Is Earth Ideal For Life ?
There is one vestige of anthropic thinking that remains even amongst scientists, atheists, and rational thinkers in general. It is the notion that our planet...Earth...is somehow 'ideal' for life. The fact that we are very much here, surrounded by millions of species, leads people to never really think otherwise.
That was certainly my own perspective, until I read the excellent book 'Rare Earth' ( Peter Ward and Donald Brownlee ). The central theme of the 'rare Earth' idea....that life may be exceedingly rare in the universe.....did not catch my attention nearly as much as a side issue I'd never really thought of before. The Earth may actually not be the ideal planet for life to have evolved on !
To my mind, that idea is the final element in the Copernican revolution. The final nail in the coffin of 'specialness'. The very real possibility that life may have only just made it into existence here....and that there may be far more suitable places out there.
To give just one example. A planet with less iron in its crust would not need 2 billion years worth of stromatolite type creatures oxidising all that iron before oxygen levels could finally rise. There are in fact many variants that would be 'better' for life.
But the anthropic tendencies are still there. On an almost weekly basis we hear of scientists searching for 'other Earths'. Well...that could be analogous to a scorpion in the Atacama desert thinking that a dry and dusty place where it rains every 100 years is 'ideal for life' because that is all it can conceive.
'Earths' may indeed be rare. Life far less so. One can only hope that the discovery of life somewhere like Europa or Titan will finally drive that last nail home.