Mystery of ancient burrows older than earliest animals has been solved

By Jason Arunn Murugesu

Animal burrows (dark cylinders) successful past quartzite rock

Stefan Bengtson

The enigma of however carnal burrows successful Western Australia could beryllium 400 cardinal years older than the earliest animals successful the fossil grounds has yet been solved. A caller investigation suggests they were made acold much precocious than antecedently thought.

These holes were thought to beryllium 1.2 cardinal years old. “That’s doubly arsenic aged arsenic immoderate known carnal successful the fossil record,” says Stefan Bengtson astatine the Swedish Museum of Natural History.

He and his colleagues person re-analysed the 1.7-billion-year-old rocks of West Mount Barren connected the seashore of Western Australia successful which the holes were dug. The burrows are astir 15 to 20 millimeters wide and 15 centimetres heavy and were archetypal analysed 20 years ago.

The researchers astatine the clip determined that the rocks had hardened 1.2 cardinal years ago. And truthful the holes either had to person been made beforehand oregon by animals millions of years aboriginal that would person been capable to penetrate the hard quartzite stone – which is fundamentally intolerable to do.

But Bengtson and his squad discovered that the quartzite particles showed grounds of truthful overmuch weathering that for astir 5 to 10 cardinal years, the rocks would person been casual to burrow into. The weathering had caused the rocks to crook into crumbly sandstone. “It’s not precise common, but it happens, particularly successful blistery and humid climate,” says Bengtson.

By comparing the samples to different rocks and fossils successful the area, and uranium-lead dating the minerals recovered successful the burrows, the squad estimated the holes were made 40 to 50 cardinal years ago. The squad recovered that the sandstone had subsequently hardened owed to the arid conditions of the region, giving the content that the burrows had been made overmuch earlier than they really were.

The squad is unsure what circumstantial animals dug the holes, arsenic burrows look antithetic depending connected the sediment they are made in. But Bengtson says they were astir apt crustaceans.

Anthony Shillito astatine the University of Oxford successful the UK says this was a enigma that needed to beryllium solved. “The information that the authors person present shown that the burrows were astir apt lone 50 cardinal years aged fits overmuch amended with our existent knowing of aboriginal carnal evolution,” helium says.

Journal reference: PNAS, DOI: 10.1073/pnas.2105707118

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