[LINK] "Oldest Homo sapiens fossil? Journalistic vaporware"

[rfmcdonald]

The Loom's Carl Zimmer doesn't think much of the recent claims that the earliest Homo sapiens comes from Israel almost a half-million years ago. It comes down to category mismatches.

The fossil record offers a picture of hominins evolving in Africa, and pulses of new lineages rolling out through Israel and neighboring regions, and then onward to Europe and Asia. Some 1.4 million years ago, for example, a species of early Homo left fossils in Israel at a site called Ubeidiya. At several sites in and around Israel, paleoanthropologists have found fossils and tools dating back 400,000 to 200,000 years ago–the same period as the Qesem site. Unfortunately, the fossils are mostly fragments that might belong to a number of different species. The tools are equally ambiguous.

Something really interesting happened later in Israel, between about 130,000 and 50,000 years ago. It appears that Homo sapiens, having evolved in Africa, expanded tentatively into the Near East for the first time. Fossils of tall, slender Homo sapiens turn up at a site called Skhul/Qafzeh. But then they vanish, replaced for tens of thousands of years by Neanderthals. Only later does Homo sapiens expand again out of Africa, and this time they don’t retreat. Instead, it’s the Neanderthals that disappear from the Near East, dwindling away to refuges such as Spain before becoming extinct.

The new paper documents the struggle of the scientists to figure out who the Qesem teeth belong to. In some ways, they seem more like Neanderthal teeth. In others, they seem more like the choppers of Homo sapiens, as represented by the Skhul/Qafzeh fossils. The authors tilt towards a relationship with Homo sapiens, but mostly because the teeth are “plesiomorphous.” That term refers to a trait that was already present before the origin of a group of species. It does not refer to a trait that closely links all individuals who have it into a single lineage.

Here’s a simple example of what plesiomorphous means. Let’s say you find a fossil at a site where you had already found dogs and birds. The new fossil has four legs. In that respect, it’s more like a dog than a bird.

But it would not make sense for you to conclude that the fossil was a dog. The common ancestor of dogs and birds had four legs, and birds evolved into two-legged animals. But alligators have four legs, too, and they’re closer to birds than to dogs. All those four legs really tell you is that the fossil isn’t a bird.