Photosynthesis first occurred 1.25 billion years ago, study reports

Scientists at McGill University have found evidence that the first instance of photosynthesis happened roughly 1.25 billion years ago, according to new research outlined in the journal Geology.  

In the study, the team analyzed the remains of Bangiomorpha Pubescens, an ancient algae that is believed to be the oldest known ancestor of modern plants and animals. Previous studies estimated the algae to be between 720 million and 1.2 billion years old. However, those dates were simple estimates.

To get a more exact age, the researchers collected black shale samples taken from rock layers around the rocks where the Bangiomorpha pubescens fossils were first discovered. They then used a dating technique on those sedimentary rocks and found that the remains were exactly 1.047 billion years old.

“That’s 150 million years younger than commonly held estimates, and confirms that this fossil is spectacular,” said study co-author Galen Halverson, an associate professor at McGill’s Department of Earth and Planetary Sciences, according to The News Recorder “This will enable scientists to make more precise assessments of the early evolution of eukaryotes, the celled organisms that include plants and animals.”

The team also noted that the chloroplast — the structure in plant cells where photosynthesis occurs — came into existence when an ancient eukaryote engulfed a simple bacterium that possessed photosynthetic properties. Those altered organisms then passed the unique DNA down to their descendants, including modern plants. Using a “molecular clock” computer model, the scientists estimate that the chloroplast must have been absorbed into eukaryotes roughly 1.25 billion years ago.

This discovery sheds light on a long-debated mystery and could give new insight into the way certain plant species evolved over time. Little is known about the origins of photosynthesis, and further study of the ancient algae may help researchers better understand out planet’s past.

“We expect and hope that other scientists will plug this age for Bangiomorpha pubescens into their own molecular clocks to calculate the timing of important evolutionary events and test our results,” said lead author Timothy Gibson, a PhD student at McGill University, in a statement. “If other scientists envision a better way to calculate when the chloroplast emerged, the scientific community will eventually decide which estimate seems more reasonable and find new ways to test it.”