OK, this really has to do with primatology, which is still a branch of biological anthropology. I was wondering if chimps, gorillas, orangutans, the three non-human apes (some would include bonobos as a fourth), are interfertile or not? To be interfertile, members of a population must have the same genes (having different alleles for any gene is not a problem), the same number of genes, usually the same number of chromosomes, correct?

OK, this really has to do with primatology, which is still a branch of biological anthropology. I was wondering if chimps, gorillas, orangutans, the three non-human apes (some would include bonobos as a fourth), are interfertile or not? To be interfertile, members of a population must have the same genes (having different alleles for any gene is not a problem), the same number of genes, usually the same number of chromosomes, correct?There are seven living species of Great Apes in four genera: Pan troglodytes (the "true" chimpanzee), Pan paniscus (the bonobo), Pongo pygmaeus (the Borneo orangutan), Pongo abelii (the Sumatra orangutan), Gorilla gorilla (the western gorilla), Gorilla beringei (the eastern gorilla), and Homo sapiens (the modern human).

In general, two species within the same genus are interfertile, although their courtship rituals may be so different that fertilization can only be accomplished by AI. (In fact, back in my day, before DNA analysis, the definition of "genus" we were taught in high school biology was "a group of interfertile species.") One would then suppose that the two species of chimpanzees, or of orangutans, or of gorillas, could probably hybridize. Certainly the odds are on at least two of the three.:) However, I'm surprised to find no information on the subject in a quick search. This probably has something to do with the fact that until rather recently there was thought to be only one species of each, and zoos routinely put them together haphazardly. There may be some hybrids out there and they just haven't been identified yet.

The Great Apes comprise the family Hominidae. There is also the family of Lesser Apes, the Hylobatidae, or gibbons. This is a more prolific family with something like twenty species spread among four genera. Hybridization among gibbon species is well documented.

The two families of Great Apes and Lesser Apes together comprise the superfamily of apes, Hominoidea, one of several intermediate taxonomic groups within the order Primata. Interbreeding occurs between a number of related pairs of primate species, especially in captivity or domestication, but occasionally in nature. With the way the definition of "genus" has changed in the last fifty years, resulting in the taxonomic reclassification of many species, there is now documented interbreeding between genera, and this occurs (at least) among baboons.

I have never seen the word "anthropology" used for the study of any animals except humans, including our ancestral species within genus Homo. Where did you pick up that usage? It was coined from those two Greek roots in order to specifically mean "the study of man."

I take it that no one ever tried to determine whether chimps, orangutans, gorillas are interfertile?

I have never seen the word "anthropology" used for the study of any animals except humans, including our ancestral species within genus Homo. Where did you pick up that usage? It was coined from those two Greek roots in order to specifically mean "the study of man."

Primatology is now under anthropology, apparently, because the latter was too "narrow".

I take it that no one ever tried to determine whether chimps, orangutans, gorillas are interfertile?

Certainly none of the three are infertile, otherwise there would be none of them at all. If you are asking, however, whether chimps could mate with orangutans and produce viable offspring, I'm not certain.

IIRC, most apes have 48 chromosomes, while humans have 46; so that pairing is out right away.
http://www.indiana.edu/~ensiweb/lessons/chr.bk1.html

The study of non-human primates is very much the domain of anthropology and primate evolution courses that deal mostly with non-human primates are often mandatory for anthropology majors.

There was also a news item last year or two ago that suggested that early hominids or even ancient humans once mated with a chimp ancestor -but I forget the context or the hows and whys this was suggested. I'll have to dig & see if I can find this again.

I take it that no one ever tried to determine whether chimps, orangutans, gorillas are interfertile?There are lots of rumors of such hybrids (and even hybrids of humans with other Great Ape species), but as far as I can see none of these are documented and thus fall into the category of urban legends, or perhaps more specifically "urban zoo legends."
Certainly none of the three are infertile, otherwise there would be none of them at all.He wrote "interfertile," not "infertile."
There was also a news item last year or two ago that suggested that early hominids or even ancient humans once mated with a chimp ancestor. . . .The family Hominidae and the term "hominid" includes all Great Ape species, not just humans.

