Explanation:

No mammal on Earth has produced young that take longer to mature or depend on the support of so many others than Pleistocene humans.

With the help of alloparents and parents, these offspring – incredibly costly and equipped with large brains – slowly grew up and enough survived to produce a population capable of penetrating into new habitats, raising children there, spreading further, and eventually populating the entire planet.

Nourished not only by their mothers but also by other members of the group, even descendants who were weaned long before they could care for themselves could slowly grow up without suffering hunger.
(German: Sarah Blaffer Hrdy 2010: Mütter und andere, Berlin, p. 377)

Because of the longer childhood and adolescence, the raising of the young has become extremely expensive for humans and their forerunners. Sarah Blaffer Hrdy, the originator of the quote, has dealt with the prolonged course of human life and its consequences.

In our context, her role as a witness is important in ensuring that mothers could not raise their children on their own but needed and received help from alloparents i.e. other helpers.