Help me debunk this racist

[sc94597]

toastboy44562 said:

Radej said:

toastboy44562 said:

The offspring cannot have offspring. A liger cannot have kids so a tiger and a lion are of a different species

A two second search says that Ligers can reproduce, so can basically? every mix of dog breed. There are 15 species of finch in the galapagos Islands, with differences as simple as the size of their beak or the color of their feathers, they can all reproduce with one another and create fertile offspring, but they're still categorized as different species.

Male ligers cannot reproduce with female ligers though i dont think. Because male ligers are sterile while female ligers are not

As for the finches, maybe they are a different species because if two different types of finches mate, their offspring wouldnt have the proper characterists to survive. Just a guess here.

Species can also be determined by behavioral reproductive barriers. Wolves, for example, have Coyote mitochondrial DNA, which implies that male wolves have mated with female coyotes. There is much less coyote Y DNA however, not because they can't reproduce, but because they choose not to (female wolves are large compared to male coyotes.) This is a barrier that allows scientists to classify them as different species (beause gene-flow is miniscule.) Often we consider Neanderthals, Denisovian man, etc, etc as different species from modern day humans, but they have as much gene-flow (if not more) with modern man than some Human African pygmee populations do with other human beings. Although, I'd say it would be better to label these populations as Homo Sapiens (which they are starting to with Neanderthals) than to consider different modern populations of human beings as different species. I'm not yet convinced either way that there are various genetic sub-species (races) of humans, as that would require a polytypic (genetically) human population, in which we can structure major geneflow groupings. As it is now, in human population genetics, we've been able to see a branching structure between all non-Subsaharan Africans sharing a much closer affinity with eachother than with Sub Saharan Africans, almost as if those who left Africa were a subset of many African "populations" (the biological term.) After this, there seems to be a continuum among non Sub-Saharan Africans, from Europe to Oceania with Native Americans acting as a very homogenous branch of North East-Asians. This is caused likely by the founder effect, but also by interbreeding with older Human "species" (neanderthals and denisovian man".) 

This is what many of the modern PCA plots look like for Human population genetics. (Source: Discover Magazine and NIH.gov) 

CEU = European (Utah White Americans) YRI = African (Yoruba Sample) JPT = East Asians (Japanese) CHB = East Asians (Han Chinese)  Each quadrant represents a different PCA plot.