Geography Reference
In-Depth Information
The cultural responses of people to nature often depend on the frequency
and ef ect of the interaction, which may be an important factor in the likeli-
hood of coevolution. When birds like corvids are rare, we often ignore or re-
vere them; but once they become competitors, we view them as pests and
despise, harass, and perhaps try to control them. Our interaction with urban
nature thus has a built-in negative feedback mechanism that favors novel cul-
tures in people and birds as the frequency and type of their interactions
change. When ravens were fewer in number and less rivals for resources, for
example, we considered them to be birds of the gods, even gods themselves,
and useful guardians, navigators for mortals, and ei cient sanitation engi-
neers. But when we felt their abundance was reducing valuable game and we
became horrii ed by their consumption of human l esh, we used guns and
control policies to reduce their numbers and change their culture. Persecuted
ravens became rare and shy around people. This contemporary rareness
evoked a sense of mystery, wonder, and concern in enough people that a cul-
ture of restoration developed. Understanding our role in such cyclical cul-
tural phenomena may be important to conservation and restoration ef orts in
urban settings.
Subtle adjustments of bird color and song to urban environments are exam-
ples of microevolution. As interesting as the changes are, they do not inevita-
bly lead to the creation of new species—what biologists call “macroevolution.”
For macroevolution to create a new species, organisms must evolve dif er-
ences that preclude interbreeding, or their hybrids must be at a distinct disad-
vantage. When house sparrows colonized Italy nearly four thousand years
ago, they injected new genes into the local sparrow gene pool and in so doing
started the creative engine of evolution. The result was a new species, the Ital-
ian sparrow.
