Can Humans and Chimps Breed?

[Humble Servant]

Matt Ridley, in his book, Genome, which I am reading with pleasure, discusses the fact that humans and chimpanzees have make-ups that, genetically, are 98% the same. Then he say, about human ancestors,
"...this little band of apes shares a large mutation: two of their chromosomes have become fused. Henceforth they can breed only with their own kind, even when the 'island' rejoins the 'mainland'. Hybrids between them and their mainland cousins are infertile. (I'm guessing again--but scientists show remarkably little curiosity about the reproductive isolation of our species: can we breed with chimps or not?)"
I searched and found that several threads (http://boards.straightdope.com/sdmb/showthread.php?threadid=28609), including this one with a very interesting exchange between Chronos and Jois (http://boards.straightdope.com/sdmb/showthread.php?threadid=28502#post534197), have addressed this issue, but I still have a few questions.

1. Are scientists really not interested in this issue? Is Ridley correct in saying that we don't really know that humans and chimps can't breed? Wouldn't the ability to interbreed be a serious issue for archaeologists attempting to establish a family tree consistent with fossil records? Does this site (http://www.don-lindsay-archive.org/creation/mule.html) or or this site (http://www.gate.net/~rwms/hum_ape_chrom.html) contradict Ridley?

2. If chimps and humans can't breed because of chromosomal mismatches, then how did the first human-like ancestor with the problematic mutation breed with anyone (the issue Chronos and Jois were discussing)? Any further thoughts on this? I haven't seen a definitive explanation I can understand.

3. Can we assume the worst about human sexual proclivities and conclude that interbreeding is no longer possible because we would otherwise be seeing the results? (No hot monkey sex comments please.)

4. I must admit to experiencing a large "ick" factor when thinking about this topic. Is my response more likely cultural or genetic?

[dolphinboy]

While not an expert of interspecies breeding I would say that while 98% common genome sounds like a pretty close match we're still talking about hundreds or thousands of differences.... anyone of which could eliminate the possibility of fertile offspring or viable offspring at all. (Remember when Planet of the Apes was first released... I think a lot people started thinking about this topic but I digress.)

Could a human and chimp have some sort of sexual encounter? Probably, but it's a pretty disgusting thought. Would a pregnancy result from that union? Probably not... and if it did a viable embryo is pretty unlikely due to the 2% difference you mentioned. Has anyone tried the experiment? I sure hope not...

[dropzone]

Originally posted by Humble Servant
3. Can we assume the worst about human sexual proclivities and conclude that interbreeding is no longer possible because we would otherwise be seeing the results?
I think that we can assume it has been tried. As we have seen no "results," we can also assume that it failed.

[Darwinself]

3. Can we assume the worst about human sexual proclivities and
conclude that interbreeding is no longer possible because we would
otherwise be seeing the results? (No hot monkey sex comments
please.)
**************************************************

Not to mention your opinion of monkey morals.


anonymouse
once again...
"Cynicism is intellectual dandyism."

[Eve]

"Can Humans and Chimps Breed?"

—Well, that WOULD explain Jerry Lewis . . .

[Darwinself]

"Can Humans and Chimps Breed?"

—Well, that WOULD explain Jerry Lewis

Eve's comment on this thread
***********************************************

To which i cant help say

Oh, Eve.....you got a lot of 'splaining to do.

anonymouse

[Cervaise]

humans and chimpanzees have make-ups that, genetically, are 98% the same
I seem to remember reading something about how the 98% figure is generally misunderstood by the lay public. In other words, it sounds like an impressive number, but reproductively speaking, all known life forms have a surprising amount of genetic overlap. Don't we also have something like 70% of our DNA in common with, say, sponges? And doesn't that make the 98% number much less significant, biologically, than it would initially appear to the lay reader?

Can anyone back up my fuzzy recollection on this?

[Chronos]

I had always heard the statistic quoted as "Humans and chimpanzies (or maybe gorillas, I'm not sure) are more genetically similar than are horses and donkeys.". The obvious implication is that us apes would be able to interbreed, but it's probably best not to read too much into it.

[Guinastasia]

Considering that mules-the offspring of a horse and a donkey-aren't capable of breeding...

[Tzel]

No, mules are not capable of producing offspring themselves, but they are products of mating between two different species. Even though humans and chimps certainly can't produce fertile offspring, even infertile offspring would be very interesting. I'm not going to say that it's a good idea though.

