Blaffer Hrdy estimates that cooperative upbringing began

Rail journey to Lake Titicaca, Peru
Rail journey to Lake Titicaca, Peru

at the beginning of the Pleistocene epoch (about 1.8 million years ago) when the African Homo erectus appeared. The author drew this conclusion from the relatively small difference in size between the sexes compared to the much older Australopithecines.

The male Homo erectus were

only 18 percent larger than the females. This degree of sexual dimorphism is only slightly more pronounced than in modern humans. (p. 384)

The plausible interpretation of Blaffer Hrdy would mean that the hominids were looking after their young together long before Homo sapiens. Therefore, the use of human communication by the helpers and thus the whole group of Homo sapiens is very plausible.

Carel van Schaik and Karin Isler also emphasise the importance of the helpers in caring for the young:

In most mammal species, the mother is on her own during the strenuous gestation and nursing periods, so any help will save the mother energy.

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Rail journey to Lake Titicaca, Peru
Rail journey to Lake Titicaca, Peru

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.

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Hypothesis 15

Taking care of the young as a joint activity

Rail journey to Lake Titicaca, Peru
Rail journey to Lake Titicaca, Peru

Once the intentional communication and cooperation between the mother and the infant are established in a social group, all individuals go through this phase as infants and all female individuals experience it from the maternal side.

Since the mothers, as has been observed in various cases, would otherwise be overwhelmed with the task of raising the children alone, fathers, grandmothers, older siblings and other relatives also take on the responsibility of looking after and caring for the offspring.

These individuals will also use the new intentional communication they have experienced and which the infant demands from them when they communicate with the infant.

Since the new form of communication does provide advantages, adolescents and then later adults will playfully make use of intentional communication and cooperation. This is how the new form of communication will become established in the social group.


The end of brain growth when Homo sapiens appeared

Palace District, Machu Picchu, Peru
Palace District, Machu Picchu, Peru

about 250,000 years ago has nothing to do with the fact that the brain, unlike the earlier hominid brains, would have been perfect (Mayr). I also consider the idea of a seamless transition from genetic adaptation to cultural tradition (Habermas) to be an unacceptable simplification,

one that does not take sufficient account of the change of era at the end of the growth in size of the human brain. Here further intermediate steps, which make this type of development plausible, are mentally necessary and are still to be described.

The prolongation of brain growth into the first year after birth makes the human brain even more expensive and leads to the problem of who can afford the costs.

The mother alone probably cannot afford the increased costs; further helpers are required. If we assume pair bonding and family structures, the father and other family members, such as older siblings, can be considered additional helpers.

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