What makes you think it will take 100,000 years? Epigenetics allows a much faster rate of change, especially in structures which are not well preserved in the

What makes you think it will take 100,000 years? Epigenetics allows a much faster rate of change, especially in structures which are not well preserved in the archeological record. For example, cortical folding patterns. And "how big the brains" is a very good question. See https://blog.frontiersin.org/2021/10/22/when-and-why-did-human-brains-decrease-in-size-3000-years-ago-new-study-may-have-found-clues-within-ants/ https://blog.frontiersin.org/2021/10/22/when-and-why-did-hum... > Studying computational models and patterns of worker ant brain size, structure, and energy use in some ant clades, such as the Oecophylla weaver ant, Atta leafcutter ants, or the common garden ant Formica, showed that group-level cognition and division of labor may select for adaptive brain size variation. This means that within a social group where knowledge is shared or individuals are specialists at certain tasks, brains may adapt to become more efficient, such as decreasing in size. https://www.frontiersin.org/articles/10.3389/fevo.2021.742639/full https://www.frontiersin.org/articles/10.3389/fevo.2021.74263...