Scientifically, it could probably be done. Humans have one pair fewer chromosomes than other apes, with ape chromosomes 2 and 4 fused in the human genome into a large chromosome (which contains remnants of the centromere and telomeres of the ancestral 2 and 4). Having different numbers of chromosomes is not an absolute barrier to hybridization; similar mismatches are relatively common in existing species, a phenomenon known as chromosomal polymorphism. All great apes have similar genetic structure. Chromosomes 6, 13, 19, 21, 22, and X are structurally the same in all great apes. Chromosomes 3, 11, 14, 15, 18, and 20 match between gorillas, chimpanzees, and humans. Chimps and humans match on 1, 2p, 2q, 5, 7–10, 12, 16, and Y as well. Some older references include Y as a match between gorillas, chimps, and humans, but chimpanzees, bonobos, and humans have recently been found to share a large transposition from chromosome 1 to Y not found in other apes. This degree of chromosomal similarity is roughly equivalent to that found in equines. Interfertility of horses and donkeys is common, although sterility of the offspring (mules) is nearly universal (with only around 60 exceptions recorded in equine history).