Yeah, I know it's early in the morning, but I can't sleep...

Bear with me on this one will you, it'll stray dangerously close to Transhuman thought with a few twists.

Toxoplasma gondii is a parasite that lives in the soil and is ingested by humans most commonly in the form or raw or undercooked meat (22% of the population of the UK have the infection while in France it is 84%). When rats are infected with this parasite they lose their fear of cats and other new things and this is termed a reduction of Neophobia (fear of new things).
When humans are infected they undergo personality changes (including a reduction of willingness to accept group standards) and are 2.65 times more likely to have road traffic accidents.
Couple this with the theory that Neophobes die sooner than those who seek out new things (in a safe environment), and you can build an interesting little chain...
The theory is this, that a Toxoplasma gondii infected person starts seeking out new experiences while shunning the "accepted norms" of society, and will live longer due to a reduction of stress. This might explain the stereotype of the wide-eyed lone genius who lives into old age. Perhaps the first (proto)humans to exploit fire were infected with this parasite, causing them to investigate and experiment rather than run in fear?
Maybe we owe our first faltering steps on the path of humanity to a little parasite that our ancient ancestors ingested...

Either way it has got to beat Kuru.