In 2 experiments, the authors examined the evolution of folkbiological reasoning in children (4 to 10 years of age) and adults from 4 distinct communities (rural Native American, rural majority culture, and suburban and urban North American communities). Using an adoption paradigm, they examined participants' intuitions regarding the inheritance of properties and the mechanisms underlying the transmission of kindhood. Across all communities and ages, there was a strong biological component underlying reasoning about the inheritance of properties. There were also differences in children's intuitions about the mechanisms underlying kindhood: Native American children were more likely than their counterparts to consider blood as a candidate biological essence. This suggests that as children search to discover the underlying essence of a biological kind, they are guided by broad essentialist notions that are shaped by discourse within their community.