Henn and Julie Granka, a graduate student in biology, recently revisited the South African Bushmen who participated in the study and took height and skin color measurements from the people whose DNA they had analyzed.
Hewever, when the researchers took height, intelligence, educational achievement and socioeconomic status of parents into :account in comparing the different genetic groups, there still remained an excessively high crime rate among the XYY, men which has not yet been explained.
The researchers got around these problems by stitching together data from five big studies that took height and weight measurements of more than 40,000 Americans multiple times over many years.
Three individuals took height and weight measurements and there may have been small systematic differences between measurers although standardized training of all workers was undertaken prior to the study to minimise this effect.
During the study visit, study nurses took height and weight for children aged <9 years and administered a standardized questionnaire on sociodemographic information, relevant medical history, and living conditions.
