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The Gentle Primates Tribe had been peaceful once.
Just like what Dennis said, it was built by the couple that was once been adopted and raised by a human after death of the same person. They wanted to re-create the society that they were used to seeing, but also wanted primates to be the one's leading tribe. This is the reason why that couple taught the monkeys that came what they know.
As time went on, the monkey couple eventually got older. One would think that they should've at least had a child or two but sadly, they were unfortunate in that aspect.
Reproduction had always been a problem for beasts, specially Demonic Beast.
The stronger their genes is, the harder it is for them to conceive a child. It's not the question of whether 'were they really trying?' either. These are beasts. Of course they're trying.
