We all know some people are born stupid but what I didn't know was that some people are born to be happy dudes while others are inherently miserable. To be precise, heritability of happiness is approximately 33%, and much higher for men then women.
This is documented in a study by De Neve, Christakis, Fowler and Frey which is even able to pinpoint specific genes associated with happiness. This suggests that if you want your kids to be happy campers that you should be very careful who you mate with, especially if you are a woman. Unless its too late. There's a cheery thought.