In some cases two species can hybridize. For example, Tigers and lions can hybridize to produce "Ligers".

Would it also be possible for humans and chimpanzees (or any other species) to hybridize ? If not, what would be the likely cause of failure?

Why do some hybridization matings produce offspring, like the Liger, and some not? What mechanisms prevent hybridizations?

  • $\begingroup$ I've rewritten your question because I saw it getting downvoted after just a few minutes online - the basic principle of the question is interesting so I wanted it to survive $\endgroup$ – rg255 Jun 26 '13 at 16:28
  • $\begingroup$ Related (but not a duplicate): Interbreedability between current humans and his ancestors $\endgroup$ – Remi.b Mar 5 '18 at 0:44

The concept of a human/chimp hybrid is called a humanzee. No humanzees have ever been recorded despite the fact that sexual intercourse between humans and chimps have been recorded on several occasions. This suggests that male-human/female-chimpanzee is not capable of producing viable offspring, at the very least.

As to why, several reasons will contribute: humans and chimps have a different number of chromosomes, making cross-fertility unlikely (although animals with different chromosome numbers can and do breed so this isn't absolute). Humans and chimps are anisomorphically quite different (i.e. the ratios of limbs are different and so on) so it's quite plausible that the growth patterns are not compatible. I'm not aware of any exhaustive studies into reasons why cross-breeding is impossible but it's also quite plausible that there are changes in the chemistry of fertilisation, etc. that will limit cross-breeding.

I'd note, finally, that there's evidence from the X chromosome that the human line continued to have some level of interbreeding with chimps for some million years after the initial split (Patterson et al, 2005).

I see that there are some later publications that have disputed the claims made in that paper. So I'll leave you to judge the merits of the arguments.

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    $\begingroup$ Goats and sheeps can mate, even though it is rare, and produce a live offspring, en.wikipedia.org/wiki/Sheep%E2%80%93goat_hybrid. Are they more closely related to each other than humans and chimps? Or is it just a numbers game, goats and sheeps try more often than humans and chimps? $\endgroup$ – d-b Apr 10 '18 at 14:14
  • $\begingroup$ @d-b There does not seem to be any good rule of thumb on exactly which species can interbreed based on relatedness. Your example is surprising given the difference in chromosome count, but sheep and goats are similar animals in body shape and size which may help. $\endgroup$ – Jack Aidley Apr 10 '18 at 16:40
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    $\begingroup$ But so are humans and chimps (or bonobos). However, goats and sheeps are frequently herded together and no one really cares if they try to mate so there has probably been a large number of attempts to produce a few results. The opposite is true for humans and chimps, very few attempts/opportunities and people in general are probably very concerned about any attempts. $\endgroup$ – d-b Apr 10 '18 at 23:14
  • $\begingroup$ @d-b Humans and chimps are not similar in shape. We're bipedal, they are knuckle walkers; our brains are several times larger; our jaws are different shapes and sizes, etc. $\endgroup$ – Jack Aidley Apr 11 '18 at 6:39
  • $\begingroup$ I need to sendong d-b's point. We know that it's not easy to hybridize with chimps. However, given that many species, even species with different # of chromosomes, have been proven capable of occasional hybridization we can't rule out the possibility that rare hybrids with either chimp or bonobo's are possible but haven't been documented. I'd say it's improbable that humans can reproduce with chips or bonobo's, but I'm not confident enough to say it's 100% impossible. Most would consider it unethical to test such a hypothesis though. $\endgroup$ – dsollen May 19 at 19:43

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