Neanderthal bodies were adapted for colder conditions. Their stocky, barrel-chested build lost less heat and offered plenty of insulating muscle, and their systems were streamlined to extract calories from food and turn them into body heat. The Skhul-Qafzeh people’s slender physiques were better at getting rid of heat than making it. Or, as Shea says, “Neanderthals liked cold and dry. Our ancestors liked warm and wet. It got cold, and humans retreated.”
Rather than the missing link, then, the Skhul-Qafzeh people seemed to represent a rare tale of failure in Homo sapiens’ official record. They came from Africa, reached the Levant, then retreated or went extinct before a second, successful wave of African Homo sapiens arrived in the region around 60,000 years ago.
Last year in the journal Nature, physical anthropologist Israel Hershkovitz described a 55,000-year-old human skull found in Manot Cave, near the Skhul and Qafzeh sites. Despite the skull’s proximity to the earlier sites, Hershkovitz does not believe it challenges the theory that the Skhul-Qafzeh people died out or moved away. Instead, he sees all the fossils in these caves as disparate remnants of a succession of small populations. Whether they were hunter-gathering bands or larger tribes, each group, in turn, reached the caves and found them favorable, but ultimately went extinct.
“Each cave was inhabited during thousands of years by many different groups who never actually met each other,” he explains. “Each group was isolated from the other with probably a lot of inbreeding.”
Hershkovitz considers his find an entirely separate lineage, a new arrival distant in time from the people of Skhul and Qafzeh by 40,000 years or more. While analysis of their DNA might solve many of the riddles about these early people, researchers so far have been unable to extract usable genetic material from the remains.
Extinction Is the Rule
Some researchers believe the Skhul-Qafzeh people were not small, isolated groups but part of a broader early movement out of Africa and into Eurasia.
In Saudi Arabia’s Empty Quarter, University of Oxford professor Michael Petraglia is in the middle of a multidisciplinary project called Paleodeserts. These desert landscapes were once fertile lake lands, and Petraglia’s team aims to unlock the role they played in human expansion. So far they have found many tools, but not one human fossil. “We know that some form of human definitely penetrated Arabia, and that some of the dates of those sites coincide with the appearance of Homo sapiens in the Levant around 100,000 years ago,” says Petraglia. According to this hypothesis, the Skhul-Qafzeh people represent the western edge of a larger wave of migration that likely continued into Eurasia. Did their contemporaries on the move also go extinct?
“The extinction of hunting and gathering populations [was] probably far more common than we realize today,” Petraglia says. “In Sahara, Arabia, the Thar Desert of India … clearly populations got into those places, but we don’t know what happened to [them].”
One intriguing possibility surfaced in Nature in February. A team analyzing multiple Neanderthal genomes uncovered strong evidence that humans and Neanderthals had interbred more than 100,000 years ago — that’s tens of thousands of years earlier than we thought. The genetic admixture appeared in an individual found in Siberia, but not in the European Neanderthals also analyzed in the study.
“It suggests that the interbreeding event may have happened in the Middle East, and that lineage then migrated east” without additional contact with Europe, says Adam Siepel, a quantitative biologist at New York’s Cold Spring Harbor Laboratory and a co-team leader for the study.
While evidence of such early contact between the two species has yet to be found at Skhul and Qafzeh, the new study adds to the theory that Neanderthals were successful, spreading across Europe and Asia, at a time when humans seem to have faltered, gone extinct or retreated back to Africa. It begs the question: Which species was, at least for a time, superior?