No laughing matter
Your sense of humour has nothing to do with the genes, and everything to do with your upbringing. A study was conducted by researchers at the St Thomas Hospital, London on 71 pairs of identical twins and 56 pairs of fraternal twins, who were raised together. The twins were asked the kids to go to a separate room and rate five cartoons of Gary Larson's The Far Side on a scale of 0 to 10 with 10 being most funny. The results showed that siblings tend to have similar views on how funny a cartoon is. But identical twins, who have exactly the same genes, were no more likely to agree on this than fraternal twins, who share only half their genes on an average, like ordinary siblings.
This suggests that it is shared environment, rather than shared genes, that make brothers and sisters laugh at the same things. This implies that there is a lot of cultural influence on humour and might explain why popular jokes vary so much between nations, says Tim Spector, who led the study. ( Twin Research , Vol 3, No 1).