>This is where the "Lights Out" book (admittedly flawed) may have some
>application.
>
>Their theory is that in the summer, when both fruit and light are bountiful,
>humans naturally stayed up late and ate more carbs.   Then in winter, when
>daylight was short lived and there was no artificial light, humans went to bed
>early and slept longer and due to the meager results from hunting and
>gathering
>in the winter, lived off their fat.


Just out of curiosity...Does the book suggest that paleolithic people went
to sleep as soon as it was dark?  What about times spent sitting around the
campfire telling stories and singing songs, etc.?  Was this done only in
the summer, when the efforts of hunting and gathering were plentiful?  Are
you suggesting that they went to bed early in the winter to conserve
energy, or from weakness due to hunger?