If an animal is fertile does it follow that both its parents of the same species (not necessarily the same species of the offspring)? Was it Mayer who said a fertile male and fertile female of two different species, if they 'reproduce' and the offspring survives it won't be fertile. Reproductive isolation I think this is called. So if an animal is fertile then both its parents should be of the same species, right?


1 Answer 1


No it isn't necessary that the parents should be of the same species. Mules (male donkey X female horse) have been found to be fertile (reference). The wikipedia page on hybrids lists many inter-species hybrids that are fertile including Beefalo (Domestic male cattle X american bison). There are also many canine hybrids which are fertile. Wholphins have been found to be fertile.

A wholphin or wolphin is an extremely rare hybrid born from a mating of a female bottlenose dolphin (Tursiops truncatus) with a male false killer whale (Pseudorca crassidens).

So in short, for a hybrid offspring to be fertile, it doesn't necessarily need to be of the same species.

  • $\begingroup$ I know this is 'heresy' but if two different species are fertile and have a fertile offspring maybe they are not really different species but different subspecies. $\endgroup$
    – user128932
    Commented Sep 19, 2014 at 5:27
  • $\begingroup$ @user128932 I wouldn't call them sub-species but atleast closely related species because a donkey and a horse can hardly be called a sub-species of one or the other. You can read this article. detectingdesign.com/donkeyshorsesmules.html $\endgroup$ Commented Sep 19, 2014 at 5:31
  • $\begingroup$ Do a donkey and a horse have a common ancestor ( with four legs)? $\endgroup$
    – user128932
    Commented Sep 21, 2014 at 5:07
  • $\begingroup$ If a fertile female 'individual' , call it 'A' ,and a fertile male 'B' of a 'similar' but distinct species ; both have important differenses in their respective physiologies ; 'A' might have an important physiological process that 'carries out a certain biological tasks yet 'B' might not have something similar to this. So when passing on their important biological info. to their offspring how are possible physiological-process differences resolved. For Example a cat and a dog must have unresolvable physiological differences ; no one has bred a Dat or a Cog. $\endgroup$
    – user128932
    Commented Sep 21, 2014 at 5:18
  • $\begingroup$ @user128932 Yes, they do have a common ancestor and your question here about the resolution of physiological processes in species crossbreeds needs to be asked as a separate question. $\endgroup$ Commented Sep 22, 2014 at 4:16

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