(Image: Sarah Howell)
I don’t think it’s an either/or question but one of difficult to predict cycles with uncertain outcomes. Scientists nevertheless try to come up with simplistic explanation for highly complex systems evolutions; the Gaia hypothesis is one of those, and the New Scientists’ article below uses the Medea metaphor to coin what it considers is the proof for the other extreme: the planet’s inherent drive to self-destruction.
Lovelock’s Gaia Hypothesis is based on the notion of homeostasis, meaning the Earth as a living organism itself constantly provides maintaining conditions that support life. “The entire range of living matter… from whales to viruses and from oaks to algae could be regarded as constituting a single living entity capable of maintaining the Earth’s atmosphere to suit its overall needs and endowed with faculties and powers far beyond those of its constituent parts,” wrote Lovelock in his groundbreaking 1979 book Gaia: A new look at life on Earth.
The New Scientist on the other hand points out that the opposite seems to be the case, citing a growing body of research which shows that life on Earth has repeatedly endured “Medean” events that brought the planet’s biosphere to the edge of total destruction. The article explains quite a few of them, grouping them into the categories of atmospheric crises, total glaciations and mass extinctions of life forms; the article also provides a link to an interactive timeline of those events.
I think our recent ancestors, while not having had our scientific tools, had a much better understanding of the changing fortunes of life on Earth and in our universe. Hindu literature of old for example talks about Brahm constantly devouring life forms while giving birth to new ones – a principle applied to the whole universe, not just to the planet we inhabit (they also knew about expansions and contractions of the universe). Maybe our scientists should now and then consult works like the Vedas when forming theories about life ;).