Writing in an accompanying commentary in the journal, Dr. Goebel said, “Here is the first skull of an adult modern human from sub-Saharan Africa that dates to the critical period, and one that can speak to the relationship of early moderns from Africa and Europe.”

The new findings pivoted on fixing the skull’s age. When it was uncovered in 1952 near the town of Hofmeyr, South Africa, the cranium was almost complete but the bone degraded. Not enough carbon remained for scientists at the time to extract a radiocarbon date.

Using new technology, Richard Bailey and other researchers at the University of Oxford, England, measured the amount of radiation that had been absorbed by sand grains that filled the braincase since its burial. They calculated the yearly rate at which radiation had collected in the sand and checked this with data from a CT scan of the bone. In this way, they determined that the Hofmeyr skull belonged to a human who lived 36,000 years ago, plus or minus 3,000 years.

Another member of the team, Katerina Harvati of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, made a detailed examination of the shapes, sizes and contours of all parts of the skull. She compared these three-dimensional measurements with those of early human skulls from Europe and with skulls of living humans in Eurasia and southern Africa, including the Khoe-San, commonly known as the Bushmen.

Because the Bushmen are well represented in the more recent archaeological record, Dr. Harvati said, they were expected to bear a close resemblance to the Hofmeyr skull. Instead, the skull was found to be quite distinct from all recent Africans, including the Bushmen, she said, and it has “a very close affinity” with fossil specimens of Europeans living in the Upper Paleolithic, the period best known for advanced stone tools and cave art.

“Much to my amazement,” Dr. Grine said in an interview, “the skull linked very closely with those from Europe at the time and not with South African remains 15,000 years on.”

Dr. Grine said these modern humans probably originated in East Africa, which is rich in fossils of ancestors of the species, and had then moved into Eurasia and also south to the tip of Africa.