4.1-billion-year-old crystal may hold earliest signs of life

Zircon crystals, composed of silicon, oxygen and zirconium, are some of the oldest artefacts available ? predating even the most ancient of rocks that formed 4 billion years ago ? to researchers studying the early Earth conditions. Image credit: Parent G?ry via Wikimedia.org, CC BY-SA 3.0.

When did life on Earth begin? Scientists have dug down through the geologic record, and the deeper they look, the more it seems that biology appeared early in our planet?s 4.5-billion-year history. So far, geologists have uncovered possible traces of life as far back as 3.8 billion years. Now, a controversial new study presents potential evidence that life arose 300 million years before that, during the mysterious period following Earth?s formation.
 
An ancient zircon crystal unearthed in Western Australia may hold evidence that life appeared on the planet 4.1 billion years ago, or about 300 million years earlier than previously thought, according to a team of US researchers.

Scientists from Stanford University and the University of California, Los Angeles said they recently collected some 10,000 multibillion year-old zircons in Jack Hills, Australia, including one believed to contain a carbon deposit that is 4.1 billion years old, give or take 10 million years.

“Its complete encasement in crack-free, undisturbed zircon demonstrates that it is not contamination from more recent geologic processes … (and) may be evidence for the origin of life on Earth by 4.1 (billion years ago),” according to a paper published by the team in the Proceedings of the National Academy of Sciences on Monday.

 Humans are believed to have first appeared on Earth only about 200,000 years ago.

The study was authored by Elizabeth Bell, Patrick Boehnke, and T. Mark Harrison of the University of California, Los Angeles along with Wendy Lao of Stanford.

E.A. Bell et al. Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon.