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Re: Neanderthals horse or mule?
Todd A. Farmerie (taf2@po.CWRU.Edu)
2 Oct 1995 07:37:17 GMT
[I think my first attempt got booted by my system. If not, I apologize for
the duplication.]
In a previous article, hubey@pegasus.montclair.edu (H. M. Hubey) says:
>sjoland@ix.netcom.com (Peter/Stephen Sjolander ) writes:
>
>>We have a modern day example to follow. The donkey and the horse.
>>They can bread and make a mule. But the mule can not bred with another
>>mule and make a mule.
>
>NOrmally that's what happens. some years ago there was a report
>in Science News about a fertile mule found in China. IF they find
>another one, there's the mule species. If not, then they can
>cross it with horses and donkeys and check the results.
>
We are getting a bit off topic, but . . .
There is a finite, but incredibly small probability that any particular
mule will successfully breed. It will occur if, and only if during
meiosis, when the chromosomes are divided to produce a gamete (egg or
sperm) with single copies of each chromosome, it perfectly resegregates the
parental chromosomes (in other words, contains only the horse copies, or
only the donkey copies). This happens, world-wide, about once every three
years (or maybe slightly more frequently, since the progeny of a successful
male mule may not be recognized as such). The progeny will be a horse, a
donkey, or a mule, depending on which parental chromosomes come from the
mule, and to which species the other partner belongs. If the progeny is a
mule, it will have no higher probability of breeding than any other mule,
since it will have the same segregation probability problem, nor will a
mule, once having produced an offspring, have a greater probability of
producing another than any other mule. You will almost never produce
progeny of two mules, because the probability of this segregation
phemonenon occurring in two mules of opposite genders at the same time
in the same herd, and that egg finding that sperm, is astronomically low.
Non-parthenogenic animals rarely produce new species by hybridization, but
instead primarily do so by isolation/genetic drift. (By the way, if you
want two species (different numbers of chromosomes) that cross breed and
produce fertile offspring, compare the common horse and the Przewalski
horse.)
If you want to consider neanderthals as hybrids, what are the two species
that hybridize to produce them? The discovery of what appear to be
families of neanderthals argue against a mule model, while if the hybrids
are fertile, their status as independent species comes into question.
Todd
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