Behind the scenes
Field Museum of Natural HistoryAn ageing brown label marked ‘extinct’ dangles from the Field
Museum of Natural History’s specimen of the Charles Island tortoise.
The creature, one of the at least 12 subspecies of the Galapagos
Islands’ giant tortoise, is believed to have died out just after Charles
Darwin made his famous voyage to the Pacific archipelago aboard
HMS Beagle in 1835. Or did it, exactly? Recent discoveries have raised
a few fascinating question marks around this notion and how ‘extinct’
or not a creature can sometimes be.
The young Darwin‘s observations of the
giant tortoises (Chelonoidis nigra) on San
Cristobal and Santiago Islands, and the
distinct variations between those living in the
humid highlands (larger, with domed shells
and short necks) versus the dry lowlands
(smaller, with flatter shells and shorter
necks) later helped him develop his theory of
evolution. He didn’t find any live specimens of
the Charles Island native, later rechristened
the Floreana tortoise when the island was
renamed. But he did find shells and noted it
was the islanders’ primary food source.
The specimen shown here was collected
by Karl Patterson Schmidt, one of the most
important herpetologists – reptile and
amphibian experts – of the 20th century, and
an assistant curator at the Field Museum in
the 1920s. In 1930, Sidney Nichols Shurcliffpublished his account of how Schmidt found it: ‘We let ourselves down
a narrow dark shaft with a long rope and came into an underground
cavern ... we discovered several dozen shells of the extinct Charles
Island tortoise, three in perfect condition ... The ones we found must
have fallen down the shaft and died in the cave through lack of food.’
It is thought that the tortoise was extinct by 1850: no live individuals
have been seen there since – although there’s a theory that whalers
and pirates may have transported them to
nearby islands. As the tortoises are known to
live up to 150 years, there is a possibility that
some of the original species are still alive.
In 2008, scientists tagged more than 1,600
tortoises living on Isabela Island, the largest in
the archipelago, and uncovered a ‘bizarre mix
of genes’ in 80 of them showing clear ancestry
to the Charles Island tortoise. In some cases,
their mothers or fathers seemed to have been
pure-bred members of the subspecies.
Further expeditions have worked to find
living tortoises with the least mixed ancestry.
The aim is to encourage these to breed and
eventually repopulate the island. If the plan
works, within just a few generations, giant
tortoises with 95 per cent of the ‘lost’ Charles
Island genes could be back crawling the
Galapagos – and an extinct species will have
Words: Lauren Heinz. Photographs: Marc Schlossman been bred back into existence.
In our latest feature on intriguing specimens in Chicago’s
Field Museum of Natural History, we consider the Charles
Island tortoise – written about by Charles Darwin and
extinct since 1850. But could the museum’s specimen help
scientists resurrect this giant Galapagos Island native?