Plenty. The concept of ‘species’ is pretty lame in the real world. In nature hybrids are quite common. Blue and humpback whales have been shown to be indulging constant outcrossing for many generations, as have wolves and coyotes.
Human induced hybrids of lions X tigers, dolphins X killer whales, and camels X llamas have been produced to name just a few. Of course camels and llamas are far more genetically, temporally and geographically distinct from each other than are humans and chimps, however I assume they at least have the same number of chromosomes, which humans and chimps don’t. Humans have 23 chromosomal pairs while other apes have 24. This alone means that a fertile or even viable offspring is going to be almost impossible. However it should be remembered that the ‘ancestral’ horse, Equus prezwalski, has 2 more chromosomes than domestic horses, yet happily produces fertile hybrids. So the speculation on human X ape hybrids can happily continue.
For those interested I suggest seeing if you can get hold of an 80s BBC series called ‘Gor/First Born’, about a human gorilla hybrid. The series traces his life, and the problems he encountered, largely owing to the fact that, although physically perfect he lacked the aggressive human side and had some fairly serious problems fitting into human society.
Interestingly enough, not only can lions and tigers produce offspring (commonly known as ligers), the offspring are fertile. This despite the fact that lions and tigers are geographically separated from one another by quite some distance and are considered to be separate species.
Horses have 64 chromosomes, donkeys 62, and mules/hinneys 63. http://boards.straightdope.com/sdmb/showthread.php?threadid=35128
Just a point of interest Tzel, the natural ranges of the Asiatic lion subspecies and the tiger probably overlapped to some extent prior to human intervention. The pre-human range of the lion included parts of India, Europe and North America. They still exist in Northern India and the Asiatic subspecies is apparently more tolerant of dense wodland than the African lion. So it’s just concievable they may have been outcrossing until geographically recent times.
Weren’t the villainous apes in Congo supposed to have been some sort of hybrid along these lines?
My problem is the way the question is posed. Humans and chimps surely do breed regularly and prolificately. Think about it. Didn’t you mean “interbreed”? Just being a supercilious snot; no offense!
Oddly enough, no one has mentioned African & Asian elephants. There was one recorded case of interbreeding, but the calf was stillborn.
Gaspode: I’ve seen at least one cite ( mentioned in Walker’s Mammals of the World ) for mitochondrial DNA work that suggests that Przewalski’s Horse isn’t ancestral for the modern domestic horse at all. I mentioned it down below in the “Fossil Record” thread. Whether that’s currently accepted as fact, I have no idea. The cite’s over a decade old as I recall.
Trucido: Hybrids are indeed very common. In my “backyard”, the SF Bay Area, Western Gulls and Glaucous-Winged Gulls seem to freely hybridize ( with the Western’s dominating ). The resultant bird looks like a very pale Western Gull. Go south to Monterey and you get the more traditional “dark” Western Gulls.
Another good example is the American Southwest’s various “species” of parthenogenetic Whiptail Lizards in the genus Cnemidophorus, which all seem to have been created by natural hybrid crosses. They have traditionally been identified and named based on morphology, but genetic work has shown multiple distinct lineages within a single named “species”, the result of multiple separate hybridization events. These lineages, parthengenetic as they are, obviously are distinct from one another in an evolutionary sense - But they’re pretty much identical in appearance and habit.
Which brings up the whole bugaboo about what constitutes a species. The Biological Species Concept, basically the species as a population that interbreeds freely under natural conditions, has fallen out of favor a bit in recent decades because of the hybridization problem ( which also becomes particularly thorny the further you move from the animal kingdom ). But it still is probably the most commonly cited definition and it has plenty of defenders.
The Evolutionary Species Concept, on the other hand, has become popular among the cladists ( a philosophical faction of systematic biologists that now dominate in academia, but probably still don’t yet represent a majority of alpha-level taxonomists, who do the actual species-level descriptions ). It defines a species as a single lineage of ancestor-descendant populations which maintains its identity from other such lineages and which has its own evolutionary tendencies and historical fate. So, in other words, Western Gulls and Glaucous-Winged gulls may hybridize in certain zones of contact, but as a whole they remain more-or-less distinct evolutionary entities.
