Posts
The Evolutionary History of Whales Is Doing Fine, Thank You Very Much
Some Background
First we need to step back a few decades to get some historical perspective. Prior to 1979 very little was known about the early evolution of whales. Mammals evolved on land long before whales appeared in the fossil record. Therefore, since whales are mammals, you would expect whales to have their evolutionary roots in land mammals. However, there wasn't much fossil evidence to go on. That started to change when, working in Pakistan, paleontologist Philip Gingerich discovered the skull of a land mammal that was similar in form to a wolf. Gingerich noticed a couple of grape-sized bones of the middle ear that were only known to exist in cetaceans (whales, dolphins, etc). This strongly suggested that the newly discovered animal, Pakicetus, was a relative of whales. Over the next few decades, Gingerich and his former student, Hans Thewissen, discovered a number of other related fossils showing various degrees of adaptation to water, and each with the distinctive cetacean middle ear bones.
Scientists initially believed that whales were most closely related to a group of extinct mammals called Mesonychids, which are related to Artiodactyls (cattle, pigs, hippos, etc). However, most experts now believe that whales are more closely related to Artiodactyls based on two principle lines of evidence [1]. First, in the late 1990s a Japanese group found that whales and hippos share some common genetic markers (LINEs and SINEs) that are not shared by other Artiodactyls, suggesting that they share a common ancient ancestor that is not shared by other Artiodactyls or Mesonychids. Second, some of those fossils discovered by Gingerich and Thewissen turned out to have an ankle bone (double-pulley astragalus) that is a defining feature of Artiodactyls.
Let's pause for a moment to make this clear. We have fossils that have one feature diagnostic for cetaceans, and another feature diagnostic for Artiodactyls. Also, modern whales share some unique genetic markers with hippos (which are Artiodactyls). It's almost as if...whales....evolved from....a group of ancient Artiodactyls [2].
The Fraud
So where does the fraud come in? A creationist named Dr. Carl Werner (apparently a physician by training) interviewed some of the paleontologists that study cetacean evolution, especially Gingerich (2001) and Thewissen (2013). Werner produced an anti-evolution video series and published an accompanying book titled, Evolution: the Grand Experiment, with one chapter devoted to whales. For the 2014 third addition of his book, Werner produced a press release that breathlessly lays out the main charges, even though much of it pertains to information over a decade old. During his filmed interviews, Gingerich and Thewissen spilled the beans on how shaky the whale evolutionary scenario is. These amazing revelations included the following:
1. Although the tail of the ancient cetacean Rodhocetus has not been found, Gingerich initially speculated that it had a fluke at the end of it. Also, initially the limbs were not recovered so he speculated that Rodhocetus had flippers. Limbs were later recovered, leading Gingerich to doubt that they were flippers, and ultimately doubt that it had a tail fluke. However, various museums were still displaying drawings of Rodhocetus with flippers and a fluke. Somehow all of this disqualifies Rodhocetus as a transitional fossil and serves as evidence that evolutionary scientists freely spread misinformation.
2. When Thewissen discovered the skeleton of Ambulocetus, part of the upper jaw was missing, along with the nasal opening. The remaining lower jaw allowed him to judge how long the upper jaw would have been. However, the location of the nasal opening is not known. Thewissen's model placed the nasal opening a few inches back from the end of the snout. Since the actual location of the nasal opening isn't known, Thewissen's model is biased and misleading.
3. In discussing the middle ear of Ambulocetus, Thewissen acknowledged that a part called the sigmoid process, which was previously thought to be diagnostic for cetaceans, was 'questionable'. This admission revealed that there was no basis to consider Ambulocetus a cetacean. When combined with #2 above, it was clear that Ambulocetus as a transitional whale fossil was a figment of wishful thinking.
More to the Story
When I first came across these claims I did some Internet searching to see if there was any response. These charges were clearly popular because all kinds of creationist websites dominated my search results. Eventually I found an anonymous message board where one of the participants claimed to have contacted Dr. Thewissen and received a reply, which he posted. Thewissen confirmed that Werner did interview him.
He had me answer the same question a number of times. Usually journalists do this when the answer that a scientist gives is too technical, so usually the scientist rephrases the answer in a more simple way. When Werner shot in my lab, he would ask the same question multiple times, and I simplified my answers more and more each time he repeated a question. He then put my answers together in a creative way that makes it all look pretty silly....Since this comes from some unidentified person on a message board, you might be skeptical that it actually came from Thewissen, as you should be. However, the response also drew attention to a video that Thewissen made to help clarify the issues around Ambulocetus, though without direct reference to the creationists. Indeed, the YouTube video does exist! And it's worth watching.
