Wendee -- Look at Mark Ridley's The Cooperative Gene. He discusses how meiosis (and thus, on some level, sex) is designed to stop genes from 'cheating' as cells alternative between diploid and haploid states. Meiosis includes recombination (via crossing over) because the random reshuffling counteracts selfish behaviors of genes such as segregation distorters. The other aspects of sex such as gender -- and the advantages proposed by The Red Queen hypothesis -- are byproducts of the 'first' purpose of meiosis -- interfering with selfish behaviors by genes.
Karen Gerhart ----- Original Message ----- From: "Wendee Holtcamp" <bohem...@wendeeholtcamp.com> To: <ECOLOG-L@LISTSERV.UMD.EDU> Sent: Friday, April 03, 2009 8:16 AM Subject: [ECOLOG-L] clarification/ parthenogenesis & sex > Just to clarify, since a couple asked offlist, what I meant when I said sex > does not have adaptive advantage to the individual, that comes from this in > my basic Biology textbook: > > "Sex is of great evolutionary advantage for populations or species...However > evolution occurs because of changes at the level of individual survival and > repro....no obvious advantage accrues to the progeny of an individual that > engages in sexual repro. In fact recombination is a destructive as well as a > constructive process in evolution....The segregation of chromosomes during > meiosis tends to disrupt adv combos of genes more often than it creates new, > better adapted combinations... In fact the more complex the adaptation of an > indiv organism, the less likely that recombination will improve it and the > more likely that recomb will disrupt it. It is therefore a puzzle to know > what a well-adapted individual gains from participating in sexual repro > since all of its progeny could maintain its successful gene combinations > reproduced asexually" > > I understand that there are 2 reigning theories at present on the evolution > of sex. One is the deleterious mutation hypothesis (Kondrashav) that sex > purges a species of genetic mutations (for this to be an evolutionary stable > strategy, according to his calculations anyway, the rate of deleterious > mutations must be less than 1 individual per generation, which is right > about the rate that deleterious mutations occur in most species). > > The other is Van Valen's Red Queen hypothesis, which says sexual repro helps > individuals fight disease and parasites. The organism is in an ever present > red-queen-syndrome battle (running fast to stay in the same place) with > disease and parasites, and sex helps mix up the gene combos. > > What I'm TRYING To understand is where/how does selfish gene theory fit in > with all this. Sometimes selfish gene theory seems at odds with Darwinian > selection on individuals, but sometimes it doesn't. > > OK does that help clarify? Any insight??? :-) > Wendee > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > Wendee Holtcamp, M.S. Wildlife Ecology > Freelance Writer * Photographer * Bohemian > http://www.wendeeholtcamp.com > http://bohemianadventures.blogspot.com > ~~6-wk Online Writing Course Start Apr 11 & Jun 6, 2009~~ > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > 'Better to light a candle than curse the darkness'
