Examining the beginnings of agriculture in the ‘Fertile Crescent’, this research team has compared the distribution of rainfall with the distribution of Y-chromosome haplogroups. The extended families signalled by J1 and J2 haplogroups seem to have had different destinies in the era of agro-pastoralist experiment: J2 were the agricultural innovators who followed the rainfall, while J1 remained largely with their flocks. Acknowledging the fuzzy edges of such mapping, the authors nevertheless escort us into new realms of the possible for the early history of peoples.