I want to understand the concept of fisherian runaway. Dawkins' book tells about this, but it's not clear enough. It can be seen that the essence of Fisher's idea is that when a male peacock with a large tail leaves offspring, these offspring receive not only large tail genes, but also genes of “love for big tails” in females. But it is not clear how positive feedback follows from this.

Let's consider a simple model. There are 100 males and 100 females in a peacock population. 80 males have long tails, 20 males have short ones. 80 females prefer long tails, 20 short ones. Further, obviously, 80 first males and 80 first females will give offspring with long tails, and accordingly 20 males and 20 females - with short ones. Thus, in the next generation, 20% of cubs will be born with short tails, and since having a short tail is beneficial from an utilitarian point of view, over time, these 20% will crowd out the remaining 80%.

Now suppose that peacocks are not monogamous, but polygamous. 1 male with a short tail will fertilize 20 females, and 4 males with long tails, respectively, 80 females. So far, nothing has changed.

Now suppose that polygamy is even more pronounced, and instead of 4 males with long tails, the harem belongs to one. And here the principle “for everyone who has will be given more, but the one who does not have, even what he has will be taken away from him”, which Dawkins mentioned, can work. Since this supermale with a long tail has 80 females, the fact of his popularity serves as additional advertising for the remaining 20 females. It works that, when all other things being equal, it is better for a female to choose a male that other females have already chosen (such a principle, on average, does more good than harm). Accordingly, this supermale will have additional females from among the remaining 20.

Is this really all that Fisher's model suggests? This argument seems to me not very convincing. Can someone apply my approach (counting the number of males and females) to correctly explain Fischer's ideas?

  • 1
    $\begingroup$ Remember that Fisherian runaway is an explanation for a thing that happens; in particular, it explains why it's stable when it happens. It's not a claim that this always happens for all traits. $\endgroup$
    – Bryan Krause
    Nov 9, 2022 at 2:47
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    $\begingroup$ I don't think the last statement of your second paragraph holds true necessarily. The long tail is obviously useful in that it attracts females, therefore mating, so it won't get out-competed by short tails. $\endgroup$
    – bob1
    Nov 9, 2022 at 3:43
  • $\begingroup$ Dawkins and Weinstein discussing the topic. $\endgroup$
    – S Pr
    Nov 9, 2022 at 13:26
  • $\begingroup$ your numbers don't add up, 80 males have long tails, 20 males have short ones. 80 females prefer long tails, 20 short ones. means way less than 20% of the next generation have short tails, because males don't encounter every female but only a small percentage, a large portion of your short tailed males may never encounter a short tail preferring female. thus many will fail to reproduce, likewise female may fail to reproduce or settle for long tailed males because that is all they encounter. $\endgroup$
    – John
    Nov 11, 2022 at 19:35
  • $\begingroup$ Now consider the simplest form of this, mating calls, making noise that attracts mates also attracts predators, but not finding a female mean your genes die out so even risky behavior that also increases your chances of finding a female will have huge gains as long as the chance of encountering a female without it is low. $\endgroup$
    – John
    Nov 11, 2022 at 19:40


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