Darwin personifies nature as “an active power” that affords better chances of occurrences for profitable variations. Changes in the conditions of life yield individuals with a wide array of variability. In this connection, the slightest differences in structure can turn the scale for the struggle of existence; individuals carrying desirable traits will survive and reproduce more. Thus, natural selection is a tool for “scrutinizing the traits”, rejecting the bad ones and preserving the good ones for subsequent generations. As one example, he states how natural selection “gives” grouse their particular color for preserving them from prey hawks, who are guided by eyesight. On a different note, he distinguishes this from sexual selection, which he calls something that depends not on the struggle for existence but on the struggle between individuals of one sex for the possession of the other sex. E.g., the male Guiana birds display their plumage to females whose primary criteria for the fittest mate is attractiveness.
Dawkins, on the other hand, is saying the same thing but blurs the line between the two. He asserts that natural selection operates in conjunction with sexual selection so as to enable “selfish machines” have as many surviving offspring as possible. The challenge comes when the asymmetry arises between the sexes as to who will invest more in producing the offspring, and that’s when sexual selection comes in handy. Females start off with the disadvantage of investing more in the form of a large egg and stands to lose more if the offspring dies than the male who can at anytime abandon without any cost; hence there must be some sort of evolutionary counter pressure against males. An example is the domestic-bliss strategy wherein females choose their males carefully, looking for fidelity and domesticity traits.
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wow your summary is very well written.I think you touched upon most of the main points with both Dawkins and Darwin. You clearly identify the difference between natural and sexual selection but just as a thought, isn't it strange that some sexual traits such as a male peacock's long tail feathers actually decrease the individual's chance of survival because of easy spotting of predators, yet females are more attracted to males with longer, brighter and healthier looking tales. It's kind of as if Natural and sexual selection are working at opposite ends. this is just my thought on it. good post!
ReplyDeleteYou use the example of the male Guiana birds displaying their plumage to females whose primary criteria for the fittest mate is attractiveness. Like the above stated... I feel that both work in tandom. If you think about the whole selfish gene theory you must ask yourself why then does sexual selection based on bright colors or long plamage in fact attract females? Isn't that a trait that a male could help pass on to another male child? Which then brings us to ask why would you want to pass on the brightest most beautiful colors to a male offspring if that is something that may in fact attract predators, and thus your offspring would potentially not survive? Just a thought...
ReplyDeleteThat was a very good summation of Darwin's view on Natural & Sexual selection. It is surprising how strongly sexual selection can affect organisms' traits, at the cost of reduced ability to avoid predation.
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