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From: RonO <rokimoto557@gmail.com>
Newsgroups: talk.origins
Subject: Brain body size evolution
Date: Tue, 16 Jul 2024 07:40:13 -0500
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https://www.sciencedaily.com/releases/2024/07/240708101004.htm

https://www.nature.com/articles/s41559-024-02451-3

The Nature article is open access.

The authors claim that they have developed a model for the relationship 
between brain and body weight for mammals and the evolutionary 
trajectory for different lineages.  With this model they can identify 
lineages that do not conform to the usual brain size evolution 
relationship to body weight.  As pretty much every other study has 
indicated humans have evolved bigger brains for their body weight and 
primates have a higher rate of brain size increase.  Some lineages have 
lower brain size to body weight than expected.  As you might expect 
these are the largest mammals.  They speculate that brains take a lot of 
energy to maintain, and that there is likely selection against larger 
brains at some point in body size increase.  Population sizes for large 
mammals have to be smaller because it takes more food to maintain 
individuals.  The estimate that I have seen is that it takes 80% of our 
energy production to run our brains.  If you have smaller brains you 
could maintain larger populations.  Hunter gatherer populations were 
probably restricted by our brain's energy needs.  With the poorer 
agricultural diet our brains actually decreased in size as our 
population increased.  We could maintain much larger populations on the 
same amount of territory, but it wasn't a diet amenable to supporting 
large brains.

Ron Okimoto