In the Chapter "How Sex Drives Evolution", Coyne describes Darwin as saying that females choose males based on "purely aesthetics". Coyne himself believes that female preferences are adaptive to types of males that help spread the female's genes. In your opinion, which is a more valid statement and why? Furthermore, consider the human species. Can you cite examples of how human females may choose their mates? Please relate to a biological theme.
To continue upon this topic, after consulting Campbell, is it selectively advantageous to have males exhibit elaborate ornamentation or perform rituals and have the female choose its mate? Or would a different system be more evolutionarily viable?
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ReplyDeleteI think the more valid statement here would be Conye’s in saying that females DON’T choose a mate based on aesthetics alone. There is evidence that female preferences are adaptive, with the goal being to choose males that help spread her genes. One example Coyne brings up is territories. Specifically he says, “a gene that tells a female to mate with males holding better territories gives her offspring who are better nourished or occupy better nests,” (162-163) which will in turn give the offspring a selective advantage since young that are better nourished and raised in better nests are more likely to survive and reproduce (compared to their less fortunate counterparts). Every generation will have more females that have the “preference gene,” (163) so the preference for males that have better territories will be higher. This relates back to adaptive preference because by wanting a mate with good territory, the female’s children will directly benefit. By not focusing on aesthetics of the mate alone and looking at these other variables, the female is doing what she can to give her kids the selective advantage. This relates to the theme of continuity and change because “changes in gene pools over time can be explained in part by natural selection for the fittest genotypes,” (COB) so female tendencies to select certain successful traits in mates (like a good territory) will strengthen over time if these choices provide benefits (like fitter offspring).
ReplyDeleteIn terms of the human species, I don’t think either Conye or Darwin was completely right. Because we are such complex thinkers and emotional creatures, a lot of the time when a female chooses a mate she isn’t focused on either gene fitness or aesthetics alone, but rather a combination of factors. Aesthetics may be important to some people, but a mate’s status and may be important to others (like, does the mate have a good job and money to ensure a secure future?). Another factor that doesn’t come in to play for other organisms is love, which is an emotional response that typically plays a big role in human mate selection.
In terms of the other part of the question, male ornamentation and mating rituals have always been around and many different types are visible in different organisms. This system does prove selectively advantageous because these displays and rituals communicate a male’s fitness to females. For example, male stalk-eyed flies are chosen by females oftentimes based on the length of the eyestalks. “Ritualized contests between males” (Campbell 1136) enables females to pick the males with longer stalks, which is significant because this ornaments “correlates with the male’s health and vitality.” (1136) So, because of the ritual between flies, the female can chose the healthiest and most genetically fit male (in comparison to blindly choosing a mate without courtship ornaments and rituals), so that her kids are more likely to survive and reproduce.
(additional source: http://www.evolutionary-ecology.com/sample/ffar2346.pdf)
NOTE: I posted this a few hours ago before Radhe, but the site kept messing up so I'm reposting.
ReplyDeleteI would agree with Darwin rather than Coyne when Darwin states that females choose mates on “purely aesthetics”. The reasoning behind my opinion is purely logical. Males often violate the most basic principles of Darwinism. For example, the Peacock has a large, colorful tail, that while pretty, is, at first glance, very harmful. The size of the tale hinders the peacock’s ability to fly, and also means that the tale is easily injured. The colors of the tail attract predators. The only reason the male peacocks have this tail is to attract mates, and therefore increase reproduction and evolutionary success(Coyne 145). So, if the tails of peacocks didn’t attract mates, it is logical to assume that these peacocks would have gone extinct. A species that has many harmful adaptations and can’t attract mates certainly wouldn’t survive natural selection. However, the fact that these peacocks still exist suggest that their tails actually do attract mates. Therefore, if these tails do in fact attract mates, then females are choosing their mates on purely aesthetics. Why would a female choose a mate that’s maladapted? She wouldn’t. So, the fact that these peacocks still exist shows that females choose the peacocks for purely aesthetical reasons.
Human females choose their mates in unique ways. Looks, financial wealth, religion, personality, etc. all are important measures for females in choosing males to marry/reproduce with. Each female probably has different criteria for choosing a male, but it’s safe to say that most women choose the fittest(tallest, strongest, best looking, smartest male). Therefore, the men with the best genes(tallest, strongest, smart, etc.) reproduce the most because those guys get the most girls. Therefore, these particular genes are passed down from generation to generation more often. This is evidenced by the fact that the average height of humans has increased by a few inches in the last few hundred years. This relates to the biological theme of continuity and change because similar genes and traits are passed down continually, but at the same time mutations cause changes(in this case, there are still lots of short people) that create new genetic combinations(new in the sense that the genetic makeup differs greatly from parents).
