Bob Rowthorn is presenting a series of lectures at Siena, which he began on Wednesday with a lecture introducing the basics of genes, altruism, and the co-evolution of culture and genes. Today's lecture (where I currently am live-blogging from, joy!) concerns altruism in families.  He's presenting his model, published in the Journal of Theoretical Biology (2006) called the 'Sibling Model' - the article is 'The Evolution of altruism between siblings: Hamilton's rule revisited'. The main conclusion of his model is that siblings are more like one another, with respect to altruism, than they are similar to the average member of the population.  This may seem unsurprising, but he derives it with a simple mathematical argument, and re-derives Hamilton's Rule using slightly different assumptions.  He also uses derives a two (altruism) allele-equilibrium in which individuals display '50% Marginal Altruism', i.e. he finds a simulated and mathematical basis for Hamilton's rule, deriving it with great clarity.   

Something else that I found interesting was that he took the quote, attributed to Hamilton saying "I will sacrifice myself for 2 of my brothers or 8 of my cousins" and restated it as follows, "I will kill 2 of my brothers or 8 of my cousins to save myself." The second feels decidedly sinister. Anyway, an interesting presentation.  Sam's questions made it all the more interesting.