And what makes tigons, ligers, zorses, geeps and other weird combinations?
The epigenetic code of course controlling the expression of genes. The interesting thing about the epigenetic code is that it is effected by ones behavior providing a genetic feedback loop.
https://notes.utk.edu/bio/greenberg.nsf/0/b360905554fdb7d985256ec5006a7755?OpenDocument
I think it is far from coincidence that socialist secularists have such a need to minimize the difference between man and animal even though such differences are so readily apparent to be undeniable by anyone who has not been hypnotized to ignore them. They need a population who believe themselves and others incapable of doing what is good for themselves without help. They need a population so focused on base needs of sex, food, and entertainment that they can be controlled by regulating the levels of each of those things. Teaching the lie of indistinctness between man and common animals is a way to further that goal.
The last thing they need is a good of people believing in the ascendancy of man with people able to rise above their base desires. They instead what a population of fools totally dependent on the creators and controllers of the bureaucracy.