Campbell Biology (11th Edition)

Published by Pearson
ISBN 10: 0-13409-341-0
ISBN 13: 978-0-13409-341-3

Chapter 34 - 34.2 - Concept Check - Page 723: 2


This is at least strong evidence of natural selection favoring the evolution of heads around 530 million years ago— perhaps there was some common selective factor, such as the recent evolution of new predators, which made having a head advantageous.

Work Step by Step

The key here is to see that the evolution of heads in multiple lineages all at once points to some common factor, but this one example doesn’t prove that a head is always favored by natural selection.
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