Earlier studies have suggested that our human ancestors likely had sexual relationship with Neanderthals and a 55,000 year old partial skull that was unearthed in a cave in Israel is giving clues as to when and where these interbreeding between the two species occurred.

The partial skull was discovered by anthropologists exploring the Manot Cave in western Galilee in Israel. In a new study published in the journal Nature on Jan. 28, researchers posited that the fossil belonged to a modern human, probably a woman, and that it was likely a love child of a human, who belonged to a group of Homo sapiens that moved out of Africa, and a Neanderthal.

The partial skull was named "Manot" after the cave where it was unearthed, and radiometric dating has determined that it is 55,000 years old.

Manot is older than the modern humans that lived in Europe 20,000 to 30,000 years ago. In fact, it is 10,000 years older than the first known Homo sapiens in Europe weakening theories that modern humans and the Neanderthals first met in Europe.

Scientists said that the shape at the base of the ancient skull looks similar to those of modern African and European skulls but is different from other anatomically modern humans from Levant. With Manot's age and its mixture of features, the researchers suspected that the skull belonged to a part Homo sapiens and part Neanderthal, a hybrid resulting from the interbreeding of the two species.

"This suggests that the Manot people could be closely related to the first modern humans who later successfully colonized Europe," the researchers wrote. "Thus, the anatomical features used to support the 'assimilation model' in Europe might not have been inherited from European Neanderthals, but rather from earlier Levantine populations."

The researchers likewise said that the skull provides the first fossil evidence from when archeological and genetic models predict that modern humans have successfully colonized Eurasia after migrating out of Africa. The skull's estimated age coincided with the theorized mass movement of the modern humans out of Africa when wetter climates may have enabled them to cross the formidable desert barriers in Africa.

"Manot clearly shows that Neanderthals and modern human lived side by side in Israel for a long period of time," said study researcher Israel Hershkovitz, from Tel Aviv University. "All recent genetic and archaeological studies predict that the interbreeding event between the Neanderthals and modern humans occurred between 50,000-60,000 years ago, and in the Near East."

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