# Cross-species mating **URL:** \ **Category:** Factual Questions\ **Created:** [February 16, 2003, 4:01am UTC](https://boards.straightdope.com/t/cross-species-mating/155374 "2003-02-16T04:01:26Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![RexDart](https://avatars.discourse-cdn.com/v4/letter/r/b77776/32.png) [@RexDart](https://boards.straightdope.com/u/RexDart)\ **Post date:** [February 16, 2003, 4:01am UTC](https://boards.straightdope.com/t/cross-species-mating/155374/1 "2003-02-16T04:01:26Z")
How does the female’s unfertilized egg know that the sperm entering it is of the wrong species? Is the sperm just unable to enter the egg? I realize it may be twisted, but there was a joke on _Sealab 2021_ about a man having sex with an orangutang and producing offspring. Surely this couldn’t happen, but I can’t exactly figure out why. ---
**Author:** ![tonbo0422](https://avatars.discourse-cdn.com/v4/letter/t/b5e925/32.png) [@tonbo0422](https://boards.straightdope.com/u/tonbo0422)\ **Post date:** [February 16, 2003, 4:09am UTC](https://boards.straightdope.com/t/cross-species-mating/155374/2 "2003-02-16T04:09:50Z")
I’m pretty sure there has to be a very specific chemical signal transmitted by the sperm that the egg is programmed to recognise. Otherwise evolution would have gone haywire long ago. I would imagine that when the species is close enough, as in dogs and most cats, cross-breeding is easier, but then again I don’t think you could cross-breed a tiger with a house cat. Don’t know why. ---
**Author:** ![AndrewL](https://avatars.discourse-cdn.com/v4/letter/a/3d9bf3/32.png) [@AndrewL](https://boards.straightdope.com/u/AndrewL)\ **Post date:** [February 16, 2003, 5:15am UTC](https://boards.straightdope.com/t/cross-species-mating/155374/3 "2003-02-16T05:15:48Z")
I think the problem isn’t the sperm entering the egg, but the DNA being too different to produce a viable embryo. ---
**Author:** ![Marduk](https://avatars.discourse-cdn.com/v4/letter/m/ecd19e/32.png) [@Marduk](https://boards.straightdope.com/u/Marduk)\ **Post date:** [February 16, 2003, 5:21am UTC](https://boards.straightdope.com/t/cross-species-mating/155374/4 "2003-02-16T05:21:27Z")
Most species have different chromosome numbers. If they don’t match up no baby. If they do match up and they are separate species there will probably be a miscarrage because the embryo doesn’t excrete the proper enzyme to keep the mother’s antibodies away from it. One of the execptions of this is with plants or specifically trees. I know they cross breed all the time. ---
**Author:** ![Will\_Repair](https://avatars.discourse-cdn.com/v4/letter/w/a698b9/32.png) [@Will\_Repair](https://boards.straightdope.com/u/Will_Repair)\ **Post date:** [February 16, 2003, 6:05am UTC](https://boards.straightdope.com/t/cross-species-mating/155374/5 "2003-02-16T06:05:41Z")
> [@](#): > > \*Originally posted by Marduk \* > **Most species have different chromosome numbers. If they don’t match up no baby.** “Consider the ass” [http://www.geocities.com/moredonkeys/aboutmules.html](http://www.geocities.com/moredonkeys/aboutmules.html) “If a group of individuals could potentially breed together in the wild to produce fertile offspring, then they belonged to the same species” [http://www.dhushara.com/book/diversit/extra/enig/senig.htm](http://www.dhushara.com/book/diversit/extra/enig/senig.htm) “Donkey has 62 chromosomes (31 pairs) and Horse has 64 (32 pairs). Thus mule (and hinny) have 63 chromosomes and meiosis during gamete formation is virtually guaranteed to go wrong.” [http://www.biols.susx.ac.uk/ugteach/cws/evol1/rims.htm](http://www.biols.susx.ac.uk/ugteach/cws/evol1/rims.htm) ---
