In our exchange with theistic evolution Karl Giberson on human "tails" as evidence of common descent, Dr. Giberson thinks we’ve been unfair to him. He tweets:
Strange ad hominem post from the Discovery Institute, obsessed with the fact that I briefly displayed an image… http://t.co/6rX3WqIOj5
— Karl Giberson (@gibersok) May 25, 2014
What? He’s referring here to a post I wrote that discusses a photo he used both in a public debate with Stephen Meyer and in an article about that debate for The Daily Beast. Casey Luskin and I have questioned the evidence he brings to his argument, while retaining the premise of Giberson as a man of scruples who would want to know that a piece of evidence is shabby so that he could discard it. That’s exactly the opposite of "ad hominem."
Continuing in the same spirit, I would ask as follows. If you follow the links, you find that the photo Giberson uses to illustrate a vestigial human tail comes from an online humor magazine, Cracked, which in turn took it from an online Iranian Muslim website. The Iranian website, Ahlul Bayt Lovers Network, identifies it (translation by Google Translate) this way:
A child with a tail "Chandr Avram" Childhood is a native of West Bengal during the birth of a tail length of 33 cm at the back. He is currently working on tea plantations in India and because of certain religious beliefs, not surgery.
There are several things that seem fishy about the image.* The tail doesn’t look like the medical images of human tails that Casey has gone through in his own very extensive research of relevant medical literature. As Giberson uses it in the article and in the debate with Meyer, the picture is meant to illustrate his claim that sometimes "babies are born with perfectly formed, even functional tails."
When the caudal appendage is critically examined, however, it is evident that there are major morphologic differences between the caudal appendage and the tails of other vertebrates. First of all, the caudal appendage does not contain even rudimentary vertebral structures. There are no well-documented cases of caudal appendages containing caudal vertebrae or an increased number of vertebrae in the medical literature, and there is no zoological precedent for a vertebral tail without caudal vertebrae.
That aside, the healthy-looking baby in the picture indeed appears to have a "perfectly formed" tail. It could be a pig’s tail, from the look of it. Medical and other photos, in contrast, show very scary-looking growths, not "perfectly formed" ones at all.
The photo makes Giberson’s point for him better than the other photos I’ve (very uncomfortably) seen. Unlike the others, it looks "perfectly formed." Also unlike the others, where the tail would connect with the body is not visible. Is Giberson’s photo, then, genuine?
There are reasons to wonder. Its immediate source, Cracked, is not a medical journal. Neither is Cracked‘s source, the Ahlul Bayt Lovers Network. A search by image, using Google, reveals no medical or other serious journals that have used the photo. A minor point, too, but if you asked me what part of the world the baby looks like it might come from, I wouldn’t say West Bengal. At a glance, for whatever that’s worth, this looks like a baby of European, not Indian, background.
Frankly, if you told me that someone Photoshopped it, adding a pig’s tail to the image of a healthy baby, I wouldn’t be surprised.
Let me be clear that I’m not at all suggesting that Giberson altered the image. Obviously, he got it from the Internet. I ask about it at all only because a picture is formidably persuasive in an argument. Which is fine if it’s authentic. That, I assume, is why Dr. Giberson has used this particular photo at least twice in presentations of his case for Darwinian evolution. Maybe he’s done so on other occasions. He must believe it to be genuine.
If he has verifying information then, please, Dr. Giberson, share it with us. If not, will you kindly confirm that you will stop using it to illustrate your point about tails, substituting a photo that probably makes a less impressive support? Or better yet, given the mass of medical evidence Casey has presented, will you stop using this now fallen evolutionary icon of human "tails" altogether to support your case?
*I haven’t included the photo in this post since we try to be careful about copyright here at ENV and I don’t care to get into a legal wrangle with whoever created the image. But you can see it here.