Why all the disgust at the thought anyway? I assume that you all don't find so much wrong in horses and donkey's mating, no?

[Arjuna34]

Originally posted by Tzel

Why all the disgust at the thought anyway? I assume that you all don't find so much wrong in horses and donkey's mating, no?

Certainly not on the first date! ;)

Arjuna34

[Guinastasia]

Okay, then YOU can have sex with Bobo the Chimpanzee!

;)

[dolphinboy]

Having worked around chimps I can attest to the fact that adult chimps are smelly disagreeable creatures and not the lovable characters you see on TV. Having sex with a chimp, or any barnyard animal for that matter, is disgusting to most people I know. If such a thing excites you you might want to consult with a professional therapist...

[barbitu8]

Originally posted by Chronos
I had always heard the statistic quoted as "Humans and chimpanzies (or maybe gorillas, I'm not sure) are more genetically similar than are horses and donkeys.". The obvious implication is that us apes would be able to interbreed, but it's probably best not to read too much into it.

Chimps are our closest relative, with orangutans a close 2d. But I thought the % was over 99%.

[wevets]

I think that we can assume it has been tried. As we have seen no "results," we can also assume that it failed.

We can? I really really hope not. [cue dramatic music] Some things Man was not meant to know... [/dramatic music]

I mean, I'm all for fighting ignorance and everything, but who'll be the first to volunteer for this particular experiment?

[Trucido]

I don't think volunteers would be a problem. If there exists the possibility for a fetish, a group of people with that fetish will congregate somewhere on the 'net.

Slight hijack, but are there hybrids other than mules? I ask because I'm having difficulty imagining the offspring of such an unholy union. Seems like a lot of physiological gaps to bridge.

[wevets]

But I thought the % was over 99%.

Jared Diamond's The Third Chimpanzee cites the similarity at 98.4% (but that's a ten year old source), so I did a search; This site says about 99% similarity. (http://www.biosci.uga.edu/almanac/archive/spring_97/bio_104/notes/mar_31.html) This page supports the 98.4% figure. (http://chimpanzoo.arizona.edu/study/chimp.html). I dunno, I'm not a geneticist, maybe the more genetically-inclined among us can tell us if this number is wrong or out of date.

Just as an aside, this page describes the anatomical differences between humans and chimpanzees (http://www.dla.utexas.edu/depts/anthro/people/faculty/cbramblett/ant301/seven.html)

[Smeghead]

I volunteered once, but the chimp turned me down.

Seriously, though, this isn't really my area, but I hang out with people that know a bit about this kind of stuff. The general impression I get is that production of a hybrid (probably infertile) wouldn't be too surprising, but it would probably take a whole lot of trying and more than a few failures first, which is why the possible attempts by a hypothetical lonely zookeeper haven't shattered our worldview yet.

[mangeorge]

Cervaise recalls, fuzzily;
I seem to remember reading something about how the 98% figure is generally misunderstood by the lay public. In other words, it sounds like an impressive number, but reproductively speaking, all known life forms have a surprising amount of genetic overlap. Don't we also have something like 70% of our DNA in common with, say, sponges? And doesn't that make the 98% number much less significant, biologically, than it would initially appear to the lay reader?

Can anyone back up my fuzzy recollection on this?
Yeah, I also have a fuzzy recollection of reading about this. My take was a little different, though.
As the similarities near 100%, each point becomes more significant. That's why we look much more like apes than like sponges. 'Cept for my ex. :D (love ya, darlin')
All living things share some DNA, I think.
Peace,
mangeorge

[Arjuna34]

Originally posted by dolphinboy
Having sex with a chimp, or any barnyard animal for that matter, is disgusting to most people I know. If such a thing excites you you might want to consult with a professional therapist...

Why- can a therapist hook me up with a chimp? ;)

Seriously, if it's possible, the most likely way it would happen is for some scientist to take some human eggs and fertilize them with chimp sperm (or vice versa), then implant the fertilized result into a chimp, to bring the offspring to term. That way no sex is involved, and you can try to mass-fertilize a lot of eggs in the hope of one taking.

Arjuna34

[Gaspode]

Originally posted by Trucido
Slight hijack, but are there hybrids other than mules? [/B]

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.

[Tzel]

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.

