An evolutionary comparison of human head and body lice has shed light on the history of clothing. 

   A team based in Germany has worked out that humans
   probably first began wearing clothes 72,000 years ago - give
   or take 40,000 years. 

   Their calculation is based on the fact that as species evolve,
   they become distinct by inhabiting different environments and
   gradually changing to suit them. 

   While head lice live solely on the human scalp, body lice 
   prefer to inhabit those areas covered by clothing.

   Dr Mark Stoneking's team, from the Max Planck Institute for
   Evolutionary Anthropology in Leipzig, worked out when the two
   organisms began to diverge and became distinct species.

http://news.bbc.co.uk/2/hi/science/nature/3142488.stm

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