Human continuity for 300,000 years appears to be much longer thanpresently accepted and continuous occupation may well imply culturalstasis. Thus the bottleneck may alternatively mean that a specialgroup made the key breakthrough around 50,000 years ago.
That also fits well with our projected time line for a ten thousandyear transition to modernity from 50,000 BP to 40,000 BP. Our owntransition has taken about the same amount of time since thePleistocene Nonconformity.
An expanding special population of modernizing humanity will simplyabsorb remnant groups back into the global DNA in much the same waythat our last tribes are been absorbed into our six billion manocean.
Tracing humanity'sAfrican ancestry may mean rewriting 'out of Africa' dates
This 2012 image showsthe structure used by inhabitants of the region for well over 200000years. Credit: Pamela Willoughby, University of Alberta.
by Staff Writers
Edmonton, Canada(SPX) Dec 18, 2012
http://www.terradaily.com/reports/Tracing_humanitys_African_ancestry_may_mean_rewriting_out_of_Africa_dates_999.html
New research by aUniversity of Alberta archeologist may lead to a rethinking of how,when and from where our ancestors left Africa. U of A researcher andanthropology chair Pamela Willoughby's explorations in the Iringaregion of southern Tanzania yielded fossils and other evidence thatrecords the beginnings of our own species, Homo sapiens.
Her research, recentlypublished in the journal Quaternary International, may be key toanswering questions about early human occupation and the migrationout of Africa about 60,000 to 50,000 years ago, which led to modernhumans colonizing the globe.
From two sites,Mlambalasi and nearby Magubike, she and members of her team, theIringa Region Archaeological Project, uncovered artifacts thatoutline continuous human occupation between modern times and atleast 200,000 years ago, including during a late Ice Age period whena near extinction-level event, or "genetic bottleneck,"likely occurred.
Now, Willoughby andher team are working with people in the region to develop this areafor ecotourism, to assist the region economically and createincentives to protect its archeological history.
"Some of thesesites have signs that people were using them starting around300,000 years ago. In fact, they're still being used today,"she said. "But the idea that you have such ancient humanoccupation preserved in some of these places is pretty remarkable."
Magubike: Home to amodern Stone Age family?
Willoughby saysone of the fascinating things about Magubike is the presence of alarge rock shelter with an intact overhanging roof. The excavationsyielded unprecedented ancient artifacts and fossils from under thisroof. Samples from the site date from the earliest stages of themiddle Stone Age to the Iron Age. The earlier deposits include humanteeth and artifacts such as animal bones, shells and thousands offlaked stone tools.
The Iron Age finds canbe dated using radiocarbon, but the older deposits must go throughmore specialized processes, such as electron spin resonance, todetermine their age. Other parts of the Magubike rock shelter,excavated in 2006 and 2008, include occupations from after the middleStone Age. Taken together, this information could be crucial totracking the evolutionary development of the inhabitants.
"What's importantabout the whole sequence is that we may have a continuous recordof human occupation," said Willoughby. "If we do-and we canprove it through these special dating techniques-then we have a placepeople lived in over the bottleneck."
Rugged, hilly terrainmay have been key to survival
The team madesimilar findings at Mlambalasi, about 20 kilometres from Magubike.Among the findings at this site was a fragmentary human skeleton thatprobably dates to the late Pleistocene Ice Age-after theout-of-Africa expansion but at the end of the bottleneck period.
The bottleneck theoryexplains what geneticists have found by studying the mitochondrialDNA of living people-that all non-Africans are descended from onelineage of people who left Africa about 50,000 years ago.
Reconstructions ofpast environments through pollen and other archeological records inIringa suggest that people abandoned the lowland, tropical andcoastal areas during that period but remained in the highlands, wherevegetation has remained mostly unchanged over the last 50,000 years.Those who moved to higher ground may have found what is likely one ofthe few places that facilitated their survival and forced theiradaptation. Further testing will determine whether these findingspoint to a clearer link to our African ancestors-a find Willoughbysays could put that region of Tanzania on many archeologists' radar.
"It was onlyabout 20 years ago that people recognized that modern Homo sapiensactually had an African ancestry, and everyone was focused on lookingat early Homo sapiens in Europe who appeared around 40,000 yearsago," she said.
"But we now knowthat as far as back as around 200,000 years ago, Africa was inhabitedby people who were already physically exactly like us today or reallyclose to being the same as us. All of a sudden, it's not Europe inthis time period that's really important, it's Africa."
Engaging communityyields co-operation, opportunity
Along with itsscientific significance, Willoughby's work may be a linchpin topotential economic growth for the region. Since 2005, when a localcultural officer showed her the sites, she has been sharinginformation about her research with local citizens, schools andgovernment-opening up opportunities for more research andco-operation.
She keeps the regioninformed of the team's findings through posters distributed aroundIringa, and has asked for and accepted assistance from localscholars. Now the community is also looking for her help inestablishing the historic sites as a tourist attraction that willbenefit the region.
Willoughby says shefeels fortunate to have the support of the Tanzanian people. Shetells people it is a shared history she is uncovering, something sheis honoured to be able to do.
"They're tellingme, 'You're putting Iringa on the map,'" she said. "As longas they keep letting me work there, and keep letting the peopleworking with me work there, we'll be happy."
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