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Mule Gives Birth
!splut writes "Thumbing it's nose as science, a Moroccan mule has given birth. Mules, hybrids between horse and donkey, are normally infertile, due to differences between the number and structure of horse and donkey chromosomes. Nevertheless, for reasons not well understood, fertile mules do occur, infrequently, with some 60 documented live births since 1527."
Nice troll, but the existence of natural phenomena that are not understood in no way represents a "failure" of science. It would *only* be a failure if science was a system of belief that purported to explain everything about the Universe (like, say, religion). It is not such a system.
Liberal (adj.): Free from bigotry; open to progress; tolerant of others.
So what is really interesting is whether the offspring are fertile. If so, then we can start breeding mules from mules, and we have a new species.
And where does the infertility in mules normally lie? Is it a male thing or a female thing? Or both?
The infertility arises from the fact that normally, during meiosis (the production of sex cells), like chromosomes in the diploid compliment of chromosomes (one chromosome from each parent) pair up, separate, and produce haploid daughter cells. Mules are in the awkward position of having 31 chromosomes from the donkey parent and 32 from the horse parent, giving them an odd number of chromosomes total, even though they are in a diploid state.
On the one hand this gives the mule "hybrid vigour" - it exhibits many of the desirable characteristics of each parent. On the other hand, this odd number of chromosomes poses problems for meiosis - the normal meiotic process just doesn't produce viable sex cells. (So, in answer to your question, the infertility is a male and female thing.)
The fact that the foal was born at all suggests that the mother, the father, the foal, or some combination has some manner of chromosomal aberration - an extra chromosome from one parent, or something along those lines - resulting ultimately in a viable diploid zygote.
Chromosomal aberrations often result in infertility to begin with... but lets pretend that the foal is fertile, and is able to breed with horses, donkeys, or future siblings. It's offspring will not exhibit the hybrid vigour that is observed in the mule, because the offspring will not have the characteristic compliment of horse and donkey chromosomes. And since that vigour is the reason why people breed mules in the first place, a new breed of fertile mule would not be that useful.
The angel in the oatmeal.
Horse mother, donkey sire - offspring is a mule. Donkey mother, horse sire - offspring is a hinny. Genetically indistinguishable from a mule. I presume the two different names predate modern genetics.
Mules are stronger, and more intelligent than horses.
Like mules, a hybrid of a zebra and a horse, or a zebra and a donkey, is infertile. Or a hybrid between any of the three species of zebra.
Fans of breeding exotic hybrids have dreamed up all kinds of "cute" names for the different crosses. Seems annoying to me.
Breeding exotic hybrids of endangered species seems very irresponsible to me. But there are people who do it. It seems to me that breeding a Liger or Tigon means you are wasting the reproductive potential of the parents. The Quagga is a recently extinct subspecies of Plains Zebra. There is a project to find Plains Zebras with the most Quagga like characteristics, and breed them, to try to restore them.
This seems like a bad idea to me too. It seems to me that it makes more sense to husband the remaing genetic heritage of the Plains Zebra.
The sixth surviving equid is the very rare Przewalskis' Horse. Extinct in the wild. 150 survive in zoos. Originally found in Mongolia. It is not too late to try to preserve this animal's genetic heritage.