The BBC has a story on a recent paper in Nature by Susanne Shultz and colleagues documenting major steps in the evolution of primates. One of them, not surprisingly (though it is nice to see it more clearly demonstrated), is that the high degree of sociality seen in most primates likely did not originate until after primates switched from primarily nocturnal to diurnal. There are lots of reasons why sociality is both easier to achieve during the day and more evolutionary advantageous (e.g. predator avoidance/defense). Also, it just goes to show that your mom/dad was right, as a good and upstanding primate you should be in bed by 9 and leave the texting, chatting and hanging out for daylight hours.
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1. Susanne Shultz, Christopher Opie & Quentin D. Atkinson, Stepwise evolution of stable sociality in primates. Nature, 479, 219–222 (10 November 2011); doi:10.1038/nature10601
