I'm going on how it looked to me and connecting a few dots. It's not designed to be a genuine scientific observation. The girls bully one another to establish dominance. However, the alpha female, displays affection for the offspring of subordinate females. The genes perpetuated? They take the infants to war. The infants who stand the best chance of survival are those who can grip the strongest. How would this be advantageous? I had a lemur and they have spectacularly poor hand to eye co-ordination. If you hand a lemur a grape, they have difficulty grabbing it and it falls to the ground. They are able to fabricate "tools" of the most rudimentary sort. Ours was capable of human style potty training. They know the difference between Animal Planet and the real world.
Why do they war? One gang lives in a garden spot, another in a desert. They war for the same reason as humans, to grab as much territory as they can.
Anyway, hand gripping, are good genes for humans to have, because we make tools. By taking their infants to war, they set in motion the sort of genes that are useful to us. That was accidental. It didn't have to be lemurs. Black bears diverged a lifeform that would become the wolf and ultimately the family dog. There was another divergeance of the bear, that gave us raccoons which are sort of lemurry. So they were a contender in the sentience sweepstakes. However, whatever went down with the lemurs 55 million years ago, set up the genome that would eventually lead to us. It was all accidental and not meant for our benefit. It just happened. Lemurs diverged from something similar to a squirrel. And we could have ended up on a path as dead end as the raccoon or rabbit.
