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PBS Eons Teaches Nonsense about Evolution

Günter Bechly

PBS Eons

Usually, you would not expect Darwin critics like me to feel compelled to school evolutionists about the details of their own theory. In this case, though, I simply can’t resist.

Where do you think your curious kids will look for answers to their questions about the world — in the local bookstore or online? Nowadays, it will mostly be online via Google, Wikipedia, or YouTube. Of course, we all know that you cannot trust Wikipedia. Even in mainstream academia it is not considered a legitimate source. But what about professional science channels on YouTube? If your kid is a science geek, he will certainly know channels like Vsauce and AsapScience, which have many millions of subscribers. For paleobiology, one of the most popular channels is PBS Eons with more than 900,000 subscribers.

In the summer of 2018, PBS Eons published Episode 46 of Season 1, “When Fish First Breathed Air.” Since then the video has amassed a staggering 805,000 views. When I first watched it last year, I was unpleasantly surprised, even shocked. At timecode 5:50-6:05 they claim as the central thesis of their video that lungs evolved from the fish swim bladder. This is such a stupid error that I thought it would certainly be corrected soon and the comments section would likely explode with critical remarks by educated viewers. Boy, was I wrong! A year passed and nothing happened. No correction and not a single comment on this issue. Same at their Facebook posting of this embarrassing video. So it falls to Darwin critics to point out the error.

What Evolution Says

Here is what modern evolutionary biology actually says about lung origins. The swim bladder and lungs are indeed considered to be similar, both having derived from an outpocketing of the gut (Perry et al. 2001, Longo et al. 2013). However, contrary to the erroneous beliefs of Charles Darwin, lungs are no longer considered to have evolved from the swim bladder. Actually, because of the different ontogenetic origins of lungs as a paired ventral and the swim bladder as an unpaired dorsal outpocketing of the gut, even their homology is questionable (Daniels et al. 2004). Paired lungs are present not only in land vertebrates and lobe-finned fish like lungfish, but also in primitive ray-finned fish like the reedfish and bishirs (Polypteriformes) (Icardo et al. 2017). Therefore they are generally considered to belong to the common ground-plan of bony fish in general. Another group of lobe-finned fish, the coelacanths, has a vestigial lung and a so-called “fatty organ” that may correspond to the other half of a paired lung (Lambertz 2017), but coelacanths possess no swim bladder. The more primitive sharks and rays lack lungs as well as swim bladders. Swim bladders are restricted to ray-finned fish (Actinopterygii), and are thus considered as a uniquely derived character within this group, apart from the most basal and relictual order Polypteriformes mentioned above (Hughes et al. 2018). The claim in the PBS video (timecode 6:02-6:06) that ancestors of early tetrapods like Tiktaalik and Ichthyostega probably had a swim bladder is complete rubbish. 

But it gets worse. PBS makes up a completely idiotic scenario where the swim bladder allegedly became bigger in some lobe-finned fish, developed more blood vessels, and then in time transformed the air bladder from a hydrostatic organ into a respiratory organ. This was then split into a paired lung in bichirs and lungfish. Again, this whole scenario is complete nonsense. It is emphatically not proposed by any evolutionary biologist!

Lungs simply could not have evolved from the swim bladder. Why? Because lungs predate the origin of the swim bladder, while the latter only appears as a parallel development in a subgroup of bony fish that has the lungs secondarily reduced. Alternatively the lungs and swim bladder might have both evolved from the primitive lungs of a common ancestor of lobe-finned and ray-finned fish (Tatsumi et al. 2016), which would be the exact reverse of the PBS fantasy scenario.

So, could PBS be excused on the grounds that this is all brand-new research they simply did not yet know about? Not really. I learned all of the above at Tübingen University nearly 25 years ago. We were told even then by our fantastic teacher Dr. Gerhard Mickoleit about the “urban legend” that lungs evolved from the swim bladder. (See his book Phylogenetische Systematik der Wirbeltiere, 2004: pp. 82 and 88, Pfeil Verlag.) 

At their Patreon fundraising site, PBS Eons advertises itself as being “devoted to making sure our content is of the highest possible quality, and that takes a lot of time and resources.” From a self-proclaimed high-class educational program, such crude errors are intolerable.

“The Highest Possible Quality”

After the sobering experience with their video on lung evolution I decided to take a look at some of their most viewed videos. These include evolutionary stories like “How the Turtle Got its Shell” (1.23 million views), “The Age of Giant Insects” (1.4 million views), “When Whales Walked” (nearly 1.48 million views), “How Did Dinosaurs Get So Huge?” (1.58 million views), “The Extinction That Never Happened” (1.87 million views), and finally, at the top of the heap, “What Happened to the World’s Greatest Ape?” (2.57 million views). Any problems with these? You bet. Here are just a few.

