The ability to study ancient DNA has revolutionized our ability to understand our own species’ past. It has clarified our relationship with Neanderthals and revealed the existence of Denisovans. But even in the most favorable environments, DNA degrades over time, setting a limit on how far back we can hope to resolve questions about our ancestors. And most of the species we’ve had trouble understanding lived in Africa, where the conditions are far less favorable for DNA’s survival.
But a large international team has now found another way to get some information about the genetics out of far older remains. They’ve extracted fragments of enamel proteins from the teeth of fossils of the species Paranthropus robustus and used them to test whether the remains truly belonged to one species, despite dramatic differences in size. Because one of the proteins is male-specific, they also found the size of the individual wasn’t necessarily related to its sex.
A complicated species
Remains that have been classified as Paranthropus show up in the fossil record nearly 3 million years ago and persist for roughly a million years. That means it overlapped both with australopithecines and early members of the Homo genus. Four different species have been assigned to this genus, but the situation is complicated. It shares a lot of similarities with some species of Australopithecus, raising the possibility of interbreeding. There’s also a lot of variation within remains identified as Paranthropus, notably in the size of individuals. Some have suggested that this might be due to male/female differences in this species (termed “sexual dimorphism”), but that has been difficult to test.