Yet humans are far from recapitulating God’s handiwork. For one thing, these creation games yield only precursor molecules, not the complex genes and proteins that made up the first life on earth 3.8 billion years ago. The chain of events leading from gases to precursors to living cells is so improbable that British astronomer Fred Hoyle likened it to a tornado whipping up the contents of a junkyard into a Boeing 747. But a new theory by Christian de Duve of Rockefeller University, a Nobel Prizewinning cell biologist, may solve the problem by replacing the windstorm with common molecules acting as aerospace engineers. His candidates: thioesters, sulfur-containing molecules that can hook amino acids, like those cooked up in Miller’s flask, into proteins.
But not any old proteins. De Duve suggests that thioesters preferentially linked amino acids into “protoenzymes.” “Present-day bacteria synthesize a number of peptides by the same kind of process,” he notes. The primitive enzyme would set off a torrent of chemical reactions, eventually turning some of the primordial sludge into highly evolved molecules never before seen on earth, including RNA. Thioesters, though not alive, would have acted as the seeds of life.
De Duve’s hypothesis rejects the current fashion in origin-of-life circles, which says that nucleic acids such as RNA and DNA - the stuff of genes - appeared before proteins. That idea is under attack because RNA and DNA are extremely difficult even for a clever biochemist to make, let alone for primordial scum. If de Duve is correct, proteins came first and eventually assembled genes. With genes and proteins in the primal pond, life could learn to live.
Chemist Robert Shapiro of New York University, who has criticized the implausibility of many origin-of-life theories, calls the thioester idea “a reasonable theory that should be tested.” De Duve is trying to interest colleagues in doing that; experiments at the Salk Institute suggest thioesters may produce protoenzymes out of Miller’s primal brew. One reason chemists haven’t tried more is that the sulfur in thioesters stinks. Another problem is that the chances of solving the mystery of the origin of life are tiny; few scientists will risk their careers on what may be an impossible quest. It takes people like de Duve, 73, who have earned their scientific laurels and can take intellectual chances without worrying about a tenure review. As he says, “The question of the origin of life is an old man’s hobby.”