Let’s first look at “The Age of Giant Insects”, which was released by PBS Eons in September 2017 and sponsored by The Great Courses Plus, which features the world’s greatest professors. Surely this video teaches the best, state-of-the-art research and only well-established facts, no? Unfortunately, not so much.

At timecode 0:52-1:07 the video allegedly shows a figure of a life-like reconstruction of the giant griffenfly Meganeura. However, the image does not even remotely resemble Meganeura. It either represents a fantasy insect or a very inaccurate reconstruction of a Megasecoptera, which belongs to a different insect superorder, Palaedictyopterida. Also, Meganeura did not have a wing span of 70 cm but rather “only” 60-65 cm. But let’s skip such minor quibbles. There are much more substantial errors.

The PBS video repeats the popular hypothesis that the common gigantism among Carboniferous arthropods was related to the much higher oxygen content during this era and the physical limits of their tracheal breathing system. Fair enough. However, the next error they make is in claiming that the high oxygen content was because wood-decomposing bacteria had not yet evolved. This error is apparently directly copied from Wikipedia, where the given reference (Foudas et al. 2012) actually does not speak about bacteria but about white rot fungi, which belong not just to a different kingdom from bacteria but to a wholly different domain of life. Wikipedia probably got this from a totally unsubstantiated claim in a popular science book (Ward 2006: 117), without any scientific reference. And there can be no reference, because lignin degradation by bacteria is such a minor phenomenon that it was long overlooked until a few years ago (see here). White rot fungi are the only organisms that are capable of substantial lignin decay. 

But even if we forgive the confusion between bacteria and fungi as a mere lapse, there is an even bigger problem with this story. New research (Nelsen et al. 2016) has shown that there is ample evidence of fungal decay in Carboniferous forests and that a delayed fungal evolution played no causal role in Paleozoic peak of coal formation. That also means it played no great role in the oxygen cycle. This fits quite well with the study of Foudas et al. (2012), which had an error margin (95 percent HPD) of 195-399 million years for their molecular clock dating of the origin of white rot fungi at 295 million years.

The next problem PBS fails to mention is that there do exist modern insects that match the body size and body mass of Meganeura. Those include some giant stick insects, which are of course nonvolant, but do prove that body size is not limited by today’s lower oxygen level.

But surely the suggested explanation works for the 2 m long Carboniferous millipede Arthropleura? No, because arthropleurids most likely had no tracheal breathing system at all (Kraus & Brauckmann 2003: 46-47), but were semiaquatic with plastron breathing. Though this has been known for more than 15 years, it did not stop PBS. They feature Arthropleura (timecode 3:10-3:14) as an example for gigantism that was possible due to a more efficient tracheal breathing system under higher oxygen content. Nor does the failure to convey accurate modern science stop there. The whole story that passive diffusion breathing with tracheal tubes imposes a size constraint on arthropods based on the available oxygen level was debunked 14 years before the video was made. Westneat et al. (2003) demonstrated with synchrotron computer tomography that tracheal breathing is not based on passive diffusion at all. Instead, it involves active ventilation by muscular pumping, with similar efficiency to vertebrate lungs, and thus is not constrained by oxygen level (Schneider & Werneburg 2010).

At timecode 3:15-3:33, the PBS video also mentions experiments by paleontologists (of course it was biologists not paleontologists) with living insects under higher oxygen levels that allegedly led to 15 percent larger dragonflies. Actually, this research was reported at a congress (GSA 2010, Peplow 2010) and in the popular media. But it was never properly published in a peer-reviewed scientific journal. The only paper from this working group (Harrison et al. 2010) that explicitly addressed the question features no such results. Promised follow-up papers have never appeared. 

Here comes the next problem. At timecode 4:13-4:23 the video states that oxygen levels plummeted about 275 million years ago during the Permian and that 299 million years ago the last Meganeura flapped its wings (timecode 5:00-5:05). If PBS had invested just a bit more research time, they would have discovered that the biggest griffinflies known were two species of the genus Meganeuropsis, with an estimated wing span of 75 cm, found in the Permian Wellington Formation, which originated 290-280 million years ago. Large griffinflies of the family Meganeuridae with a 45 cm wing span are known from the Late Permian (Lower Kazanian, ca. 270 Ma) of Lodève Basin in France, when oxygen levels were already much lower. This strongly contradicts the narrative that insect gigantism is related to high levels of atmospheric oxygen (Nel et al. 2008). This was known and published almost ten years prior to the PBS video. Oops! 

