In the early twentieth century, paleoanthropologists interpreted the differences between specimens of an expanding human fossil record as reflecting taxonomic and evolutionary diversity. Why, then, in the 1940s, did geneticist Theodosius Dobzhansky reconfigure human evolution into one, profoundly morphologically variable lineage which changed slowly through time? Neanderthals exposes, for the first time, the history of how conceptions of race have configured interpretations of the first-found human fossils; how assumptions underlying human fossils were and still are interpreted as to species and their evolutionary relationships.

No matter how "different" Nazis thought living humans were, differences between Neanderthals and bigger-browed, chunkier-faced specimens and living humans trivialized the differences between living humans. In 1950, without basis, taxonomist Ernst Mayr lumped all fossil and extant humans into three transforming species of genus Homo: transvaalensiserectussapiens; sapiens subsumed humans, Neanderthals, and even less morphologically sapiens-like specimens. In 1962, at a Wenner-Gren Foundation meeting, participants voted to keep these specimens, Neanderthals, and humans in Homo sapiens.

Even when Neanderthals were returned to species neanderthalensis, the assumption remained: humans and Neanderthals interbred. In a press release, the Committee that awarded Svante Pääbo the Nobel Prize for "demonstrating" human inheritance of Neanderthal "genes" made clear that his claims were predicated on assuming Neanderthal-human interbreeding. It's remarkable how received wisdom continues to influence paleoanthropologists and molecular anthropologists who then present as fact, to a naïve public, assumptions that are biologically and evolutionarily wrong.