Middle Eastern hominids keep an early date.

Age estimates based on a new analysis of fossil teeth found in three Israeli caves confirm reports that Neandertals and anatomically modern humans lived virtually side by side in the Middle East around 100,000 years ago, a team of scientists asserts in the May 20 NATURE.

The role played by Middle Eastern hominids (members of the human evolutionary family) in the emergence of modern humans remains controversial, however.

Modern humans inhabited the region first and lived near later-arriving Neandertals for at least 40,000 years, argue Frank McDermott, a geologist at University College in Dublin, Ireland, and his co-workers, who obtained the new dates from animal teeth found near the hominid remains. Neandertals died out after little or no interbreeding with modern humans, who originated about 250,000 years ago in Africa and spread throughout the world, the group contends.

Other anthropologists, including David W. Frayer at the University of Kansas in Lawrence, assign all Middle Eastern hominid remains to an early form of Homo sapiens (SN: 6/8/91, p.360), which they also believe encompasses European fossils usually classed as Neandertals (SN: 6/20/92, p.408). H. Sapiens emerged as many as 2 million years ago and evolved simultaneously in several parts of the world, according to these researchers. Dates provided in the new report and in other recent studies help establish the antiquity of "archaic" H. sapiens in the Middle East, in their view.

Frayer and four colleagues defend this "multiregional" theory of evolution in the March AMERICAN ANTHROPOLOGIST.

McDermott and his associates analyzed tooth fragments of ancestral cows or oxen found in the same sediment as hominids at three Israeli caves: Skhul and Tabun on Mount Carmel, south of Haifa, and Qafzeh near Nazareth. The investigators classified the heavier bones at Tabun as Neandertals and the slighter skeletons at Qafzeh and Skhul as modern humans.

Prior studies of animal teeth at the three sites, based on measurements of electrons that accumulate in bone as a result of environmental radiation after burial, yielded age estimates of about 100,000 years old (SN: 4/29/89, p.263).

The new dates, derived from chemical analysis of tooth scrapings in a mass spectrometer, reflect the time elapsed since the bones began to acquire uranium through exposure to groundwater after burial.

Of two teeth taken from hominid-bearing sediment at Skhul, one dates to around 106,000 years ago and the other to 89,000 years ago, the researchers hold.

Three teeth from fossil layers at Tabun date to between 98,000 and 105,000 years ago, they contend.

One tooth a Skhul yields a date of about 80,000 years old, but several others cluster around 40,000 to 45,000 years old, McDermott and his colleagues note. Skhul hominids may segregate into earlier and later populations, they suggest.

Of the 15 dates generated in the new experiment, 11 closely match dates for the same sites already calculated through other techniques.