Human Males Evolve At a Faster Pace Than Females

Tisha_AH writes "A report by the Whitehead Institute indicates that the human Y chromosome present in males is evolving at a furious pace. Across the chromosome there can be as much as a 33% difference within humans alone. The portions of the chromosome evolving fastest are related to sperm production."

Comments

interesting factoid:

[circletimessquare]

testicle size in simians is correlated with female permissiveness. such that, in chimpanzees, where a female in estrus is pretty much a gangbang, chimpanzees males have evolved humongous testicles. they need to, because in such a situation, the only strategy available to the male to ensure his genetic continuance is to simply overwhelm other male's sperm with sheer ejaculate volume

meanwhile, in highly monogamous simians who mate for life, such as gibbons, the testicles are tiny. there's simply no need for so much ejaculate volume, its a waste of resources. she's not going anywhere

interestingly enough, human males have intermediate sized testicles, owing to the fact that human females are semi-monogamous/ semi-polygamous

however, i've always wondered why testicles appeared on the outside of the male mammalian body. it seems a ridiculous vulnerability and i've never heard a good explanation as to why. for example, dolphins aren't swimming around with their balls out: the need to be streamlined. of course sperm need a lower temperature to develop, but thats an effect, not a cause. i'm saying wouldn't it be better to have your testicles inside your body and evolve sperm that develop at a higher temperature? its pretty ridiculous to have such an important organ dangling outside unprotected. i never understood why

Re:Males are not a population

[Anonymous Coward]

Male-only sexual selection has been seen before. I can't remember the species, but its sperm has become cooperative, not swimming solo like your regular sperm, but hooking up in huge clusters, so they can swim faster than the sperm of the competition. Although that case was related to promiscuity, you could theoretically even get effects like this in monogamous species, although at a far lower pace. Suppose a mutation in one sperm stem-cell makes its y-chromosomes contain some useful trait. Then its offspring might stand a better chance beating other sperm from the same individual even.

Re:So from what I can gather...

[TheRaven64]

Mod parent down. The point he made is entirely wrong.

According to the grandparent's hypothesis, genes would mutate more frequently in men than in women. Genes that are shred between the genders would mutate more in men than women, but in each child a mixture of the more-mutated and less-mutated genes would be provided by the two parents and so they would average out. The genes only present in the male (i.e. on the Y chromosome) would not have this averaging effect and so would contain a higher total level of mutation. X chromosomes inherited from the male parent in women would be more likely to be mutated than the ones inherited from the mother. Y chromosomes do not appear in females, so they would only come from the father and would be subject to a greater amount of potential mutation. Multiply this by a few thousand generations, and you'd see a greater level of mutation in the Y chromosome than in the rest of the genome which is exactly what TFA says is seen

The grandparent produced a hypothesis that supported the observation. The next step according to the scientific method is to design a test that would contradict the grandparent's hypothesis but not the observed evidence. Not simply to say 'mod parent down'.