Ongoing debates: convergence as the principle cause?

The 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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