The Definition of Life

HELEN

DEFINE LIFE. YOU CAN’T? NEITHER CAN THE SCIENTISTS!

That is the heading of an article in New Scientist for 27th July 2002, page 13. The article by Rachel Nowak begins by saying:

Don’t even bother asking what life is. Coming up with a definition right now is impossible, according to US researchers. In recent decades, scientists have been worrying about this question more than ever. Without a definition, how will astronomers looking for life on other planets know if they’ve found it? If we created life artificially, would we even know?

But in an upcoming issue of ‘Origins of Life and Evolution of the Biosphere,’ philosopher Carol Cleland of the University of Colorado at Boulder, and biologist Chris Chyba of the SETI Institute, California, argue that we should admit defeat – for now. It won’t be possible to define life until biologists have a theoretical explanation of it, they say. We might never work out a theory that explains life. If so, ‘this argument is going to be interminable,’ says Chyba.

In the meantime, the hunt for alien life continues. Jupiter’s moon Europa, one of the most likely homes for extraterrestrial life in the Solar System, was named this month as a priority for exploration by the US National Research Council. But NASA’s working definition of life, ‘a self-sustained chemical system capable of undergoing Darwinian evolution,’ is far from ideal. It risks excluding some novel life forms that could exist, such as ones that replicate so haphazardly that natural selection is not an option. And there’s a practical problem – just how long are you going to hang around Europa to see whether potential life forms are evolving?

Instead, the search will have to rely on a list of expected characteristics, such as the presence of complex organic molecules, or entities with a morphology that can’t be explained by chemistry alone.

The emphasis is mine. Is 'evolution' a sacred cow or WHAT? Now life is being defined, at least by NASA, as something that can evolve?

I guess cockroaches aren't alive...they don't seem to have evolved at all. No wonder they can be so hard to get rid of! They aren't even really alive if you ask NASA!

 

PAUL OF EUGENE

Hmm - it is a tricky subject. Life seems to always involved a local lowering of entropy (at, of course, the expense of higher entropy in the environment). But that's not a sufficient definition, unless you want to count my refrigerator as alive.

Live always seems to include reproduction. But I'm still alive and I've had a vasectomy. So that's not really a necessary condition.

Same goes for evolution. Lots of people never have kids, therefore don't participate in Darwinian evolution, but they are alive.

Live always seems to involve maintaining an internal organization against environmental degradation by means of dynamic interactive responses.

Live always seems to involve a dynamic energy flow, a processing of some sort that utilizes energy as it goes.

So what do you think. If something has a dynamic energy flow that utilizes energy on a continuous basis, and if it maintains an internal organization against environmental degradation by means of dynamic responses, and if it maintains a local constant entropy level in spite of the the use of its energy, is it alive?

 

CHRYSOPRASUS

Is that a fancy way of asking if flowers are alive? Just wondering!