No, we're not making this up.
New research from the University of Cambridge - as in, that place full of excessively clever people, not nutters - suggests that our arms and legs share a 'genetic programme' with gills of cartilaginous fishes such as sharks and skates.
It all links to a gene that some mavericks at Harvard Medical School named the 'Sonic hedgehog' - a gene employed in limb development named after the video game character due to the similarity of the blue hero's spines.
Ridiculous as it might sound, the relationship between our appendages and shark gills is actually very old; 138 years ago German anatomist Karl Gegenbaur proposed the theory that paired fins and limbs evolved from the gills of fishes. New research carried out by Cambridge’s Department of Zoology and published in the journal Development indicates that the way in which the Sonic hedgehog gene is active in human limb development (helping the body differentiate between fingers and arms) is mirrored in the development of skate embryos.
"Gegenbaur looked at the way that these branchial rays connect to the gill arches and noticed that it looks very similar to the way that the fin and limb skeleton articulates with the shoulder," said Dr Andrew Gillis, from the University of Cambridge’s Department of Zoology. "The branchial rays extend like a series of fingers down the side of a shark gill arch."
The study interrupted the growth of skate embryos to see how the Sonic gene would behave, revealing close parallels with how humans develop their own limbs and fingers.
"However, it could also be that these structures evolved separately, but re-used the same pre-existing genetic programme," said Gillis. "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."
So there you have it. Your fingers share something in common with the gills of sharks and skates thanks to Sonic the Hedgehog. Bonkers, right?
(Images: Andrew Gillis)