Researchers at the University of Texas in Austin claim to have identified the world's oldest bug. The specimen is a millipede ancestor found on the island of Kerrera in Scotland, and it dates back 425 million years. The team says that this finding implies that insects underwent a rapid phase of evolution.
“Bug” is a pretty casual term, but in this case, the team says it refers to any insect, arachnid, or any other creepy-crawly creature. That’s quite a wide net, but makes it more impressive that this fossil is the oldest of them all.
The specimen is an extinct millipede species called Kampecaris obanensis. While the fossil itself was discovered as far back as 1899, it’s only just now been accurately dated.
To do so, the team used radiometric dating on zircons in the sediment. Zircons are tiny mineral grains that are incredibly durable, so they survive all kinds of geologic events that deep time can throw at them. That makes them perfect time capsules.
Image specimen number: UK.BGS.GSE10835 sourced GB3D website: http://www.3d-fossils.ac.uk/home.html
Released: https://creativecommons.org/licenses/by-nc-sa/3.0/
Using this process, the team dated zircons from three fossil sites in the UK, all of which are known to have some of the earliest millipede specimens. As mentioned, the Kampecaris was found to be the oldest, at 425 million years. Fossils from a second site, Ludlow, were 420 million years old, and others from Cowie were 414 million years old.
The team says that this finding raises some interesting questions about insect evolution. Other fossil evidence shows that bugs were widespread by 407 million years ago, and huge communities of insects and related creatures were thriving in forests by 385 million years ago. That suggests that insects underwent fairly rapid evolution, within about 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,” says Michael Brookfield, lead author of the study. “It seems to be a rapid radiation of evolution from these mountain valleys, down to the lowlands, and then worldwide after that.”
Interestingly, the team also believes that the fossils described here are not just the oldest bugs discovered so far – they’re among the oldest bugs, period. They say that older bug fossils have not been found in older deposits that are known to preserve other delicate fossils.
That said, the hypothesis clashes with another method known as molecular clock dating. This technique estimates when types of species arose based on tracing back the rate of DNA mutations. According to the molecular clock, millipedes should be about 500 million years old – 75 million years older than these fossils.
The researchers aren’t declaring themselves irrefutably correct, of course. Instead, they say they’re just setting up hypotheses that can be tested in future work.
The new study was published in the journal Historical Biology.
Source: University of Texas at Austin