Vestigial limb muscles in human embryos show common ancestry—for the

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@Patrick, @that’s such a great summary of a lot of important science! And it got me thinking about this: A few years ago I had a nerve transduction surgery. In the recovery room the surgeon informed me that during the procedure he discovered and removed an accessory muscle, a muscle that was putting unnecessary pressure on the nerve while serving no useful purpose. He told me that in a typical month of dozens of nerve transduction surgeries, he will find and remove one or two accessory muscles on average as contributors to the nerve problems (e.g., peripheral neuropathy.)

Once I was back home I researched the topic of accessory muscles and discovered a virtual “encyclopedia” of accessory muscles of the arms and legs. Each one had its own Latin anatomical name (always a three-word label.) Even though these accessory muscles are relatively rare in the population at large (e.g., 1 in 1000), surgeons expect to find them every now and then in the course of their work.

Accordingly, the article you linked got me wondering: Are any of these accessory muscles atavisms? I tried to answer this with some online searches but was unsuccessful. Perhaps some of the biologists or physicians on Peaceful Science can address this. To pose my question in another (although not synonymous) way, is it possible that the rare accessory muscle removed during my surgery is commonly found in some other primate species? Or perhaps a treeshrew species? Or some more distantly related Euarchonta?

Meanwhile, if Peaceful Science had a “Evolution Fundamentals” reading list, the article you linked would deserve to be on it.

Some of the accessory muscles seem to be atavistic, for example see Kumud and Anupama (2013) and Tagliafico et al. (2010).
Diogo et al. (2019), the subject of the this OP, discusses these and more in a good amount of detail.


That’s truly quite fascinating—although not at all surprising. (After all, it’s not like atavisms clearly evident in human anatomy are all that unusual, as per wisdom teeth, the appendix, and the coccyx.)

Thanks much for the links!

This topic has led me to start a thread on research into another common human atavism: the musculus palmaris longus. Scientists studied its impact on keyboard exhaustion among musicians:

Hey @NLENTS Nathan can you comment on this thread. Would these be considered “Human Errors”?

I will admit that some people may consider me a “human error.” But I always try to do my best.

You’re not a “human error” but are the best that a mindless unintelligent process can accomplish so far. And your grandchildren are even better. :sunglasses: