The Bird Digit Mystery

What is the origin of bird digits? This question has caused a lot of head-scratching and beard-stroking in evolutionary biologists. Paleontological evidence suggests that the three digits in birds develop from digit position 1, 2 and 3 (thumb, index and middle finger). Embryological evidence points towards digits 2, 3 and 4 (index, middle and ring finger). Vertebrates are ‘programmed’ to develop five digits on each limb, but there are exceptions. Such as birds, which have three. But which three?read more

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