It's said that you can see forever in the clear air of our desert. But that's for animals like us, good-visioned creatures active during the day, whereas our nocturnal animals tend to rely much more on scent. This is not especially surprising, of course. But consider—there aren't many animals really good at both sight and smell. Why not? After all, if our sense of smell was as good as our eyesight, our ancestors could possibly have ruled the night as well as the day. Or, if not have ruled, at least have been forewarned of nighttime danger.
We're now getting some insight on color vision versus smell. Of
about 1,000 human genes involved in smelling, only about 40% work, while in the
color-blind mice and dogs, some 80% are functional. DNA sequencing among humans, apes,
and Old World and New World monkeys pretty much shows a tradeoff. Why? Apparently
because visual and olfactory sections of the brain require a lot of space—there just
doesn't seem to be enough room to excel in both.
Listen to the Audio (mp3 format) as recorded by KTEP, Public Radio for the Southwest.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
Holden, C., ed. 2004. An eye for a nose. Science 303:621.