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Fifteen year ago , a stale snap froze much of Florida ’s wildlife to expiry — let in many of the commonwealth ’s invasive Burmese pythons ( Python bivittatus ) . But in this selection from " Slither : How Nature ’s Most Maligned Creatures Illuminate Our World " ( Gand Central Publishing , 2025 ) , science writer Stephen Hall reveals that a subset of these pythons were genetically predisposed to pull round the cold , fructify the phase for rapid evolution that could help the invasive snake spread further into North America .
In former January 2010 , a historic and prolonged rich freeze sweep across the southeastern United States , pass on all the way into the subtropical Everglades . Temperatures brood around 50 degrees Fahrenheit ( 10 degree Celsius ) for 48 hours ; on Jan. 11 , thermometers in South Florida dipped as low-down as 24.8 F ( minus 4 C ) . Most people remember it , if at all , for the frosty common iguana thatdropped out of treesand exposure ofcitrus trees encased in icicles , like some momentary Minnesota wintertime funfair smuggle into the Deep South .
Only a subset of Florida’s Burmese python population survived a cold snap in January 2010.
But to wildlife and invasive species experts , the Big Freeze marked the start of the Big unintentional experimentation .
The immediate impact on the Burmese python universe was clear . carcase of all in snakes littered roadstead ; frozen specimens turned up in surreptitious burrows ; farther northerly in South Carolina , in the infamous " Where ’s Waldo " python inclosure , all 10 snake in the grass go during the regional cold elasticity .
Researchersattributedthe quite a little die - off to " maladaptive behavior , " mean many snake try on to bask above ground in the Lord’s Day despite the frigid temperatures , rather than seeking thermal tax shelter in underground or aquatic burrows . Python " removals " — seizure by hunters , which serve as a pugnacious indication of the universal universe — had top out in 2009 in the national park but plummeted almost five - folding in the following two or three years . It all looked like good news , at first .
Temperatures during the 2010 cold snap dropped so low, cold-blooded animals like iguanas were immobilized and lost their grip while perching on trees.
But population number were still lacking , and " model " are still just models . Genesare where the rubber of biology forgather the route of environmental challenge , and this is when the geneticist move into the fib . They were less interested in the many snake that had died , and more interested in the few that had live .
Like all snakes , Burmese python are ectotherms — they rely on warmth from the environment because they do not engender their own metabolic heat — so they have to develop biologic illusion in their behaviour or in their physiological resiliency in the look of life - threatening frigidity to make it freeze issue that do not occur in their native range . As the United States Geological Survey ( USGS ) overview put it , " some portion of the southerly Florida population survived " the 2010 case , " and these snakes and their offspring make up the current universe . "
By 2014 , the number of python removal in Everglades National Park had render to pre - freeze levels . In genetic parlance , the 2010 halt was a " bottleneck case " — only a few squash through and survived . But the ones that did , in the scriptural sense , went forth and multiplied .
Burmese pythons bask in the sun to stay warm, but this behavior proved fatal for many snakes during the 2010 cold snap.
Beginning around the year 2015 , several researchers study python genomes to understand their metabolic process became curious about the after effects of the large freezing . Daren CardandTodd Castoeof the University of Texas at Arlington teamed up withMaggie Hunterof the USGS office in Fort Lauderdale to look for evidence of what is called speedy adjustment , which might be thought of as an up - pacing version ofDarwinian evolution .
They essay the DNA of these survivor Hydra to see if there were any genetic clues as to why certain Python were able to resist an lengthened freezing ; more exactly , they equate the desoxyribonucleic acid of python that lived before the frost event with the DNA of Python that had survived to see if they could identify any difference that might explain the resilience of the survivors at the molecular level .
The scant and disturbing ( although not authoritative ) answer was : yes .
The offspring of the surviving Burmese pythons likely inherited their parents' cold-adapted genes.
It turn out that the survivors seemed to share genetic changes in areas of their genome bed to ascertain thermoregulatory behavior and metabolism . " We saw a set of thing that just as luck would have it overlapped with a mountain of the same form of nerve pathway and genes that we were meditate in parallel of latitude , in a much more master fashion , using more research laboratory experimentation in Todd ’s work on Burmese pythons , " Card told me . " As we delved into them , we started to see a lot of genes that are affect in thing like thermal permissiveness . "
The finding , published in 2018 , suggested that the survivors deal variations in their genetic makeup that seemed to confer not bad dusty tolerance and great metabolic flexibleness — two traits that Castoe ’s lab had been investigating since 2011 . These snakes were more inclined behaviorally to seek protection in hush-hush refugia to outlast the coldness — a effective adaptation to the environmental realness of occasional frost . And the metabolic change seemed to prefer a behavior that promote smaller and more frequent meals — a honest adjustment to the bionomical world that , having already decimated populations of large mammals in the Everglades , the python might need to modify their diet .
This is not definitive news — the study was modest , no one ( surprisingly ) has followed up on it , and , as Card put it , researchers still only have a eyeshot from 30,000 feet of what happen on the genetical layer in the python that survived the Big Freeze . Whatever it is , the genetic changes — or , more accurately , theselectionfor genes that enhanced selection — appears to have encounter very quickly . And that is , possibly , very big news . It suggests that the python are on the move , genetically as well as geographically .
The implication is that the 2010 freeze act as a vast selection event , as evolutionary biologists put it — an environmental stress so awful , so extreme , that it has the effect of rapidly winnow out individual holding a bad transmitted hand and " selecting " the lucky one that hold in winning genetic deal .
The freeze culled out individuals that were susceptible to cold temperatures and selected individual that possessed , at the inherited spirit level , some form of dusty - boldness . Those gene were presumptively passed down — immediately , dissolutely and of course , cryptically — to their hundreds of progeny .
The suggestion of speedy adaption in the Burmese python universe in Florida again contradict our traditional whimsey ofevolutionas a glacial process of genetic selection and refinement that requires millennia , eons and geologic epochs . " We typically cerebrate of phylogenesis as go on over generally quite retentive time scales , on the order of several generations at the scurvy death up to potentially thousands to millions of eld , " Card said . " I consider with a raft of the tool that we ’ve formulate more late , especially in thing like genomics , hoi polloi have take a laborious aspect at how quickly phylogenesis can come about … And in general , when you see such an utmost matter fall out , it really suggests that there ’s very strong option . Something ’s bechance . "
In fact , Castoe believes theimportation of so many pythonsfrom so many dissimilar regions of Asia — all packing in their biological luggage a all-inclusive variety of familial variants , known as alleles , for their trip to North America — set the table for a rapid genetic adaptation . As Castoe put it : " If you ’ve go a good amount of familial variant , given impregnable selection , this can happen in a heartbeat . ' If I ’ve got the allelomorph , what the underworld am I waiting for ? I ai n’t waiting for nothing ! ' "
At a time whenroughly 40%of Americans do not accept the notion of development , the python that survived the Big Freeze in Florida appear to believe in it 100 % . The take - home genomics subject matter from the snakes is that evolution is tangible , it ’s apparently happening at blindingly degenerate speed , and it argue that the 2010 cold snap may have created a subset of Python intimately capable to survive frigid temperature — and thus better adapt to spread beyond the northerly boundaries of its current chain of mountains .
Excerpted fromSLITHER : How Nature ’s Most Maligned Creatures Illuminate Our World © 2025 Stephen S. Hall and reissue by permit from Grand Central Publishing / Hachette Book Group .
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