rw wrote in news:44c55670$0$24181
:


Primates (including humans) apparently re-evolved a third type of cone
(toward the blue end of the spectrum), probably because they had to
distinguish between different types of ripe fruit.



Some primates have interesting dimorphisms. In the squirrel monkey, for
example, all of one sex are trichromats, and something like 70% of the
other sex are bichromats.

--
Scott
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