Evidence suggests that a segment of our species did mate with Neanderthals, since Neanderthal DNA is within the genome of non-African humans, but that Neanderthals were simply absorbed into Homo sapiens.
The clymene, on the other hand, is now viewed as being distinct from striped and spinner dolphins.
Amaral and her colleagues explained that DNA analysis shows the clymene's mitochondrial genome most resembles that of the striped dolphin. Its nuclear genome, however, is more closely related to that of the spinner dolphin.
Striped and spinner dolphins don't even look the same, making the love match all the more surprising.
"Physically, they possess different coloration patterns and their skulls differ in their shape and size," Amaral said. "These differences, however, do not prevent the dolphins from mating and producing fertile hybrids."
Naturally occurring hybrids are not so rare among plants, fishes and birds. It's not because they are more amorous. It's just primarily due to the fact that genetic and embryonic development factors in mammals tend to prevent their hybrid offspring from being viable.