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Do We Know What Life Is?

Tuesday, March 18, 2014

Neil deGrasse Tyson and the Cosmos: A Spacetime Odyssey team dropped the ball in the episode on life and evolution that just aired.

It's not that Tyson and his team said anything wrong. So what was missing?

They beautifully illustrated how natural selection works by analogy with the sort of artificial selection that got us from wolves to domesticated dogs in 15,000 years. If artificial selection could produce such radical change in 15,000 years, think what natural selection could do over billions of years.

The example chosen to show natural selection at work was bears. Tyson told the story of how a random mutation in genes responsible for the color of fur led to the birth of bears with white fur. In a snowy environment, these bears would have had advantages over brown ones. In particular, they'd have better odds of sneaking up unnoticed on their prey. The white bears would get more food, live longer and have a better chance of raising young. Over time, white bears would proliferate in the arctic environment. In time, and through processes like these, a new species, the polar bear, came to be born.

The example is well-chosen. It makes sense and it puts the basic elements of the theory of evolution by natural selection on display. Random mutation at the level of genes gives rise to random variation in populations. Precarious conditions take care of the rest. Populations are pruned by demanding environments. This is natural selection; design without a designer.

My concern is not with what Tyson said. It's with what he didn't say.

He explained how natural selection operates once you've got bears. But where did the bears come from? Well, bears are the evolutionary descendants of other species which are in their turn the "offspring" of other species. And so on. All the way back.

But all the way back to what? To the first organism.

And where did the first organism, that is, the first living being, come from?

Tyson was open about the fact that we don't know how life began. He referred to this as one of science's great mysteries (in the show's first episode). And he opined that science is happy to admit ignorance; it's much better to admit ignorance than to pretend to a knowledge one does not really have.

But I'd say he misdescribed, or under described, the character of our ignorance.

For Tyson the lack of knowledge in question is historical. There's very little evidence left from so long ago. So it's impossible to know what happened. Based on what we do know, he asserted modestly, life probably required high temperatures to get started.

Here's what he didn't say: Darwin's theory of evolution doesn't speak to the question of how life got started.

Darwin shows how environmental pressures sculpt and shape organisms. But the existence of organisms, the existence of life, is not explained in Darwin's theory; it is presupposed. This is not a criticism of Darwin or of the power of natural selection as a force determining evolution. It's to say that the question of life's origins is a different kind of question than the question of the origin of the polar bear. Tyson's presentation didn't make that clear. Indeed, it struck me that it almost concealed it.

Now, there is good science on the origins of life. Our own Stuart Kauffman is a leader in this field. And Marcelo wrote on this not too long ago here at 13.7, as well as speaking about it in a TEDxEast talk.

But, crucially, good science in this domain isn't only, or even primarily, historical science. What is required is an account of how purely inorganic, chemical processes, could yield entities that have the distinctive features of living beings. To do that, one needs an account of what the distinctive features of living beings are. What is life?

Do we know what life is?

I wish Tyson had let his audience appreciate the beauty and unresolved importance of that question.

I wonder why Cosmos skipped it? Maybe they thought it better to stick to dogs and bears and other cute creatures; to keep things short and to pretend that all we need, going forward, is to color between the lines.


You can keep up with more of what Alva Noë is thinking on Facebook and on Twitter: @alvanoe

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