Jamie Jones visits Google to discuss the evolution, ecology, and adaptation of the human species. Rationality has taken a hit recently. Recent work in psychology and economics has challenged the notion that the human brain is designed to make rational decisions. However, this observation raises a paradox. By almost any measure, Homo sapiens is a spectacularly successful species. From humble origins approximately two million years ago, humans have grown to a population that exceeds seven billion and have colonized nearly every terrestrial biome. This phenomenal growth suggests that our ancestors made very good decisions. Yet this work from psychology and economics suggests that the decision-making software that our brains run is profoundly flawed — that we are, in a word, irrational. How is it possible that a species apparently so defective in its ability to generate sound decisions can be so incredibly successful? It turns out that the rules for a living organism, anchored in the present and subject to a force of selection which is extremely averse to extinction, are quite different from the rules of abstract, formal rationality. In this Talk, Jones will show how the all-important need to avoid extinction in a world that is at best incompletely known has profound implications for preferences, utility, and rationality. By ignoring the condition of existential uncertainty, the theory of rational decision-making has developed distorted expectations of how an organism working in its own best interest should behave. Originally published in March of 2018. Visit YouTube.com/TalksAtGoogle to watch the video.