[Taxacom] larger brained taxa correlated more to diet (than to sociality or habitat)?

John Grehan calabar.john at gmail.com
Wed Nov 14 21:41:54 CST 2018


Dear All,
      I watching a PBS program tonight on squirrels, and one researcher
suggested tree squirrels have larger brains than ground squirrels since
they have to navigate a more complex arboreal habitat.

Or, to avoid teleology, one could just say that squirrels are able to
navigate a more complex arboreal habitat because they have larger brains.

 And there are also some squirrels that have brains that are larger in the
autumn when they are trying to remember where they hid their caches of nuts
and their brains then shrink to normal the rest of the year.  Very
interesting.

How did the research know the squirrels were 'trying' to remember?

HOWEVER, some research seems to suggest that diet is a more important
factor, at least in primates.

meaning what?

If so, since rodents and primates are in the same clade (Glires), perhaps
the rich diet of nuts in autumn accounts for larger squirrel brains that
time of year, which also just happens to correlate with the need to
remember the location of those hidden nuts?

But that does not have any necessary realtionship to the evolution of
permanently larger brains.

Anyway, here is a link to a paper on the subject in primates, suggesting
frugivores have bigger brains than folivores.  Folivores would not have a
diet rich in fats (as in nuts) or sugars (as in fruits) that seem necessary
for higher brain activity.

Meaning, if you have a bigger brain you better be able to feed it.

Of course, sociality and arboreality could be secondary factors in some
taxa,

Secondary as what?

but folivores seem to be the least likely to develop larger or more complex
brains that require more nutrients and energy.

If a food source is inadequate to support a larger brain then it follows
that a larger brain could not exist.

John Grehan




On Wed, Nov 14, 2018 at 9:56 PM Kenneth Kinman <kinman at hotmail.com> wrote:

> Dear All,
>       I watching a PBS program tonight on squirrels, and one researcher
> suggested tree squirrels have larger brains than ground squirrels since
> they have to navigate a more complex arboreal habitat.  And there are also
> some squirrels that have brains that are larger in the autumn when they are
> trying to remember where they hid their caches of nuts and their brains
> then shrink to normal the rest of the year.  Very interesting.
>       HOWEVER, some research seems to suggest that diet is a more
> important factor, at least in primates.  If so, since rodents and primates
> are in the same clade (Glires), perhaps the rich diet of nuts in autumn
> accounts for larger squirrel brains that time of year, which also just
> happens to correlate with the need to remember the location of those hidden
> nuts?  Anyway, here is a link to a paper on the subject in primates,
> suggesting frugivores have bigger brains than folivores.  Folivores would
> not have a diet rich in fats (as in nuts) or sugars (as in fruits) that
> seem necessary for higher brain activity.  Of course, sociality and
> arboreality could be secondary factors in some taxa, but folivores seem to
> be the least likely to develop larger or more complex brains that require
> more nutrients and energy.
>        https://www.nature.com/articles/s41559-017-0112
>
>                              ----------------Ken Kinman
>
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