If you ever manage to build a time machine, you might not want to visit ancient Earth. According to a new study, millions of years ago, the planet may have smelled like rotten eggs.
Scientists uncovered fossil evidence of microbes that ate other ancient microbes. These organisms are called "heterotrophs," meaning that unlike plants, they can't make their own organic nutrients, and have to eat other life forms to survive.
The study found that the result of this food chain would've resulted in a distinct hydrogen sulfide smell.
"In this study, for the first time, we identify how it was happening and 'who was eating who,'" study researcher Martin Brasier said in a statement. "In fact, we've all experienced modern bacteria feeding this way, as that's where that 'rotten egg' whiff of hydrogen sulfide comes from in a blocked drain."
Brasier is also a professor at Oxford University's department of earth sciences. His team analyzed the remains of several types of ancient bacterium to come to this conclusion.
Further research also indicates that fossils of a bacterium called Gunflintia showed signs that other bacteria had been eating them. The tubular sheaths of the bacteria were spotted with perforations where others had made a snack out of them.
Additionally, it was found that iron sulfide had replaced some segments of the Gunflintia sheaths. Iron sulfide is a waste product of several types of heterotrophic bacteria that breathe sulfate.
"Whilst the Gunflintia fossils are only about half as old, they confirm that such bacteria were indeed flourishing by 1,900 million years ago," said David Wacey, a postdoctoral researcher at the University of Western Australia. "And that they were also highly particular about what they chose to eat."
The research was published earlier this week in the journal Proceedings of the National Academy of Sciences.