Tuesday, October 13, 2020

Obscure controversies in Cenozoic marine vertebrate paleontology 2: the whale jaw that didn't disprove evolution

Note: This post discusses young earth creationism. I do not take young earth creationism seriously, and neither should you - though it is a serious threat to science communication and science education. Nothing is gained from me linking to the individual articles by creationist authors, so I am making no attempt to cite them or link to them. I do not want to give those trolls the attention (positive or negative) they so desperately crave. Since this is a science blog, I also will not tolerate any creationist nonsense here and will enthusiastically delete any creationist comments: engaging with creationists directly is a waste of time and elevates highly problematic pseudoscience; science and young earth creationism do not overlap except in a theology class or a court room.


Seymour Island, Antarctica, is one of the few fossil localities in Antarctica that is not covered with ice year round. It's quite far north, and located off the east side of the Antarctic Peninsula, at about 64 degrees south - the same distance from the equator as Fairbanks, Alaska. Owing to the lack of ice cover, we know quite a bit about the geology - and it is richly fossiliferous. Seymour Island preserves a thick sequence of rocks dating from the late Cretaceous through the Oligocene - chronicling faunal change and recovery from the K/Pg extinction and the subsequent 30 million years of faunal change. Chief among these discoveries are scores of fossil penguins, the extinct toothed baleen whale Llanocetus denticrenatus (higher up towards the very top of the La Meseta Formation), and more recently - archaeocete whales.

The geographic location and geology of Seymour Island and the La Meseta Formation in particular. From Jadwiszczak and Mörs, 2017.

In 2011 the discovery of archaeocete whales, mostly basilosaurids, was announced. Among these was a surprisingly early occurrence of a basilosaurid whale, claimed as dating to 49 Ma - squarely in the Ypresian stage (56-47 Ma), otherwise known as the early Eocene. Now, there are some serious issues with this, and a brief recap of early whale evolution is needed for you to appreciate the controversy. The earliest known cetaceans, including Pakicetus and Ambulocetus, are from the Ypresian, with the oldest known cetaceans dating to about 53.5 Ma (Himalayacetus). Ypresian whales are chiefly all four-legged whales, including the long-legged and dog-like pakicetids, the crocodile-sized ambulocetids, the otter-like remingtonocetids, and the much larger seal-like protocetids. Pakicetids and ambulocetids were mostly restricted to freshwater thanks to fossil occurrence data and isotopic analyses, whereas remingtonocetids inhabited fresh and saltwater. Remingtonocetids were the first to leave Indo-Pakistan, being found as far west as Egypt - but protocetids were the first oceangoing cetaceans, and the first to reach the western North Atlantic and the Pacific. They still had functional hindlegs and could at least amble about on land clumsily like a seal. Most protocetids date to the middle Eocene. Basilosaurids had hindlegs, but they were tiny, no longer attached to the vertebral column, and likely vestigial as far as locomotion was concerned - and possibly retained for gripping mates during mating. These were therefore the first whales to be fully dedicated to a marine lifestyle. As a result, the same genera (and in some cases, species) have been reported from across ocean basins - the most extreme of which is a skull belonging to Zygorhiza from the Eocene of New Zealand, suggesting that Zygorhiza inhabited both the Atlantic and Pacific and both the southern and northern hemispheres (Kohler and Fordyce, 1997). We'll talk more about that specimen later on. In general, the transition from dog-like pakicetids to basilosaurids, until recently, was considered to take place over a 10-15 million year timescale. The date on the new fossil is only 4.5 million years younger than Himalayacetus. This would have some profound implications.