And of course both of those concepts have trouble with the Whiptails, I cited above 
( 'though the ESC works in a fashion, from a practical standpoint it’s a pain in the ass ).
And there’s more theories yet 
. The Morphological Species Concept. The Phylogentic Species Concept ( basically an iteration and refinement of the ESC ). Probably a couple more. All agressively debated. Systematists, like most scientists, just love to argue 
.
- Tamerlane
I was going to skip this one for lots of good reasons but saw the reference to a old thread with Chronos and, well, got sucked in!
Eight plus months later I’ve read a lot of discussions about breeding and hybrids and what can mate with what. This is going to ramble.
Ligers and all: Mammals have some variety of signals to indicate that they are willing and able to mate. Some do not produce ova until after days of hanging around with prospective mates, for example. In the wild it isn’t easy to get one species to produce the right behavior to let the other species what’s cooking. Chimpanzees come in 3-4 sub-species (traditionally 3, just lately someone is pressing for a 4th) and they look alike except for some fine detail, the one that comes to mind is a difference in the molars. Chimps are bought and sold by appearance. Sub-species come from different locations. If a zoo wants a 4 year old female, they might not know where she came from and if they are caging her and expecting her to mate with another of her own sub-species. Zoos are just now correcting this, partly with simple mtDNA tests on chimp hair, but now the humans are scratching their heads and wondering if the sub-species differences were enough to make the reproduction of chimps in zoos less than perfect. Were the cultural differences between the sub-species enough to account for the mamas who wouldn’t care for their offspring (not getting groups support the way they would have if they had been with their own sub-species)?
Maybe a caged tiger and a caged lion left long and lonely enough might figure something out, I don’t know how the ligers are created, but when pushed in other discussion groups, no one has produced a cite for fertile offspring, so far. (I remember the whale business and the dog-wolf discussions, if you are interested in the dog/wolf especially, email me for literature or “specialist” on the
topic.
Why not ask about cheetah and lion mixes? They live in the same areas, might be a more reasonable thing to think about than since they inhabit the same ranges IIRC.
While we may be cousins to the chimps and apes and bonobos, we are not first cousins, certainly not kissing cousins. In another thread I said that there have been two news reports that said new discoveries in the fossil field will overturn evolution history (something like that) but actually it is more like 4 times in thirty days if DNA studies are counted, too. There is no straight line between chimps and humans and bonobos. These lines were called trees and branches but the more fossils found and DNA studies done, the more and more it looks like evolutionaly history will have to be drawn as bushes. There is nothing neat and orderly about evolution.
The pre-pre-pre-chimp and pre-pre-pre-pre-homo that gave rise to whatever it was that eventually became us certainly mated back and forth for hundreds or thousands of years. At some point some kind of separation had to occur and it is separation that gives speciation a chance. Cavalli-Sforza gave something like a minimum of 1,000,000 years apart as the amount of time needed for speciation in an organism like ourselves.
The ethics of creating a human/chimp being prohibits the trying of such a thing and if someone tried it anyway, the ethics involved would be a great factor in not wanting to announce to the world that you’d done it.
The human sperm doesn’t just enter the human ova, yes, they lied to all of us in school! There has to be a “hundred” more things that happen. Things that range from our pH, enzymes in the ova that destroy odd bits of chromosome from the sperm, fussy details about motility - when I start looking at this in detail I wonder that we ever make babies at all. Some recent paper has found fetal changes depending on where the sperm entered the ova? I can’t remember which species this was. There isn’t much that is neat and straight forward about this process either.
With the sequencing of the genome it is now known that the functional part of the genome is very small and once again it looks like things are more complicated than anyone ever thought. Crick’s Central Dogma* may come undone as more work is done on how the chromosomes function to make us come out human again and again. More steps involved in very process.
Good Night!
Jois
*Another great topic.
Hmmm, thanks for the clarification regarding lions and tigers. (resisting the temptation to continue on with a phrase that ends in “Oh my!”)
My professor in my Intro to Human Evolution class, who happens to be the anthropology department chair of my school was the one who had told me about ligers being fertile, but the info I have dug up seems to indicate the opposite. I will speak to him and see if I can find out where he got his information so I can find out what is the case. In the meantime, I offer my deepest apologies for making unsupported statements.
