Most of the differences are probably related with cultural differences. Mostly what they eat how you eat, work, sleep, stress, little walks, constant laughs, sex...well all those stuff that the scientific community knows so well but somehow nobody cares about...

These are really dificult to pinpoint to markers and are only uncovered doing high number of statistics and tracking the biochemistry...

In any case..only a fool will pick up the american system.

A pleasure

I therefore claim to show, not how men think in myths, but how myths operate in men's minds without their being aware of the fact. Levi-Strauss, Claude