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A Fascinating New Theory About the Human Mind, Evolution and Mortality

Why have other species failed to evolve human-like intelligence? The answer may lie in our conception of mortality.

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Once I got over the shock of this unexpected and sad news, I scoured the published literature to see if Danny had ever written about his idea, but I found no evidence that he had. One day soon thereafter I saw a dedication to Danny in a research article on an unrelated topic by a well-known scientist named Sean Carroll. I contacted Sean, who told me that Danny had in fact talked to him and to a few other friends about some of his ideas. Sean had even read and commented on some writings Danny had begun on the subject—efforts cut short by Danny’s untimely death. I was now even more convinced that the basic idea needed to be published. As it happened, I had previously gotten to know Philip Campbell, the editor in chief of the prestigious journal Nature , as he had once approached me to write an article about the ethics of doing research on great apes. I contacted Campbell and explained the situation. He was interested and suggested that I write a formal “letter to the editor” on the topic.

Before writing the letter, I spent more time reading the literature and grew to appreciate the importance of a psychological concept called “theory of mind”—also variously called mind-reading, attribution of mental states, perspective taking, mindsight, and multilevel intentionality. These jargonistic terms refer to various aspects of the human ability to go beyond self-awareness of our own minds to the full comprehension that other humans are also self-aware and have independent minds of their own—and to thus put ourselves into their mental shoes. For example, the reason I could have a discussion with Danny was that we both knew that the other had a mind capable of independent thought and reasoning. And by now, you, the reader, may have started developing a theory of mind about both of us authors, including the one who is not even alive today.

I also consulted learned colleagues from CARTA in relevant disciplines to determine whether Danny’s basic theory was truly original. It turned out that many other writers had already touched on the first half of the concept. Even ancient Indian Vedic texts had addressed the surprising fact that we humans deny the reality of our own mortality—easily—though we know its certainty. And in modern times, Ernest Becker’s Pulitzer Prize–winning 1973 book The Denial of Death emphasized the point further, suggesting that many aspects of human behavior and culture can be explained by this denial mechanism. But the second part of Danny’s idea—that the realization of our own mortality might have been a barrier to the emergence of a humanlike mind until our species was finally able to deny that realization—was unique; I found nothing like it in anything I read. I wrote the letter to Nature, and it appeared in August of 2009. The relevant sentences from the letter are reproduced below:

Among key features of human uniqueness are full self-awareness and “theory of mind,” which enables inter-subjectivity—an understanding of the intentionality of others. These attributes may have been positively selected because of their benefits to interpersonal communication, cooperative breeding, language and other critical human activities. However, the late Danny Brower, a geneticist from the University of Arizona, suggested to me that the real question is why they should have emerged in only one species, despite millions of years of opportunity. Here, I attempt to communicate Brower’s concept. He explained that with full self-awareness and inter-subjectivity would also come awareness of death and mortality. Thus, far from being useful, the resulting overwhelming fear would be a dead-end evolutionary barrier, curbing activities and cognitive functions necessary for survival and reproductive fitness. Brower suggested that, although many species manifest features of self-awareness (including orangutans, chimpanzees, orcas, dolphins, elephants and perhaps magpies), the transition to a fully human-like phenotype was blocked for tens of millions of years of mammalian (and perhaps avian) evolution. In his view, the only way these properties could become positively selected was if they emerged simultaneously with neural mechanisms for denying mortality. Although aspects such as denial of death and awareness of mortality have been discussed as contributing to human culture and behaviour, to my knowledge Brower’s concept of a long-standing evolutionary barrier had not previously been entertained. Brower’s contrarian view could help modify and reinvigorate ongoing debates about the origins of human uniqueness and inter-subjectivity. It could also steer discussions of other uniquely human “universals,” such as the ability to hold false beliefs, existential angst, theories of after-life, religiosity, severity of grieving, importance of death rituals, risk-taking behaviour, panic attacks, suicide and martyrdom. If this logic is correct, many warm-blooded species may have previously achieved complete self-awareness and inter-subjectivity, but then failed to survive because of the extremely negative immediate consequences. Perhaps we should be looking for the mechanisms (or loss of mechanisms) that allow us to delude ourselves and others about reality, even while realizing that both we and others are capable of such delusions and false beliefs.

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