[barbitu8]

Horses have 64 chromosomes, donkeys 62, and mules/hinneys 63. http://boards.straightdope.com/sdmb/showthread.php?threadid=35128

[Gaspode]

Originally posted by Tzel
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. [/B]

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.

[Trucido]

Weren't the villainous apes in Congo supposed to have been some sort of hybrid along these lines?

[blandart]

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!

[Lumpy]

Oddly enough, no one has mentioned African & Asian elephants. There was one recorded case of interbreeding, but the calf was stillborn.

[Tamerlane]

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 :D ( '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 :p .

- Tamerlane

[Jois]

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.

[Tzel]

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.

[Tzel]

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.

[G. Nome]

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.

[Tzel]

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.)

[Tzel]

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

[pezwookiee]

"God, Shmod. I want my monkey-man!"
--Bart Simpson

[Tzel]

Hmmm, I don't get it. I've had this problem before. Well, the URL is there.

[handy]

Humans & chimps can breed. But can't bear children. Whew.

[Colibri]

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.

[Jois]

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

[Freedom]

Having worked around chimps I can attest to the fact that adult chimps are smelly disagreeable creatures and not the lovable characters you see on TV.



If they were the lovable charachters we see on TV, would you be attracted to them?

:)

[Allworthy]

March 31, 2001 (AP) - Scientists at the Woodley Labs in Tacoma Park, MD, have announced the termination of the controversial National Chimpanzee-Human Hybridization Program, citing the prohibitive cost of the massive quantities of banana daquiris necessary to the success of the project.

[Lumpy]

Originally posted by Jois
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.
This raises an interesting idea regarding speciation. Perhaps humans and chimps are technically compatable as far as their chromosomes or development genes go; but suppose the human/chimp lineage split due to a single mutation in the enzymes that allow a sperm to fertilize an egg. For that matter, maybe some cases of human infertility are caused by such a mutation. It could be that humans and chimps aren't naturally interfertile, but it could be accomplished with a minimum level of biochemical intervention.

[Jois]

Hi Lumpy,

I agree it wouldn't take much to make the system not work and maybe that the reverse might not be that difficult either. Just seems the former is always more difficult than the latter!

Allworthy, I thought those newspaper just showed up one day in advance. :)

Jois

[Colibri]

To directly address a few of the points in the OP:

Originally posted by Humble Servant
Matt Ridley, in his book, Genome, which I am reading with pleasure, discusses the fact that humans and chimpanzees have make-ups that, genetically, are 98% the same. Then he says [snip] . . .(I'm guessing again--but scientists show remarkably little curiosity about the reproductive isolation of our species: can we breed with chimps or not?)"

[snip] . . . I still have a few questions.

1. Are scientists really not interested in this issue? Is Ridley correct in saying that we don't really know that humans and chimps can't breed? Wouldn't the ability to interbreed be a serious issue for archaeologists attempting to establish a family tree consistent with fossil records? Does this site (http://www.don-lindsay-archive.org/creation/mule.html) or or this site (http://www.gate.net/~rwms/hum_ape_chrom.html) contradict Ridley?

The ability to interbreed, or to produce viable hybrids, between apes and humans, is not really of any great theoretical interest. There is no question that humans and chimps are different species, by any usual definition. (Even the production of a fully-fertile hybrid would not invalidate that, according to a modern application of the biological species concept.) Genetic analysis demonstrates that the genomes are very close. However, although there is something of a correlation between the degree of genetic similarity and the ability to produce fertile/viable hybrids, that correlation is not strict. Some forms that closely similar genetically are not interfertile, and while other forms that are less similar may be perfectly fertile. Hybrid fertility/viablity may depend much more on the details of the genetic changes that have taken place, rather than simply on how many there have been.

Note that the figure of "99% (or whatever) similarity" between chimps and humans refers to differences in nucleotide sequence in the genetic material. Many such subsitutions are "silent," that is, have no effect on the protein produced by a gene, or occur in non-coding sections of the DNA. Such figures also do not take into account such important genetic changes as inversions, translocations, and chromosome fusions, etc, that can have major impacts on fertility and viability. Finally, the morphological differences between chimps and humans are most likely due to mutations in regulatory genes and/or changes in developmental pathways, in which a relatively minor genetic change can produce major changes in morphology.


