A Very Cultured Species

This chapter deals with the question of why Homo sapiens are the only Homo species left.  Homo sapiens evolved in Africa about 200,000 years ago, and started to migrate out of Africa between 100,000 and 80,000 years ago.  However, modern humans descended from a relatively small group of only 14,000 individuals.  This resulted in a current population that is very genetically similar.  Additionally, from fragments of DNA extracted from Neanderthal fossils, it was discovered that 2-5% of the human genome is from Neanderthals.  As Homo sapiens moved out of Africa, they settled in every continent except for Antarctica.  And at the same time, Homo erectus and Neanderthal populations went extinct.  What makes Homo sapiens different?  Lieberman argues that Homo sapiens were better able to invent tools and think creatively.  He also argues that while Neanderthals certainly had language, the short and retracted face of Homo sapiens would be better able to communicate clearly and rapidly.  However, Lieberman explains that the adaptation of clearer speech comes with a disadvantage.  To gain this advantage, the larnyx in humans is dropped a couple centimeters, which allows for clearer speech, but also creates the risk of choking.  It is unknown if the extinction of other species is a result of a lower birth rate or competition with Homo sapiens, but clearly, Homo sapiens had an evolutionary advantage.  Lieberman argues that this advantage could have been cultural evolution, meaning the advancement of technology and clothing.  If this technology could have helped them survive in harsh conditions, it would keep the population alive long enough to select for beneficial adaptations.  Finally, Lieberman argues that humans are adapted to be adaptable.  We have the capabilities to communicate, cooperate, invent, and think, and this allows humans to adapt to different environments.  Lieberman concludes that it is our cultural achievements such as farming and writing that have allowed humans to thrive.