The Soap Opera that is Human Evolution

For decades, scientists hotly debated whether or not Neandertals ever interbred with anatomically modern humans.  That question was finally answered to nearly everybody’s satisfaction a few years ago.  Neandertals lived not only in Europe but in Siberia and the Middle East.  It was in the Middle East, not long after anatomically modern humans (i.e. Cro Magnons) left Africa, that it happened.  In fact, the DNA evidence suggests that it happened twice:  the first about 60,000 years ago, then again c. 45,000 years ago.

A few years ago, DNA was extracted from a finger bone and some teeth found in a cave in Siberia.  Thus was discovered an unknown species of human.  These same caves, the Denisova caves, hence the name given to our newly discovered cousins, the Denisovans, was also inhabited at various times by both Neandertals, to whom the Denisovans were more closely related than to us, and modern humans.  Apparently, a home is not all they shared:  Fossil genome reveals ancestral link.

Recently, the genomes of both the Denisovans and the Neandertals have been refined, bringing them into sharper focus.  This new clarity brought to light the even more ancient DNA embedded within the Denisovan genome.  They interbred with someone else before us.  We don’t know who these other ancients were.  Have we already discovered and classified their remains?  Or are they something completely new?

Here’s a good summary of everything so far:  The long First Age of mankind.  This also touches on the “surprising” discovery of European DNA in a Siberian boy who lived about 24,000 years ago, that could have interesting implications for the genetic history of the First Americans.  Although, to be honest, anyone who has read Bryan Sykes’s The Seven Daughters of Eve is already aware of the presence of so called “European” DNA in America’s ancestral populations through the mtDNA lineage of “Xenia”.

Meanwhile, back in Africa, approximately 35,000 years ago, DNA evidence suggests that our ancestors were interbreeding with yet another hominid lineage that diverged from our own about 700,000 years ago.  They may even have done so before that.

Now, as if all that isn’t complicated enough, in yet another genetic study published last week, bones found within a place in Spain called , appropriately, Sima de los Huesos (pit of bones), and classified as Homo heidelbergensis, have mtDNA more closely related to Denisovans than Neandertals.  And, yet, they look more like Neandertals.  Plus, there is, as yet, no proof of Denisovans ever living outside of Asia.  There’s some speculation that these H. heidelbergensis, or, more likely, their immediate ancestors, may have interbred with yet another species found in caves not that far away called Homo antecessor.  The H. antecessor remains are about 100,000 years older than those of the H. heidelbergensis used in this study.  From the Nature website: Hominin DNA baffles experts.  The experts aren’t the only ones baffled.

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