Positive evidence that Noah's Flood didn't happen, hence the biblical account is incorrect. You can say it's magic if you want.
Let me break it down for you;
1) Cheetahs have an extremely low graft rejection rate.
2) Other animals have high graft rejection rates.
3) It is therefor assumed that cheetahs went through a population bottleneck.
4) According to the Biblical account of the flood, all terrestrial animals went through a population bottleneck.
5) It is very difficult for other animals to receive grafts from donors. Ergo
6) The other animals (including humans) did not go through a bottleneck therefor...
7) No flood.