Four ancient species of cockroach thought to have originated in Europe may actually have gotten their start in North America.
Members of the Ectobius genus are among the most common types of cockroach, and their descendants still populate portions of Europe and Africa. The Ectobius genus was thought to have originated about 45 million years ago in the Baltic region during the early Eocene epoch, which began roughly 10 million years after the last T. rex had left the building.
But instead of proving the Old World as their birthplace, more recent fossil evidence shows that the true home of these ancient cockroaches may be the 49 million-year-old Green River Formation near Rifle, Colo. In the past few years, four cockroach members of the Ectobius species were discovered in the formation, which is about an hour away from Aspen.
"About 65 years ago, several entomologists in the northeastern United States noted that four [living] species of Ectobius were present in North America," Conrad Labandeira, a curator of fossil arthropods for the Smithsonian Institution and corresponding author of the article describing the findings, said in a release. "It was always assumed that these four newcomers were the first Ectobius species to have ever lived in North America. But the discovery in Colorado proves that their relatives were here nearly 50 million years ago."
Scientists don't know for sure why these cockroaches disappeared from North America or when, but Labandeira notes that "climactic conditions deteriorated."
A temperature change is believed to have caused the extinction of some aquatic animals, which were later reintroduced by humans. Cockroaches may have followed this same pattern: Having learned to adapt to cold weather, they emigrated once more back to North America.
"At some point – we don't know when and we don't know where – this lineage became extinct in North America," he says. "Meanwhile, in the Old World, in particular Europe and maybe also Eurasia, they survived, they persisted, to the present day."
So what difference does it make where ancient cockroaches were first bred?
"Without understanding the serendipitous nature of science, one may come to the conclusion that scientists have already figured out the natural history of deep time and that there is nothing left to study and to learn," Labandeira says. "The fact is that there is much more to understand — in this case, the fossil record."