Each Monday, this column turns a page in history to explore the
discoveries, events and people that continue to affect the history being
made today.
Boobies and lava gulls and giant tortoises, oh my!
The Galapagos Islands host a faunal freak show of rare animal species
endemic only to those volcanic specks isolated in the Pacific Ocean.
While still very interesting to ecologists today, in the 19th century
the life there proved key in Charles Darwin's seminal study on the evolution of species.
Darwin (and some of his colleagues) had suspicions about the nature of
speciation in years' prior and solidified his theories in the years that
followed, but it was the fantastic menagerie of the Galapagos that
ultimately lit the fire under the theory of natural selection, which changed biology forever and fuels debates still today.
Isolated islands created unique species
When the young British naturalist landed in the Galapagos at San
Cristobal Island in 1835, he compared the hot and dusty place to the
infernos of hell, and mused at the strange animals that seemed unafraid
of their new human visitors.
Indeed, most of the Galapagos wildlife had limited contact with humans and, therefore, no reason to be afraid.
When the Galapagos were first spotted by humans in 1535, its animals had
already spent thousands of years adapting and readapting to their
island home. Located 500 miles off the western coast of South America,
the unique conditions of the isolated islands created a variety of
species unlike any others across the globe, differing slightly even from
island to island. Giant tortoises, for example, grew so large there
because their smaller ancestors that first swam over from the mainland
no longer had predators to hide from, scientists think.
Darwin observed the giant tortoises (and, unfortunately, ate many of
them), iguanas and sea lions on the Galapagos, but it was the enormous
variety of birds on the islands that especially captured his attention.
Eighty-five percent of Galapagos birds can't be found anywhere else,
including the famous finches.
Beaks developed from natural selection
Thirteen species of finch are endemic to the Galapagos Islands, similar
in look except for the distinct shapes and sizes of their beaks. The
different beaks allow them to take advantage of the unique food sources
of their particular island. Some eat like woodpeckers, others use sticks
to dig insects out of holes, and still others are nourished by ticks
and mites plucked from the backs of tortoises.
Over five weeks in 1835, Darwin made careful observations of the
peculiar birds on each island, but did not have his great eureka! moment
about evolution while on the Galapagos, contrary to popular belief.
It was only in 1839, after comparing his notes with fellow scientists,
that Darwin's observations jelled into a theory with a name — natural
selection. Each living thing that Darwin catalogued had adapted to its
specific environment over many generations because its ancestor
possessed characteristics favorable to its survival and the survival of
its offspring, he supposed.
The idea that animals develop gradually from simpler to more complex
organisms was not a new one — naturalists had proposed that theory in
the late 18th century — but it was the "how" of this transformation that
eluded scientists. Natural selection, as displayed in real time in the
Galapagos Islands, connected the dots.
With the groundwork essentially laid, Darwin went about collecting
evidence to support the then heretical notion that his observations in
the Galapagos could be applied to all animals, including humans. It took
20 more years before he felt comfortable enough to publish his work in
"The Origin of Species."
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