Marsupial brains evolved their own neuron patterns, not just ancestral ones
In short: Researchers who studied the brains of 10 marsupial species found that while basic scaling relationships are shared with eutherian (placental) mammals, Australasian marsupials have broken from the ancestral pattern in a notable way: their cerebella contain more neurons than similarly sized eutherian cerebella, and their ratio of cortex-to-rest-of-brain neurons resembles that of primates and artiodactyls.
This challenges the view that marsupial brains are simpler or more primitive versions of eutherian brains. The findings suggest that how neurons are packed into brain regions can evolve independently of the mechanisms that govern overall brain scaling, even across mammal lineages that diverged early in evolution.
The researchers examined cellular composition, counting neurons and other cells, across 10 marsupial species and compared the results with earlier data from eutherian mammals. As a cross-species comparison, it reveals patterns rather than explaining the evolutionary pressures behind them.
Why it matters: Marsupial brains are not just simpler, ancestral versions of other mammal brains - they've evolved their own distinctive ways of allocating neurons.
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Sources
- Summary by Intellect · source: Research: Santos et al. (2017). Cellular Scaling Rules for the Brains of Marsupials: Not as “Primitive” as Expected. Brain Behavior and Evolution.
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