Showing posts with label paleontology. Show all posts
Showing posts with label paleontology. Show all posts

Saturday, October 7, 2023

Empty Skepticism at the Discovery Institute

What makes a hypothesis scientific, vs a just-so story, or a religious fixation?

"Intelligent" design has fallen on hard times, after a series of court cases determined that it was, after all, a religious idea and could not be foisted on unsuspecting schoolchildren, at least in state schools and under state curricula. But the very fact of religious motivation leads to its persistence in the face of derision, evidence, and apathy. The Discovery Institute, (which, paranthetically, does not make any discoveries), remains the vanguard of intelligent design, promoting "skepticism", god, alternative evolutionary theories, and, due to the paucity of ways to attack evolution, tangential right-wingery such as anti-vaccine agitation. By far their most interesting author is Günter Bechly, who delves into the paleontological record to heap scorn on other paleontologists and thereby make room for the unmentioned alternative hypothesis ... which is god.

A recent post discussed the twists and turns of ichthyosaur evolution. Or should we say biological change through time, with unknown causes? Ichthyosaurs flourished from about 250 million years ago (mya) to 100 mya, with the last representatives dated to 90 mya. They were the reptile analogs of whales and dophins, functioning as apex predators in the ocean. They were done in by various climate crises well-prior to the cometary impact that ended the Cretaceous and the reign of dinosaurs in general.

Bechly raises two significant points. First is the uncertain origins of Ichthyosaurs. As is typical with dramatic evolutionary transitions like that from land to water in whales, the time line is compressed, since there are a lot of adaptations that are desirable for the new environment that might have been partially pre-figured, but get fleshed out extensively with the new ecological role and lifestyle. Selection is presumably intense and transitional fossils are hard to find. This was true for whales, though beautiful transitional fossils have been found more recently. And apparently this is true for the Ichthyosaurs as well, where none have been found, yet. There is added drama stemming from the time of origin, which is right after the Permian exinction, perhaps the greatest known extinction event in the history of the biosphere. Radiations after significant extinction events tend to be rapid, with few transitional fossils, for the same reason of new niches opening and selection operating rapidly.

Ichthyosaur

Bechly and colleagues frequently make hay out of gaps in the fossil record, arguing that something (we decline to be more specific!) else needs to be invoked to explain such lack of evidence. It is a classic god of the gaps argument. But since the fossils are never out of sequence, and we are always looking at millions of years of time going by with even the slimmest layers of rock, this is hardly a compelling argument. One thing that we learned from Darwin's finches, and the whole argument around punctuated equilibrium, is that evolution is typically slow because selection is typically not directional but conservative. But when selection is directional, evolution by natural selection can be startlingly fast. This is an argument made very explicitly by Darwin through his lengthy discussions of domestic species, whose changes are, in geological terms, instant. 

But Bechly makes an additional interesting argument- that a specific hypothesis made about ichthyosaurs is a just-so story, a sort of hypothesis that evolutionary biologists are very prone to make. Quite a few fossils have been found of ichthyosaurs giving birth, and many of them find that the baby comes out not only live (not as an egg, as is usual with reptiles), but tail-first. Thus some scientists have made the argument that each are adaptations to aquatic birth, allowing the baby to be fully borne before starting to breathe. Yet Bechly cites a more recent scientific review of the fossil record that observes that tail-first birth is far from universal, and does not follow any particular phylogenetic pattern, suggesting that it is far from necessary for aquatic birth, and thus is unlikely to be, to any significant extent, an adaptation. 

Ha! Just another story of scientists making up fairy tales and passing them off as "science" and "evolutionary hypotheses", right?  

"Evolutionary biology again and again proves to be an enterprise in imaginative story-telling rather than hard science. But when intelligent design theorists question the Darwinist paradigm based on empirical data and a rational inference to the best explanation, they are accused of being science deniers. Which science?" ... "And we will not let Darwinists get away with a dishonest appeal to the progress of science when they simply rewrite their stories every time conflicting evidence can no longer be denied."

