Migration of Early Humans From Africa Aided By Wet Weather

Science Daily ^ | 8-30-2007 | Geological Society of America

[blam]

Source: Geological Society of America
Date: August 30, 2007

Migration of Early Humans From Africa Aided By Wet Weather

Science Daily — The African origin of early modern humans 200,000--150,000 years ago is now well documented, with archaeological data suggesting that a major migration from tropical east Africa to the Levant took place between 130,000 and 100,000 years ago via the presently hyper-arid Saharan-Arabian desert.

This migration was dependent on the occurrence of wetter climate in the region. Whereas there is good evidence that the southern and central Saharan-Arabian desert experienced increased monsoon precipitation during this period, no unequivocal evidence has been found for a corresponding rainfall increase in the northern part of the migration corridor, including the Sinai-Negev land bridge between Africa and Asia.

Passage through this "bottleneck" region would have been dependent on the development of suitable climate conditions.

Vaks et al. present a reconstruction of paleoclimate in the Negev Desert based on absolute uranium series dating of carbonate cave deposits (speleothems). Speleothems only form when rainwater enters the groundwater system and vegetation grows above a cave.

Today the climate in the Negev Desert is very arid and speleothems do not form, but their presence in a number of caves clearly indicates that conditions were wetter in the past. Vaks et al. dated 33 speleothem samples from five caves in the central and southern Negev Desert.

The ages of these speleothems show that the last main period of increased rainfall occurred between 140,000 and 110,000 years ago. The climate during this time consisted of episodic wet events that enabled the deserts of the northeastern Sahara, Sinai, and the Negev to become more hospitable for the movement of early modern humans.

The simultaneous occurrence of wet periods in the northern and southern parts of Saharan-Arabian desert could have led to the disappearance of the desert barrier between central Africa and the Levant.

The humid period in the Negev Desert between 140,000 and 110,000 years ago was preceded and followed by essentially unbroken arid conditions; thus creating a climatic "window" for early modern human migration to the Levant. Vaks et al.'s study suggest that climate change had an important limiting role in the timing of dispersal of early modern humans out of Africa.

Reference: Desert speleothems reveal climatic window for African exodus of early modern humans, Anton Vaks, Hebrew University, Institute of Earth Sciences, Edmond Safra Givat Ram Campus, Jerusalem 91904, Israel; et al. pages 831-834.

Note: This story has been adapted from a news release issued by Geological Society of America.

[Old Professer]

Gump! Is that you??

[shuckmaster]

Good find, Blam. This falls right into the time frames suggested by Oppenheimer

[Old Professer]

Run for Scotland’s Children

http://www.runglasgow.org/senior/prepare/training3.php

[blam]

"Gump! Is that you??"

In Bayou La Batre, hit by Katrina, movie drama becomes all too real

[Old Professer]

“The prices for the fuel to run the boats — just like for automobile gasoline — have been very high in recent years. Nonetheless, Gulf shrimpers must now compete with the cheap frozen shrimp imported from countries with lower labor costs.”

That’s not news, everybody knows that Chinese shrimp work for sesame nuts.

[SunkenCiv]

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[SunkenCiv]

Evolution in Your Face
by Patrick Huyghe
Omni

Lake Victoria, Africa's largest lake, is home to more than 300 species of cichlids. These fish, which are popular in aquariums, are deep-bodied and have one nostril, rather than the usual two, on each side of the head. Seismic profiles and cores of the lake taken by a team headed by Thomas C. Johnson of the University of Minnesota, reveal that the lake dried up completely about 12,400 years ago. This means that the rate of speciation of cichlid fishes has been extremely rapid: something on average of one new species every 40 years!