Scientists have shown that evolution has built-in one-way gates, mutational processes which ensure that the benefits of millions of years aren’t undone by accident.
Evolution takes an unimaginably long time - so long that opponents refuse to believe it’s possible, or that even the amount of time is possible. Progress is incredibly slow as random tiny mutations are screened over millions of years to discover which work best. Backsliding would be even worse - the only thing worse than using a hundred million years to optimize a regulatory protein would be accidentally undoing the work over the next hundred kilo-millenia. Now University of Oregon investigators have discovered a genetic ratchet which prevents such extremely anti-productive reversals.
Tracking a modern protein across time and species, they studied a modern human glucocorticoid receptor (GR) protein compared to an ancient example from almost half a billion years ago. GR regulates our stress response, and is probably extremely confused about why its owners are now more upset about little pieces of paper than they used to be about saber-tooth tigers.
The researchers found seven important changes between the two, but when they attempted to reverse them the modern protein simply refused to work. Further study found five more unimportant-looking changes which acted as one-way markers - they didn’t affect the function of the latest iteration, but attempts to move backwards won’t work with them present. When all twelve alterations were undone, the protein functioned just as it had four hundred million years ago.
Of course, these evolutionary advantages only work on our DNA. Seventeen million people watch Dancing With The Stars. We’ve found other ways to undo humanity’s progress.
Luke McKinney
Evolutionary Ratchet http://esciencenews.com/articles/2009/09/23/ratchet.genetic.mutations.make.evolution.irreversible
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