Hmmm, to provide a cite for this liger hijack, here is one source that provides documentation of at least one fertile female tigon (fathered by a tiger, as opposed to ligers, fathered by a lion), and alludes to the existence of other fertile female ligers and tigons.
As is the case too often I can offer no proof for what I say by way of a link - I’d need access to the archives of my local newspaper. In that paper in the late 70s there was a shocking story which seemed to have validity. It was about a Chinese scientific program the aim of which was to create a subhuman being very much resembling a human/ape hybrid. This species was to be used for dirty, dangerous physical work in mines and quarries etc. I’ll never forget the illustration that went with the story because it was surely done by an artist who (in keeping with everyone who read the story) found the idea completely repulsive. They had drawn a picture of a bigfoot creature in chains which had a face of awful sadness and despair. It had too much intelligence to be an animal and looked too animalian to be a human. That’s genetic engineering for you.
Hey Tzel, how about actually posting that link?
What a great idea, why didn’t I think of that?
http://www.google.com/search?q=cache:www.envy.nu/ankhlet/tigonliger.html+ligers+fertile&hl=en
(Here’s a webpage from google’s cache. The page itself is gone now, but it contains a passing reference to female ligers being quite often fertile.)
http://www.loadstar.prometeus.net/tiger/hybrids.html
(Here is the above mentioned link.)
Hmmm, that first link isn’t my fault–I didn’t do the tags manually.
http://www.google.com/search?q=cache:www.envy.nu/ankhlet/tigonliger.html+ligers+fertile&hl=en
“God, Shmod. I want my monkey-man!”
–Bart Simpson
Hmmm, I don’t get it. I’ve had this problem before. Well, the URL is there.
Humans & chimps can breed. But can’t bear children. Whew.
Just a clarification on chromosomal mismatches: Having a different number of chromosomes will not prevent two species from producing a viable hybrid. It may, however, be the direct cause of the hybrid being sterile itself.
In body cells, chromosomes occur in pairs. One member of the pair comes from the male parent, one from the female. Basically all genes in body cells are duplicated (ignoring the X and Y sex chromosomes). Human body cells have 46 chromosomes, those of apes 48.
Eggs and sperm are haploid; that is they contain only one member of each pair of chromosomes. However, these single copies contain all the genetic information necessary to create an individual of a species. Human gametes have 23 chromosomes, those of apes 24.
A human-chimp hybrid would contain 23 chromosomes from the human parent, and 24 from the chimp, for 47 in total. However, there will be a complete (single-copy) set of all genes from each parent. As long as there are not too many conflicts in the developmental program set by each set of genes, such a hybrid could be perfectly viable.
Where the problem would arise is when the hybrid produces gametes. In this process, called meiosis, the chromosomes must line up in pairs so that they may be evenly divided and each gamete receive the proper haploid number. In the case of the human-ape hybrid, the mis-matched “pair” of chromosomes (single in humans, double in apes) might be unable to segregate properly, and most of the gametes might be non-functional due to having too few or too many chromosomes. (However, some could be viable because they would receive the “right” number of chromosomes just by chance.) Therefore the hybrid would probably be infertile.
Given the close genetic similarity between chimps and humans (despite the different chromosome numbers) and the fact that many intergeneric hybrids, of species at least as different in appearance as humans and chimps, have been observed in nature, I would not see any theoretical reason why a hybrid could not be produced by in vitro fertilization. However, as I mentioned there could be developmental conflicts between human and chimp genes that could make a hybrid non-viable.
Good catch, Tzel, this site seems to speak with more authority than the others I’ve seen.
To date, I’ve read about species interbreeding between bears, arctic gulls, ravens of the north west, some whales, wild and house cats, wolves-coyotes-dogs and something about fish, blind and otherwise; these are the examples most frequently discussed.
The problem here is that the animals we say are separate species may in fact, not be. Even the debate about wolves, coyotes and dogs gets hot sometimes. Maybe DNA will resolve some of these problems, but mtDNA and DNA work done on chimps doesn’t seem to have made a great amount of difference.
JOis
If they were the lovable charachters we see on TV, would you be attracted to them?
