Ancient cave formations found in Israel
provided the first concrete evidence that climate change allowed
early humans to migrate out of Africa, according to researchers
A team of Israeli scientists studied stalactites
and stalagmites, or speleothems, which had been found in five
caves deep in the Negev Desert in southern Israel. They found that
the growth patterns of the formations, which only develop in the
presence of rain water, revealed a major cluster of unusually rainy
periods beginning some 140,000 years ago.
The rainy spells matched the period which saw
the first modern human settlements in the Middle East. The
scientists found that the period of enhanced rainfall which allowed
the growth of speleothems occurred roughly between 140,000 to 110,000
years ago, with its height being 130,000 to 125,000 years ago.
These dates correspond with modern human settlements
which have been 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 ago. The wet periods formed
what, essentially, were climatic windows that allowed migration north
through the Sahara and up into Asia via a 'land bridge' on the Sinai
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
The Nile became a highway
The researchers analysed the cave deposits using
high-precision spectrometry to measure their periods of growth.
According to the Israeli team, the wet seasons reflected in the
formations most likely helped ancient humans to 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. It is reasonable to
see 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.