Monday, April 21, 2008

When a biologist talks about chemistry

The famous Miller Urey experiment

When browsing websites related to the Expelled movie, I came across the following critique of PZ Myers of Caroline Crocker, a teacher who claims to have been ‘expelled’ from her university, because she taught Intelligent Design. Myers replies here to an article in the journal Nature describing her ordeal.

Nature article:
Crocker said that subsequent research had shown that chemicals used in the experiment [Miller's] did not exist on Earth 4 billion years ago. "The experiment is irrelevant, but you still find it in your books," she said.

PZ Myers:
This is not true; the issue is more complex than she lets on. Our understanding of the nature of the atmosphere has changed since Urey and Miller, but the experiment still stands as valid and interesting—it shows that complex chemical precursors to life can arise without intelligent guidance. Similar experiments have been done with different atmospheres, with similar results.

My comment to that:
Sure, „complex“ molecules can form under simulated early earth conditions. I don’t know which chemicals Myers considers ‚complex’, but molecules formed in the Miller Urey experiment are various amino acids, nucleo bases, sugars, etc. They are formed because thermodynamics and the reaction condition favour the reaction from ‚simple’ carbon dioxide and ammonia to ‚complex’ alanine, for example. But what Myers does not take into account ist hat the same thermodynamic laws forbid the formation of REALLY complex molecules such as DNA or polypeptides. There is not a single report that functional polymers have been formed under Miller Urey conditions. And those experiments do require intelligence (of the scientist planning and carrying out the experiment).