In the limestone ranges of Western Australia's Kimberley region, near the town of Fitzroy Crossing, you'll find one of the world's best-preserved anc… - Kate Trinajstic

Here lie the remnants of myriad prehistoric marine animals, including placoderms, a prehistoric class of fish that represents some of our earliest jawed ancestors.

Imagine trying to identify and compare equivalent bits of anatomy shared between an oyster, a beetle and a blue whale. That is essentially the problem we face with early vertebrate fossils.

If all jawed vertebrates, including humans, are nothing more than highly evolved placoderms, then key features of ourselves should be traceable to structures that first appeared in our fishy placoderm ancestors. This would include particular jaw and skull bones and the proportions of our face and brain.