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Accumulating change
Microevolutionary change might seem too unimportant to account for such amazing
evolutionary transitions as the origin of dinosaurs or the radiation of land
plants — however, it is not. Microevolution happens on a small time scale —
from one generation to the next. When such small changes build up over the course of
millions of years, they translate into evolution on a grand scale — in other
words, macroevolution!
The four basic evolutionary mechanisms — mutation, migration, genetic drift,
and natural selection — can produce major evolutionary change if given enough
time. And life on Earth has been accumulating small changes for 3.8 billion years
— more than enough time for these simple evolutionary processes to produce its
grand history.
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