The Nash equilibrium, a solution concept in game theory famously proposed by John F. Nash in 1950, is broadly considered as the standard mathematical embodiment of rationality in at least two ways: most people use it, and every new solution concept is judged against it. Yet a few years ago, it was shown by this group that the concept has a serious drawback of an algorithmic nature: finding such an equilibrium is a computationally intractable problem, and thus unlikely to be routinely and universally achievable in practice. This project investigates certain novel and tractable conceptions of rationality, most notably one inspired by a certain well known dynamics called multiplicative weight update algorithm (MWUA). It also explores a remarkable and intriguing new connection, recently discovered by this group, between MWUA and the theory of evolution.