Many ancestors and they were busy

Several stories from recent Science News issues paint a picture of human ancestors 2.8 million years ago shaping stone tools as their brains grew in size, and then around 40,000 years ago, Homo sapiens crowded out Neanderthals with the help of dogs (says one author).  The 3/21/15 issues has a story about finding a human gene that promotes larger brains which wrinkle it up to squeeze it all in.  A chimpanzee has a similar gene but it does not promote as much growth.  They found this out by injecting the genes into mouse embryos (remember the movie, Secret of NIMH?).  Further research on our variant indicates that it appeared in our lineage about 5 million years ago around when our stock split off from the chimpanzees.  One researcher points out our brains did not really begin to increase in size until 2 million years ago so this gene was not fully functional, maybe, for 3 million years.

skulls of different hominds

skulls of different hominds

Two articles in the 4/4/15 issue speak to the 3 million year mark.  One is about the controversy on how to classify a newly found fossil from 2.8 million years ago.  Is it part of Homo, which was just emerging from the gene pool, or an ancestor like the Lucy fossil, Australopithecus afarensis, or some transitional species in between?  In that same issue is a story about research into tools, presumably from some hominid line.  Though stone tool industry increased noticeably in the archeological record around 40,000 years ago, some shaped stone tools have been dated back to 2.6 million years ago.  Wow, I had not realized tool making was that old an art.  The story tells of the controversy between those who classify the tools by time/location and those who say that is not very informative and instead classify by the techniques used to form the tool.  Several of this latter group are expert stone ‘knappers’ themselves and that seems a good study.

Tool use in modern humans is supported by the left parietal lobe, the center for praxis.  If I remember my brain evolution correctly, our brain’s early enlargement came in the parietal lobe and then the temporal lobe, then later on frontal areas expanded.

parietal in yellow, temporal in green

parietal in yellow, temporal in green

Where these two lobes meet is where language abstraction is centered in Wernicke’s area.  So we have a gene which promotes brain growth in the embryo beginning to come on strong around 3 million years ago and shortly thereafter tool making appears.  We do not know how such creatures organized socially nor how they communicated.  We can be sure that empathic connectedness had emerged and that tool making techniques continued to develop over this time suggests cultural transmission and change.  Quite a history a long ways back.

Also in the 4/4/15 issue is a review of a book by anthropologist Pat Shipman who traces the domestication of dogs to 40,000 years ago when Homo sapiens left Africa and migrated into Europe.  Shipman finds linkages between modern humans and dogs and the eventual disappearance of Neanderthals, Denisovans, and large mammals like mammoths and cave bears.  Thus, the “Fido hypothesis” offers some explanation as to Homo sapiens ascendance during that time.  Oh, and other articles in those two issues speak about dogs’ abilities to read our emotions.  Yes, early humans traveled far and wide and met many friends along the way.  Travel on.

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