufficient resources that she doesn’t have time to brood the eggs. Thus, in jacanas large aggressive females defend large territories against other females that contain many smaller, inconspicuous males that each brood a nest of their own. Females are always trying to steal males from each other so they can start an another nest. In this situation, males become choosy about the female they hook up with, and females welcome all newcomers.It seems from reading the first page of this article that she and her colleagues are really only challenging the ”notion’ that female choice is necessarily based on ”genetic quality’. I don’t think this is a very deep challenge to the theory. There have been plenty of models showing how females can potentially choose on the basis of traits that are negatively correlated with fitness. I am sure you are familiar with Zahavi’s ”handicap principle’ and its recent resurrection. Indivdual females may also simply make the wrong choice as a function of their own sub-optimal genetics. And when there is reciprocal intersexual selection, both sexes have to ”settle’ for a mate that is commensurate with their own level of fitness, at least when the situation reaches equilibrium. So I don’t see that conventional sexual selection theory faces any difficulty in “sustaining a stable genetic hierarchy within a gene pool in the face of continued directional selection for high-fitness genotypes”. There are many constraints on directional sexual selection and SS-traits are ultimately limited by their survivability. And from whence the assumption that this perceived hierarchy is necessarily stable? This is a straw man argument and it wouldn’t have made it into science if it hadn’t had some novel application of Maynard Smith’s game theory.I hope this clarifies my take on the issue, but I am not sure I understand how you see this as relating to “favored mutation directions”, or in any way contradicting Gould. I’ll have to pull out my copy of “Structure..” and look through it for his passages on SS.

Great-This pretty much cleared up my questions. I was trying to get a sense of your take as *possibly* different than RAZDs'. Razd can now correct me if I say something misrepresenting him. Don’t worry about the mutation direction area just yet if you don’t want to, that is just me.Seeing that you do see some possibility for some notion of "social biology", I can redress any other points I want to make appropriately. It was just strange to me that the particular example you and Razd were discussing was the same as brought up in the letters to Science (I didn’t show those yet).As far as I read it Roughgarden et al were only trying to set up an "alternative" to be tested against. I did not see evidence of "debunking" but I CAN say that the attitude of the whole relation of the neurobiology and behavior dept to the PSYCHOLOGY dept at Cornell is related to sexual selection, pretty much in exclusion to any REAL WORK in social biology(Cornell established a "BIOLOGY AND SOCIETY" dept instead), and this despite the writings of Wallace on the very thing. There is not enough cross over into the depts. of ecology ,evolution and systematics and I can see the reason has to do with how MATH not physics or chemistry is involved is the reason. The biologists simply have not "decided" to try to do so and because they have the "psychologists" on this side there is little academic social reason to do so. Roughgarden did. I new of Roughgarden's work on lizards before reading this. And in fact if you wait for a bus in Florida one can end up in "conflict" with a Brown Anole MALE, that will flash its dewlap if you just repeatedly point a finger at it and in that case I was just trying to go to the doctor, I had made no "investment" to seek out the lizard(as I had done on many other "herpetological" occasions). I was just standing there and it started in on me. I think the mate should have "remembered" that it was really on a pole in CUBA (ha ha, as if lizards were us...).This message has been edited by Brad McFall, 05-13-2006 07:12 AM

In Message 1 of How Evolution changed humans’ appearance on Proposed New Topics WJK writes:

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Theme: How evolution improved human beauty!

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In our society we not only see beauty or attractiveness in the bodies of other people, but we mentally grade it and in some cases measure it in the form of beauty competitions for females and body development competitions for men amongst other competitions centred around appearance of our bodies. An outstanding competition for females is the Miss World competition for beautiful women from around the world. The winner of a Miss World competition must be considered near the pinnacle of female beauty.

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If we could determine the genealogical lineage of Miss World, we would see that lineage going back generation by generation without a break back to a single living cell, but for our purposes here, consider the line back near to the start of our species, say some 200,000 years ago. The line would be through a female at every generation, some tens of thousands of generations. Let’s choose a random generation at about the 200,000 year mark and give the female mother of that generation the title MotherOne. We can call her partner in producing a daughter for the next generation, FatherOne.

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My limited research does not allow me to conjecture up images of MotherOne and FatherOne of that generation, but I would guess that in appearance they would be closer to other Great Apes than to Miss World. So what happens during the succeeding generations that changes the images of the women to finally arrive at Miss World.

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The daughter of MotherOne and FatherOne inherits physical characteristics from both parents through Chromosomes X and Y and introducing FatherOne into the line could make significant changes to the child’s appearance, but they need not improve her appearance or beauty level. But there is the possibility of another factor being introduced into the biology of the child, and that is the introduction of a hereditary mutation. The probabilities of a mutation effecting an improvement in the appearance of the child may be very low, but as it can occur at every generation, in tens of thousand of generations the probabilities improve.

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As the generations from MotherOne unfold, changes in the appearance of the progeny are affected by the factors mentioned above, but is there another factor that may have a greater effect on the appearance of Miss World’s female ancestors? At each generation Motherx will have a Fatherx from the local male population. In many of those generations Motherx will have a choice for Fatherx and may well choose according to the beauty level of available and suitable adult males in the local population. This introduces a bias in favour of increased beauty in many succeeding generations, culminating in Miss World.

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If we accept that in Miss World’s earlier generations humans recognised beauty levels in each other, then the above hypothesis may be reasonable, with mate selection being a strong driving force. I wonder if recent scientific research throws any light on the hypothesis.

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WJK in Adelaide, South Australia.

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The answer is sexual selection. See Message 1, and see how there are several aspects of human evolution that show evidence of runaway sexual selection, selection that is still ongoing ... seeRunaway sexual selection shows up as a skewed selection towards one extreme end of what is available within the breeding population, where the desired trait can actually be outside the realm of availability, while normal selection would show up as a normal curve within a breeding population.
Enjoy

RAZDSexual selection is basic to my hypothesis. As humans developed through times of cavemen to tribes to villages, etc., the breeding population increased and my Motherx had a greater selection of possible Fatherx and these increased populations increased the chance of a suitable male having increased attractiveness through hereditary mutation.
Could you expand on "runaway". The meaning escapes me!!!!
Regards
WJK

Well, there is some of that, but a good portion of what constitutes beauty is not hereditary. Some of it is likely diet, exercise, surgery, makeup, and maybe even extensions and some Photoshop. The video seems to illustrate that quite well.I suspect that applies to Miss World as well.

That's when sexual selection causes the species to evolve a trait that otherwise is not useful for survival. The poster-child is the Peacock's tail. It doesn't aid them in survival, and in fact it is actually costly for them to produce, but since the chicks dig it, the sexual selective pressure makes it happen anyways.Here's a link:Page not found