Another phenomenon that Achim Peters describes is body downsizing,

a phenomenon that can already be detected in lower vertebrates such as fish. When food shortages or a protracted illness occur, tissue recedes. Peters:

In the history of the human species, which ranges from Homo Australopithecus to Homo erectus to us, there were long periods of crisis such as ice ages and periods of drought (…)

If we look at the era some 50,000 years ago as an example of such a long-term supply crisis in the tribal history of humans, it perhaps provides us with the reason why the human body underwent such a sustained transformation, became more delicate, therefore providing the brain with greater access to energy in modern Homo sapiens. This is supported by the fact that about 50,000 years ago, with the beginning of the last ice age, progressive body downsizing began. (p. 49)

Hypothesis 9 dealt with the special position of the brain among the organs of animals and humans. The high energy consumption makes it a risky organ for living beings. The effort is only worthwhile if there are major advantages that offset the negatives.

The steady growth of the brain during animal evolution shows that the advantages were so great that animals with larger brains were able to assert themselves evolutionarily. The theory of the Selfish Brain gives us insight into the energy regulation of the brain, with which the human brain secures its energy supply and thereby ensures that it functions properly.