As I understand it, animals sometimes grow more vibrant colors, bigger feathers, elaborate dances, build shiny nests, all to impress the other sex. However, these are all superfluous to survival -- any nutrition or energy spent developing these attributes or conducting these rituals are no longer usable for hunting or child rearing, for example. Given the same animal who does one of these wasteful practices versus the same animal who doesn't, in theory the latter should have the advantage in its chances of passing its genes down.

Why is it then, that sexual preference grows towards these wasteful growths and habits, rather than ignoring these sexual displays for sheer survival efficiency?


2 Answers 2


Short answer

Survival does not get your genes into the gene pool, reproduction does.

thus reproduction based selective pressures can be stronger than survival based ones. there are plenty of organisms that die during or right after mating because of this.

Consider an example In species A finding a mate is fairly rare, it may only happen a few times in an organisms life. if individual X is guaranteed to mate and reproduce when they find a mate but will die after mating, and individual Y will not die after mating but only has a low chance to mate then the genes from X will spread much faster than the genes for Y, because mating is already a rare event, but X genes spread every time while Y genes will also only spread once or often not at all, and will also take much longer.

Or to put it another way, a chicken is just an eggs way of making another egg, the survival of the chicken is only useful as much as it facilitates reproduction.

Any mutation that happens to make you better at attracting a mate will spread, how it does so is basically irrelevant as long as it works, loud noises, bright colors, eye spots anything that draws the females attention works. studies on several bird species have shown even the colored bands used to identify birds for study effect their mating chance is they are right colors. Animals often already have a variety of biases for their attention hijacking them is an easy way to improve your chances of mating. Of course once a way evolves that reliably improves mating chances preference for that becomes favorable as well which can lead to a run away selection feedback loops AKA Fisherian runaway


  • $\begingroup$ I don't understand, how does this explain the development of sexual display traits and the attraction to them? $\endgroup$ Jan 15, 2020 at 16:31
  • 1
    $\begingroup$ @personjerry What part don't you understand. $\endgroup$
    – John
    Jan 15, 2020 at 22:59
  • $\begingroup$ You've explained why a male would develop such features if the female finds it attractive, but why would the female evolve to find these features attractive in the first place? $\endgroup$ Jan 15, 2020 at 23:01
  • $\begingroup$ @personjerry they don't have to anything that grabs the females attention works, there are plenty of existing attention managing processes tp exploit survival has already shaped brains to notice things that stand out with bright colors, to notice eyes, and react to loud noises. to use a human example we evolved to notice red colored fruit and plenty of males and advertisers exploit this with red coloration. there was a study on crows that showed putting any brightly colored tag on a bird made it more likely to mate. $\endgroup$
    – John
    Jan 15, 2020 at 23:05
  • $\begingroup$ So it's not so much that we evolved a taste for sexual display specifically, rather sexual display traits hijacked existing systems to become relevant? Do you have any citation for that? And if you edit this part into your answer Ill accept it $\endgroup$ Jan 16, 2020 at 1:15

The point is that it's not only wasteful, but counter-productive to survival.

If you're a red bug in the lush green of the amazon you are painting a target on yourself. This has the effect of increasing your selective pressure. If you survive with a target on your back, and wasting energy on pigments, then you must be very good all of the other things necessary for survival.

So, with natural selection, the higher selective pressure on an organism with a target on its back will be a more selective filter, only allowing the most performant little red bugs to survive and mate with each other, "quickly" giving them an edge over their less colorful brethren, and resulting in a biodiversity that flaunts its ability to survive today with extravagant colors and nests.

The mating dances might be a different story, I'll let someone else tackle that.

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    $\begingroup$ Don't many of these displays also function as health indicators, as unhealthy individuals are likely to have less vibrant colors/feathers? $\endgroup$ Jan 9, 2020 at 10:18
  • $\begingroup$ How could natural selection come up with the logic to figure out that surviving with a target on your back suggests a more fit individual? $\endgroup$ Jan 15, 2020 at 18:35
  • $\begingroup$ Natural selection doesn't come up with anything. You have 100 bugs, 10 of them are bright red and die at a faster rate than the other 90. So of these 10 bugs at a disadvantage, 9 die before reproducing. The last one, with the highest fitness, is the only one to reproduce, so its offspring inherit its fitness. For the other 90 non-bright red bugs, that process is less selective, because they have an easier time surviving with their natural camouflage. So fitness enhancing changes take longer to set in the population. $\endgroup$
    – Thymine
    Jan 16, 2020 at 12:57

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