As Zilhão said, the mental capacity for this and other skills must predate their actual manifestation. The capacity, he believes, must have been present in the common ancestor of Neanderthals and modern humans. This ancestor is thought to have lived about 500,000 years ago.
The related cognitive hardwiring could even go back to 1.5 million years ago, when fossils suggest that humans were evolving larger brains than their primate ancestors.
"That material culture, archaeologically visible manifestations, only appears after 200,000 years ago probably means that it is at a time when individual and social interactions became so complex that conventions, signs, and symbols became necessary for the transmission of information about status, territory, ethnicity, rights over the resources of land, etc.," Zilhão explained.
Israel Hershkovitz, an expert on early human evolution at Tel Aviv University, notes that the dates of the Spanish cave art coincide with an extensive modern human migration out of Africa. Hershkovitz, who did not work on the new studies, told Seeker, "Members of this group could have reached the Iberian Peninsula through the Gibraltar Straight."
He added, "I am aware that, for the time being, fossil evidence for modern humans (in Spain) is dated to less than 45,000 years ago, but this is for the time being. I would not be surprised if they were there much earlier."
On the other hand, he said that he "would not be surprised" if the cave art and decorated shells were produced by Neanderthals.
"Why not?" he asked. "After all, Neanderthals and modern humans share the same tool technology, and by judging from tool assemblages alone there is no way to know whether a given site was inhabited by Neanderthals or modern humans."
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Hoffmann and his team faced somewhat similar challenges in teasing apart the ancient from the more recent paintings in the Spanish caves.
"You need to think about cave walls the same way as you would about the walls of a medieval church," Zilhão explained. "They were painted and repainted over the ages, so it is entirely possible that paintings made 60,000, 40,000, 20,000, or 10,000 years ago co-exist on the same surface, even on the same panel. The only way to constrain the age of a given painting is by dating the calcite found on top, or under it."
Chris Stringer of the Natural History Museum in London is one of the world's leading authorities on human evolution. He suspects that primitive members of both the modern human and Neanderthal lineages could have co-existed in western Asia.
"Could western Asia have been the conduit for exchanges of ideas between more ancient human populations in Africa and Eurasia, in either direction, and could this have included traditions of artistic expression?" he asked.
"From the new evidence, it could even be argued that the Neanderthals taught traditions of cave art to modern humans when they encountered them about 45,000 years ago, and indeed, modern humans could certainly have encountered earlier Neanderthal markings in caves and embellished them," Stringer told Seeker.
He quickly added, however, that the Sulawesi cave art could have been produced by modern humans, who might have brought such skills from their African ancestral homeland.
Pettitt said that East Asia is still poorly understood in terms of human populations. It appears that Neanderthals did not produce the Sulawesi cave art, but yet another early human group, the Denisovans, might have created it, he said. Future research could solve the mystery.
As for what happened to the Neanderthals, Zilhão shared that the "genetic evidence is crystal clear: Neanderthals were assimilated into the wider 'modern' human gene pool." He further believes that more than 50 percent of the Neanderthal genome is still around.
"Your great-grandparents probably are no longer alive, but would you refer to them as extinct? As a distinct population, Neanderthals ceased to exist between 35,000 and 42,000 years ago, but they live on inside each one of us," he said, referring to people of European and Asian ancestry.