Since the clade of humans, genus Homo, and the clade of chimpanzees, genus Pan, together comprise a higher-order clade, there may well have been a point near the separation of the two when their DNA was still close enough that they could have interbred. But perhaps their offspring were not fertile (like horses and donkeys), so they became neither a bridge between the two bloodlines preventing the separation, nor progenitors of a third bloodline.

As River points out:
IIRC, most apes have 48 chromosomes, while humans have 46; so that pairing is out right away.eventually our DNA diverged to the extent that crossbreeding was no longer possible. I'm sure this is the typical course of clade separations.

Difference in the number of chromosomes is not in itself sufficient to prevent interfertility, especially since the human chromosome 2 is two ape chromosomes stuck together. Down Syndrome and several other diseases result from having more than 46 chromosomes, yet they do not prevent interfertility between people. If chimps, gorillas, and orangutans are indeed interfertile, it might make a strong argument for the existence of human (and ape) "races".

Difference in the number of chromosomes is not in itself sufficient to prevent interfertility, especially since the human chromosome 2 is two ape chromosomes stuck together. Down Syndrome and several other diseases result from having more than 46 chromosomes, yet they do not prevent interfertility between people. If chimps, gorillas, and orangutans are indeed interfertile, it might make a strong argument for the existence of human (and ape) "races"."Interfertile" just means that mating can result in the birth of viable offspring. Right? The offspring themselves have to be fertile, or at least interfertile with a purebred individual, before they have any impact on the evolution of either species. That's why I mentioned the horse and donkey. In domestication they routinely mate and give birth to healthy hybrid offspring, but the number of those mules who are capable of reproducing and producing another generation is statistically negligible.

Pet breeders are always trying to come up with exotic hybrids because there's a steady and lucrative market for them. "Mule" has been generalized into a code word for infertile first-generation hybrids that cannot be bred into a second generation, and it happens routinely.

The family Hominidae and the term "hominid" includes all Great Ape species, not just humans.

Yeah, yeah...

I was posting on the sly from work and not trying to get into a book length description. Fingers were typing while the brain was doing work stuff.... :)

Anyway, I was thinking hominin not hominid, hominidae or even Homonoidea. It was more typo than sloppy thinking.

Hominin, of course, is generally used to refer to the sub-family of humans, archaic humans and human ancestors since divergence from the ape lineage (although I won't quibble over whether or not humans are apes, etc. -these are all constructs of human understanding and labels that suit our own needs to begin with).

The paper I was referring to appeared in Nature in 2006 and here's an excerpt:
We suggest a provocative explanation for multiple features of these data: that the hominin and chimpanzee lineages initially separated but then exchanged genes before finally separating less than 6.3 Myr ago (Fig. 1e). First, this could explain how Toumaï could have dates older than hominin speciation and yet still have hominin features17, 18, 19. Second, it could explain the wide range of divergence times (more than 4 Myr): at some loci human and chimpanzee lineages share ancestry around initial separation, whereas at others the genetic ancestry is more recent at the time of hybridization. Third, it could explain the low divergence of human and chimpanzee on chromosome X. An empirically observed pattern, documented in Drosophila, tsetse flies, mosquitoes, butterflies and guinea-pigs24, is that "the genes having the greatest effect on hybrid sterility and inviability are X-linked"24. The reasons for this 'second rule of speciation'24 are not fully understood25, 26, 27, although they are thought to be related to Haldane's rule about hybrid sterility affecting the heterogametic sex more than the homogametic sex28. A corollary—not previously suggested—is that if gene flow between two diverged populations occurs, chromosome X should be subject to strong and rapid selection to eliminate alleles, from one parental population or the other, that contribute to reduced fitness. The presence of multiple hybrid incompatibility loci could lead to selection across much or all of chromosome X, as in our data (Fig. 3). As a specific example, if human and chimpanzee ancestors initially speciated and then interbred, hybrid males might have been infertile, consistent with Haldane's rule. A viable population could then only have arisen if the fertile females mated back to one of the ancestral populations (for example, chimpanzee ancestors), producing fertile male hybrids when they transmitted X chromosomes derived almost entirely from that ancestral population. This could explain why humans and chimpanzees are most closely related throughout chromosome X. We note that in wild mice in the European Mus musculus/domesticus hybrid zone there has been reported to be a gradient of genetic variants on the autosomes, but a sharp geographic transition for chromosome X (ref. 29). This indicates that wild mouse hybrid populations might have difficulty carrying X chromosomes from multiple ancestral populations, which is consistent with what would be expected from our model and proposed corollary to the second rule of speciation.

