Scott Alexander explores a theory suggesting that complex features of human biology evolved as defenses against parasite manipulation, discussing its implications for understanding psychiatric medications and biological complexity. Longer summary

This post discusses a theory proposed by Marco del Giudice in his paper 'Brain Evolution Through The Lens Of Parasite Manipulation'. The theory suggests that many complex features of human biology, particularly in neurotransmitter systems, evolved as defenses against parasite manipulation of host behavior. The post outlines various strategies that organisms might use to defend against such manipulation, including complicated signaling cascades, feedback loops, pulse-based communication, individual variability, and the use of antimicrobial substances as neurotransmitters. Scott Alexander explores the implications of this theory for understanding psychiatric medications, tolerance effects, and the complexity of human biology. He concludes by discussing the strengths and potential weaknesses of the theory, noting that while it's an interesting perspective, it's too early to determine its full validity or impact. Shorter summary

Scott Alexander attempts to understand and explain Karl Friston's complex 'free energy' principle in neuroscience, exploring its various interpretations and potential implications. Longer summary

Scott Alexander explores Karl Friston's work on 'free energy', a complex concept in neuroscience that has been described as a unified brain theory. The post delves into various interpretations of free energy, from its mathematical origins in Bayesian equations to its application in explaining perception, cognition, homeostasis, and action. Scott struggles to fully grasp the concept, acknowledging its complexity and the widespread difficulty in understanding Friston's work. He presents different perspectives on free energy, including its role in uncertainty reduction, its connection to predictive processing, and its potential to explain biological systems and the origin of life. The post concludes with a tentative synthesis of these ideas and raises questions about the implications of the free energy principle for machine ethics. Shorter summary