Protein flaws responsible for 'complex life'

This would have made them more adhesive and more likely to end up working together, building up complex function, say the scientists. Michael Lynch, an evolutionary theorist at Indiana University, who teamed up with Ariel Fernandez of University of Chicago, looked specifically at protein structure for their research published in the Nature journal.

“It’s opening up a new evolutionary pathway that didn’t exist before,” he said. The scientists considered 106 proteins shared among 36 modern-day organisms of widely varying complexity, from single-celled protozoa up to humans. They were studying “dehydrons” — regions of proteins that make them more unstable in watery environments.

These dehydrons make the proteins more sticky in water, thereby raising the probability that they will adhere to other such proteins. “We’ve opened up the idea that roots of complexity don’t have to reside in purely adaptational arguments,” Lynch was quoted by the BBC as saying.

The analysis showed that organisms with smaller populations — such as humans — had accumulated more of these defects than simpler organisms with vastly higher population numbers.

The suggestion is that it is the acquisition of these defects, with sticky proteins more likely to work together in ever-more complex protein-protein interactions, that nudged cellular complexity upward.

“We’ve tried to bridge the gap between protein structure and evolution and believe we’ve uncovered evidence that proteins develop mild defects in organisms with smaller population sizes, over the great divide from bacteria to unicellular eukaryotes to invertebrates up to us vertebrates,” said Prof Lynch.