Why do organisms have some traits that do not appear to have any evolutionary advantage?

  • $\begingroup$ Also, let me know if this question should be merged should be merged with this thread: biology.stackexchange.com/questions/35532/…. They are fairly similar. $\endgroup$ – C_Z_ Jun 27 '15 at 2:52
  • $\begingroup$ You could have answered there itself. $\endgroup$ – WYSIWYG Jun 27 '15 at 6:27
  • 2
    $\begingroup$ @WYSIWYG Fair enough, the reason I didn't is because I figured the question "Why didn't X trait evolve if it would be advantageous" and "Why did X trait evolve if it isn't advantageous" are different enough to warrant two separate questions. $\endgroup$ – C_Z_ Jun 27 '15 at 15:42

There are many reasons why an organism might have a trait that does not appear to be beneficial.

  1. The trait is actually advantageous even if it does not appear to be.

  2. The trait is a byproduct of another trait, which is beneficial. Not all traits are the product of direct selection; traits that are byproducts of other traits are known as "spandrels", a trait coined by Stephen J. Gould and Richard Lewontin

  3. The trait was fixed by some process other than natural selection, such as genetic drift. Genetic drift can fix traits that are neutral or even evolutionarily disadvantageous.

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