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Broccoli
Wild mustard
Caulifl ower
Kale
Cabbage
◗
Figure 18.3
Artifi cial Selection Humans have practiced artifi cial selection for thousands of years,
thereby giving rise to dozens of varieties of domestic dogs, pigeons, and vegetables. For example, wild
mustard was selectively bred to yield broccoli, caulifl ower, kale, cabbage, and two other vegetables
not shown here.
nothing more than light-sensitive spots, crude image makers,
or image makers as in vertebrate animals, are all fully formed
and useful. Of what use is half a bird's wing? Of course, this
argument presupposes that wings were always used for fl y-
ing exactly as they are now, which is not necessarily true. The
earliest birds may have used rudimentary wings for gliding
or for capturing prey. Even today, young partridges have tiny
wings of no use for fl ying and yet to avoid predators they run
up trees while fl apping their wings. Juvenile partridges with
their wings taped down cannot climb trees.
One persistent misconception about natural selection
stems from its popularization as “survival of the fittest,”
a phrase that was never used by Darwin or Wallace. Stated
this way, it seems to imply that only the biggest, strongest,
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