Well, that certainly is a damning indictment. Trial and sentencing to follow! But let's think a little more about what makes an explanation and a hypothesis, on the scientific, that is to say, empirical, level. Hypotheses are always speculative. That is the whole point. They try to connect observations with some rational or empirically supported underlying mechanism / process to account for (that is, explain) what is observed. Thus the idea that aquatic birth presents a problem for mammals who have to breathe represents a reasonable subject for an hypothesis. Whether headfirst or tailfirst, the baby needs to get to the surface post haste, as soon as its breathing reflex kicks in. While the direction of birth doesn't seem to the uninitiated (and now, apparently to experts with further data at hand) to make much difference, thinking it does is a reasonable hypothesis, based on obvious geometric arguments and biological assumptions, that it is possible that the breathing reflex is tied to emergence of the head during birth, in which case coming out tailfirst might delay slightly the time it takes between needing to breathe and being able to breathe. 

This argument combines a lot of known factors- the geometry of birth, the necessity of breathing, the phenomenon of the breathing reflex initiating in all mammals very soon after birth, by mechanisms that doubtless are not entirely known, but at the same time clearly the subject of evolutionary tuning. And also the paleontological record. Good or bad, the hypothesis is based on empirical data. What characterizes science is that it follows a disciplined road from one empirically supported milestone to the next, using hypotheses about underlying mechanisms, whether visible or not, which abide by all the known/empirical mechanisms. Magic is only allowed if you know what is going on behind the curtain. Unknown mechanisms can be invoked, but then immediately become subjects of further investigation, not of protective adulation and blind worship.

In contrast, the intelligent design hypothesis, implicit here but clear enough, is singularly lacking in any data at all. It is not founded on anything other than the sentiment that what has clearly happened over the long course of the fossil record operates by unknown mechanisms, by god operating pervasively to carry out the entire program of biological evolution, not by natural selection (a visible and documented natural process) but by something else, which its proponents have never been able to demonstrate in the least degree, on short time scales or long. Faith does not, on its own, warrant novel empirical mechanisms, and nor does skeptical disbelief warrant them. Nor does one poor, but properly founded, hypothesis that is later superceded by more careful analysis of the data impugn the process of science generally or the style of evolutionary thinking specifically.

Imagine, for example, if our justice system operated at this intellectual level. When investigating crimes, police could say that, if the causes were not immediately obvious, an unnamed intelligent designer was responsible, and leave it there. No cold cases, no presumption of usual natural causality, no dogged pursuit of "the truth" by telegenic detectives. Faith alone would furnish the knowledge that the author of all has (inscrutibly) rendered "his" judgement. It would surely be a convenient out for an over-burdened and under-educated police force!

Evolution by natural selection requires a huge amount of extrapolation from what we know about short time scales and existing biology to the billions of years of life that preceeded us. On the other hand, intelligent design requires extrapolation from nothing at all- from the incredibly persistent belief in god, religion, and the rest of the theological ball of wax not one element of which has ever been pinned down to an empirical fact. Believers take the opposite view solely because religious propaganda has ceaselessly drilled the idea that god is real and "omnipotent" and all-good, and whatever else wonderful, as a matter of faith. With this kind of training, then yes, "intelligent" design makes all kinds of sense. Otherwise not. Charles Darwin's original hypothesis was so brilliant because it drew on known facts and mechanisms to account (with suitable imagination and extrapolation) for the heretofore mysterious history of biology, with its painfully slow yet inexorable evolution from one species to another, one epoch to another. Denying that one has that imagination is a statement about one's intelligence, no matter how it was designed.

  • Only god can give us virulent viruses.
  • The priest who knew it so well, long ago.
  • A wonderful Native American Film- Dance me outside.
  • With a wonderful soundtrack, including NDN Kars.
  • We need to come clean on Taiwan.
  • Appeasers, cranks, and fascist wannabes.
  • Vaccines for poor people are not profitable.
  • California is dumbing down math, and that will not help any demographic.

Saturday, December 31, 2022

Hand-Waving to God

A decade on, the Discovery Institute is still cranking out skepticism, diversion, and obfuscation.

