Little or Big Changes?
Not all changes improve fitness, they may:
Improve the fitness of an organism (very unlikely)
Be neutral, having no effect on fitness
Be detrimental, decreasing an organisms fitness (most likely)
The bigger the change the more likely it is to be
Darwin argued that evolution is the accumulation of
many small changes that improve fitness, big changes
are unlikely to
result in improved fitness.
“Many large groups of facts are intelligible only on the
principle that species have been evolved by very small
The Origin of Species
Chapter VII under “Reasons for disbelieving in
great and abrupt modifications”