X-Message-Number: 31723
Date: Fri, 5 Jun 2009 15:30:30 -0700 (PDT)
From: un person <>
Subject: population density and culture

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Party Animals: Early Human Culture Thrived in Crowds

Buzz UpSendSharePrintJeanna BrynerSenior WriterLiveScience.com aC" Thu Jun 4, 
2:12 pm ETParty planners know that scrunching a bunch of people into a small 
space will result in plenty of mingling and discourse.A new study suggests this 
was as true for our ancestors as it is for us today, and that ancient social 
networking led to a renaissance of new ideas that helped make us human.The 
research, which is published in the June 5 issue of the journal Science, 
suggests that tens of thousands of years ago, as human population density 
increased so did the transmission of ideas and skills. The result: the emergence
of more and more clever innovations."Our paper proposes a new model for why 
modern human behavior started at different times in different regions of the 
world, why it disappeared in some places before coming back, and why in all 
cases it occurred more than 100,000 years after modern humans first appeared," 
said study researcher Adam Powell of the Arts

 and Humanities Research Council Centre for the Evolution of Cultural Diversity 
 at University College London.The idea that demography is linked to modern human
 behavior has been around for decades, but this is the first time scientists 
 have run computer models and actually tested out different hypotheses, said 
 Richard Potts, an anthropologist and director of the Human Origins Program at 
 the Smithsonian Institution's National Museum of Natural History in Washington,
 D.C.Potts, who was not involved in the current study, applauded the team for 
 not relying solely on computer models but also including genetic and 
 archaeological data to make their argument.Modern humansScientists have known 
 that anatomically modern humans, or Home sapiens, (characterized by big brains 
 and other features we sport today), were around at least 160,000 to 200,000 
 years ago. Some thought boosts in brain power or advances in language led to 
 modern human behavior, which includes the

 crafting of abstract and realistic art, body decoration, musical instruments 
 and hunting and trapping technologies.But our big brains didn't seem to bear 
 any cultural fruit until much later. In fact, archaeological evidence of art 
 and technology beyond basic stone tools doesn't appear until about 90,000 years
 ago in sub-Saharan Africa. There, remnants of modern human behavior 
 disappeared around 65,000 years ago and then re-emerged about 40,000 years 
 ago."In Europe and western Asia this advanced technology and behavior explodes 
 around 45,000 years ago when humans arrive there, but doesn't appear in eastern
 and southern Asia and Australia until much later, despite a human presence," 
 said study team member Stephen Shennan of the University College London's 
 Institute of Archaeology.Sharing ideasThe researchers ran computer simulations 
 of different population densities, grouping humans into subpopulations that 
 migrated. The model revealed that at a certain

 subpopulation density there was an accumulation of ideas and skills. To figure 
 out whether this phenomenon of skill-sharing was real, the team used genetic 
 data to estimate population sizes in different regions at different times. Sure
 enough, when the critical population density was reached or there was a 
 certain degree of migration between subgroups there was also archaeological 
 evidence of modern human behavior."As population density increases, people 
 migrate between groups more," Thomas said during a telephone interview. "That 
 increases the probability that any skill that's difficult to learn doesn't get 
 lost or decay."For instance, population density was similar in sub-Saharan 
 Africa, Europe and the Middle East when modern behavior first appeared in these
 regions. Results also showed that population density would have dropped due to
 climate changes at the time when modern human behavior temporarily disappeared
 in sub-Saharan Africa."The basic idea

 conceptually is you can have individuals who are really great at inventing 
 ideas and concepts and ways of approaching the world, but you need a certain 
 population density to be able to have that stuff catch hold and spread," Potts 
 told LiveScience.He added, "You could imagine that there may have been very 
 innovative individuals on occasion, but with very small population sizes and 
 mobile foragers who didn't run into other groups very often, those innovations 
 were probably very short-lived and almost invisible in the archaeological 
 record."



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