Ancient Israeli caves reveal climate change allowed humans to migrate out of Africa

Archaeologists have discovered ancient cave formations in Israel, which they say, provides the first concrete evidence that climate changes allowed early humans to migrate out of Africa.

Washington, Aug 31 : Archaeologists have discovered ancient cave formations in Israel, which they say, provides the first concrete evidence that climate changes allowed early humans to migrate out of Africa.

The researchers studied stalactites and stalagmites, or speleothems, found in five caves deep in the Negev Desert in southern Israel.

The growth patterns of the formations, which only develop in the presence of rainwater, revealed a major cluster of unusually rainy periods beginning some 140,000 years ago.

They said the rainy spells matched the period of the first modern human settlements in the Middle East.

"We found that the period of enhanced rainfall allowing the growth of speleothems ... occurred roughly 140,000 to 110,000 years ago, with its height being 130,000 to 125,000 years ago," said Anton Vaks, a doctoral student with the Geological Survey of Israel (GSI) and the Hebrew University of Jerusalem.

He said these dates corresponded with modern human settlements found slightly farther north in Israel's Carmel region and near Nazareth. Archaeological evidence has dated those sites to about 100,000 to 130,000 years old.

Vaks said the wet periods formed what were essentially climatic windows that allowed migration north through the Sahara and up into Asia via a "land bridge" on the Sinai Peninsula.

"The desert began to shrink both from the south and also from the north. The entire Sahara turned into something much, much smaller, and the desert barrier [out of Africa] was much less significant," he said.

He said analysis of the cave deposits using high-precision spectrometry to measure their periods of growth, also revealed that the wet seasons reflected in the formations likely helped ancient humans pass through the otherwise arid region.

"These monsoon rains strengthened the Nile's flow, forming a northbound 'highway. The climate along the shoreline of the Red Sea was also much less extreme during this period, and archaeologists have found evidence of migration along the coasts," said Vaks.

"It is reasonable that there is a connection between a wet period along the Sinai-Negev land bridge and the appearance of early modern man for the first time outside of Africa," he said.

Hebrew University geographer and research team member Amos Frumkin said while experts have been examining the influence of climate on human migration and evolution for years, this was the first time researchers had turned up hard evidence.

"This is the first time there is both evidence and exact dating. This evidence fits within a network of other information we have on the migration of modern humans from Africa to Asia," National Geographic quoted Frumkin as saying.

Emory University anthropologist John Kingston, who was not involved in the study, said the new find provided important physical clues to the history of early human migration.

"This is really significant in providing empirical evidence for ideas that existed already. To have empirical evidence like this is golden," he said.

"The connection between the rainy spells seen in the cave formations and the existing archaeological evidence in Carmel and Nazareth is also reasonable," he added.

The findings appear in the current issue of the journal Geology.

ANI