Tuesday, September 29, 2009
Evolutionary Stable Strategy
In the Selfish Gene, Dawkins describes the concept of the evolutionary stable strategy (ESS) as a strategy that depends on the actions of the majority of individuals in a given population in an attempt to maximize their own success. As the strategy continues, it evolves and it cannot be bettered by an altering strategy, “selection will penalize deviation from it.” (Dawkins, 69) Fisher applied this concept to sex ratios, arguing that an equal sex ratio (50:50) is an ESS. We can imagine a scenario in which males could bias sperm production or females bias the rate of fertilization as to favor the generation of one. Both Dawkins and Fisher counter such scenario by stating that following an environmental change or instability, an ESS will be achieved again. I believe that sex chromosomes favor an equal sex ratio as an ESS. Fisher supported this by explaining what the outcome would be if a specific gender persisted, reproduction would decrease and the opposite gender will bias its generation, thus equalizing the ratio. One could think that cytoplasmic elements are an ESS, however this cannot be true because all elements are not used equally and tend to favor one sex over the other.
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So far you are the first one that has said the sex chromosomes are a 50:50 ratio. I also had wrote that they were but by reading what others had said I am leaning more towards them being biased.
ReplyDeleteI understand where you're coming from when you say that sex chromosomes favor equal sex ratios but have you thought about them having bias ratios because they choose between male or female?
ReplyDeleteI understand your point -and Fisher's in that sex chromosomes should favor 50:50, in fact we see that in nature. But, is it posible in theory, to say also that sex chromosomes could favor a sex ratio that maximizes reproductive success? I believe now that it dependes on the species' and mating system that is considered.
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