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Desert Diary
Mammals/Neck Bones


To some degree, we're all a captive of our past. Viewed from the perspective of deep time, what we are has been shaped by events over several billion years of evolution. In some broad sense, we're free to vary wildly in many ways. If we look at the mammals, the group to which we belong, we find creatures varying from whales to bats to intellectual giants—that's us—to tiny shrews weighting less than a penny.

Yet, our past history often sets limits, frequently in unexpected ways. For example, strangely enough, the necks of everything from giraffes to our almost neckless Chihuahuan Desert kangaroo rats share a common trait—exactly seven bones in the neck. Only a handful of odd mammals like sea cows and sloths vary from this formula. What's so magical about this number? We can only speculate that some phase of embryological development necessary for normality is set in stone. Thus while the swan, with its numerous neck bones, is considered the epitome of gracefulness, the poor giraffe is only an object of ridicule.
pen and ink


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.



Gunderson, H. L. 1976. Mammalogy. McGraw-Hill Book Company, New York. 483 pp.

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