Past studies have shown that in ape society, males are hierarchical and females are mostly egalitarian..low status males who stay behind as the alpha male and party goes to hunt/forage sometimes end up impregnating the females. The cuckolded alpha male would never know. Female pregnant apes will also spontaneously abort if a new group of alpha males enters and ousts the prevailing alpha. This is called the Bruce effect. Pregnancy and birth is highly expensive to females and they will do their best to conserve energy and resources. Males place a high value on investing in their own offsprings and it behooves the females to hedge her bets if alpha males get killed or ousted when a new group comes in..Alphas get cuckolded all the time because they are violent and always at risk of being ousted by rival alpha ape in group or from
outside...no one knows who is father except the mother. And often the lower status males are a good bet because they are less likely to get killed. And they will take care of their offsprings. Ape studies are fascinating.