The missing digits have previously been a bit of a mystery, leading scientist to think that fingers came much later and developed abruptly.All land animals with a backbone, otherwise know as tetra pods, evolved from lobe-finned fish that existed hundred of millions of years ago….These fish had lungs and muscular paired fins. The fin bones of both fossil lobe-finned fish and the four surviving species of related fish are similar to those of tetra pod limbs, but they do not appear to have any bones that could have gone on to produce digits.
This assessment has now changed. The fins of most fish develop in one stage, whereas tetra pod limbs develop in two stages. In tetrapods the limb bones developed first then the Hoxd13 gene is switched on to grow the digits. Research at a Swedish university has found that the Australian lungfish fins goes through a two stage development. The second stage triggered by the Hox13 gene. In the lungfish Hoxd13 controls the growth of the radials.
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Question for debate: Does the hoxd13 gene successfully demonstrate that lobe fish and tetra pods have a common ancestor?