Creationists *hate* whales

The first implication was that this was *immediate* cannon fodder for Young Earth Creationists (YEC). If you're not familiar, especially for foreign readers, YEC is a big phenomenon here in the USA, largely driven by folks who subscribe to a literal interpretation of Genesis and much of the rest of the Bible. Most YEC folks are fundamentalist or evangelical Christians; I've never met a Catholic who was staunchly YEC (I was raised Catholic, for what it's worth). There is quite the spectrum of nonoverlapping beliefs amongst creationists in general - ranging from "a creator started everything off, and evolution took its course" (a fairly modern, liberal viewpoint accommodating most science) to theistic evolution (evolution is real, but was guided by a creator), to "evolution is real, but only for non-humans" (because we're created in God's image), to the extreme endpoint, which is YEC: the earth is under 10,000 years old and evolution is a lie. There are many disagreements amongst YEC folks, largely consisting of differences in which bits of science they're willing to admit are real and use to fit a narrative, and if the earth is precisely about 4,000 years old, 10,000 years old, or an undefined number of thousands of years. Creationism obviously stems from a belief system and "Creation science" is pseudoscientific rather than scientific. The failure of most creationists to agree on anything other than 'evolution is wrong' and parts of (or all) of the bible is right tells me everything you need to know: there is no consensus, and highlights the lack of scientific reproducibility. Nobody has reproducible results; reproducible results are what a consensus develops from. Creationists cannot agree on anything, including how much of evolution is real (all? some? none? if some, how much?) how old the earth is, or even what parts of the bible to interpret literally v. figuratively. My own perspective on YEC is that it's nonsense, and the bible was clearly never intended to be interpreted literally (there are talking snakes in there and stuff, and a LOT in Leviticus about not mixing different types of fabric together). Noah's story is lifted straight out of the Epic of Gilgamesh. These are parables intended to guide you on your spiritual and moral journey through your life - and have value in very much the same way Aesop's Fables do (in my opinion). 


Generalized depiction of archaeocete evolution using images of the actual fossil skeletons - young earth creationists (YECs) really, really hate these diagrams so I make sure to use them a lot. From Biologos.org.

Strict YEC adherents frequently push the narrative that scientists are lying to everyone about evolution, and it's never always the same reason: sometimes we're just stupid, and have yet to see the light, and other times there's a big conspiracy. This frequently dovetails with the "scientists are pushing the global warming conspiracy" and actually saying ludicrous shit like we're all in cahoots to make money off of criticizing oil companies, or that we're trying to lure young children into satanism, or something. We're really not that competent, and quite frankly, the inability of the white house over the past four years to keep any real secrets has deeply eroded my ability to take stock in any government-involved conspiracy theory. For example, if alien bodies and flying saucers were kept in a hangar in Roswell, Trump would have tweeted about it back in 2017. Paleontologist Jack Horner delivered a great public lecture at the 2010 SVP conference in Las Vegas where he said "you know how I know evolution is true? what my evidence is in favor of it? All of you-" he waved magnanimously at the crowd filled with paleontologists. "All of you are competing for grants and papers in top tier journals; disproving evolution would be the discovery of a lifetime. And that has not happened."

 What is the goal behind YEC and Intelligent Design? It's largely a far right wing, conservative Christian political movement aimed at legally weakening the separation of church and state in the United States. This is well-established by the "Wedge Document", drafted in secret in 1998 by the "Discovery Institute" (a pseudoscientific think tank) and publicly leaked in 1999. The document essentially laid out the Wedge Strategy: intelligent design could be used to sneak creationism into public schools, and if awarded a legal victory, could be used to push for further 'reforms' and widen the influence of evangelical christianity into US politics. Advances on many fronts, including abortion rights, gay rights, euthanasia, were sought by this plan. This more or less remains the dominant strategy of the Discovery Institute. Spreading Intelligent Design, Young Earth Creationism, and attempting to disprove evolution and/or natural selection are all part of the same game here, and it is not intended to convert scientists: it's intended to convince enough parents out there that their kids should not be learning about evolution in schools. YEC promoters are inherently distrustful, and are caught red-handed, again and again, deliberately misinterpreting or misusing science to prove to their flock - and undecided parents - that evolution is not real. Many of these folks are actually quite intelligent - you have to be smart to be a successful charlatan - and I've met my own fair share of sociopaths in science, and recognize the signs. They are often quite familiar with the science and know how to weasel things around in order to twist the narrative. YEC/ID proponents really hate whale evolution, because the evidence is so astoundingly wonderful. This evidence has largely accrued in the past thirty years - with a few kinks here and there - that YEC folks LOVE to whittle away at. You can tell how much they hate a particular topic based upon how much they write about it: there are a lot of articles in YEC "journals" about whale evolution.

So, it came as no surprise that shortly after this announcement, YECs pounced on this press release - a preliminary announcement - and immediately claimed that this whale disproved evolution by forcing all of archaeocete evolution into a ~5 million year period. Evolutionary biologist JBS Haldane joked in the early 20th century that the discovery of a "rabbit in the Cambrian period" would disprove evolution. This is not quite that: this is a preliminary announcement of a specimen that's unusually old, but it does not actually pre-date the oldest known whales. It's still younger: it just would indicate that the whole sequence is a bit more telescoped. Or, another possibility - maybe something is wrong with the dates? Usually, one out-of-sequence fossil at a single locality suggests to reasonable paleontologists that there's more likely to be something wrong with the dating, rather than "holy shit this disproves everything we know!"


        Mandible and molar of an indeterminate basilosaurid whale, MLP 11-II-21-3, Eocene La Meseta Formation, from Buono et al. (2016).

Skull and mandible of Zygorhiza kochii, Eocene of southeastern USA, from Kellogg 1936 (Review of the Archaeoceti).

The Specimen in Question: Stratigraphy and Dating

Specimen MLP 11-II-21-3 was discovered in the TELM 4 horizon of the La Meseta Formation - also known as the base of the Cucullaea I allomember (allostratigraphy is similar to sequence stratigraphy, and has been used to subdivide the Pisco Basin/Formation in Peru as well; it's not used by everyone). This is a thick shellbed with many shells of the large ark clam Cucullaea raea as well as naticid (moon snail) and nassariid (dog whelk) gastropods. This shellbed has also produced the holotype of the astrapothere Antarctodon sobrali (Astrapotheres were strange elephant-like 'notoungulate' land mammals unique to South America, and otherwise known only from this locality in Antarctica) as well as many sharks, rays, bony fish, and some marsupials and other indeterminate notoungulates. Though no age-diagnostic plankton were found in association with the mandible, MLP 11-II-21-3 was definitely collected from this horizon, so evidence collected by other researchers from the same bed can be interpreted.

Stratigraphy and dating of the La Meseta Formation. On left: stratigraphic and geochronologic framework from Buono et al. (2016); on right: dinocyst biostratigraphy of the same strata from Douglas et al. (2014).

TELM 4, and other parts of the La Meseta Formation Strontium isotopes are frequently used to date Cenozoic marine strata: the ratio of 86Sr and 87Sr has varied through time. The gist of it is this: the radioisotope Rubidium 87, which naturally occurs in some rocks, decays to 87Sr by losing a beta particle. It's got a super long half life (49 billion years). As a result, 87Sr is added to seawater over the course of geologic time; 86Sr naturally occurs in seawater (for similar reasons as salt, calcium, and magnesium - weathering of terrestrial rocks) and therefore, through time, the ratio 87Sr/86Sr ratio increases with there being proportionally more 87Sr through time. This ratio jogged up and down several times during the Paleozoic and Mesozoic, but has more or less been an upward trend since the Cretaceous - meaning we can measure the ratio, and plug it into the curve and get a fairly accurate date. There are caveats, however: fossils sampled cannot be reworked. If reworked, you're actually dating a fossil that is older than the rock layer it was finally entombed within (we'll come back to this). Diagenesis (rocks getting messed up during burial, by compaction or groundwater chemistry) and metamorphism (heating and extreme burial causing mineral/chemical changes in the rock) can both screw with the ratio. If the curve oscillates, or goes flat (e.g. no change for several million years), the ratio is less informative and there are bigger error bars on the age determination. Lastly, because Strontium is similar enough chemically to Calcium, invertebrates frequently incorporate Strontium atoms into their shells, and therefore, ratios can be measured through destructive isotopic sampling of mollusk shells. 87Sr/86Sr ratios from shells collected from TELM 4 and the base of TELM 5 (just above the TELM 4 shellbed) are similar to TELM 3 (just underneath the TELM 4 shellbed), and suggest an age of 54-48.8 Ma for TELMs 2-5. This age corresponds to the early middle Eocene or Ypresian and Lutetian stages - and overlaps with the age of Pakicetus and Himalayacetus as well as some of the older protocetids, and if correct, is an objectively surprising date for a basilosaurid.

