Well, that's actually a very excellent point. The reason I assumed they'd know something was out-of-whack with the kid is because it would presumably look deformed.
Through advances in DNA technology, paleoanthropologists have been able to extract genetic material from some of the Neanderthal bones and compare their genes with those of modern humans. The modern genes, Klein argues, "derive exclusively" from the African ancestors of modern humans, and not from Neanderthals.
That's a highly contentious point. Other anthropologists, such as Erik Trinkaus of the University of Pennsylvania and Milford Wolpoff of the University of Michigan, contend that many modern humans carry at least some genes of Neanderthals mixed in with their own.
Three years ago, Trinkaus and a team of Portuguese scientists described the skeleton of a young boy found in a shallow grave more than 25,000 years old and said they determined from his bones that the youngster was at least part Neanderthal.
In interviews last week, both Trinkaus and Wolpoff argued that this was clear evidence that Neanderthals and modern human ancestors not only lived side by side but also mated and interbred. "The so-called modern humans are a 50-50 combination of ancestry from both peoples," Wolpoff says. "In many Europeans today, you can clearly see the physical features of a Neanderthal past."
To Trinkaus, Klein's conclusions "overemphasize and distort the differences between Neanderthals and modern humans, while downplaying the similarities. The Neanderthals and the Cro-Magnons interbred and produced offspring." From here.