In the New York Times, Piet van den Berg and Tim W. Fawcett tell us that it is a near universal phenomenon in human cultures that human parents try to influence their children's choice of mates, and since it is universal there might be an explanation from evolution for this behavior. So they computer-modeled this. Simplified, evolutionary success - having more successful offspring - means parents invest in their daughters' children, and this leads daughters to be less picky about choosing men who will help them raise children and further this results in parents' trying to pick more responsible son-in-laws.
The first problem with this is that cultural evolution would produce exactly the same results - that is, this behavior need not be encoded in our genes, but in our cultures.
But there is a bigger problem. The authors tell us:
To my dismay, what Google gives first is this:
http://www.sciencedirect.com/science/article/pii/S0003347207005301
Now, Google is perhaps a bad way to approach this, but for something so central to this evolutionary theory of sexual selection, I would have thought that the research was all done and settled and much before 2008. It seems to me that these just-so stories from evolution have made a huge number of people forget what science really is - it is not a set of plausible stories that work in computer simulations (or in mathematical computations); it is the confrontation of theory/model with the real world. Figuring out how evolution works is not a matter of coming up with plausible scenarios. This same rot we see in particle physics. Given that the theory of sexual selection "has been hugely successful", I'm hoping there is a whole literature out there that sews up the case of the peacock's tail.
The first problem with this is that cultural evolution would produce exactly the same results - that is, this behavior need not be encoded in our genes, but in our cultures.
But there is a bigger problem. The authors tell us:
When thinking about mate choice, the natural starting point is the theory of sexual selection. This theory, which focuses not on the struggle for existence but on the competition to attract sexual partners, has been hugely successful in explaining the diverse courtship behaviors and mating patterns in the animal kingdom, from the peacock’s flamboyant tail to the chirping calls of male crickets.We are told that the evolution of the peacock's tail can be explained by the peahen preferentially choosing to mate with peacocks with more flamboyant tails. This is a nice, intuitively plausible theory, and it leads to a definite prediction about the observable behavior of peahens. So surely there is an extensive literature of peafowl observations confirming this nice theory.
To my dismay, what Google gives first is this:
http://www.sciencedirect.com/science/article/pii/S0003347207005301
Peahens do not prefer peacocks with more elaborate trainsFurther search reveals that what peahens do is still a matter of some controversy. Also, putting aside whether peahens prefer peacocks with more elaborate trains or not, in an experiment with peahens randomly mated with peacocks, those matings with peacocks with more elaborate trains produced more eggs (so maybe something else is at play, not sexual selection).
Animal Behaviour, Volume 75, Issue 4, April 2008, Pages 1209–1219
Now, Google is perhaps a bad way to approach this, but for something so central to this evolutionary theory of sexual selection, I would have thought that the research was all done and settled and much before 2008. It seems to me that these just-so stories from evolution have made a huge number of people forget what science really is - it is not a set of plausible stories that work in computer simulations (or in mathematical computations); it is the confrontation of theory/model with the real world. Figuring out how evolution works is not a matter of coming up with plausible scenarios. This same rot we see in particle physics. Given that the theory of sexual selection "has been hugely successful", I'm hoping there is a whole literature out there that sews up the case of the peacock's tail.
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macgupta 81p · 598 weeks ago
Peahens do not Prefer Peacocks with more Elaborate Trains
Traditionally, peafowl experts believe that the male train is the major morphological trait that directly influences mating success. In class, we discussed the possibility of the elaborate peacock train as a signal to coax females or potentially as a status of reproductive success of an individual. The train is an elaborate morphological characteristic and can vary in length and number of ocelli (eyespots). It is thought to have continually evolved in response to female preferences in mates and could be an indicator of males with “good” genes associated with a high reproductive success rate. However, there is evidence both for and against the male train as an indicator of mating success and there is no consensus as to which characteristics of the train are most favored by females. The purpose of this study was to investigate whether peahens prefer peacocks with longer trains or more ocelli, if symmetry of ocellar arrangements affects male mating success and if the male shivering train display affects male mating status.
Researchers defined male mating success as the total number of copulatory events per year. They determined male mating status (rank) based off of female courtship behaviors. Females made frequent visits, termed “run-rounds,” to preferred peacocks prior to every copulation. Each train was photographed to determine the number of eyespots present. A fluctuating asymmetry (FA) index was calculated for each train to indicate the degree to which the eyespots were symmetrical. Complete symmetry was assigned an FA of 0; the smaller the FA, the more symmetrical the train. In addition, researchers looked for “shivering” behaviors which were classified by a peacock that would shake his train in the direction of a nearby female to produce a rustling sound.
Over a seven year period, results showed that train length and the number of eyespots were not related. The length of train had no effect on variances in mating success. In a comparison study of those peacocks that were predated upon versus those that survived, there was no difference in number of eyespots. However, train length in predated males was significantly greater while FA indexes were only slightly greater. More successful males did produe more bouts of shivering and spent a longer amount of time shivering. Since this shivering was provoked by female “run-rounds,” it was deemed dependent on female presence.
The results of this study contradict previous studies that concluded that: male train morphology positively influences mating selection, mating success increases as the number of eyespots increases and males with longer trains showed greater survival rates. In the present study, females did not choose males with a greater number of eyespots nor did they prefer males with symmetrical ocelli. Ultimately, none of the male train measures consistently influenced female preference.
This study produced no evidence that supported the claim that peahens express preference for peacocks with more elaborate trains. Researchers concluded that peacock trains were not the universal target of female choice. They speculated that the male train is a characteristic for which female presence has waned over many years; however it still exists because it is some sort of cue to receptive females. In conclusion, peahens are likely to choose mates based on cues other than those exhibited by the peacock train.
Takahashi, M., Arita, H., Hiraiwa-Hasegawa, M., & Hasegawa, T. (2008). Peahens do not prefer peacocks with more elaborate trains. Animal Behavior. 75, 1209-1219