An astonishing new study claims that our limbs evolved from sharks, believe it or not.

Scientists say that new genetic evidence indicates that our limbs may have evolved from the gill arches found on sharks, skates, and rays, according to a University of Cambridge statement.

Gill arches are essentially looped bones that help support the gills. Biologists believe the gill arches led to paired fins in early fish, and may have eventually resulted in paired limbs in mammals, but the new discovery is the first time genetic evidence has backed this theory up — a finding that the lead researcher called “fascinating.”

Scientists believe it is caused by a gene they’ve called “Sonic the hedgehog.” This gene produces a signaling protein that helps determine limb skeleton growth.

It’s part of ongoing research that will continue this summer as scientists look into whether other genes play a role in the development of gill arch appendages, called branchial rays, which are believed to be a big part of the evolution of vertebrate animal appendages.

“Taken to the extreme, these experiments could be interpreted as evidence that limbs share a genetic programme with gill arches because fins and limbs evolved by transformation of a gill arch in an ancestral vertebrate, as proposed by Gegenbaur,” Dr. Andrew Gillis, the lead researcher who hails from the University of Cambridge’s Department of Zoology and the Marine Biological Laboratory, said in the statement. “However, it could also be that these structures evolved separately, but re-used the same pre-existing genetic programme. Without fossil evidence this remains a bit of a mystery — there is a gap in the fossil record between species with no fins and then suddenly species with paired fins — so we can’t really be sure yet how paired appendages evolved.

“Either way this is a fascinating discovery, because it provides evidence for a fundamental evolutionary link between branchial rays and limbs,” Gillis added. “While palaeontologists look for fossils to try to reconstruct the evolutionary history of anatomy, we are effectively trying to reconstruct the evolutionary history of genetic programmes that control the development of anatomy.”

The findings were published in the journal Development.