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.
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.
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
To directly address a few of the points in the OP:
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.
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.
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.
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.
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.)
Which 4 reports are you referrring to? I like to try to keep up.
Humble Servant promises;
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
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
“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
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
Humble Servant:
Short answer - They don’t 
.
Nope . 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 
. 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.
Subspecies are defined however you like . Isn’t this fun ?
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 .
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…
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
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
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
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, 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?
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…
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.”
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.
Humble Servant, you need a hotmail.com address. If you had one I’d send you the expired article.
Jois
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.
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
Jois–it’s hservant@hotmail.com and many thanks.