Human agricultural economy is, and likely always was, largely based on kinship - Why?

We question the sequence of evolutionary transitions leading to ultrasociality in humans proposed by Gowdy & Krall. Evidence indicates that families are, and likely always have been, the primary productive units in human agricultural economies, suggesting that genetic relatedness is key to understanding when the suppression of individual autonomy to the benefit of subsistence groups, that is, extended families, evolved.