October 14, 2008, "Did ancient river channels guide humans out of Africa?" by Ewen Callaway
Posted on 11/12/2009 5:56:28 PM PST by SunkenCiv
Wet spells in the Sahara may have opened the door for early human migration. According to new evidence, water-dependent trees and shrubs grew there between 120,000 and 45,000 years ago. This suggests that changes in the weather helped early humans cross the desert on their way out of Africa...
While about 40 per cent of hydrocarbons in today's dust come from water-dependent plants, this rose to 60 per cent, first between 120,000 and 110,000 ago and again from 50,000 to 45,000 years ago. So the region seemed to be in the grip of unusually wet spells at the time.
That may have been enough to allow sub-Saharan Stone Age Homo sapiens to migrate north: the first fossils of modern humans outside Africa date from 93,000 year ago in Israel. And both genetic analysis and archaeology show that humans didn't spread extensively beyond Africa until 50,000 years ago, suggesting a second migration at the time of the second wet spell.
(Excerpt) Read more at newscientist.com ...
October 14, 2008, "Did ancient river channels guide humans out of Africa?" by Ewen Callaway
The African Source Of The Amazon’s Fertlizer
Science News Magazine | 11-18-2006 | Sid Perkins
Posted on 11/18/2006 4:22:58 PM PST by blam
http://www.freerepublic.com/focus/news/1740969/posts
I like that closing sentence -- "future decision-making could be made based on scientific data and not on political expediency". I wouldn't count on it, but that would be great.Caves reveal clues to UK weatherAt Pooles Cavern in Derbyshire, it was discovered that the stalagmites grow faster in the winter months when it rains more. Alan Walker, who guides visitors through the caves, says the changes in rainfall are recorded in the stalactites and stalagmites like the growth rings in trees. Stalagmites from a number of caves have now been analysed by Dr Andy Baker at Newcastle University. After splitting and polishing the rock, he can measure its growth precisely and has built up a precipitation history going back thousands of years. His study suggests this autumn's rainfall is not at all unusual when looked at over such a timescale but is well within historic variations. He believes politicians find it expedient to blame a man-made change in our weather rather than addressing the complex scientific picture.
by Tom Heap
Saturday, December 2, 2000
Stalagmites reveal past climateThe researchers examined four stalagmites from Crevice Cave, the longest cave known in Missouri, located about 75 miles south of St. Louis. The stalagmites appeared to have been broken by natural forces such as floods or earthquakes and were found about 80 feet below the ground surface, says Dorale. The team determined when the stalagmite layers were deposited, then deduced paleotemperatures and the general types of vegetation growing in the vicinity during that era by examining the carbon and oxygen isotopes within the calcium carbonate. The profile showed that the area had been covered by forest 75,000 years ago, but by 71,000 years ago, it was savannah and by 59,000 years ago, had become a prairie. Between 55,000 and 25,000 years ago, the forest had returned and persisted. Dorale explains that the pattern is consistent with climatological records from the ocean.
by Kristina Bartlett and Devra Wexler
GeoTimes, March 1999
Evolution in Your FaceLake 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!
by Patrick Huyghe
Omni
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“Stone Age humans crossed Sahara in the rain”
They moved to Detroit.
I’ve always wondered what treasures and ancient civilizations are burried under the Sahara.
Oceans linked to Sahel droughtThe droughts, in which over a million people are thought to have died, were initially blamed on human degradation of the local environment... The study looked at the Pacific - in particular the effect of the El Nino phenomenon and the effect on the Sahel rainfall - Atlantic, and Indian oceans. It was found that the Indian Ocean was a powerful indicator of the level of precipitation in the Sahel over the long term, while the Pacific affected seasonal rainfall... There were broadly two hypotheses to explain what happened in this semiarid region of Africa. One blamed the drought on changes brought about by human land use... The other hypothesis focused on temperature changes in the global oceans as the main culprit behind the drought... It is hoped that, with such a link established, the model can now be used to predict future rainfall in the Sahel. This could be crucial in giving time to plan for any forthcoming drought.
The Green Sahara, A Desert In Bloom
Science News, ScienceDaily | September 30, 2008
Christian-Albrechts-Universitaet zu Kiel
Posted on 10/03/2008 11:55:57 AM PDT by SunkenCiv
http://www.freerepublic.com/focus/chat/2096856/posts
“This means that the rate of speciation of cichlid fishes has been extremely rapid: something on average of one new species every 40 years!”
Wow!, I find that rate absolutely astounding.
Me too. Qattara Depression seems like a good place to start, but I also recall (not for the first time, even on FR) seeing a Nat Geog photog of a living olive tree, thousands of years old apparently, within dozens of yards of what was at that time the geographic center of the Sahara. Paintings on cliff faces showing agricultural activity have been identified, and they are, uh, pretty old. :’)
I’d walk a mile for a camel, assuming the camel were somewhere near a vehicle with an engine, all fueled up and ready to go. ;’)
40 per cent of hydrocarbons in today’s dust come from water-dependent plants
?????????????????????????????????????????????????????????
:’) That’s just the average, of course it would greatly help to know how many new species have been known to emerge (not merely newly discovered) since the Lake was first available for study by non-Africans.
40 per cent of hydrocarbons in today's dust come from water-dependent plantsFrogs eat the plants, then fart... ;')
'The desert crocodiles have adapted to the changing environment in northern Africa; 8,000 to 10,000 years ago, what is now desert was probably lush savannah and grasslands. Today the Sahara is hot and arid, the land sandy, rainfall minimal, and vegetation sparse. '
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