Modern genetics confirm ancient relationship between fins and hands

Jan 15, 2015

Courtesy of the Shubin Lab

By John Easton

Paleontologists have documented the evolutionary adaptations necessary for ancient lobe-finned fish to transform pectoral fins used underwater into strong, bony structures, such as those of Tiktaalik roseae. This enabled these emerging tetrapods, animals with limbs, to crawl in shallow water or on land. But evolutionary biologists have wondered why the modern structure called the autopod—comprising wrists and fingers or ankles and toes—has no obvious morphological counterpart in the fins of living fishes.

In the Dec. 22, 2014, issue of the Proceedings of the National Academy of Sciences, researchers argue previous efforts to connect fin and fingers fell short because they focused on the wrong fish. Instead, they found the rudimentary genetic machinery for mammalian autopod assembly in a non-model fish, the spotted gar, whose genome was recently sequenced.

“Fossils show that the wrist and digits clearly have an aquatic origin,” said Neil Shubin, the Robert R. Bensley Distinguished Service Professor of Organismal Biology and Anatomy and a leader of the team that discovered Tiktaalik in 2004. “But fins and limbs have different purposes. They have evolved in different directions since they diverged. We wanted to explore, and better understand, their connections by adding genetic and molecular data to what we already know from the fossil record.”

Initial attempts to confirm the link based on shape comparisons of fin and limb bones were unsuccessful. The autopod differs from most fins. The wrist is composed of a series of small nodular bones, followed by longer thin bones that make up the digits. The bones of living fish fins look much different, with a set of longer bones ending in small circular bones called radials.


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6 comments on “Modern genetics confirm ancient relationship between fins and hands

  • 2
    NearlyNakedApe says:

    I think the key to answering your question lies in the following sentence from the article:

    We wanted to explore, and better understand, their connections by adding genetic and molecular data to what we already know from the fossil record.

    IOW, the fossil record already provided good evidence but it had “holes” in it:

    Initial attempts to confirm the link based on shape comparisons of fin and limb bones were unsuccessful….

    The bones of living fish fins look much different, with a set of longer bones ending in small circular bones called radials.

    So my understanding is that sequencing the genome of the gar fish provided scientists with better evidence fror what was already strongly suspected. What may mislead readers is that Neil Shubin used the words “already know” which is not quite accurate.



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  • You know, every time I read something about our ancestors I feel so proud. I feel such immense joy to be related to plants and other animals. To the Universe at the end. 🙂



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  • Beautiful! I often forget that there is this web page. 😉 When I look at the graphic or any other pictures that are explaining evolution I am always impressed how simple that principle actually it is.



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