Scientists at Canada's McGill University finally managed to resolve a long-standing mystery over the age of world's oldest algae fossils, which were first discovered in rocks in 1990.

According to the report, the fossilized algae, believed to be the oldest known direct ancestor of modern plants and animals, is 1,047 billion years old.

"That's 150 million years younger than commonly held estimates, and confirms that this fossil is spectacular," says Galen Halverson, senior author of the study and an associate professor in McGill University's Department of Earth and Planetary Sciences.

Fossilized algae, named Bangiomorpha pubescens, was discovered in rocks in Arctic Canada but its age was only poorly dated, with estimates placing it somewhere between 720 million and 1.2 billion years.

To determine the accurate age of the algae fossils scientists reportedly used the Rhenium-Osmium (or Re-Os) dating technique, applied increasingly to sedimentary rocks in recent years.

Based on this study, published in the journal Geology, the researchers also estimate that the basis for photosynthesis in today's plants was set in place 1,25 billion years ago.