This is an article about an anthropologist that contends American parents don't need to spend as much one on one time as they do, and if anything it's pretty weird: http://www.boston.com/news/globe/ideas/articles/2007/07/14/leave_those_kids_alone/?p1=MEWell_Pos4
My reaction to his hypothesis, and he actually acknowledges this with his Inuit exception, is that Americans are really isolated and we don't have a lot of friends or other kids for our kids to play with, so they're not going to get the same interaction that a kid growing up on the Serengeti might get with others. As a personal opinion, I do feel the whole "Baby Einstein" syndrome thing has gotten WAAAY out of hand.
The second one is about an anthropologist in Finland who is looking at genealogy and birth, death, and marriage records and is finding some really interesting stuff. For example: the girl in a set of mixed-gender twins will have less kids overall. http://www.sciam.com/article.cfm?articleid=C0D3CD91-E7F2-99DF-3D5399013D3691D5&chanId=sa011
What's nice is she acknowledges the combination of biology vs. culture, like with the farmland moms versus the "wilderness" moms. I would really like to see this kind of study done in other regions too.