How does new knowledge change the way scientists look at old discoveries?
Around 1909, Charles Doolittle Walcott received a bit of interesting
news. Canadian railroad workers were collecting “stone bugs” that they had
found while cutting a path through the Rocky Mountains. Walcott was the
head of the Smithsonian Institute, and a respected paleontologist, so he
rushed to see what kinds of fossils had been found.
From 1910 to 1917, Walcott collected more than 65,000 specimens from
the area—a massive fossil bed he named the Burgess Shale. After Walcott
returned to Washington, D.C. with his fossils, he began the task of
categorizing them. He didn’t recognize many of the creatures, so he
classified them as odd examples of organisms already known to have existed
in Earth’s prehistoric past. Eventually, the fossils ended up in drawers at the
Smithsonian, and there they sat, mostly forgotten, for almost 50 years.
In the 1960s, Canadian scientists decided to take another look at the
Burgess Shale. They discovered even more fossils, and a new study, led by
Harry Whittington began. He traveled to D.C. and reexamined Walcott’s
forgotten fossils. Many years had passed since their discovery. A lot of new
information was known about Earth’s earliest life-forms and how they had
evolved into the diverse organisms of today. Whittington and the other
scientists were shocked to discover such a huge collection of creatures that
looked like no other organisms they’d ever seen before.
Most fossils have an evolutionary line that can be traced to other
creatures in the fossil record, or even to organisms that exist today. Many of
the creatures in the Burgess Shale fossils, though, seemed to have appeared
at just this one time in history. They didn’t slowly evolve over time into other
known organisms. Instead, something seemed to have happened that caused
them to become extinct soon after this one appearance in the fossil record.
In his popular book, Wonderful Life,
evolutionary biologist Stephen Jay Gould
argued that this characteristic helped prove
his idea that luck plays as much, if not more,
of a role in evolution than natural selection
does. Gould’s book angered the scientists who
were still studying the fossils. They felt that
Gould was misinterpreting their data to
support his hypothesis.
By the 1990s, paleontologists Derek
Briggs and Richard Fortey had reclassified
most of the unusual Burgess Shale organisms
as arthropods. The fossilized creatures were
ancient relatives of insects—not completely
unique life forms that had never evolved.
fossil bed: an area of
land that contains
fossils
diverse: of different
kinds, forms, or types
evolutionary line: the
sequence of
organisms that
descend from one
particular organism
evolutionary
biologist: a scientist
who studies the
origins and evolution
of living organisms
misinterpreting:
understanding or
explaining incorrectly
arthropods: the
largest phylum in the
Animal kingdom, it
includes insects,
spiders, and
crustaceans
Trilobite fossils found at the Burgess Shale helped scientists date the other creatures found there to the Cambrian period, which lasted from 530 to 520 million years ago. This period in Earth’s history saw a phenomenal increase in the diversity and abundance of Earth’s life forms within a relatively short time. Another of Stephen Jay Gould’s debated hypotheses was that evolutionary change occurs in sudden bursts, followed by long periods of stability.
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