The evidence suggests that children who were related to one another — who shared parents or grandparents or other close biological relationships — were deposited in the chultún together, or at least that related children were included among those deposited over the centuries of the feature’s use.

Whether this was deliberate selection — whether families contributed multiple children, whether relatives were chosen together — or whether it reflects the specific social structure of the families from which sacrificial children were drawn, cannot be determined from the genetic evidence alone.

And then there were the twins.

Two Pairs of Identical Twins

Among the 11 close-relative pairings identified in the study, two were identified as pairs of monozygotic twins — identical twins, arising from the division of a single fertilized egg rather than from two separate eggs fertilized at the same time.

Identical twins, or monozygotic twins, share essentially all of their genetic material.