BrainStuff Classics: How Fast Can Lizards Evolve?

Over the course of one frigid winter, green anole lizards in Texas changed their genetic makeup to better tolerate cold. Learn about this example of super-quick vertebrate evolution in today's classic episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:01):
Welcome to brain Stuff, a production of I Heart Radio
Pay brain Stuff. I'm Lauren volk Baum and this is
a classic episode from our former host, Christian Sagar. We
usually think of evolution as being a near cosmically slow process,
and often it is. After all, living beings in our
relationships with our environments can be really complex, with dozens

(00:24):
of genes coming together to create the traits that help
or hurt our chances of survival. But you don't have
to be a germ, or a fruit fly or a
peace shoot to show change quickly. Today's episode is the
strange story of a particularly swift lizard evolution. Hey, brain Stuff,
it's Christian Sager here. So evolution takes time, but just

(00:48):
how much time it takes is the issue. How long,
for instance, did it take therapod dinosaurs to evolve into
modern birds tens, if not hundreds of millions of years.
But since the turn of the last century, when American
biologist Herman Bumpust noticed that individual sparrows in a population
became larger as the result of one huge snowstorm, scientists

(01:11):
have been observing instances of short bursts of evolutionary progress
over a significantly brief period of time. Definitive instances of
rapid evolution are tough to come by, though, even in
these days of advanced genetic testing, but a recent study
published in the journal Science finds that over the course

(01:33):
of just a few months, green annully lizards living in
the area of the Mexico Texas border evolved a rapid
genetic tolerance to cold weather after an unusually frigid winter.
Green Annullies are warm weather reptiles that evolved on the
Caribbean island of Cuba. They found their way to the

(01:55):
mainland long ago, but a prolonged and extreme cold snap
can really put the hurt on a population of annuls.
The winter of did just that before that year's famed
polar vortex hit. However, the research team collected annulis in
August to find out just how cold one of these

(02:17):
lizards could get before its motor function was compromised, specifically,
that is, when it couldn't right itself when it was
knocked over. They collected annuals from five different sites across
Texas and found that when gradually cooled in a chamber
in the lab, the individuals from the southernmost site became
uncoordinated at around fifty two degrees fahrenheit or eleven degrees celsius,

(02:43):
but the ones collected from the northernmost site became unable
to right themselves at around forty three degrees fahrenheit or
six degrees celsius. Because the scientists already had genetic samples
from the lizards in the first study, When a few
months later temperatures plummeted to lows that hadn't been seen

(03:05):
in fifteen years, the researchers went out and collected some
of the surviving lizards from all five sites. They placed
them in the same cooling chambers and found the southernmost
Annullies exhibited much more cold resistance than the ones that
had been collected back in the summer. They could now

(03:25):
stand strong in the face of forty three degrees fahrenheit
or six degrees celsius. RNA sequencing before and after the
cold front also revealed significant differences between individuals from the
southern genomic regions before and after the weather event. By
the way, did you know that Annulli's living in urban

(03:48):
areas have stickier feet than their country cousins. Apparently it's
an evolutionary adaptation to having to cling to class and metal.
Now I want to be bitten by a radioactive annually
so I can crawl waltz with them. Today's episode was
written by Jesselyn Shields and produced by Dylan Fagan, Little Berlante,

(04:08):
and Tyler Clang. For more on lit and lots of
other topics, visit how stuff works dot com. Brain Stuff
is a production of I Heart Radio. For more podcasts
my heart Radio, visit the iHeart Radio app, Apple Podcasts,
or wherever you listen to your favorite shows.