Parasites

I don't believe in free will, but up until about 30 minutes ago I thought that at least I was being worked like a puppet by my own genes and brain chemistry. No longer. Is it accurate to say that the rabies virus knows more about human aggression than the finest minds in neuroscience? Possibly, rabies can alter your thoughts so thoroughly as to make you want to bite someone, thus propagating itself, neuroscientists cannot.

Toxo is a cat parasite. The only place it can reproduce is within the feline gut. The cat shit, now enriched with toxo eggs, is then eaten by rats. Now the toxo has a problem, how is it going to get back into the gut of a cat? It can't just whisper in the rat's ear, convince it to get eaten by a cat. Instead it invades the cat's brain and hijacks the normal response that a rat has to cat pheromones. Now, instead of fearing them, the rat is actually sexually attracted to them. With predictable results.

Now, this would be extremely interesting in and of itself, but wait, it gets so much better. It turns out that the genome of the toxo actually has a pathway for hacking into the dopamine system found in mammals, and that's how it changes rat behaviour. So what happens when a human is infected? It was thought that a toxo infection was largely asymptomatic (except in pregnancy, where it causes developmental problems with the fetal nervous system), but recent studies have shown that a toxo infected male is 4 times more likely to die in a car accident as a result of speeding. That is stunning. This parasite, which startlingly is very prevalent, can affect human behaviour in a completely undetectable way. What else is screwing with you? What else is stealing your free will? Did you have any in the first place? Scary stuff.

You have to watch this video: Sapolsky on toxo. There is so much more in this video I can't even begin to start, best 25 minutes I've spent all week. Sapolsky also wrote a fantastic book, A Primate's Memoir, about his time as primatologist in Africa.