Gaia and Natural Selection – A new perspective
By Paul Kieniewicz
The observation that for over 3 billion years the Earth’s average temperature has remained within a narrow range, while the sun’s temperature has increased by 20 % required an explanation. The Gaia Theory, of James Lovelock and Lynn Margullis proposed that living processes acted in such a way as to maintain a habitable environment on Earth. The Earth behaved as if it were a living entity! Biologists and Evolutionists immediately criticized the theory on the grounds that it apparently contradicted the notion of natural selection. How could a planet evolve if it only contained one living being — Gaia? Though Lovelock subsequently modified his theory to include Natural Selection as a basic mechanism — in his famous Daisyworld experiment, the new theory did not satisfy many critics either.
A recent paper by Timothy Lenton and Stuart Daines of the University of Exeter proposes new mechanisms that could explain the observations. One mechanism — sequential selection, suggests that systems or life forces that take the planet out of equilibrium do not last long. They produce mass extinctions, that then return the planet to its previous equilibrium. During this stable period, the planet’s systems acquire other features that help the life systems persist. Some mechanisms, such as the regulation of marine nitrogen, may be controlled via the Black Queen Hypothesis. An evolutionary mechanism recently gaining support, Black Queen was proposed to explain the observation that many bacteria, that lose the ability to produce a life-giving substance, nevertheless survive — though they should be doomed by natural selection. It is their companions, who are still able to produce the substance, that keep the defective bacteria alive. In evolution, the individual is not all important. The community that surrounds him matters just as much.
The new study offers new support for the Gaia Theory, and ways in which the Earth self-regulates. It is not likely to be the last word on the Gaia Theory, but it has certainly reignited the debate.