they could only interbreed in specific circumstances, and many of the children had birth defects, depending on whether the mother or the father was neanderthal or homo sapiens. donkeys and horses also breed. breeding is not the only criteria. clearly you don't understand the distinction species - genus - race.
But since you asked me to spell it out for you, here goes:
We are animals. Our phylum is Cordata, our class Mammalia. The order is primates, the family is hominidae. Our genus is homo. This genus includes, for example, Homo Erectus or Homo Habilis. They are a different genus from us, they are not a different race. Interbreeding with Homo Erectus, for all we know, would not be possible, or at the very least it would be a stretch. Then we finally get to species. There are different species of humans: Homo sapiens, Neanderthal, Denisovan. These different species can partially interbreed, but are still distinct enough genetically for problems to occur. Different species of humans are not races. Now within the species homo sapiens people have developed another taxonomy and called that taxonomy race. Race is only concerned with the individuals and groups within one species. Race is not concerned with Neanderthals and Denisovans. There wasn't "one race" in the beginning, there were no races. To be exact, there were no human races and there was no idea of "race" (there were other taxonomies or in-out groups in place) until the 17th century, when this specific taxonomy arose.
So there, you got your long answer. I hope you can now finally stop with this "1 race" bullfeathers, you can finally stop misusing the word and applying it in contexts where it makes zero sense, we can hopefully move on and develop a more sensical, useful and less arbitrary repertoire of concepts and definitions to talk about human genetic diversity, or really just human diversity in general, because that is what's at heart of this debate.
