Cockroaches Originated In North America, Not Europe; Proof Comes From Amateur Fossil Find
An amateur fossil collector in Colorado has single-handedly upended a long-standing theory that cockroaches originated in Europe. Fossil hunter David Kohls, 77, from western Colorado, found four cockroach fossils in the nearby Green River Formation that predates the oldest cockroach in Europe by about five million years. Even more amazing is the fact that 49 million years after it's ancestors left the New World from the old, the cockroach made a return trip back. The astounding find is described Sunday in the January issue of the Annals of the Entomological Society of America in an article called "Native Ectobius From the Early Eocene Green River Formation of Colorado and Its Reintroduction to North America 49 Million Years Later."
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The cockroach genus Ectobius, of Europe and Africa, appears in countless European fossils, going back to its most ancient appearance in 44-million-years old piece of Baltic amber, while the Americas had no fossil evidence of roaches at all. "The discovery in Colorado proves that Ectobius's relatives were here nearly 50 million years ago," the study's author, Dr. Conrad Labandeira, Senior Scientist and Curator of Fossil Arthropods at the Smithsonian Institution National Museum of Natural History, told the International Science Times.
Kohls, who has been fossil-hunting "madly" ever since he dug up his first fossil about 20 years ago — his 150 thousand insects from 31 thousand slabs of shale now form the Kohls Green River Fossil Insect Collection in the Smithsonian's Department of Paleobiology — was surprised to learn that his find has made such an impact on paleontology.
Labandeira believes that as the American continent — once graced with palm trees and crocodiles — cooled, the cockroach departed North America and gradually traveled over the Bering Strait. Five million years later, it began to thrive in Western Europe, before spreading out to Asia and Africa. The Ectobius cockroach's history is similar to that of horses, who were galloping around North America until they died out during the late Pleistocene era, but made their way over the Bering Straight to Africa and Europe. Spanish explorers reintroduced them to the New World 11 thousand years later. Remarkably, Labandeira said, the Ectobius has recently made its way back, too, also with the help of humans.
"That lineage of the Ectobious died out; but other species of cockroach prospered in the interim in Europe, Eurasia, and most of Africa before being introduced back to North America by humans 65 years ago," Labandeira said. "Now different species of the Ectobious are found to occur in Maine, Vermont, Massachusetts, expanding its range south — into adjacent Quebec and the Maritimes." The cockroaches could have arrived in a shipment or luggage. It's ironic, he added, that these cockroaches are now reentering North America via the northern latitudes and the colder climes that drove them from this continent so long ago. "They've had at least 49 million years to transform themselves gradually into something that is resistant to much colder temperatures," he told the International Science Times.
Kohls, who retired from collecting a year and a half ago in favor of a new hobby, macro photography, was surprised to find out from the International Science Times that his discovery was so noteworthy. "I didn't realize the absolute significance of it," Kohls said. "I knew it was a nice specimen. But to me it was just another insect to include in my shipment to the Smithsonian."
"Dave is a wonderful amateur collector," Labandeira said, noting that "co-author Peter Vršanský, did the honors of naming the species after him, at my suggestion." Though Kohls was surprised to hear of the cockroach Ectobius kohlsi, this wasn't the first time that he's had a species named after him. "There's a paleontologist in Moscow who took the liberty of naming several ants on my behalf," he told the International Science Times.
It's hard to know who's more persistent — the cockroaches, or Kohls.
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