A post a couple of weeks ago mentioned that the Discovery Institute offered a knowledgeable critique of the lineages of the Ediacaran fauna. They have raised their scientific game significantly, and so I wanted to review what they are doing these days, focusing on two of their most recent papers. The Discovery Institute has a lineage of its own, from creationism. It has adapted to the derision that entailed, by retreating to "intelligent design", which is creationism without naming the creators, nailing down the schedule of creation, or providing any detail of how and from where creation operates. Their review of the Ediacaran fauna raised some highly skeptical points about whether these organisms were animals or not. Particularly, they suggested that cholesterol is not really restricted to animals, so the chemical traces of cholesterol that were so clearly found in the Dickinsonia fossil layers might not really mean that these were animals- they might also be unusual protists of gigantic size, or odd plant forms, etc. While the critique is not unreasonable, it does not alter the balance of the evidence which does indeed point to an animal affinity. These fauna are so primitive and distant that it is fair to say that we can not be sure, and particularly we can not be sure that they had any direct ancestral relationship to any later organisms of the ensuing Cambrian period, when recognizable animals emerged.

Fair enough. But what of their larger point? The Discovery Institute is trying to make the point, I believe, about the sudden-ness of early Cambrian evolution of animals, and thus its implausibility under conventional evolutionary theory. But we are traversing tens of millions of years through these intervals, which is a long time, even in evolutionary terms. Secondly, the Ediacaran period, though now represented by several exquisite fossil beds, spanned a hundred million years and is still far from completely characterized paleontologically, even supposing that early true animals would have fossilized, rather than being infinitesimal and very soft-bodied. So the Cambrian biota could easily have predecessors in the Ediacaran that have or have not yet been observed- it is as yet not easy to say. But what we can not claim is the negative, that no predecessors existed before some time X- say the 540 MYA point at the base of the Cambrian. So the implication that the Discovery Institute is attempting to suggest has very little merit, particularly since everything that they themselves cite about the molecular and paleontological sequence is so clearly progressive and in proper time sequence, in complete accord with the overall theory of evolution.

For we should always keep in mind that an intelligent designer has a free hand, and can make all of life in a day (or in six, if absolutely needed). The fact that this designer works in the shadows of slightly altered mutation rates, or in a few million years rather than twenty million, and never puts fossils out of sequence in the sedimentary record, is an acknowledgement that this designer is a bit dull, and bears a strong resemblence to evolution by natural selection. To put it in psychological terms, the institute is in the "negotiation" stage of grief- over the death of god.

Saturday, December 17, 2022

The Pillow Creatures That Time Forgot

Did the Ediacaran fauna lead to anything else, or was it a dead end?

While to a molecular biologist, the evolution of the eukaryotic cell is probably the greatest watershed event after the advent of life itself, most others would probably go with the rise of animals and plants, after about three billion years of exclusively microbial life. This event is commonly located at the base of the Cambrian, (i.e. the Cambrian explosion), which is where the fossils that Darwin and his contemporaries were familiar with began, about 540 million years ago. Darwin was puzzled by this sudden start of the fossil record, from apparently nothing, and presciently held (as he did in the case of the apparent age of the sun) that the data were faulty, and that the ancient character of life on earth would leave other traces much farther back in time.

That has indeed proved to be the case. There are signs of microbial life going back over three billion years, and whole geologies in the subsequent time dependent on its activity, such as the banded iron formations prevalent around two billion years ago that testify to the slow oxygenation of the oceans by photosynthesizing microbes. And there are also signs of animal life prior to the Cambrian, going back roughly to 600 million years ago that have turned up, after much deeper investigations of the fossil record. This immediately pre-Cambrian period is labeled the Ediacaran, for one of its fossil-bearing sites in Australia. A recent paper looked over this whole period to ask whether the evolution of proto-animals during this time was a steady process, or punctuated by mass extinction event(s). They conclude that, despite the patchy record, there is enough to say that there was a steady (if extremely slow) march of ecological diversification and specialization through the time, until the evolution of true animals in the Cambrian literally ate up all the Ediacaran fauna. 

Fossil impression of Dickinsonia, with trailing impressions that some think might be a trail from movement. Or perhaps just friends in the neighborhood.
 
For the difference between the Ediacaran fauna and that of the Cambrian is stark. The Ediacaran fauna is beautiful, but simple. There are no backbones, no sensory organs. No mouth, no limbs, no head. In developmental terms, they seem to have had only two embryological cell layers, rather than our three, which makes all the difference in terms of complexity. How they ate remains a mystery, but they are assumed to have simply osmosed nutrients from their environment, thanks to their apparently flat forms. A bit like sponges today. As they were the most complex animals at the time, (and some were large, up to 2 meters long), they may have had an easy time of it, simply plopping themselves on top of rich microbial mats, oozing with biofilms and other nutrients.

The paper provides a schematic view of the ecology at single locations, and also of longer-term evolution, from a sequence of views (i.e. fossils) obtained from different locations around the world of roughly ten million year intervals through the Ediacaran. One noticeable trend is the increasing development or prevalence of taller fern-like forms that stick up into the water over time, versus the flatter bottom-dwelling forms. This may reflect some degree of competition, perhaps after the bottom microbial mats have been over-"grazed". A second trend is towards slightly more complexity at the end of the period, with one very small form (form C (a) in the image below) even marked by shell remains, though what its animal inhabitant looked like is unknown. 

Schematic representation of putative animals observed during the Ediacaran epoch, from early, (A, ~570 MYA, Avalon assemblage), middle, (B, ~554 MYA, White River and other assemblages), and late (C, ~545 MYA, Nama assemblage). The A panel is also differentiated by successional forms from early to mature ecosystems, while the C panel is differentiated by ocean depth, from shallow to deep. The persistence of these forms is quite impressive overall, as is their common simplicity. But lurking somewhere among them are the makings of far more complicated animals.

Very few of these organisms have been linked to actual animals of later epochs, so virtually all of them seem to have been superceded by the wholly different Cambrian fauna- much of which itself remains perplexing. One remarkable study used mass-spec chemical analysis on some Dickinsonia fossils from the late Ediacaran to determine that they bore specific traces of cholesterol, marking them as probable animals, rather than overgrown protists or seaweed. But beyond that, there is little that can be said. (Note a very critical and informed review of all this from the Discovery Institute, of all places.) Their preservation is often remarkable, considering the age involved, and they clearly form the sole fauna known from pre-Cambrian times. 

But the core question of how the Cambrian (and later) animals came to be remains uncertain, at least as far as the fossil record is concerned. One relevant observation is that there is no sign of burrowing through the sediments of the Ediacaran epoch. So the appearance of more complex animals, while it surely had some kind of precedent deep in the Ediacaran, or even before, did not make itself felt in any macroscopic way then. It is evident that once the triploblastic developmental paradigm arose, out of the various geologic upheavals that occurred at the bases of both the Ediacaran and the Cambrian, its new design including mouths, eyes, spines, bones, plates, limbs, guts, and all the rest that we are now so very familiar with, utterly over-ran everything that had gone before.

Some more fine fossils from Canada, ~ 580 MYA.


  • A video tour of some of the Avalon fauna.
  • An excellent BBC podcast on the Ediacaran.
  • We need to measure the economy differently.
  • Deep dive on the costs of foreign debt.
  • Now I know why chemotherapy is so horrible.
  • Waste on an epic scale.
  • The problem was not the raids, but the terrible intelligence... by our intelligence agency.

Saturday, December 4, 2021

Supergroups in Search of Their Roots

The early stages of eukaryotic evolution are proving hard to reconstruct.

There is normal evolution, and then there are great evolutionary transitions. Not to say that the latter don't obey the principles of normal evolution, but they go by so fast, and render so many transitional forms obsolete along the way, that there is little record left of what happened. Among those great transitions are the origin of life itself, the origin of humans, and the origin of eukaryotes. We are slowly piecing together human evolution, from the exceedingly rare fossils of intermediate forms and branch off-shoots. But looking at the current world, we are the lone hominin, having displaced or killed off all competitors and predecessors to stand alone atop the lineage of primates, and over the biosphere generally. Human evolution didn't violate any natural laws, but it seems to have operated under uniquely directional selection, especially for intelligence and social sophistication, which led to a sort of arms race of rapid evolution that laid the groundwork for an exponential rate in the invention of technologies and collective social forms over the last million years.