Speciation in animals is generally believed to occur by allopatry—that is, by the formation of an isolation barrier with no subsequent gene flow. When subsequent hybridization does occur, it is generally believed that the resulting population dies out30, 31. However, there are known examples of adapted hybrid populations in nature32, 33, 34, and hybridization could be advantageous, allowing nascent species to derive traits from several ancestral populations, combining them to adapt to new environments35. The failure to observe more instances of successful hybridizations in field studies so far30, 31 might simply be due to ascertainment bias—the fact that hybridizations occur too episodically to be observed practically. With comparative genomic methods, one can project backwards in time to make inferences about what happened at the time at which speciation occurred. Allopatric speciation without subsequent gene flow predicts that population genetic structure before and after speciation should be similar30, 31. By contrast, hybridization predicts a wide range of divergence times and different coalescence times in parts of the genome, such as chromosome X. By comparing the genomes of modern species, one could systematically test whether hybridization is a widespread process in evolution.

We have shown that human and chimpanzee speciation was complex; furthermore, our model makes predictions that can be tested with larger data sets36. First, it predicts that evidence of natural selection should be seen not only on chromosome X but also at some autosomal loci. Such ancient selective sweeps might be detected as long regions with unusually low (or high) rates of human–chimpanzee divergence and HG and CG sites. (It might even be possible to identify autosomal genes under selection). Second, if a hybridization involving a single episode of gene flow occurred, it might result in a bimodal distribution of tau(x). Third, speciation involving hybridization could give rise to distinctive patterns of 'frozen linkage disequilibrium': differences in the lengths and distribution of HC, HG or CG clustering (Fig. 2). All these hypotheses can be tested once the gorilla genome is complete and aligned to the genomes of humans, chimpanzees and more distant primates.

The entire thing can be found online if you have access to Nature or, perhaps, its made available in limited capacity on their sites as they so often do.

Patterson, Nick; et al (2006). Genetic evidence for complex speciation of humans and chimpanzees. Nature, 441, pp. 1103-1108.

I only just noticed that it is At World's End who is asking questions about mules. Clever. Was that deliberate, At World's End? Does it represent the foundation of your purpose here on sciforums?

The paper I was referring to appeared in Nature in 2006 and here's an excerpt. . . .To pick out one point: Hybridization is more common now because of the impact of man on the environments of other species.

In the past, each of two related species had adapted ideally to its environment, and a hybrid of the two would not be as well-adapted to those environments as either of them. The constructions of man have made the sudden appearance of new environments more common and frequent, which may no longer be perfectly suited to either ancestral species. For example, stands of hybrid plants are a common sight along roadways, where the drainage, etc., is different from the conditions their ancestors adapted to.

There used to be a vast forest along the Mississippi River, and the rose-breasted grosbeak had adapted to the environment of the ancient geology to the east, whereas the black-headed grosbeak was better suited to the more rugged land mass in the west. Man came along and replaced the forest with farms, teeming with fruit and other delectables that attracted both species. They began interbreeding and today hybrid grosbeaks have spread out widely, into the lands now populated by man with his alien flora. They show up at the totally artificial environment of our feeding stations two thousand miles away in California.

Macaws are curious, gregarious, highly intelligent birds who are sometimes adventurous enough to experiment with inter-species dating where their ranges overlap in the wild. In domestication, the species boundaries break down and there is now a spectrum of hybrid macaws in a rainbow of colors.

He wrote "interfertile," not "infertile."The family Hominidae and the term "hominid" includes all Great Ape species, not just humans.
facepalm. whoops.