How old is animal life on Earth? Bizarre fossils unearthed recently in Namibia suggest the earliest animals were around 100 million to 150 million years earlier than scientists once thought.
The kind of animals we're used to hadn't evolved yet, but their earliest ancestors had: hollow, sponge-like globs, no bigger than a speck of dust. They were found in rocks that dated between 760 million and 550 million years old, overturning the long-held notion that the first animal species appeared around 635 million years ago.
And that's not all. According to the researchers, the odd little animal may be mankind's earliest ancestor.
"If one looks at the family tree and projects this backward to where you have what's called the stem group, the ancestor of all animals, then yes, this would be our great-great-great-great-great-great-great grandmother," co-author Tony Prave, a geologist at the University of St. Andrews in Scotland, told AFP.
Although the findings, published in South African Journal of Science, overturn major assumptions about the fossil record, they fall in line with what evolutionary geneticists have thought for years. Using a dating method that looks at a species' "molecular clock" - genetic sequences combined with historical species information - scientists can hypothesize a species' age. From these methods, they estimated animal life began closer to the time period that this Namibian fossil came from.
"The aspect of this that's rather satisfying, at least intellectually, is that it is in broad agreement with what geneticists would tell us, based on looking at molecular clocks, when we should see the first advent of large multi-cellular life forms," Prave said.
See some early fossils collected by Charles Darwin and his colleagues in the slideshow below: