In “Widen the goal in the search for alien life” (New Scientist, 24 May 2012), Bob Holmes interviews astrobiologist Charley Lineweaver, who argues proposes a new approach to defining life:
Many biologists define life as anything that undergoes Darwinian evolution.
We pretend that makes sense, but if you look it makes no sense at all. What is the unit of Darwinian evolution? Is it the gene? Is it the cell? Is it a multicellular organism? Is a city evolving? How about Gaia? Is that a life form?
So how would you define life?
To the extent that the question makes sense, as a “far-from-equilibrium dissipative system”.
That, it turns out, could include a hurricane or a star, a result that Holmes seemsti find a bit disappointing.
And Lineweaver responds, “I’m moving the bar in what I consider to be a reasonable way. ”
‘Kay, Charley. But … the main reason we don’t use so broad a definition on Earth is that there really is lots of life here. And we are moving the bar for the exoplanets because … come again?
See also: Carbon from Mars not biological, study says