Where diseases come from
There's an interesting review article on infectious diseases in today's issue of Nature (May 17, 2007). It's titled " Origins of Major Human Infectious Diseases " and authored by 3 researchers at UCLA, Nathan Wolfe, Claire Dunavan and Jared Diamond (author of Guns, Germs, and Steel ). There have always been opportunistic diseases of one sort or another. Even bacteria (germs) can get "sick" from viral infiltration. However humans have artificially created a situation today in which they get sick a lot more than they did in the distant past. You see, since the advent of agriculture around 10,000 years ago humans have maintained large stationary populations and also segments of the human population have stayed in direct contact with populations of other animals (chickens, goats, cows, dogs, etc). Both of these trends have culminated in a number of diseases that would not have occurred in hunter/gatherer societies. This article explores the evolutionary st...