The question of how life began on a molecular¹ level has been a longstanding problem in science. However, recent mathematical research sheds light on a possible mechanism² by which life may have gotten a foothold（立足处） in the chemical soup that existed on the early Earth. Researchers have proposed several competing theories for how life on Earth could have gotten its start, even before the first genes³ or living cells came to be. Despite differences between various proposed scenarios⁴, one theme they all have in common is a network of molecules⁵ that have the ability to work together to jumpstart and speed up their own replication -- two necessary ingredients for life. However, many researchers find it hard to imagine how such a molecular network could have formed spontaneously -- with no precursors⁶ -- from the chemical environment of early Earth.

 

"Some say it's equivalent to a tornado⁷ blowing through a junkyard and assembling the random⁸ pieces of metal and plastic into a Boeing 747," said co-author Wim Hordijk, a visiting scientist at the National Evolutionary⁹ Synthesis Center in Durham, North Carolina, and a participant in an astrobiology meeting held there last year.

 

In a previous study published in 2004, Hordijk and colleague Mike Steel of the University of Canterbury in New Zealand used a mathematical model of simple chemical reactions to show that such networks might form more easily than many researchers thought. Indeed, biochemists have recently created such networks in the lab.

 

In a new study published this year, Hordijk, Steel, and colleague Stuart Kauffman of the University of Vermont analyzed¹⁰ the structure of the networks in their mathematical models and found a plausible¹¹ mechanism by which they could have evolved to produce the building blocks of life we know today, such as cell membranes¹² or nucleic acids.

 

"It turns out that if you look at the structure of the networks of molecules [in our models], very often they're composed of smaller subsets of molecules with the same self-perpetuating capabilities," Hordijk explained.

 

By combining, splitting, and recombining to form new types of networks from their own subunits, the models indicate that these subsets of molecules could give rise to increasingly large and complex networks of chemical reactions, and, presumably, life.

 

"These results could have major consequences for how we think life may have originated from pure chemistry," Hordijk writes.

 

The study will appear in the December 2012 print issue of the journal Acta Biotheoretica.

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