Brett Smith for redOrbit.com – Your Universe Online
While birds’ three fingers appear analogous to our own thumb, index and middle fingers, embryonic evidence has shown that the “pinky” side of a bird’s claw develops first, which some theories have said is evidence of the three bird fingers being an index, middle and ring finger.
According to a new study published in the Journal of Experimental Zoology, as dinosaurs evolved into birds, they actually lost their pinky and thumb, making bird fingers an index, middle and ring finger.
The earliest known bird, Archaeopteryx, has fingers that resemble those of the dinosaur Deinonychus, a probable relative. According to fossil analyses, two fingers on the pinky-side of the hand were reduced over the generations in the ancestor of Deinonychus. This evidence supports the identification of these fingers in birds as a thumb, index, and middle finger identification. Also, the genes active in the development of the first bird finger match up with genes in the developing thumb of other animals, and not those of the index finger.