The third hypothesis says that rapid climate change played the critical role.
'The idea that it's been a major step forward for Prozac to select serotonin only is just hypothesis,' says Malcolm Lader, professor of clinical psychopharmacology at the Institute of Psychiatry.
The Airy hypothesis says that Earth's crust is a more rigid shell floating on a more liquid substratum of greater density.
The idea, known as the amyloid hypothesis, says the disease occurs when a toxic protein, beta amyloid, accumulates in the brain.
"My hypothesis", says Sir Michael, "is that how much control you have over your life will be an important predictor of mortality and health after retirement".
This hypothesis says that approximately two-thirds of the topography is compensated by the root formation (the Airy model) and one-third by Earth's crust above the boundary between the crust and the substratum (the Pratt model).
The best known explanation, the hygiene hypothesis, says we've become too clean: born into sterile environments and growing up in dirt-free homes with safe drinking water, our children aren't exposed to the harmless microbes and parasites that help develop a properly regulated immune system that won't overreact to harmless substances.
The Bischof-Köhler hypothesis says that only humans can mentally separate themselves from what they are experiencing to envisage how they might feel about future events.To test whether this is so, Dr Clayton and her colleagues sought to tease apart scrub-jays' momentary desires from their planning for future needs.
"My hypothesis", says Michael Jensen, a former professor at Harvard Business School and now a director at the Monitor Group, a strategic consultancy, "is that they overreached to try to become all things to everybody, to become the world's greatest company.
Sound hypothesis says that it protects brain during hypoxia.
That result argues against the inbreeding hypothesis, says Barbujani.