2. If chimps and humans can't breed because of chromosomal mismatches, then how did the first human-like ancestor with the problematic mutation breed with anyone (the issue Chronos and Jois were discussing)? Any further thoughts on this? I haven't seen a definitive explanation I can understand.

The difference in chromosome number between chimps and humans seems to be due to the fusion of two ape chromosomes into one human chromosome. When this first took place, the two ape chromosomes might still have been able to "pair up" somehow with the fused partner during meiosis, resulting in viable gametes. Fertility might be reduced, but occasional reproduction would still possible. Also some viable gametes could be produced just by chance. Once a few individuals with the fused chromosomes were produced, close inbreeding could preserve the change.

Differences in chromosome number between closely related species is actually not that uncommon, so something like this process must happen regularly.

Once a separate lineage was established, subsequent translocations and inversions in the chromosomes could prevent them from pairing up in meiosis and result in infertility.


3. Can we assume the worst about human sexual proclivities and conclude that interbreeding is no longer possible because we would otherwise be seeing the results? (No hot monkey sex comments please.)

As others have said, given human sexual proclivities we can probably assume that intercourse has sometimes taken place. But intercourse does not equate with fertilization, and fertilization does not equate with the production of a viable offspring. Production of a hybrid could be almost impossible in vivo, while quite feasible in vitro.

[Humble Servant]

Thanks for all the responses, especially to Colibri for trying to directly answer my perhaps poorly worded OP. I assure you all that my questions are serious and not prurient.

Originally posted by Jois
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)?Ok, I think I need a quick primer on subspecies--given the issues with defining species Tamerlane and others have mentioned, how does anyone agree on subspecies? Is there a recognized body that decides what subspecies can be recognized? If subspecies are defined by geographic location and "culture," would it ever be appropriate to classify humans by subspecies on a similar basis? (I realize how extrememly charged this question may be--I have read with interest the recent threads refuting (successfully, I thought) the idea that race can be found in human genes.) 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.Which 4 reports are you referrring to? I like to try to keep up.

[mangeorge]

Humble Servant promises;
I assure you all that my questions are serious and not prurient.
Ok, as long as you promose, I'll tell you about it.
It wasn't my fault. I was on safari and had smoked a couple bowlfuls, you see. And I decided to take a little walk by myself in the jungle. All of a sudden this pack of female bonobos jumped me and, and... well, you get the picture. Let's just say they "knew" me, in the bibical sense. For about three days they held me captive. Fed me bananas and such.
But I didn't enjoy it.
If there were any offspring nobody told me about it. Anybody seen any green-eyed bonobos?
Peace,
mangeorge

[Jois]

Hi Humble Servant,

I'd commented in an earlier post: "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."

To which you replied: "Which 4 reports are you referrring to? I like to try to keep up."

http://www.independent.co.uk/news/UK/Science/2001-01/dna090101.shtml

Mitochondrial DNA sequences in ancient Australians: Implications for modern human origins Gregory J. Adcock, Elizabeth S. Dennis, Simon Easteal, Gavin A. Huttley, Lars S. Jermiin, W. James Peacock, and Alan Thorne PNAS 2001;98 537-542

http://www.pnas.org/cgi/content/abstract/98/2/537


"Nanjing Man" (Anything you can find.)

The article rather than news reports:
Hanson, B. (2001) Dating Nanjing Man. Science. 291 (5506). 947

http://www.cnn.com/2001/TECH/science/03/21/ancient.skull.ap/index.html

http://dailynews.yahoo.com/h/ap/20010321/sc/ancient_skull_1.html

http://www.washingtonpost.com/wp-dyn/articles/A39106-2001Mar21.html

New York times: Skull May Alter Experts' View of Human Descent's Branches By JOHN NOBLE WILFORD Paleontologists in Africa have found a 3.5 million-year-old skull from what they say is an entirely new branch of the early human family tree, a discovery that threatens to overturn the prevailing view that a single line of descent stretched through the early stages of human ancestry.

Science vol. 291 (no. 5508), pg. 1460, 23 Feb. 2001, Pickford and Senut have chosen to name a new genus and species for Millennium Man: _Orrorin tugenensis_. "Orrorin" apparently means "original man" in a local dialect.

http://www.boston.com/dailyglobe2/079/science/In_China_strange_bronze_heads_rewrite_history+.shtml

That should boil down to four without the DNA article. Some are about the same topic, many newsreports have already expired, hopefully you'll find one on each topic just the same.

