|Peter Ward - image from wired.com|
Ward came to be viewed by some as a contrarian with the publication in 2000, along with co-author Donald E. Brownlee, of Rare Earth: Why Complex Life is Uncommon in the Universe. Their hypothesis, simply put, is:
The emergence of complex life requires a host of fortuitous circumstances. A number of such circumstances are set out below under the following headings: galactic habitable zone, a central star and planetary system having the requisite character, the circumstellar habitable zone, the size of the planet, the advantage of a large satellite, conditions needed to assure the planet has a magnetosphere and plate tectonics, the chemistry of the lithosphere, atmosphere, and oceans, the role of "evolutionary pumps" such as massive glaciation and rare bolide impacts, and whatever led to the still mysterious Cambrian explosion of animal phyla. The emergence of intelligent life may have required yet other rare events.The Rare Earth Hypothesis, seen as being opposed to the Principle of Mediocrity, itself a development of the Copernican Principle, never had its fierce, media savvy PR man, as did the latter two, through the advocacy and popularity of Carl Sagan.
In order for a small rocky planet to support complex life, Ward and Brownlee argue, the values of several variables must fall within narrow ranges. The universe is so vast that it could contain many Earth-like planets. But if such planets exist, they are likely to be separated from each other by many thousands of light years. Such distances may preclude communication among any intelligent species evolving on such planets, which would solve the Fermi paradox.
The work that has vaulted Ward to a more central place in visionary aspects of science is his development of the anti-Gaian Medea Hypothesis, detailed in his 2007 book, Under a Green Sky: Global Warming, the Mass Extinctions of the Past, and What They Can Tell Us About Our Future. Simply put, this idea stems from the proposition:
that multicellular life, understood as a superorganism, is suicidal; in this view microbial-triggered mass extinctions are attempts to return the Earth to the microbial dominated state it has been for most of its history.Understandably, Ward's work on the Rare Earth Hypothesis and the Medea Hypothesis is less popular than ideas which point to larger chances of human life or habitability prospects for such life existing elsewhere, or for a more positive outcome for our extremely carbon-based civilization's future evolution.
It is named after the mythological Medea, who killed her own children. Medea represents the Earth, and her children are multicellular life.
Past "suicide attempts" include:
Methane poisoning, 3.5 billion years ago- but does not include the K–T event, since this was, as least partially, externally induced by a meteor impact.
The oxygen catastrophe, 2.7 billion years ago
Snowball earth twice, 2.3 billion years ago and 790–630 million years ago
At least five putative hydrogen sulfide-induced mass extinctions, such as the Great Dying, 251.4 million years ago
In the following video, Dr. Ward shows clearly why he's not just the most important communicator on past mass extinctions. He's also remarkably optimistic in the face of enormous changes to our climate and environment cascading down, as our political, economic and military worlds mask us from reality or just plain fail.
Visionary #3 will be anti-deforestation pragmatist, Moses Sanga
Visionary #1 - Paul Stamets