Anyone who has taken high school biology has likely come into contact with a ciliate. The much-studied paramecium is one of 7,000 species of ciliates, a vast group of microorganisms that share a common morphology: single-celled blobs covered in tiny hairs, or cilia. These cilia — Greek for “eyelash” — are used to propel a microbe through water and catch prey.
Today these hairy microbes are ubiquitous in marine environments. However, it’s unclear how long ciliates have inhabited Earth: After they die, members of most species simply disintegrate in their watery environs, leaving behind no fossilized remains.
Now, geologists at MIT and Harvard University have unearthed rare, flask-shaped microfossils dating back 635 to 715 million years, representing the oldest known ciliates in the fossil record. The remains are more than 100 million years older than any previously identified ciliate fossils, and the researchers say the discovery suggests early life on Earth may have been more complex than previously thought. What’s more, they say such prehistoric microbes may have helped trigger multicellular life, and the evolution of the first animals.
“These massive changes in biology and chemistry during this time led to the evolution of animals,” says Tanja Bosak, the Cecil and Ida Green Career Development Assistant Professor in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “We don’t know how fast these changes occurred, and now we are finding evidence of an increase in complexity.”
Bosak and her colleagues have reported their findings in a paper posted online this week in the journal Geology.