Today, more than eight million animal species have inhabited earth, but in the beginning of the world, there were very few species. The first form of life that set up home on the planet was a simple sea sponge, claimed a new study by Massachusetts Institute of Technology (MIT) in Cambridge.

MIT researchers conducted genetic tests and confirmed that molecules found in 640-million-year-old rocks were produced by sea sponges. The rocks in the study are older than the 540 million years old period, known as the Cambrian explosion, when many animal species dwelled in different regions of the world.

The new study has been published in the Proceedings of the National Academy of Sciences. The researchers said the genetic tests have offered the oldest evidence for animal life. “We brought together paleontological and genetic evidence to make a pretty strong case that this really is a molecular fossil of sponges”, said David Gold, a researcher at the Department of Earth, Atmospheric, and Planetary Sciences (EAPS) of MIT.

‘Earth’s first species’ has been a topic of debate since a long time. Many paleontologists around the world struggled to discover which species first inhabited the planet. They have conducted several tests on remains from the start of the Cambrian explosion, but the 640-million-year-old rocks are the oldest to be examined.

Roger Summons, EAPS Professor at the MIT, has been working for last 20 years to discover more on the animal kingdom’s extended evolutionary tree. Summons and other researchers at his lab have been searching for clues by analyzing molecular fossils that may reveal about earth’s early animals.

The new study’s results offered strong evidence suggesting that sea sponges lived on earth 640 million years ago, much earlier than any other life form.