Research by a team investigating ancient human burials in Israel’s Tinshemet Cave has uncovered evidence of interactions between Homo sapiens and Neanderthals in ancient times, indicating that they shared daily life moments and customs.

The team’s study, published today in Nature Human Behavior, examined stone tools, hunting strategies, and social aspects of the two human groups, revealing a more significant level of interaction in the area than previously thought.

Israel Hershkovitz, an anthropologist at Tel Aviv University and co-author of the study, stated in an email to Gizmodo, “Neanderthals and Homo sapiens are sister populations. Biologically, they are not different species, but morphologically, they are. The two groups interbred throughout the Middle Paleolithic.”

Neanderthals (Homo neanderthalensis) were a group of humans who interbred with anatomically modern humans (Homo sapiens) but had distinct physical characteristics, including barrel chests, stocky frames, and pronounced brows.

Last year, landmark studies in Nature and Science narrowed down the time frame of some of the earliest Homo sapiens interbreeding with Neanderthals in Europe, based on the analysis of hundreds of genomes. The new research suggests that the two groups may have interacted even earlier in the Levant.

“Instead of competing for food resources and killing each other, they managed to share knowledge and technology (and, of course, genes) to the level that their habitation sites are indistinguishable,” Hershkovitz added.

In 2021, Hershkovitz was part of a team that studied 120,000-year-old hominin bones that were not quite Homo sapiens but not quite Neanderthal either. The archaic hominin fragments—a skull, a mandible, and teeth—from the Nesher Ramla site complicated the previously straightforward evolutionary picture of humankind, in which either Neanderthals or Homo sapiens exclusively occupied the Levant.

The Nesher Ramla Homo, as the ambiguous human group is now known, indicated to the team that there was more interaction between the two human species than previously known, though not everyone agrees. More specific dating of the fossil remains would help determine the identity of the fossil remains and the timeline of human expansion and occupation of the Levant and beyond. Regardless, the new paper further muddies the waters, stating that genetically distinct groups of Homo sapiens, Neanderthals, or a bit of both may have overlapped to the extent that their cultural products, hunting methods, and social structures were homogenized, if not practically indistinguishable.

Hershkovitz added that several questions remain, including what happened to the early Homo sapiens at nearby sites (including the famous site of Qazfeh), the timing of the first encounters between the Nesher Ramla humans and Homo sapiens, and what the cadence of human migration was out of Africa.

“These strata broadly share a uniform lithic [stone] technology, the use of ochre, a large-ungulate hunting pattern, the presence of articulated human remains, and the presence of grave goods or non-utilitarian artefacts,” the team wrote, concluding that the uniform cultural aspects across the sites “could be a result of intensifying social interactions and admixture among African H. sapiens and Eurasian Neanderthal-like hominins in the mid-MP Levant.”

Moreover, Hershkovitz added, it remains a possibility that the Nesher Ramla individuals were the ancestors of the Neanderthals that paleoanthropologists find across Europe, those who disappear from the fossil record about 40,000 years ago.

Neanderthals are generally thought not to have gone extinct but to have been subsumed into anatomically modern human populations. Neanderthal DNA persists in our genetics today, and even some human traits are associated with our closest human relatives.