Jois

[Jois]

I've bumped this up so maybe someone will answer Humble Servant's question about species:

"Ok, I think I need a quick primer on subspecies--given the issues with defining species Tamerlane and others have mentioned, how does anyone agree on subspecies? Is there a recognized body that decides what subspecies can be recognized? If subspecies are defined by geographic location and "culture," would it ever be appropriate to classify humans by subspecies on a similar basis?"

Jois

[Tamerlane]

Humble Servant:

...how does anyone agree on subspecies?

Short answer - They don't :D .

Is there a recognized body that decides what subspecies can be recognized?

Nope :D . What does exist are boards that regulate nomenclature. So there is a Zoological Board of Nomenclature and a Botanical Board of Nomenclature ( which subsumes Fungi due to historical connections ). Not sure if a similar organization exists for Protists - Most likely the Zoological subsumes them ( again, for historical reasons ). These boards act solely to prevent duplication of names and to lay down rules on how the naming process is to be done.

These rules can be bewilderingly complex at times, especially when it comes to minutia like designating "type" specimens ( i.e. all species must have an actual physical type specimen, from which the description of the species in question was based on, deposited in a museum somewhere - Hence all those drawers and drawers of preserved critters you see in museums ). There are about a dozen names for different types of "types" ;) .

Nor are the rules necessarily congruent between the two organizations I've named. So botanists must write up a full description in Latin when describing a new species. Zoologists need not. Duplication of scientific names in a single binomial, i.e. the Red Fox, Vulpes vulpes, is permitted under the zoological rules and verboten under the botanical ones. Etc.

The boards also sit in judgement of questions of naming priority. If two people assign different names to the same organism, the first published name takes priority. Sometimes ( rarely ) this is amended if there is an ancient obscure name someone digs up that should have priority, but the community petitions to keep the old one to prevent confusion. I believe this happened with the Boa constrictor.

However, what these boards don't do, is sit in judgement of what is a valid species ( or subspecies ). That is a task of the scientific community at large. If you publish it and follow the proper procedural rules - It exists. This even goes down to self-published vanity papers. Of course if you publish in a peer-reviewed journal you are much more likely to be taken seriously ( unless you work on a very obscure group like my roomie - The major papers in his little specialty were self-published back in the 50's and thus must be tracked down ). And of course whatever you publish is subject to revision by other scientists. And thus battle is joined :p . Is the Pacific Treefrog more properly included in the genus Hyla or Pseudacris? Consensus seems to have shifted to the newer view of Pseudacris, but I've seen it go back and forth a couple of times.

If subspecies are defined by geographic location, and "culture"...

Subspecies are defined however you like :D . Isn't this fun :p ?

The concept of the subspecies is a much debated one. Some hardcore evolutionary biologists have little use for it, because it de facto contains no useful large-scale evolutionary info. i.e. the ESC is already tracking the smallest lineage on a single trajectory, the subspecies is already part of that larger trajectory. Many others however, point to its presumed utility in the field.

So let's take an example I used in a "race" thread - the salamander Ensatina eschscholtzii. Very common critter, with no real common name - Folks call them "Ensatina's". It has several subspecies, some of them markedly different in coloration. Here, in the Bay Area, we get E. eschschotzii xanthoptica. It's a "classic" Ensatina body-color-wise, with the lower half of its eyeball colored a shimmery gold ( the upper half is pitch black ). North we get E. eshsholtzii oregonensis, which is identical, except the whole eye is black. Around Mendocino county they intergrade - the result is a critter with a black eye with a few flecks of gold ;) . So are the differences between these two subspecies significant? Nope. They just have one tiny character that's expressed differently and has been maintained because these aren't outstandingly vagile critters. It probably isn't even an adaptive character - More likely a persistent "neutral" mutation.

So is it worth it to designate the two variations above as separate subspecies? You tell me - I have no idea :D .

There is no consensus on what, exactly, constitutes a subspecies. Every taxonomist defines it differently depending on what organism they work on. Primate people may use "culture". Are "transient" Orca's that tend to roam nomadically and feed much more heavily on sea mammals a distinct subspecies from "resident" Orca's that eat mostly fish? Dunno - ask a whale guy ;) .