With regards to the last question, this question relates to our first biology unit of the year, animal behavior and ecology. We extensively studied various behaviors and other actions that are selectively advantageous to animals. I’d say that it is more selectively advantageous to have males vie for the females and then have the females choose their mates. This doesn’t necessarily have to do with elaborate ornamentation, but a common male behavior/ritual is to fight with other males in order to “win” the female. For example, male eastern grey kangaroos engage in a fighting ritual to see which animal is best for the female; this is an example of agonistic behavior. The female then mates with the male that proved to be the strongest(Campbell 1136). This is definitely selectively advantageous for the female because her mate is now the best fit to protect her and the offspring as well as find food for the family. Overall, these mating rituals result in more evolutionary fit males mating with females, which is clearly a selective advantage; mating with weaker or slower or dumber males would be less evolutionarily advantageous for the female.
I believe the more valid statement generalizing the animal kingdom would be Darwin's argument that females choose mates based on aesthetics only. As Malis stated in his post, the males of many species such as peacocks develop elaborate displays and coloration in order to attract a mate. I would argue that these displays actually aid the female in choosing the most fit mate however, as elements such as the colorful plumage of male greenfinches offer indicators of the health of organism overall. In the case of greenfinches, the carotenoids that provide the bright coloration of male greenfinches indicate the the strength of the male's immune system, a trait that would both aid the female in choosing the best mate. (http://www.ncbi.nlm.nih.gov/pubmed/12647136)
ReplyDeleteHuman females also choose mates on a variety of factors that indicate the male's viability in the gene pool. Which traits the female prefers tends to differ between individuals. Females would generally gravitate toward traits that would both endow the child with better genetic material as well as better care for the child. For this reason, strength, intelligence, and wealth are common factors in selecting a male.
I would have to argue that coloration and ornamentation would be the best traits for males to utilize in attracting a mate. While the coloration could make the male vulnerable to predators, coloration provides a fast visual indication to other organisms of the male's health and results in less antagonistic behaviors that could result in limiting the species population. Also, the dangers that bright coloration can cause can be limited if coloration is only displayed during the mating season through regulation of the bright coloration with external stimuli that indicate the mating system, which connects to the biological theme of regulation. Territoriality obviously limits the specie's population in that each individual organism requires a larger tract of land. Territoriality is also much more difficult for the female to judge than coloration. Fighting could result requires a great deal of energy expenditure and could possibly harm the winning male, which would limit the male's ability to raise the child after copulation.
I agree with Kevin and Ray that Darwin's explanation that a female preference is "purely aesthetics" is the more valid argument. I do not think that females look for males that could help pass on the female genes, but rather males with superior genes so that the offspring possess those same genes. Like both Kevin and Ray mentioned, males are often very colorful even though bright colors not only attract females but predators too. In some cases, like with peacocks, I believe coloration is solely a way to attract females, since (as Kevin said) peacock tails pose huge difficulties in flying and escaping predators. The females are attracted to the males because they are beautiful. Mating with attractive males also ensures that the offspring of the female too will be attractive and able to find a mate. As Ray mentioned, the coloration of greenfinches indicates health, and so females tend to choose males with bright coloration. Here, too, I think preference for coloration may have risen from aesthetic beauty, but eventually became an indicator of fitness. Again, this would ensure that the offspring will possess these fit features of the male. The female is not invested in spreading her own genes, but in spreading the male genes to her offspring. As Radhe, Kevin, and Ray all said, the idea of coloration and attracting females has everything to do with the theme of continuity and change. Males that have the right attraction and females that have the preference gene will pass their genes onto their offspring, thus producing more flamboyant males and choosy females. However, males that do not possess the right amount of color, or eyelets, or the right length tail, will not find mates and therefore their “bad” genes will not be passed onto the next generation.
ReplyDeleteI think for humans, like Radhe said, females tend to choose males based on both aesthetics and a male’s genetics and success. Females are first attracted to males according to their appearance. Like Kevin said, many women look for men who seem fittest—strong and better looking. But like Radhe said, humans are very complex creatures, and I agree. For that reason it is not enough to say that women choose their partner solely based on aesthetics, though looks often display a person’s health. Similar to the territory factor that plays a role in the choosing of a mate with animals like the red-winged blackbird of North America, women tend to choose a mate with a good occupation and/or financial background. A male’s success can show the female that both she and her children will be cared for.
Finally, in my opinion, even though male coloration and ornamentation can attract predators, these features are a selective advantage, aiding males in attracting a female mate. As Coyne reinforces in this chapter, “the currency of selection is not really survival, but successful reproduction. Having a fancy tail or a seductive song, doesn’t help you survive, but may increase your chances of having offspring” (148). So although flamboyant features like long tails or bright colors attract predators, they also help attract mates. What good would it be for an animal to survive without attracting females to reproduce with? There would be no advantage; these individuals would not be able to pass their genes onto the next generation. Bright coloration and mating rituals are a huge selective advantage because they can aid a male (or female) in reproduction. I believe that coloration and males fighting to “win” a female are both good methods of mate selection. Both methods have their pros and cons, and I do not see one as being better than the other. Overall, though, these methods are selective advantages for mate selection, and seeing that both methods have “passed” the test of evolution, coloration/ornamentation and competition prove to be good mating behaviors.