Scientists are getting very excited about the remains of an animal that lived around 47 million years ago.
The fossil - nicknamed Ida - was in London for one day only so Gavin went along to find out what the fuss is about.
"When I arrived at the Natural History museum to see a new fossil, I was really surprised at how many people had shown up to see it. There were loads of other camera crews, photographers and media people for it!
The discovery is called Ida - and she's kind of like a cross between a lemur and a monkey.
Scientists are really excited by her because they reckon it could tell us some key things about how we as humans have developed over millions of years.
Ida was one of the earliest forms of primate - so experts say there could be a direct link from the fossil to us! Wow.
Ida is over 47 million years old, and I was part of a few lucky people to get up close and personal with it!
And in the process I got to meet one my heroes who was there for the unveiling - Sir David Attenborough. He's a really famous broadcaster and knows loads about species and evolution.
So I got to interview him about the fossil. I actually still have goosebumps because I got to chat to him! Check out my interview.
The fossil had the remains of its last meal still preserved in it. And the bones looked small and fragile - but still intact. I was amazed at how delicate it looked.
Ida's being taken away today, but the museum will have a replica fossil in place for anyone who wants to go and have a look. You never know - you might be related!"