Diamond

I have two questions to the text of Diamond. First, it is out of the main point, he said that difference between species and race is whether a group of populations would interbreed other group or not. However, there are the example that break away this theory. 

It is an animal interbred between a pig and a sheep. 

It is "Liger" which is interbred between a lion and a tiger.

Like these, species interbreed other species. I know that there are another factors to detect the species. But the division of the species become unclear because of the development of the technology. I'd like to connect this fact with bioethics.

Second, Diamond suggest some alternative to detect the race, and human can be divided in many ways. But they are not easy to notice at one glance and they need scientific investigate like genes. If the group of race is useful for science, human should be divided. However, if the division leads discriminations, human should not be divided. What I want to say that human could be divided depend on the purpose,  for instance, for police evidence human can be divided based on finger print or skin color, for medical research based on digestion or resistance, for politic based on nationality.