[continued from previous message]   
      
   > evolutionary timescales to which the question refers.  Even accepting   
   > for arguments sake that a single homo species inevitably had to   
   > prevail over its many ecological cousins, there's no obvious reason   
   > why that one species turned out to be us.  Given the genetic evidence   
   > that we experienced an extreme population bottleneck, that would argue   
   > H.sapiens could have been among those missing homo species.   
   >   
      
   Denisovans and Neanderthals may have shared the same population   
   bottleneck with modern humans.  Both have reduced genetic variation like   
   modern humans and likely went through a population bottleneck.  It may   
   have been the same event because the time of the bottleneck keeps   
   getting pushed further and further back in time.  The current claims   
   indicate that the bottleneck occurred around 800,000 years ago, about   
   the same time that the Neanderthal-Denisovan lineage left Africa, but   
   after the chromosome fusion event that created Chromosome 2 that is   
   thought to have occurred around 900,000 years ago.  When the   
   Neanderthal-Denisovan left Africa there were already Homo populations in   
   Europe, Asia and even out into Indonesia.  The Denisovans may have   
   interbred with one of these Homo populations, but all the indigenous   
   Homo were displaced from the mainland, but some may have survived on   
   Indonesian islands into the last ice age if the Hobbit fossils are   
   derived from Homo erectus ancestors.   
      
   The current claim is that two distinct populations of Homo coexisted in   
   Africa for more than 900,000 years to interbreed with the lineage that   
   became African modern humans a couple of times within the last 800,000   
   years, but this population may have comeback from outside of Africa.   
   This population may not have had the chromosome 2 fusion.  After the   
   last interbreeding event with this population within the last couple   
   hundred thousand years, they disappeared.  They survived because they   
   were probably physically isolated from Modern humans or there would be   
   more interbreeding events between them and Modern humans.   
      
   Other Homo survive when our lineage did not want to live where they were   
   living or we could not get there.  This occurred with the   
   Neanderthal-Denisovan branch of our family tree when they left Africa,   
   and it happened with the African branch when they finally left Africa in   
   enough numbers to displace the Neanderthal and Denisovan populations   
   that existed outside of Africa.   
      
   What is a mystery is how did two distinct populations of Homo evolve in   
   Europe and Asia.  They left Africa as likely one population, but one   
   survived 7 or 8 ice ages in Europe and the other in Asia.  They both   
   displaced the indigenous Homo populations, but somehow they evolved as   
   distinct populations even though they obviously shared some of the same   
   territory.  The Denisovan caves have both Neanderthal and Denisovan   
   remains though they are found at different sedimentary levels, so they   
   did not occupy the site at the same time, but they were obviously using   
   the same territory.  There was pretty minimal interbreeding that left   
   genetic traces within each population, so if hybrids were common they   
   did not contribute to the surviving populations.  How did the   
   populations remain separated?  If the Dragon Man skull is Denisovan,   
   Denisovans obviously looked a lot like Neanderthals.   
      
   My guess is that Neanderthals and Denisovans shared the same cultural   
   (us VS them) attitude, but when they came back into contact with each   
   other they were not able to displace the other, so they had a sort of   
   stalemate existence.  When modern humans left Africa 60,000 years ago   
   they had the same cultural attitude, but they had the technology and   
   reproductive capacity to displace the Neanderthal and Denisovan   
   populations.  For some reason Neanderthals were ultra cultural   
   conservatives.  They did not adopt modern human stone blade technology   
   until just before they went extinct.  You could make more tools out of   
   the same amount of stone by making blade generating stone cores, but   
   even though Neanderthals had to transport stone a couple hundred   
   kilometers they did not adopt the modern human technology until they   
   were down to their last surviving family groups.   
      
   Modern humans left Africa during the last glacial period (the current   
   estimate is around 60,000 years ago).  The glacial maxium would not   
   occur until around 25,000 years ago, so conditions in Europe were   
   getting worse interms of loss of habitat for Neanderthal.  Modern humans   
   took over the prime habitat and pushed the Neanderthals into more   
   marginal territories as conditions were getting worse, so by around   
   30,000 years ago Neanderthals were gone.  Modern humans quickly   
   displaced Denisovans from the temperate Asian coast line and were in   
   Australia by 40,000 years ago.  There were several interbreeding events   
   with Denisovans in Asia and Indonesia, but my guess is that Denisovans   
   went extinct around the same time as Neanderthals before the glacial   
   maximum because they had been forced into marginal habitat and when   
   things got worse they could not migrate into warmer ice free conditions.   
     If there were modern humans in South America 25,000 years ago that   
   would mean that modern humans already occupied the habitable regions of   
   North East Asia over 25,000 years ago.  Where was there left for Denisovans?   
      
   Ron Okimoto   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)