Other dating methods used include biostratigraphy using dinoflagellate cysts - which are a type of plankton. Dinoflagellate biostratigraphy for the La Meseta Formation is calibrated using paleomagnetic dating for the Southern Ocean - the study of changes in magnetic polarity of the earth's magnetic poles, reversing and switching back to normal throughout earth's history. Dinoflagellate biostratigraphy actually suggests a younger age. The dinocyst Enneadocysta partidgei, in particular, suggests an age of 45 Ma, and in total, the cyst fauna suggests an age no older than 49 Ma - the date assigned in the original press release, and coveted by creationists. Now, it is best recognized as an extreme possible end point in a murky cloud of dates. Buono et al. briefly cite an earlier paper by Douglas et al. (2014), who conclude that based on dinocysts and paleomagnetism, that TELM 4 is about 41-46 Ma in age. Buono et al. follow these dates instead, which is much more consistent than the cetacean fossil record. At least one article written by YEC hacks wildly misinterprets the way in which Buono et al. cited this paper, claiming that the evolutionists* are trying to sweep it under the rug. The YEC proponent who wrote that failed to understand that most of my colleagues who wrote that paper do not speak English as a first language (Dr. Monico Buono is Argentinean), and occasionally there will be some subtle language differences. The second is that, had this YEC actually read the Douglas et al. paper, there is a pretty clear outline of the dinocyst biostratigraphic framework in the supplementary materials that they did not read. OOPS. Buono et al. (2016), being scientists, did actually read the paper they were citing. The YEC critic did not. And, no, as I said above, I refuse to link to the YEC article itself. But I bet you can find it in five minutes on google if you're so motivated - it was published as a response to Buono et al. (2016).

*if you ever hear someone use the word "evolutionist", run!


Strontium curve and dates from the La Meseta Formation. The Strontium curve from the middle to late Eocene is pretty wavy, meaning that dates could slide forward or backwards in time based on small errors in the ratio, or snap to a different part of the curve altogether! There is quite a spread in ratios for TELMs 2-4 and many points are off the curve altogether, which immediately suggests limited confidence. Young earth creationists know this caveat about Strontium isotope dating just as well as geologists do, and are lying to your face about it. The method HAS drawbacks, but YECs don't tell you that geoscientists acknowledge these caveats, because they'd rather push the narrative that scientists are lying to you (oh, the irony). From Ivany et al. (2008).

What could account for the unusually old Strontium dates for TELM 4 and 5? Buono et al. point out that many of the fossil invertebrates from TELM 4 and 5 are reworked, and therefore if those shells were the ones sampled, the age is going to be misleadingly old. It's difficult to rework plankton, on the other hand, since the tiny size and delicate skeletons quickly abrade and become unrecognizable. Given the possibility or likelihood of reworking, it's better to use the plankton. That brings us to another really critical point: the biostratigraphic framework, though already existing to some degree, was published three years after the initial press release on the discovery. So, in a sense, the last author on the paper, Thomas Mörs, did not have all the biostratigraphic data at the time when he made that press release. Lastly, Buono et al. also point out that the middle Eocene is a period where the Strontium curve has some oscillations - and therefore, Strontium ratios might be inaccurate or have quite a spread on them (e.g. if there is a 'valley' on the graph, the ratio could either be on one of two slopes of the graph - the older part or the younger part, which have the same ratio) This is very much the case - see the Sr curve from Ivany et al. (2008) and the range of dates for the La Meseta Formation from the different members.


Identification of the fossil: is it a basilosaurid?

This is an important question to ask, given that it's just a mandible. The mandibles of protocetids and basilosaurids are not that different - though the large size of this specimen led the authors to identify it as a basilosaurid rather than a protocetid. There is considerable overlap between the smallest basilosaurids and the largest protocetids - the basilosaurid Zygorhiza has a skull the same size as the protocetid Georgiacetus, for example - and this mandible is about 60 cm long as preserved. That's actually within the size range of protocetids, to be honest. Just like both groups, it has a long mandibular symphysis, double rooted teeth, embrasure pits, and a large mandibular foramen. One of the only diagnostic traits is that it's got a big cheek tooth with numerous accessory cusps - which is a basilosaurid feature. BUT - we don't have many protocetids that are transitional in dental anatomy between a protocetid and a basilosaurid, suggesting there are still some fossils out there to find. Something that is transitional between a protocetid and a basilosaurid could very well have a tooth like this, but pre-date basilosaurids by several million years. I'm not saying that this is the case - I would have made the same identification as Buono et al. - I'm just saying that these alternative hypotheses are possible given the fragmentary nature of the specimen.


