A male horse and a female donkey have a hinny. A female horse and a male donkey have a mule.
But hinnies and mules can't have babies of their own. They are sterile because they can't make sperm or eggs.
They have trouble making sperm or eggs because their chromosomes don't match up well. And, to a lesser extent, because of their chromosome number.
A mule gets 32 horse chromosomes from mom and 31 donkey chromosomes from dad for a total of 63 chromosomes. (A horse has 64 chromosomes and a donkey has 62).
Chimeras, Mosaics, and Other Fun Stuff | June 20, 2007 | Monica Rodriguez
Once in a while there are offspring (poorly documented, anecdotal evidence, and probably not yet genetically tested) but the offspring will be either a donkey (with a donkey mother) or a horse (with a horse mother), rather than a hybrid offspring. Similarly, the chimp (and bonobo I suppose), gibbon, gorilla, and orangutan (and perhaps the cryptoanimal the orang-pendek) have 24 chromosome pairs; humans have 23 chromosome pairs. Reportedly/supposedly there have been attempts by some infamous dictators to create a chimp-human hybrid and then mass-produce them for use in a fast-maturing hybrid ape-man army. Bupkis.
My original question was about whether Neanderthals and Homo Sapiens were of different species. If they could ‘bross-breed’ with resulting offspring, then, they were of the same species.
Found one:
...Lee Millon, cytogeneticist at the veterinary genetics laboratory at the University of California at Davis, carried out genetic tests on Kule Mule in 2007. He said the animal's genetic makeup would have probably caused the physical malformation.
"It's like a jigsaw puzzle," Millon said. "It's made up of pieces of donkey and horse."
Millon said that many owners keeping only horses, mules or donkeys added to the popular belief that mules were generally infertile. He said that births to mules were not impossible, just highly unlikely.
Mules are a hybrid of a female horse, which has 64 chromosomes, and a male donkey, which has 62 chromosomes. This leaves female mules with 63 chromosomes, which cannot be split evenly to produce a fertile egg.
Female mules do, however, produce mosaic eggs that contain an even number of chromosomes, but those eggs rarely contain a chromosome half-set that is complementary to another half-set from a male sperm cell.
But Kule Mule beat the odds. Millon said the animal's genome included cells of 63 chromosomes and cells of 64 chromosomes, even though further tests were not carried out because of monetary constraints and because a sample from Kule Mule's father, a donkey jack, was not available.
Colorado miracle mule foal lived short life, but was well-loved
See, the problem is, the shuffling of the chromosome pairs will result in the leaving out of 2 chromosomes, or the inclusion of 1 extra, or 2 extra (1,2,1, total of 4 possible outcomes).
I lost track of this yesterday and then got pulled away. I really do understand the mechanics of it. Got to run out of town this AM, but will try to get back to this discussion.