Research from the Milner Centre for Evolution suggests modern snakes evolved from a handful of ancestors that survived the asteroid that killed the dinosaurs.
By Vicky Just at the University of Bath
September
14, 2021 -- A new study suggests that all living snakes evolved from a handful
of species that survived the giant asteroid impact that wiped out the dinosaurs
and most other living things at the end of the Cretaceous. The authors say that
this devastating extinction event was a form of ‘creative destruction’ that
allowed snakes to diversify into new niches, previously filled by their
competitors.
The research, published in Nature
Communications, shows that snakes, today including almost 4000 living
species, started to diversify around the time that an extra-terrestrial impact
wiped out the dinosaurs and most other species on the planet.
The study, led by scientists at the
University of Bath and including collaborators from Bristol, Cambridge and
Germany, used fossils and analysed genetic differences between modern snakes to
reconstruct snake evolution. The analyses helped to pinpoint the time that
modern snakes evolved.
Their results show that all living snakes
trace back to just a handful of species that survived the asteroid impact 66
million years ago, the same extinction that wiped out the dinosaurs.
The authors argue that the ability of
snakes to shelter underground and go for long periods without food helped them
survive the destructive effects of the impact. In the aftermath, the extinction
of their competitors - including Cretaceous snakes and the dinosaurs themselves
- allowed snakes to move into new niches, new habitats and new continents.
Snakes then began to diversify,
producing lineages like vipers, cobras, garter snakes, pythons, and boas,
exploiting new habitats, and new prey. Modern snake diversity - including tree
snakes, sea snakes, venomous vipers and cobras, and huge constrictors like boas
and pythons - emerged only after the dinosaur extinction.
Fossils also show a change in the shape
of snake vertebrae in the aftermath, resulting from the extinction of
Cretaceous lineages and the appearance of new groups, including giant sea
snakes up to 10 metres long.
"It's remarkable, because not only
are they surviving an extinction that wipes out so many other animals, but
within a few million years they are innovating, using their habitats in new
ways," said lead author and recent Bath graduate Dr Catherine Klein, who
now works at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) in
Germany.
The study also suggests that snakes
began to spread across the globe around this time. Although the ancestor of
living snakes probably lived somewhere in the Southern Hemisphere, snakes first
appear to have spread to Asia after the extinction.
Dr Nick Longrich, from the Milner Centre
for Evolution at the University of Bath and the corresponding author, said:
“Our research suggests that extinction acted as a form of ‘creative
destruction’- by wiping out old species, it allowed survivors to exploit the
gaps in the ecosystem, experimenting with new lifestyles and habitats.
“This seems to be a general feature of
evolution - it’s the periods immediately after major extinctions where we see
evolution at its most wildly experimental and innovative.
“The destruction of biodiversity makes
room for new things to emerge and colonize new landmasses. Ultimately life
becomes even more diverse than before.”
The study also found evidence for a
second major diversification event around the time that the world shifted from
a warm ‘Greenhouse Earth’ into a cold ‘Icehouse’ climate, which saw the formation
of polar icecaps and the start of the Ice Ages.
The patterns seen in snakes hint at a
key role for catastrophes - severe, rapid, and global environmental disruptions
- in driving evolutionary change.
Catherine G. Klein, Davide Pisani,
Daniel J. Field, Rebecca Lakin, Matthew A. Wills & Nicholas R. Longrich
(2021) “Evolution
and dispersal of snakes across the Cretaceous-Paleogene mass extinction” is
published in Nature Communications DOI:
10.1038/s41467-021-25136-y
Read more about this research on Dr
Longrich's blog: How the end-Cretaceous mass extinction drove the evolution
of modern snakes.
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