https://www.tandfonline.com/doi/abs/10.1080/15298868.2017.1350601?journalCode=psai20
We revisit the thesis we first offered in 1997, namely, that the human capacity called “the self” is the product of evolutionary pressures. A review of the literature accumulated in the intervening 20 years prompted three changes to the original thesis. First, we expanded our 1997 conception of the self. We argue that the self consists of a multiplicity of cognitions, each of which may reflect the action of a different neural system. Second, we revised the timeline for the evolution of the human self. At least some components of the human self were present in hominids earlier than the 100,000 years-old date that we speculated served as the oldest-age boundary for the emergence of the self. Third, we supplemented the evidentiary basis by relying on advances in brain structure, brain function, and the genetic underpinnings of the brain. In comparison to the state of knowledge in 1997, there is more reason to assert in 2017 that humans have the capacity to experience a self because this trait was selected via evolution.
https://journals.sagepub.com/doi/10.1207/s15327957pspr0101_6 (1997)
We propose that the capacity for a symbolic self (a flexible and multifaceted cognitive representation of an organism's own attributes) in humans is a product of evolution. In pursuing this argument, we note that some primates possess rudimentary elements of a self (an objectified self) and that the symbolic self (a) is a trait that is widely shared among humans, (b) serves adaptive functions, and (c) could have evolved in response to environmental pressures, with ecological and social pressures being of particular relevance. We suggest that these two environmental pressures caused the symbolic self to emerge in the Pleistocene epoch as an adaptation for Homo erectus, and we review the possible functions served by such an adaptation.
https://www.tandfonline.com/toc/psai20/18/1?nav=tocList
see also
https://onlinelibrary.wiley.com/doi/abs/10.1046/j.1468-5914.2003.00223.x
https://www.imprint.co.uk/the-evolution-of-the-self/
https://www.youtube.com/watch?v=bhRNMj6UNYY&t=3s
https://www.amazon.com/Evolving-Self-Problem-Process-Development-ebook/dp/B003772KJC/ref=sr_1_4?dchild=1&keywords=robert+kegan&qid=1586748398&s=books&sr=1-4