The written piece that you sent me, I had never seen before. It does not discuss the critical piece of information that shows that Pakicetus and Ambulocetus are whales: the thick inner part of the tympanic bone of the ear, called the involucrum. It is not clear to me why this is not presented, as scientists agree that this is the most critical feature. Instead, the video focusses on another part of the tympanic bone, the outer part, which indeed is different in shape in different whales, and occurs in some whale relatives too (artiodactyls are the closest relatives to whales, no wonder that their ears have similarities). So, that feature needs to be qualified when it is explained. In a simple sound bite such as the ones that Dr. Werner presents, those qualifiers are not present and that causes that particular feature to look pretty inconclusive in the way it is presented there.
Let's return to the issue of the sigmoid process and the involucrum for a moment. Werner's website quotes a 1998 publication by another whale expert (Zhe-Xi Luo) as follows.
"Other diagnostic characters, such as the sigmoid process as discussed below, are now open to question in the wake of the new fossil evidence from Pakicetus...[The] sigmoid process [in Pakicetus] is a simple plate [and is] equivocal, [since it is also] present in the artiodactyl Diacodexis...compromising its utility as a "dead ringer" apomorphy [unique trait] for cetaceans."However, this editing leaves out an important preceding sentence from the original publication (a book, by the way, that was edited by Thewissen) (bolding added).
Cetaceans including pakicetids have only one unambiguous bullar synapomorphy that is absent in all noncetacean mammals--the involucrum, or the pachyosteosclerosis of the medial margin of the bulla. Other diagnostic characters, such as the sigmoid process, as discussed below, are now open to question in the wake of the new fossil evidence from Pakicetus and Ichthyolestes.Luo's argument is rather technical, but the gist seems to be that the sigmoid process should not be considered a definitive sign that an ancient fossil is a cetacean. However, as stated by Luo, that still leaves the involucrum! I wonder if Werner missed that sentence.
Summary and Conclusion
So let's summarize the answers to the supposedly devastating admissions by Gingerich and Thewissen, numbered as above.
1. So far as I know, Gingerich never responded to Werner. Paleontologists often do not recover all of the bones of a fossil skeleton, so their reconstructions sometimes contain some guesswork based on other information. Carl Zimmer's book, At the Water's Edge, which profiled Gingerich's work, stated that most of the tail of Rodhocetus was missing, "preventing [Gingerich] from knowing whether it had grown flukes at its tip." Zimmer's book was published two or three years before Werner interviewed Gingerich, so Gingerich was hardly making a new admission to Werner. Werner's complaint has some justification as far as accuracy of reconstructions go. However, that does not negate the features that make Rodhocetus a cetacean that could function both on land and in water. Rodhocetus retains its place in the evolutionary transition of cetaceans from land to water.
2. Although Thewissen did not know exactly where the nasal opening of Ambulocetus was, its close relation to another fossil suggested that the opening had migrated a bit from the tip of the snout. The exact location of the opening is not important. When you look at the broad picture of cetacean evolution, you see the nasal opening migrate back from from the tip of the snout toward the eyes, where we know it in modern cetaceans as the blowhole.
3. The sigmoid process is a strong indicator of being a cetacean, but is apparently now considered not entirely definitive. However, the involucrum is considered definitive, and all of the fossils in question have an enlarged involucrum.
There are other issues I have not addressed, on both sides. Werner and other creationists have a few other criticisms that I haven't run down, some of which are rooted in a cartoon version of how evolution or science works. Similarly, there are other evidences derived from both living and ancient cetaceans that yield further evidence of, and insight into, cetacean evolution.
In conclusion, the notion that evolution, both in general and as applied to whales, has fallen like a house of cards remains a creationist fantasy. Nor is there any evidence of actual fraud; only some perhaps ill-advised artistic license. In this case, Werner has employed classic creationist tactics of selective quotation and ignoring important context. The evolutionary history of whales remains in good shape.
Further Reading:
These three are easy reading:
Understanding Evolution: Whales - Source of the images above.
National Geographic: Valley of the Whales
Evolution of Cetaceans - Wikipedia
This one is a little more challenging, but more detailed.
From Land to Water: the Origin of Whales, Dolphins, and Porpoises
Notes:
1. There are actually a number of other characteristics that support the relationship, but they are more subtle.
2. Either that, or God created whales on the fifth day of creation, some with a distinctive ankle bone they hardly used, if at all. And then, for some reason, He created a bunch of land Artiodactyls on the sixth day of creation with that same ankle bone, and in a few cases threw in the whale-like middle ear for good measure.
Continue reading...
