The merit fallacy
I philosophize thus:
In a clan, a band, even a modern family, everyone is carried along more or less equally. This idea current in modern society - the "Meritocracy" - that some people are less able, less intelligent, less worthy generally does not hold water in the intimate context.
You don't abandon your sibling to whatever fate because their IQ is lower than yours, or they don't read as well, or they are less motivated. The clan or band doesn't leave someone behind because they are below average. They do leave the gravely ill behind, but that is as good as dead. If you can walk and make a contribution, however small, you stay in the group.
Power is not equal, but wealth is largely equal. If some of the band eats, everybody eats. Division of work by gender tends to be very strong in the traditional band, and family. Is there a connection between that and cohesiveness, inclusiveness?