- Umbilical cord;
- Female body fat;
- Maternal love;
What's up here? Kin selection and group selection are basically the same thing.
I don't pretend to have a complete explanation for this - but I think the group selection enthusiasts were led astray by the urge to distinguish themselves from kin selection enthusiasts. If discussing family groups, it was obvious that kin selection applied to it - and explained it. The group selection advocates therefore focused their attention elsewhere - where it seemed as though there was more chance to explain new phenomena that kin selection failed to cover. This hypothesis explains the migration of group selection enthusiasts to cultural evolution - since that is obviously not down to shared DNA.
Eventually, there was nowhere else to run, and the group selection advocates mostly gave up their claims that group selection was something new and different. Now the rhetoric in the area has mostly shifted to other issues.