A new study is challenging the start of life on Earth, detailing geological evidence that dates back 4.1 billion years, some 300 million years earlier than previously thought.

Published in the journal Proceedings of the National Academy of Sciences, the new study examined a large crystal of zircon. Of particular interest were microscopic fragments of graphite with a carbon ratio that appears similar to that of organic matter.

"Twenty years ago, this would have been heretical; finding evidence of life 3.8 billion years ago was shocking," study co-author Mark Harrison, a professor of geochemistry at the University of California, Los Angeles (UCLA), said in a press release. "Life on Earth may have started almost instantaneously.

"With the right ingredients, life seems to form very quickly."

The researchers believe the zircon sample offers a rare glimpse at the Hadean eon, which Science Magazine called the Earth's "first chapter."

"They are pretty much our only physical samples of what was going on on the Earth before 4 billion years ago," study lead author Elizabeth Bell, a geochemist at UCLA, told the magazine. "On Earth today, if you were looking at this carbon, you would say it was biogenic.

"Of course, that's more controversial for the Hadean."

The study could also offer insight to what the Earth looked like early in its existence.

"The early Earth certainly wasn't a hellish, dry, boiling planet; we see absolutely no evidence for that," Harrison said. "The planet was probably much more like it is today than previously thought."