The Verdict

So, does this specimen destroy evolution and eliminate the pesky land-to-sea transition of whales that YECs hate so badly? Not even close. To broadly paraphrase Bertrand Russell - 'extraordinary claims require extraordinary evidence'. The extraordinary claim is that MLP 11-II-21-3 disproves whale evolution. Here are my conclusions/responses to this absurdity:

    1) MLP 11-II-21-3 is from a stratigraphic unit with two slightly offset suites of dates, one of which seems to be affected by reworking. 

    2) On a smell test level, which is more likely: that a single specimen destroys everything we know about the chronology of whale evolution, but *only* if you ignore half of the available dating? Or, when you look closely at the data and realize one dating method has some problems, and that the other dating method somehow actually does line up OK with the rest of the basilosaurid fossil record?

    3) Even if both sets of dates were not subjected to reworking, they're not that far off: we're talking about a difference of 4-5 million years. It would certainly telescope whale evolution further, and whale evolution is already quite rapid.

    4) This is so laughably far from finding a "rabbit in the Cambrian" that this point is not really worth considering further - other than, if genuine, all it really tells us is that we need to go out and find some more whales and refine dates for existing discoveries. We may find older examples of protocetids that could accommodate an older maximum age for Basilosauridae.

    5) While not 100% precise, the ability of these two methods to provide ballpark ages that are actually reasonably close tells me that the science is *working* rather than failing. You need to step back a moment and give it a big picture look: if these YEC jerks were right, why would the two methods independently give ages only a few million years off? Why wouldn't one say "Triassic" and the other "Pleistocene"? In my opinion, it's because the methods work, but sometimes there are wrinkles. Which doesn't mean that the "evilutionists" are lying: we're being totally honest and transparent, and these YEC folks are going apeshit trying to make mountains out of methodological molehills. 

    6) I know that these YEC folks know exactly what they're doing - and they're doing it because they're shameless charlatans on a crusade against secularism and science in the name of transforming America into a theocracy. They've said it themselves, no need to take my word for it (e.g. the wedge document/strategy). Their intention is to sow confusion about science and give just enough ammunition to scientifically uninformed Christian folks who may be honestly looking for the truth - and being directed to crazy right wing pseudoscientific garbage. So remember, YECs writing this tripe know what they're writing is carefully cultivated garbage. 

    7) That brings us to the moral of the story. Scientists: be careful, and don't step too far away from the data. We're all desperately searching for amazing fossils that make it into high profile journals - don't strain credulity and ruin your credibility. Competitive science needs to calm down every now and then, and to paraphrase Ferris Bueller - science "moves pretty fast. If you don't stop and look around once in a while, you could miss it."

References/Further Reading

Buono et al., 2016:  https://bioone.org/journals/ameghiniana/volume-53/issue-3/AMGH.02.02.2016.2922/Eocene-Basilosaurid-Whales-from-the-La-Meseta-Formation-Marambio-Seymour/10.5710/AMGH.02.02.2016.2922.short

Buono et al., 2019: http://www.aps-polar.org/paper/2019/30/03/A190617000001

Douglas et al., 2014: https://www.pnas.org/content/111/18/6582

Fordyce and Marx, 2018: https://www.sciencedirect.com/science/article/pii/S096098221830455X

Ivany et al. 2008: https://pubs.geoscienceworld.org/gsa/gsabulletin/article/120/5-6/659/2280/Eocene-climate-record-of-a-high-southern-latitude

Jadwiszczak and Mörs, 2017. https://polarresearch.net/index.php/polar/article/view/2635

Lastly, the wedge document - National Center for Science Education: https://ncse.ngo/wedge-document