**Author:** ![Spiratu](https://avatars.discourse-cdn.com/v4/letter/s/47e85d/32.png) [@Spiratu](https://boards.straightdope.com/u/Spiratu)\ **Post date:** [February 16, 2003, 6:11am UTC](https://boards.straightdope.com/t/cross-species-mating/155374/6 "2003-02-16T06:11:18Z")
Campbell’s _Biology_, a textbook I happen to have lying around, lists numerous barriers to cross-breeding. The sperm of one species may not be able to survive in the reproductive tract of another. In many species, there are specific molecules on the gel coating of the egg that only a sperm of the same species can adhere to. As stated above,too, if the two species have different numbers of chromosomes, that can prevent hybridization as well. If the sperm does manage to fertilize the egg, many hybrids fail to complete development because their DNA isn’t close enough to create necessary proteins. Finally, some hybrids manage to live, but are unable to reproduce (such as mules). ---
**Author:** ![Marduk](https://avatars.discourse-cdn.com/v4/letter/m/ecd19e/32.png) [@Marduk](https://boards.straightdope.com/u/Marduk)\ **Post date:** [February 16, 2003, 6:15am UTC](https://boards.straightdope.com/t/cross-species-mating/155374/7 "2003-02-16T06:15:30Z")
Yes yes, exceptions do exist to the rule acid, and if you want a REALLY specific answer you’d have to do it species by species as to why they can’t mate. Listing just a few examples: Mismatching of the required sexual organs. Opposite species refuses to answer to improper mating call/act/dance/etc. The animal in question is actually asexual. The sperm is not identified by the mother as such. And even these topics can be broken down into smaller things such as specific enzymes not being present. But as in almost all biology, there are always exceptions and exceptions to the exceptions and exceptions to the exceptions to the exceptions. But its all about generizations. ---
**Author:** ![Marduk](https://avatars.discourse-cdn.com/v4/letter/m/ecd19e/32.png) [@Marduk](https://boards.straightdope.com/u/Marduk)\ **Post date:** [February 16, 2003, 6:59am UTC](https://boards.straightdope.com/t/cross-species-mating/155374/8 "2003-02-16T06:59:38Z")
Just an interesting article that relates to this a tid bit: [http://news.bbc.co.uk/2/hi/in\_depth/sci\_tech/2003/denver\_2003/2767671.stm](http://news.bbc.co.uk/2/hi/in_depth/sci_tech/2003/denver_2003/2767671.stm) ---
**Author:** ![RexDart](https://avatars.discourse-cdn.com/v4/letter/r/b77776/32.png) [@RexDart](https://boards.straightdope.com/u/RexDart)\ **Post date:** [February 16, 2003, 12:34pm UTC](https://boards.straightdope.com/t/cross-species-mating/155374/9 "2003-02-16T12:34:33Z")
> [@](#): > > \*Originally posted by Marduk \* > \*\*Yes yes, exceptions do exist to the rule acid, and if you want a REALLY specific answer you’d have to do it species by species as to why they can’t mate. > > \*\* OK, so what’s preventing a human and an orangutang, as in the example that sparked my query, from producing viable offspring? Chromosome counts, inability to survive in the reproductive tracts, egg’s gel coating? ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [February 16, 2003, 6:02pm UTC](https://boards.straightdope.com/t/cross-species-mating/155374/10 "2003-02-16T18:02:52Z")
Big one would be what is delicately termed “pre-zygotic isolating mechanisms”. Meaning that we don’t respond to an orangutang’s sexual signals and they don’t respond to ours. How many times have you looked at an orangutang and said “Check out those sexy cheek and throat pads!” It may very well be possible to create a hybrid zygote. I don’t beleive the experiment has ever been carried out, and if it has been carried out no one is advertising that fact. ---
**Author:** ![Marduk](https://avatars.discourse-cdn.com/v4/letter/m/ecd19e/32.png) [@Marduk](https://boards.straightdope.com/u/Marduk)\ **Post date:** [February 16, 2003, 6:06pm UTC](https://boards.straightdope.com/t/cross-species-mating/155374/11 "2003-02-16T18:06:32Z")
Actually it has been carried out… Michael Jackson is a bit more than 1/2 man 1/2 plastic… ---
**Author:** ![tonbo0422](https://avatars.discourse-cdn.com/v4/letter/t/b5e925/32.png) [@tonbo0422](https://boards.straightdope.com/u/tonbo0422)\ **Post date:** [February 16, 2003, 6:24pm UTC](https://boards.straightdope.com/t/cross-species-mating/155374/12 "2003-02-16T18:24:29Z")
How about those species which share 99.9% of DNA? Would a Chimpanzilla ever be possible? Or a Manzilla? Hmm . . . there WAS Bubbles the Chimp . . . who probably shared Jacko’s bed . . . and the result has been hidden away in Neverland. Seriously, though, I guess that would not be possible, since Neanderthals weren’t able to mix with H. Sapiens and died out as a result. ---
**Author:** ![Will\_Repair](https://avatars.discourse-cdn.com/v4/letter/w/a698b9/32.png) [@Will\_Repair](https://boards.straightdope.com/u/Will_Repair)\ **Post date:** [February 16, 2003, 8:03pm UTC](https://boards.straightdope.com/t/cross-species-mating/155374/13 "2003-02-16T20:03:57Z")
> [@](#): > > \*Originally posted by tonbo0422 \* > **How about those species which share 99.9% of DNA? Would a Chimpanzilla ever be possible? Or a Manzilla?..I guess that would not be possible …** As shown by mules and hinnys it is possible. For all we know many more crosses are possible but other factors have prevented it. ---
**Author:** ![Tamerlane](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tamerlane/32/7602_2.png) [@Tamerlane](https://boards.straightdope.com/u/Tamerlane)\ **Post date:** [February 16, 2003, 9:05pm UTC](https://boards.straightdope.com/t/cross-species-mating/155374/14 "2003-02-16T21:05:51Z")
> [@](#): > > How about those species which share 99.9% of DNA? Would a Chimpanzilla ever be possible? Or a Manzilla? > [@](#): > > \*Originally posted by AcidKid \* > As shown by mules and hinnys it is possible. For all we know many more crosses are possible but other factors have prevented it. In this particular case, no it is not possible. For further discussion see: [http://boards.straightdope.com/sdmb/showthread.php?threadid=64664](http://boards.straightdope.com/sdmb/showthread.php?threadid=64664) [http://boards.straightdope.com/sdmb/showthread.php?threadid=77064](http://boards.straightdope.com/sdmb/showthread.php?threadid=77064) Just because some closely related species can cross, doesn’t mean all can. Also, as your link notes, the Biological Species Concept ( species as a group that can interbreed to produce fertile offspring under natural conditions ), though the most commonly cited, has many detractors and a number of exceptions. For example wolves and coyotes will interbreed to produce fertile offspring in the wild and it is likely the “Red Wolf” was one result of such crosses. They don’t _commonly_ do so, but they can and will. Yet for a number of reasons including overall genetic distance from each other as a group ( while having in comparison far less genetic diversity, even over large geographic areas, _within_ either species ), the restricted geographic nature of hybrid zones, the peculiar behavioral nature of such hybridization events ( almost always female coyotes with male wolves, whose offspring cross back with wolves ), and other reasons, they are still considered distinct species. - Tamerlane ---
**Author:** ![tonbo0422](https://avatars.discourse-cdn.com/v4/letter/t/b5e925/32.png) [@tonbo0422](https://boards.straightdope.com/u/tonbo0422)\ **Post date:** [February 16, 2003, 9:38pm UTC](https://boards.straightdope.com/t/cross-species-mating/155374/15 "2003-02-16T21:38:18Z")
Hmm, those threads have pretty much said it ALL on this subject . . . ---
**Author:** ![Will\_Repair](https://avatars.discourse-cdn.com/v4/letter/w/a698b9/32.png) [@Will\_Repair](https://boards.straightdope.com/u/Will_Repair)\ **Post date:** [February 16, 2003, 10:09pm UTC](https://boards.straightdope.com/t/cross-species-mating/155374/16 "2003-02-16T22:09:11Z")
> [@](#): > > \*Originally posted by Tamerlane \* > **Just because some closely related species can cross, doesn’t mean all can.** I was not confining the possiblity to outside the test tube.