You will recall my post: A genetic cause of rapid degeneration in some Alzheimer's patients. Well, now it (the topic) is a Ted Video. But before you watch it, I need to take down Nicholas Christakis for saying the dumbest thing I've heard all week.
No, Nicholas, it is not true in any way whatsoever that humans did not have complex social networks prior to "emerging" from the "African Savanna" ... nor would the implication that you make that those still living in Africa, or the savanna therein, fail in this way. That's just you being an ignorant racist westerner. Otherwise your talk is moderately interesting, and since it relates to the above linked post, I'll be happy to put it on my blog.*
*Note: The casual and probably unintentionally offensive remark implying that humans really didn't become human until leaving the Dark Continent could have been left unused. It added nothing to the talk. But it was an example of casual racism which, like casual sexism, is bad but unlearnable.