Swift Lizard Evolution

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Episode Transcript

Speaker 1 (00:02):
Welcome to brain stuff from how stuff works. Hey, brain stuff,
it's Christian Sager here. So evolution takes time, but just
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.

(00:23):
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
have been observing instances of short bursts of evolutionary progress
over a significantly brief period of time. Definitive instances of

(00:45):
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
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.

(01:10):
Green Annullies are warm weather reptiles that evolved on the
Caribbean island of Cuba. They found their way to the
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

(01:32):
polar vortex hit. However, the research team collected annulis in
August to find out just how cold one of these
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

(01:53):
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,
but the ones collected from the northernmost site became unable
to right themselves at around forty three degrees fahrenheit or

(02:16):
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
in fifteen years, the researchers went out and collected some
of the surviving lizards from all five sites. They placed

(02:37):
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
stand strong in the face of forty three degrees fahrenheit
or six degrees celsius. RNA sequencing before and after the

(02:58):
cold front also revealed six 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 areas have stickier feet than their country cousins. Apparently
it's an evolutionary adaptation to having to cling to class

(03:20):
and metal. Now I want to be bitten by a
radioactive Annulli so I can crawl walls with him. Today's
episode was written by jess Lynn Shields and produced by
Dylan Fagan. For more on this and other topics, please
visit us at how stuff works dot com.