A key ingredient for preserving some of the earliest forms of complex life found

Fossil hunting?

Kaolinite is a mineral found in certain fine-grained rocks around the world.

A new study confirmed that kaolinite is a crucial ingredient for preserving some of the earliest forms of a complicated life.

The significance of kaolinite in the fossilization procedure has prompted a bias in the early fossil record toward organisms that lived in places where kaolinite forms.

Senior author Derek Briggs, the G. Evelyn Hutchinson Professor of Geology & Geophysics in the Yale Faculty of Arts and Sciences, said, “This insight may provide a blueprint for paleoenvironments that are conducive to ancient fossils on Earth and possibly on other planets, like Mars.”

Scientists aimed to determine the fossilization process for complex life forms that lived before the evolution of several skeletons during the so-called Cambrian era, which began about 541 million years ago. For details, they investigated microscopic, soft-bodied pre-Cambrian organisms as old as around 800 million years from sites in Russia, the Canadian Arctic, and the Norwegian archipelago Svalbard.

They discovered that such hints of early life were encased in halos of the clay known as kaolinite. The presence of kaolinite stifled the decay of the cells of these organisms — which include bacteria, fungi, and algae — empowering their fossilization. A comparable association promoted the preservation of soft-bodied Cambrian animals such as those in the Burgess Shale of British Columbia.

Briggs said, “This suggests that the early fossil record may be biased to tropical environments or periods of high clay production.”

Ross Anderson, a graduate student in the Briggs lab who is now at the University of Oxford and the first author of the study said, “Our discovery that animals are absent in 800-million-year-old rocks where conditions are ideal for soft-tissue preservation suggests they had yet to evolve and constrains the timing of animal origins.”

Co-authors of the paper are from Oxford, Harvard, MIT, and Diamond Light Source in the United Kingdom.

The study appears in the journal Interface Focus, which is published by the Royal Society.

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