When hominids were still evolving and natural selection had yet to decide which version was best suited to live on Earth, humans and Neanderthals coexisted for a few hundred thousand years. During this time, the species lived in relatively separate areas, but their domains overlapped in parts of what is now eastern Europe. Although we share a common ancestor, scientists have been unable to find any traces of when the two species split. Part of the difficulty has been gaps in the fossil record, which are a result of the unpredictable nature of the natural preservation of remains. Another confounding element comes from the frequent cross-breeding between humans and Neanderthals. However, a recent discovery in Italy may provide some clues as to when the two species officially split.

Similar, Yet Different

The earliest remains of modern humans date back to between 200,000 and 300,000 years ago. During that time, Earth was experiencing one of its many ice ages. Our ancient ancestors had to compete with a completely different class of animals called megafauna, which included wooly mammoths and saber-toothed tigers. Neanderthals are speculated to have evolved some 650,000 years ago, though the oldest remains we’ve found to date are only 400,000 years old.

Roughly 650,000 years ago, Earth was in the middle of one of its coldest ice ages, which lasted roughly 50,000 years. Records show that the Neanderthal species died out around 40,000 years ago, leaving us with at least 160,000 years of coexistence, during which time genetic records show that interbreeding occurred. Still, the two species remained different enough that the smarter Homo sapiens outlasted the brawnier Homo neanderthalensis. What interests scientists more is what caused the two similar species to split from their common ancestor.

The Hominid Family Tree

From about 700,000 to 300,000 years ago, Homo heidelbergensis dominated the hominid niche. Scientists believe that these early Stone Age relatives were the mysterious ancestor from which humans, Neanderthals, and Denisovans all evolved. Sometime in that 400,000-year window, the lineage split into those three subgroupings, but until recently, scientists hadn’t been able to pinpoint a link that confirmed that divide.

Scientists found 450,000-year-old teeth in Italy that exhibit features of both modern humans and Neanderthals. The age of the teeth places them right around the time when scientists expect a divergence to have occurred. While a single data point doesn’t leave much room for extrapolation, other excavation sites held the promise archaeologists had been hoping for. Similar teeth were found in two different locations, one near Rome and the other outside of Trieste, makes the discovery even more exciting.

Uncovering The Truth

A majority of the Neanderthal fossils found date between 130,000 and 40,000 years old, so discovering these mid-Pleistocene teeth is incredibly rare. What’s more, similar fossils of humanoid teeth that lack the Neanderthal traits have also been found, indicating the possibility of multiple hominid subgroups existing in the area during the time of divergence. The discovery of these fossils supports the running theory that human evolution is less linear than the popular model suggests. Instead, our evolution was more branched, with Neanderthals, Denisovans, and possibly other hominids existing alongside modern humans.

Researchers intend to study these ancient dental records to learn more about our ancestors, including what they ate and how they lived. By analyzing their diets, we can hope to gain more knowledge about primitive hominid societies and their relative levels of technology. Our family tree is full of twists and knots, but these recent discoveries are gradually helping us unravel the truth about our humble origins.