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EA - A concern about the “evolutionary anchor” of Ajeya Cotra’s report on AI timelines. by NunoSempere

AI Safety: Technical


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Welcome to The Nonlinear Library, where we use Text-to-Speech software to convert the best writing from the Rationalist and EA communities into audio. This is: A concern about the “evolutionary anchor” of Ajeya Cotra’s report on AI timelines., published by NunoSempere on August 16, 2022 on The Effective Altruism Forum. tl;dr: The report underestimates the amount of compute used by evolution because it only looks at what it would take to simulate neurons, rather than neurons in agents inside a complex environment. It's not clear to me what the magnitude of the error is, but it could range many, many orders of magnitude. This makes it a less forceful outside view. Background Within Effective Altruism, Ajeya Cotra's report on artificial general intelligence (AGI) timelines has been influential in justifying or convincing members and organizations to work on AGI safety. The report has a section on the "evolutionary anchor", i.e., an upper bound on how much compute it would take to reach artificial general intelligence. The section can be found in pages 24-28 of this Google doc. As a summary, in the report's own words: This hypothesis states that we should assume on priors that training computation requirements will resemble the amount of computation performed in all animal brains over the course of evolution from the earliest animals with neurons to modern humans, because we should expect our architectures and optimization algorithms to be about as efficient as natural selection. This anchor isn't all that important in the report's own terms: it only gets a 10% probability assigned to it in the final weighted average. But this bound is personally important to me because I do buy that if you literally reran evolution, or if you use as much computation as evolution, you would have a high chance of producing something as intelligent as humans, and so I think that it is particularly forceful as an "outside view". Explanation of my concern I don't buy the details of how the author arrives at the estimate of the compute used by evolution: The amount of computation done over evolutionary history can roughly be approximated by the following formula: (Length of time since earliest neurons emerged) (Total amount of computation occurring at a given point in time). My rough best guess for each of these factors is as follows: Length of evolutionary time: Virtually all animals have neurons of some form, which means that the earliest nervous systems in human evolutionary history likely emerged around the time that the Kingdom Animalia diverged from the rest of the Eukaryotes. According to, an online resource for estimating when different taxa diverged from one another, this occurred around ~6e8 years ago. In seconds, this is ~1e16 seconds. Total amount of computation occurring at a given point in time: This blog post attempts to estimate how many individual creatures in various taxa are alive at any given point in time in the modern period. It implies that the total amount of brain computation occurring inside animals with very few neurons is roughly comparable to the amount of brain computation occurring inside the animals with the largest brains. For example, the population of nematodes (a phylum of small worms including C. Elegans) estimated to be ~1e20 to ~1e22 individuals. Assuming that each nematode performs ~10,000 FLOP/s,the number of FLOP contributed by the nematodes every second is ~1e21 1e4 = ~1e25; this doesn't count non-nematode animals with similar or fewer numbers of neurons. On the other hand, the number of FLOP/s contributed by humans is (~7e9 humans) (~1e15 FLOP/s / person) = ~7e24. The human population is vastly larger now than it was during most of our evolutionary history, whereas it is likely that the population of animals with tiny nervous systems has stayed similar. This suggests to me that the average ancestor across our entire evolutionary history was likely tiny and performed very few FLOP/s. I will as...