Donna Blackmond, a chemist at Imperial College London.

strong evidence for the RNA world

'RNA world' hypothesis, which suggests that life began when RNA, a polymer related to DNA that can duplicate itself and catalyse reactions

chemists had thought the subunits would probably assemble themselves first, then join to form a ribonucleotide

three distinct parts: a ribose sugar, a phosphate group and a base

RNA polymer is a string of ribonucleotides

efforts to connect ribose and base together have met with frustrating failure

researchers have now managed to synthesise

ribonucleotides

remedy is to avoid producing separate ribose-sugar and base subunits

makes a molecule whose scaffolding contains a bond that will

be the key ribose-base connection

atoms are then added around this skeleton

final connection is to add a phosphate group

influences the entire synthesis

acting as a catalyst, it guides small organic molecules into making the right connections

What we have ended up with is molecular choreography

objectors to the RNA-world theory say the RNA molecule as a whole is too complex to be created using early-Earth geochemistry

flaw is in the logic — that this experimental control by researchers in a modern laboratory could have been available on the early Earth

Robert Shapiro, a chemist at New York University

early-Earth scenarios

heating molecules in water, evaporating them and irradiating them with ultraviolet light

results showing that they can string nucleotides together

ultimate goal is to get a living system (RNA) emerging from a one-pot experiment

need to know what the constraints on the conditions are first

Shapiro sides with

another theory of life's origins

because RNA is too complex to emerge from small molecules, simpler metabolic processes

eventually catalysed the formation of RNA and DNA