Ongoing debates: convergence as the principle cause?
third view assigns a still more prominent role to the environment and so
considers convergence to be a significant force. Where a Gould landscape has
an arbitrary or flat shape when viewed from a great distance, this view holds
that all life on Earth has a fitness landscape with a specific planet-wide
morphology because all terrestrial life faces similar challenges. For example,
Earth currently presents all land mammals with the same oxygen-rich atmosphere
of a particular pressure and a 1G gravitational field. These factors will
constrain the kinds of organisms that could possibly evolve. While allowing
that the fitness landscape is shaped by chance events such as asteroid impacts,
this view characterises such changes as only minor wrinkles that do not
substantially change the overall contours of the landscape. This view considers
one of the causes of biological history to be the particular properties of the
Earth-environment as a whole. It is agnostic as to the cause of the
biofriendly nature of the Earth.
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