Generally the term is used as to describe a semi-coherent population, generally with a more-or-less well-defined geographic range, that consistently exhibits some minor characteristic ( usually morphological - often color ) not found in other related populations - But these characteristics are not considered enough ( in the mind of that particular researcher ) to split them off as a separate species. So folks give it a name and make the linnaen binomial, a trinomial. Some other folks don't bother. It's purely a voluntary philosophical decision :) .

I'm not generally opposed to the idea. Another level of categorization is not a huge hindrance as long as you remember that it generally lacks evolutionary significance. It can be a handy, if imprecise, shorthand if you want to look at variation in the field and catalogue natural gene-flow, for instance.

However...

...would it ever be appropriate to classify humans as subspecies on a similar basis?

IMNHO - NO

Why not? Because "race" has become a politicized term and subspecies is roughly synonomous with race. Biologists sometimes use the term race, when referring to what other biologists refer to as subspecies. And both of those, are in turn, sometimes used as a synonym with population. Though in fact population is the most precise term, and can be used for any size group, outwardly distinct or not.

Population, is, I think, a neutral enough term. We CAN refer to distinct human populations.

But race in humans has been tainted by its association with the racialist ( often a synonym for racist ) notion of the classic "five races", which, in affect, attempted to partition humans into discrete species ( even though this was explicitly denied ) and which completely lacked any basis in biological reality. Using subspecies, which most folks don't grasp as the insignificant ( and often imprecise ) term that it is, brings in the word "species" and causes unnecessary confusion. For purely associative reasons I think it should be avoided.

- Tamerlane

[Tamerlane]

Addenda to my earlier post: There is also a board that regulates the common, English names of birds and only birds. To the best of my knowledge it is the only one that exists for common names. So a Cinnamon Teal is always a Cinnamon Teal. Whereas a "Drum" or "Perch" might be any of a dozen different types of unrelated fish.

This is why when I took Veretbrate Natural History ( but not Ornithology of course ), birds were the only group of animals we weren't required to learn latin binomials for.
As a result of that experience, to this day I know far fewer scientific names for birds ;) .

- Tamerlane

[Tamerlane]

Just to round out to an even 150 posts ;) .

Further comments Re: Human subspecies - Humans are so outstandingly vagile now and so overwhelmingly panmictic that the categorization of subspecies in humans is probably a useless exercise anyway. At least if you want such designations to have any predictive value. Sure we can probably delineate thousands of discrete human populations at any point in time, by sequencing data, or cultural designation, or whatever. But the borders are going to be so fuzzy, so malleable, and subject to so much rapid change through time, that all but the most isolated, endogamous populations are going to fracture and morph rapidly. By the time you assigned names to all of the human populations out there, half may have disappeared, merged or changed from there original defining parameters.

Humans really ARE different from most ( all ) other animals in this regard.

- Tamerlane

[Humble Servant]

Excellent! Superior posts, Jois and Tamerlane! Thanks for spending your 150th here.

The "China strange bronze heads" report is the most elusive--I can't find anything at all online on it. Here is a link to an abstract on the date of Nanjing man (http://www.gsajournals.org/gsaonline/?request=get-abstract&issn=0091-7613&volume=029&issue=01&page=0027), but I couldn't find much available on that either. The Kenyan skull and the Australian dna articles are easier to find and I had read those reports--the Leakeys are publicity machines.

Just to speculate, if some unethical ("mad") scientist was determined to try in vitro work on chimp/human dna, where do you think it would most likely occur? I.e., where are the controls/peer review/pressure most lax, but the equipment/skills most available?

[JosephFinn]

Just for the hell of it, here is a picture of a liger named Hobbs:

http://www.sierrasafarizoo.com/animals/liger.htm

Impressive sucker, no? Take a look at the size estimate: 800-1200 pounds, twice the size of a Siberian tiger. Let's have a hearty "hurray" that they don't occur naturally.

From the web page:

"Hobbs: Hobbs, with a mane like a lion, the long body of a tiger, and more mass than either, is a striking animal. He exhibits traits of both parents, his mother was a Bengal tigress and his father an African lion. He roars like a lion and swims like a tiger. He's definitely all cat. He likes to play, and for all his incredible bulk he moves just as silently as any other cat."

And we have a contender in that "What Animal can Beat Another Animal?" thread.....

