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3 and never rebuilt. No one followed up his “I’ve always Instead of challenging them with heat, was repeatable, he hoped to get similar
work. In retrospect, Dallinger may have
been fascinated
Lenski decided to challenge his microbes results in many of them. “I’ve always been
been too far ahead of his time.
by the tension
between chance
with a cycle of feast and famine. He reared fascinated by this tension between chance
It took about a century before scientists
and necessity,
his E coli in a standard laboratory broth, and necessity, the randomness of mutation
returned to Dallinger’s domain. Lenski the randomness and gave them only a meagre supply of and the predictable aspects of natural
was one of them. He chose to study E coli,
of mutation and
glucose, which they used up in a few selection,” Lenski says.
because it was the best-understood microbe
the predictable
hours. The following morning, Lenski and He also wanted a fossil record that would
aspects of
known to science. It also had the advantage
natural selection”
his colleagues would draw a little of the preserve each evolutionary step. Every few
of growing quickly on a diet of sugar – a bacteria and squirt them into a fresh ﬂ ask, weeks, Lenski’s team takes some of the
single organism can produce billions of where they could feast again. bacteria from each ﬂ ask and puts them in
descendants in a single day. Lenski wanted to see if the bacteria one of the cofﬁ n-sized refrigerators in a
would be altered by natural selection. room across the hall from the incubator.
E
S
M
In each generation, some would mutate There are over 100,000 samples in the
spontaneously. A few of those mutations freezers, labelled with names of mythical
ORK TI (often caused by mistakes when copying resting places of heroes, like Valhalla
DNA) might make them grow and reproduce and Avalon, along with the motto: ‘when
faster in the ﬂ ask so they would out- needed they shall revive’. Lenski’s team can
compete the others. Over time, natural thaw out these ancestors to extract their
selection might transform the bacteria in DNA or see how they behave compared to
2
, EYEVINE/NEW Y
A X
measurable ways. their descendants.
JEL A single run of the experiment would At ﬁ rst, Lenski’s plan was to run his
not reveal much. The results might be experiment for a couple of years to see if
J
A HA
a ﬂ uke of the particular mutations that anything interesting happened. It did: by
struck a particular batch of bacteria. So the early 1990s, Lenski had clear evidence
AER/NEER in 1988 Lenski used his bacteria to start that the bacteria had evolved. They were
Zachary Blount with some of the thousands
12 genetically identical lines, each of growing faster than their ancestors. And it
BRIAN B of samples he’s studied during the research which lived in its own ﬂ ask. If evolution wasn’t just one line that was growing, but
38 February 2009 www.bbcfocusmagazine.com
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