The arrival of plants on Earth changed the planet and its inhabitants in big ways, and a new study suggests they arrived far earlier than thought. University of Bristol researchers now say that land plants evolved from pond scum about 500 million years ago—a whopping 100 million years earlier than the history books tell us, per a release. The date we've long used is based on the fossil record, but fossils aren't so great when it comes to plants because they are far less likely to be preserved than, say, an animal with bones. Hoping to find the answer outside of the fossil record, study co-author Mark Puttick and a team of researchers looked for differences in the DNA of more than 100 plant and algal species to see when they diverged on the evolutionary scale, reports Science.
The study dates the first land plants to 500 million years ago in the middle Cambrian period, which also saw the first appearance of terrestrial animals, who would have enjoyed protection, additional oxygen, and a cooler planet as a result of the plants, researchers say. Their research, published in PNAS, "changes the entire timeline for the origin of terrestrial life and the subsequent pace of evolutionary change in plants and associated animal (and fungal) groups," plant biologist Pamela Soltis, who was not involved in the study, tells Science. There's still some debate over which plants came first, but the BBC reports they were similar to moss. According to researcher Philip Donoghue, they "would have tickled your toes but not reached much higher." (Behold the "holy grail" of plant breeding.)