Stepping back in time in Western Australia

By John Pickrell 7 November 2013
Reading Time: 2 Minutes Print this page
Until 1961 stromatolites were only known from fossils. But we now know that living colonies remain in a few isolated sites in WA.

AG’s deputy editor takes a trip to southwest WA and reports back on some of the natural wonders worth checking out next time you find yourself near Perth.

THESE MUDDY GREY humps fringing the shore of a shallow lake in WA’s Nambung National Park aren’t much to look at, but they were once the dominant form of life on Earth and we have them to thank for the oxygen that allowed us and all other complex life to evolve.

“They are lustreless and grey, and look…like very large cow-pats,” says travel writer Bill Bryson about similar structures up the coast at Shark Bay. “But it is a curiously giddying moment to find yourself staring at remnants of the Earth as it was 3.5 billion years ago.”

I’ve read about stromatolites before, but I’ve never had the opportunity to see any, so this wasn’t a chance I was going to readily turn down. On my third day in Perth I make a long trek 250 km up the coast to Nambung NP – partly to the see the Pinnacles Desert, but also to check out the stromatolites and thrombolites (which are similar but have a lumpy structure, rather than layered one) in Lake Thetis.

Stromatolites are layered rock-like structures formed over thousands of years by colonies of cyanobacteria, which harness energy from sunlight and produce oxygen in the process. We know that very early on in the history of life they were once very abundant on our planet, partly because of a series of remarkable 3.4 billion-year-old fossil sites in the Pilbarra and other parts of WA. These are some of the oldest known fossils on Earth.

Until 1961 stromatolites were only known from fossils. But following a chance discovery, we now know that living colonies remain in a few isolated sites in WA, where conditions are no good for grazing animals. The most famous are in Hamelin Pool in the Shark Bay World Heritage Area, 850 km north of Perth, but you can also see them in Lake Clifton, south of Perth. The stromatolites currently living at both at Shark Bay and here are around 3500 years old.

What I think is most remarkable about these unremarkable-looking colonies of organisms is that they have remained pretty much unchanged — just hanging out, doing what stromatolites do — for nearly four billion years. They’ve made it through five cataclysmic mass extinctions (and are now making it through a sixth).

Now that is a living fossil. Our own species, which sprang onto the evolutionary playing field around 200,000 years ago, seems piddlingly insignificant in comparison.