Difficulties with Dinosaurs

But surely PBS gets it right with the dinosaurs, don’t they? Their video “How Did Dinosaurs Get So Huge?” was released in October 2017. They start by introducing the newly discovered sauropod genus Patagotitan as the largest dinosaur. Well, stop right there. They simply fell for some popular media hype. As paleontologist Matt Wedel explained in a blogpost, “Don’t believe the hype.” Patagotitan is not the biggest dinosaur known, and not bigger than other very large sauropods like Argentinosaurus and Puertasaurus (Wedel 2017). Admittedly, these are minor quibbles. 

After some reasonable elaborations about the different reproductive systems and bone structure of mammals and dinosaurs that allowed the latter to grow to much larger sizes, the narrator correctly mentions that we have no clue why many dinosaurs grew to such large sizes. That is an appropriate answer to the question posed in the video’s title. But then, towards the end, the video really goes downhill. The narrator asks whether big size was really an advantage at all, since the large dinosaurs are all gone. That is a very strange question for an evolutionary program. It implies that gigantism would have to have evolved multiple times in sauropod dinosaurs (Sander et al. 2011), totally against the Darwinian mechanism of natural selection and survival of the fittest. Apart from that, it would be ridiculous to consider an adaptation as non-advantageous, if it persisted from the Late Jurassic to the Late Cretaceous, some 85 million years. That would be a very long success story for a failed construction. No evolutionary biologist or paleontologist believes such nonsense. However, your children will absorb it as “modern science” and many adults will as well.

More “Modern Science”

Finally, let us look at the PBS Eons episode “The Extinction That Never Happened.” This one was released in August 2017. The title refers to a supposed mass extinction of the weird fauna that originated with the Cambrian explosion. Now, it would clearly be ludicrous to interpret the mass extinction of these animals as complete. Otherwise the sudden origin of animal phyla in the Cambrian explosion could not be considered as ancestral to the modern animal phyla. Therefore, species of all these lineages must have survived. 

The real question is this: Was there a major extinction event at the end of the Cambrian that weeded out a significant portion of the previous biodiversity? This is clearly the case and cannot be refuted by referring to a few exceptions. However, at timecode 6:35 the narrator claims that because of the discovery of an Ordovician fossil locality in Morocco, “paleontologists realized that the Cambrian extinction never happened.” Nothing could be further from the truth. Actually, there are three undisputed mass extinction events in the Cambrian era: the End-Botomian event (ca. 517 Ma), the Dresbachian event (ca. 502 Ma), and finally the Cambrian-Ordovician event (ca. 488 or 485.4 Ma). The former two events eradicated about 40 percent of all marine animal species. The latter mainly decimated trilobites, brachiopods, and conodonts. None of these three Cambrian mass extinction events is refuted by the new discovery. However, it is noteworthy that none of them was ever ranked among the big 5 mass extinctions in Earth’s history, as identified by Sepkoski & Raup (1982).

So, what does the discovery (Van Roy et al. 2010) of the Fezouata Biota from the Early Ordovician of Morocco really show? Anything like surviving “weird wonders” of the Burgess Shale, such as Aysheaia, Dinomischus, Hallucigenia, Nectocaris, Odontogriphus, Opabinia, Pikaia, Wiwaxia, or Yohoia? None of these, except for a tiny fragment that could possibly belong to an armored lobopod. Certainly, there were marellomorph arthropods, and later an anomalocaridid was found (Van Roy & Briggs 2011). But that was hardly a surprise. These groups were already known from the much younger Devonian Hunsrück shale in Germany (Kühl et al. 2009). Otherwise, there were just more “usual” and more modern animals like arthropods (tribolites and xiphosurans), molluscs, annelids, brachiopods, echinoderms, bryozoans, and graptolites, etc. The title of the PBS video is completely sensational and has no basis in real science.

Occasional Wheat, Frequent Chaff

Of course, not all PBS Eons videos are as bad. Some are of relatively decent quality, such as their video on Gigantopithecus, or on the origin of the turtle shell, even though I would of course emphasize that the latter only correctly presents the Darwinian narrative. It fails to recognize that this process definitely would have required new information from outside the system. However, since these educational videos mainly address a lay audience, which cannot easily separate the occasional wheat from the more frequent chaff, we must conclude that you should not and cannot trust this material, even as an evolutionist.

If you cannot trust highly reputed evolutionary media like PBS Eons to teach the proper views of their own favored theory, how much should you trust their material that attacks proponents of intelligent design, notably including PBS Nova’s documentary “Judgment Day: Intelligent Design on Trial”? The answer is obvious and simple: You can’t trust this material at all. For more on the latter, see the website Darwin’s Failed Predictions.

Photo: Tiktaalik, Field Museum, by Eduard Solà [CC BY-SA 3.0], via Wikimedia Commons.