Apex chert

These pieces of chert from Pilbara, Western Australia are around 3,462 million years old.

The jury is still out on whether they contain the world's oldest evidence of life on Earth in the form of filamentous microbes. The alternative is that the structures they contain are just mineral growths that resemble simple organisms.

The 'Apex Chert' caused a flurry of excitement in 1993, when it was first described by US scientist Bill Schopf during a sabbatical at the Natural History Museum. Schopf entered the type specimen into the Museum's collection, where it still sits today.

The most recent analysis of Apex Chert supports the theory that the structures are mineralogical, not biological. But the debate rages on and the specimens are still in demand for further study.

The Apex Chert 'fossils' ignited conversations about the age of life on Earth, a fundamental part of understanding the mechanisms and timescales of evolution.