Khantazm said:
So, possibly I'm looking for the explanation according to Richard Dawkins, but I'd welcome all points of view. Why do women dress more brightly (when men still do the courting), while in other animals the sex that is courting is more bright (and loud)?
I conjecture that it has something to do with the way that chromosomes determine sex. In animals where the gender is determined by the chromosomes, a pair of sex chromosomes determines the gender of the individual. There is usually one sex chromosome that is very small which the other sex chromosome doesn’t cross with. I’ll call that the unsocial chromosome. The other sex chromosome is large and tends to cross with other sex chromosomes like it. I’ll call that the social chromosome.
One gender has a matched set of sex chromosomes, which is called the homozygous gender. By matched, I mean that it has a pair of social chromosomes. The other gender has a mismatched set of chromosomes, which is called the heterozygous gender. By mismatched, I mean that it has one social chromosome and one unsocial chromosome.
The more ornamented gender is usually the heterozygous gender. I conjecture that is due to natural selection on the gene level. If two copies of the same gene are in the same individual, then the genes can augment each other. Therefore, genes in the social chromosome have a fitness incentive to pair with genes in another social chromosome. So genes that make ornamentation and which make the attraction toward the ornamentation have a better chance to survive than genes that don’t attract the corresponding chromosome.
Mammals are different from birds. In mammals, the male is the heterozygous gender. The male has an XY pair of sex chromosomes, and the female has an XX pair of chromosomes. Among mammals, the female tends to be the more ornamented gender. In birds, the female is the heterozygous gender. The male has a WW pair of sex chromosomes, and the female has a ZW pair of sex chromosomes. Among birds, the male tends to be the more ornamented gender. In both cases, the homozygous gender is the more oriented.
There are some other animals where the male is the homogenous gender. It appears to me that the homogenous gender tends to be the more ornamented.
I don't remember where I heard this conjecture. It may have been from Richard Dawkins, but I am not sure. In any case, it is a "gene centric" conjecture. The idea is that the genes in chromosomes that cross over to other chromosomes are more likely to be beneficial to copies of themselves.
Here are some links associated with sex chromosomes. The first presents the hypothesis that I just stated, although it doesn’t go into it in great detail.
http://www.ucl.ac.uk/mank-group/images/reprints/2011Evol%20DosageComp.pdf
“Is it possible that in ZW taxa, where the sex-determination system is predicted to favor the evolution of exaggerated male ornaments through female choice (e.g., birds and butterflies: Reeve and Pfennig 2003; Kirkpatrick and Hall 2004; Albert and Otto 2005), incomplete dosage compensation has enabled differential gene expression in males and females of other Z-linked loci important in sexual dimorphism to occur? To date, there are no data available linking gene expression levels of such sexually selected traits in butterflies and birds to examine this possibility.”
This link just says that in most animals other than mammals, the male is the homogenous gender.
http://en.wikipedia.org/wiki/Sex-determination_system
“The ZW sex-determination system is found in birds, reptiles, some insects and other organisms. The ZW sex-determination system is reversed compared to the XY system: females have two different kinds of chromosomes (ZW), and males have two of the same kind of chromosomes (ZZ). In the chicken, this was found to be dependent on the expression of DMRT1.[22] In birds, the genes FET1 and ASW are found on the W chromosome for females, similar to how the Y chromosome contains SRY.[11] However, not all species depend upon the W for their sex. For example, there are moths and butterflies that are ZW, but some have been found female with ZO, as well as female with ZZW.[20]”