[JosephFinn]

And another liger (god, I love cats). These have people next to him, so you get a sense of scale:

http://www.tigers-animal-actors.com/about/liger/liger.html

All I can say is: "Whoah."

[Lumpy]

One good argument against considering different groups of humans as subspecies is that there is no consistancy in the traits that one might use to classify them. Pick skin color as your basis of classification, and you group various peoples together. Pick a completely different criterion, such as Rh blood factor, and you end up lumping together another set of peoples entirely. Ditto minor but distinct things like tooth patterns, overall body build, eye folds, etc.

In short, there doesn't seem to be any group of people who have a set ofunique characteristics distinguishing them from the rest of humanity. As far as genetics studies go, humans seem to consist of three different kinds of Africans, and everybody else put together.

[Jois]

Humble Servant, you need a hotmail.com address. If you had one I'd send you the expired article.

Jois

[Badtz Maru]

Originally posted by Lumpy
One good argument against considering different groups of humans as subspecies is that there is no consistancy in the traits that one might use to classify them. Pick skin color as your basis of classification, and you group various peoples together. Pick a completely different criterion, such as Rh blood factor, and you end up lumping together another set of peoples entirely. Ditto minor but distinct things like tooth patterns, overall body build, eye folds, etc.

In short, there doesn't seem to be any group of people who have a set ofunique characteristics distinguishing them from the rest of humanity. As far as genetics studies go, humans seem to consist of three different kinds of Africans, and everybody else put together.


I think the same is true of many subspecies classifications, however. Often the only distinguishing characteristics between two sub-species is one physical trait, like coloration, length of tail, etc. If humans were just another animal to us, we would probably have them divided into several subspecies.

[Tamerlane]

Badtz Maru: Which is one reason some systematists think the use of subspecies should be abandoned :) - It's a vague device which often conveys only superficial data.

But I think I should make the point, again, that humans are NOT like other animals:

1.) Humans are circum-global, and have been for a fairly long time.
2.) Humans currently have HUGE populations.
3.) Humans intergrade ceaselessly across many planes of contact - More than any other species I can think of, because of that global distribution and their penetration of every environment.
4.) Humans are the MOST vagile and adaptive species of animal ever. Birds may travel thousands of miles in a year, but any given species is restricted to certain types of habitat. Humanity has never had that restriction.
5.) As a result of the above, the same phenotype has evolved multiple times at widely separate points with similar environmental conditions. But these similar phenotypic expressions are independent of genetic relatedness, as Collounsbury, tomndeb, Edwino and others have repeatedly pointed out.

You don't find these sets of conditions among other animals. Over in Great Debates, tomndeb just made a comparison between Andaman Islanders and the people of the Congo Basin - phenotypically similar, yet genotypically distant ( relatively speaking of course ).

If you attempted to classify people into "several subspecies" based on gross morphology, you'd have to group those two together. And that not only would not be informative - It would be downright obsfucatory. NO other species complex has that sort of confusion. There are very few species of animals that has widely separated populations, populations separated by numerous other populations, that express the same phenotype, but are genotypically remote. Those that are, are not placed in the same subspecies. I daresay Mexican and Indian Wolves appear somewhat similar ( smallish, adapted to hot climes ) - but they aren't classified together. Subspecies generally do have a congruence of many genetic traits, when you bother too look at them, even if they were originally identified by morphological markers. That's because they generally have a linear geographic distribution and aren't being constantly penetrated and re-penetrated by different populations from different directions. Most new species probably have arisen not from immigration/emigration ( although that happens - i.e. Darwin's Finches ), but rather from vicariance events that partition populations ( and may alter local environmental factors ).

Nope - You can't do "several subspecies" of humans. Or you can try, but it's been discredited. That's the classic "negroid/capoid/caucasoid/mongoloid" trap that's been proposed before. Classifying people by skin color or the like may be a handy cultural shorthand. But it is important to realize the lack of biological grounding.

What you can do is refer to the many hundreds of distinct human populations, like the Andaman Islanders, who may share a few distinct characters ( but always subject to change, the more so as modern life has accelerated the number of directions and sources of gene flow ).

And I still dislike using the term "subspecies" for those populations, which I think implies to the public at large a greater permanence and separation than actually exists.

- Tamerlane

[Humble Servant]

Jois--it's hservant@hotmail.com and many thanks.