A partial human skull found in northern Israel  excited paleontologists because it seemed to hold clues about when and where humans and Neanderthals might have interbred.

The Manot Cave is a natural limestone formation that had been sealed for 15,000 years. It was discovered by a bulldozer clearing the land for development and the partial skull, sitting on a ledge, was found by spelunkers exploring the newly-opened cave. Five excavation seasons uncovered a rich deposit, with stone tools and stratified occupation levels covering a period of time from 55,000 to 27,000 years ago. 

There was just one problem -  precisely determining the age of the skull after it had been moved.  “Because it was already removed from the layer where it was presumably deposited,” says Dr. Elisabetta Boaretto, head of the Weizmann Institute’s D-REAMS (DANGOOR Research Accelerator Mass Spectrometry) laboratory, “we had to look for clues to tell us where and when it belonged in the setting of the archaeological record in the cave.”


The Manot specimen is on the computer screen, in lateral view (left) and from inside (right).
Copyright: Gerhard Weber

 The age of the skull was first determined to be 54.7 thousand years old by the uranium-thorium method, which was applied to the thin mineral deposit on the skull, but the estimated possible error in that type of method is plus or minus 5.5 thousand years. To obtain independent confirmation of the date, a different type of dating was required, radiocarbon dating.

To narrow down the possible range of the skull’s age and determine when the skull’s owner had lived in the cave, the archaeological team led by Prof. Israel Hershkovitz of Tel Aviv University, Dr. Ofer Marder of Ben Gurion University and Dr. Omry Barzilai of the Israel Antiquities Authority turned to Boaretto. She and her team participated in the excavation of the cave and applied radiocarbon dating to carefully selected charcoal remains, so that the whole cave, and thus the timing of human occupation, was mapped.

The agreement between the two methods – carbon and uranium-thorium – provided the necessary support for the “correction” in the original uranium-thorium dating of the skull, which then helped fix the true age of the skull at around 55,000 years. 

The combined dating provides evidence that Homo sapiens and Homo neanderthalensis could have lived side by side in the area and the shape of the Manot Cave skull also provides some intriguing evidence that humans and Neanderthals might have interbred sometime during the human trek out of Africa, most likely as the former passed through the Middle East before spreading out north and east.

The 55,000-year-old partial skull is the first evidence of a human residing in the region at the same time as Neanderthals, whose remains have been found at several nearby sites. Archaeologists are now searching for more evidence of ancient human habitation in the cave. If, indeed, the mixing between humans and Neanderthals took place in this area, it would suggest that the owner of the skull and his kin may have been the ancestors of all modern non-Africans. 

Citation: Levantine cranium from Manot Cave (Israel) foreshadows the first European modern humans. Hershkovitz, I., Marder, O., Ayalon, A., Boaretto, E., Caracuta, V., Alex, B., Frumkin, A., Goder-Goldberger, M., Gunz, P., Holloway, R., Latimer, B., Lavi, R., Matthews, A., Sloan, V., Bar-Yosef Mayer, D., Berna, F., Bar-Oz, G., May, H., Hans, M., Weber, G.W., Barzilai, O., Nature, 29 January 2015, DOI: 10.1038/nature14134.