The Oldest Bug

November 11, 2020

A 425-million-year-old millipede fossil from the Scottish island of Kerrera is the world’s oldest “bug” — older than any known fossil of an insect, arachnid or other related creepy-crawly, according to researchers at the Jackson School of Geosciences.

The findings offer new evidence about the origin and evolution of bugs and plants, suggesting that they evolved much more rapidly than some scientists believe, going from lake-hugging communities to complex forest ecosystems in just 40 million years. “It’s a big jump from these tiny guys to very complex forest communities, and in the scheme of things, it didn’t take that long,” said Michael Brookfield, a research associate at the Jackson School and adjunct professor at the University of Massachusetts Boston. “It seems to be a rapid radiation of evolution from these mountain valleys, down to the lowlands, and then worldwide after that.”

The research was published in May 2020 in the journal Historical Biology. Brookfield led the study with co-authors including Elizabeth Catlos, an associate professor in the Department of Geological Sciences and Stephanie Suarez, a doctoral student at the University of Houston who made improvements to the fossil dating technique used in the study when she was an undergraduate at the Jackson School. The team found that the ancient millipede fossil is 425 million years old, about 75 million years younger than the age other scientists have estimated the oldest millipede to be using a different technique known as molecular clock dating, which is based on DNA’s mutation rate. Other research using fossil dating found that the oldest fossil of a land-dwelling, stemmed plant (also from Scotland) is also 425 million years old, about 75 million years younger than molecular clock estimates.

If that’s the case, it means both bugs and plants evolved much more rapidly than the timeline indicated by the molecular clock. Bountiful bug deposits have been dated to just 20 million years later than the fossils. And by 40 million years later, there’s evidence of thriving forest communities filled with spiders, insects and tall trees. “Who is right, us or them?” Catlos said. “We’re setting up testable hypotheses — and this is where we are at in the research right now.”