Focus Magazine

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Natural selection is quicker than you think
– you might see it at work in your own
lifetime. Carl Zimmer meets the scientist
who’s been watching evolution as it happens
ichard Lenski opens an incubator. has exploded and turned their ﬂ ask cloudy.
R
A collection of ﬂ asks sit inside, Lenski now wonders whether they should
each holding a splash of liquid. even be called E coli any more. But it will
Lenski carefully takes one out and spins take months of experiments before he is
the ﬂ ask as he inspects the sloshing liquid. willing to say they’re a new species.
“It’s a little cloudy,” he says, as if judging a Lenski’s research shows just how
ﬁ ne wine. “If you had a glass of water that far evolutionary biology has come
colour, you wouldn’t want to drink it.” He since Darwin. Darwin did not run any
puts the ﬂ ask back in the incubator and experiments to observe evolution in action.
draws out another. “Now this one looks like He believed it proceeded too slowly to be
milk and water mixed together,” he says. perceived by humans. Instead, he looked
There’s a profound signiﬁ cance in the to the evidence of evolution’s effects that
colour of the two ﬂ asks, a signiﬁ cance that had accumulated over billions of years. But
Lenski is using to study the workings of Darwin lived long enough to get a glimpse
evolution. Both are loaded with E coli – a of an experiment in evolution.
species of bacteria common to the human In 1878, Darwin received a letter from the
gut. Twenty-one years ago, Lenski used Reverend William Dallinger. An amateur
a single microbe to establish 12 identical scientist, Dallinger was raising microbes
lines of bacteria, each of which lived in a water-ﬁ lled copper vessel. He could
in its own ﬂ ask. Since the experiment control the temperature and over several
started, the bacteria have been evolving months, raised it to 65°C – a temperature
and the scientists in Lenski’s laboratory that instantly killed ordinary microbes
at Michigan State University have been – to see if they could evolve the ability to
tracking their evolution closely. Along the survive. Dallinger ended up with microbes
way, some bacteria have undergone some that thrived in hot water.
extraordinary transformations. Darwin replied to Dallinger praising his
The microbes in the ﬂ ask Lenski is experiment. “Your results, I have no doubt,
holding have experienced perhaps the will be extremely curious and valuable,”
Richard Lenski at work, tracking
most extraordinary change of all. They’ve he wrote. Unfortunately, experimental
E coli evolution, in his lab evolved a new way of making a living, one evolution came to a screeching halt in 1886
that’s so successful that their population when Dallinger’s vessel was destroyed 3
www.bbcfocusmagazine.com February 2009 37
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