Remember that creepy scene in The Thing when biologist Blair (Wilford Brimley) realizes the alien could take over all life on Earth at the cellular level? Well, keep that in mind, because a new scientific study suggests it's possible that scenario already happened, billions of years ago – and you could be the result.
According to an article in I Fucking Love Science, a paper entitled Characterizing the Purple Earth was published by a team of Spanish astrophysicists looking for new methods of detecting life conditions on other earth-like planets.
Their research describes the Archaean period – an era between 2.5 and 4 billion years ago – during which purple photosynthetic bacteria covered much of the Earth's surface. The scientists modeled possible arrangements of similar organisms, which could theoretically be viewed from space, especially in the infrared spectrum.
If these creatures are common on other earth-like planets, then our instruments can be made to tune out the light waves reflected by the purple bacteria (which could be hard to detect due to heavy cloud cover, another sign of an earth-like world) and narrow the search to more complex lifeforms.