Similarly, it is clear that however the origin of life started out, it was a very humble affair, with each innovation quickly displacing its progenitors, just as the early cell phones came out in quick succession, until a technological plateau was reached from which further development was / is less obvious. While the origin and success of eukaryotes did not erase the prokaryotic kingdoms from which they sprang, it does seem to have erased the early stages of its own development, to the point that those stages are very hard to reconstruct, especially given the revolutionary and multifarious nature of their innovations.

Eukaryotes differ from prokaryotes in possessing: nuclei and a nuclear membrane with specialized pores; mitochondria descended from a separate bacterial ancestor (and photosynthetic plastids descended from yet other bacterial ancestors in some cases); sex and meiosis; greater size by several orders of magnitude; phagocytosis by amoeboid cells; internal membrane organelles like golgi, peroxisomes, lysosomes, endocytic and exocytic vesicles; cyclins that run the cell cycle; microtubules that participate in the cell cycle, cytoskeleton, and cilia; cilia, as distinct from flagella; an active actin-based cytoskeleton, with novel motor proteins; a greatly elaborated transcriptional apparatus with modular enhancers and novel classes of transcription regulators; histones; mRNA splicing and introns; nucleolus and small nucleolar RNAs; telomeres on linear chromosomes; a significant increment in the size of both ribosomal subunits. Indeed, the closer one looks at the molecular landscape, the more differences accumulate. This was quite simply a quantum leap in cellular organization, which happened sometime between 1.8 and 3 billion years ago. Indeed, eukaryotes are not just the McMansions of the microbial world, but the Downton Abbeys- with dutiful servants and complex and luxurious internal economies that prokaryotic cells couldn't conceive of.

Major lineages of eukaryotes are traced back to their origins in a molecular-based phylogeny. Animals (and fungi!) are in the Opisthokonta, plants in the Chloroplastida. So many groups connect right to the "root" of this tree that there is little way to figure out which came first. Also, the dashed lines indicate uncertainty about those orderings/rootings as well, which leaves a great deal of early eukaryotic evolution obscure. Some abbreviations / links are- CRuMs: collodictyonids (syn. diphylleids) + rigifilida + mantamonas; excavates, hemimastigophora, haptista, TSAR:  telonemids, stramenopiles, alveolates, and rhizaria.


A recent paper recounts the current phylogenetic state of affairs, and a variety of other papers over the last decade delve into the many questions surrounding eukaryotic origins. While molecular phylogenies have improved tremendously with the advent of faster, whole-genome sequencing and the continued collection of obscure single-celled eukaryotes, (aka protists), the latest phylogeny, as shown above, remains inconclusive. The deepest root is both uncertain with regard to its bacterial progenitor, and to which current eukaryotes bear the closest relation. There are occasional fossil kelps, algae, and other biochemical traces back to 2.0 to 2.7 billion years, (though some do not put the origin earlier than 1.8 billion years) but these have not been able to shed any light on the order of events either.

Nevertheless, the field can agree on a few ideas. One is that the assimilation of mitochondria (whether willing or unwilling) is perhaps the dominant event in the sequence. That doesn't mean it was necessarily the first event, but means that it created a variety of conditions that led to a cascade of other consequences and features. The energy mitochondria provided enabled large cell sizes and the accumulation of a whole new household full of junk, like lipids in several new membrane compartments. The genome that they contributed brought in thousands of new genes, including introns. 

Secondly, the loss of cell walls and the adoption of amoeboid carnivory is likely one of the first events in the evolutionary sequence. Shedding the obligatory cell wall that all bacteria have necessitates a cytoskeleton of some kind, and it is also conducive to the engulfment of the proto-mitochondrion. For while complicated co-symbiotic metabolic arguments have been devised to explain why these two cells may have engaged in a long-term mutual relationship long before their ultimate consumation, the most convenient hypothesis for assimilation remains the simplest- that one engulfed the other, in a meal that lasted well over a billion years.

Thirdly, the question of what the progenitor cell was has been refined somewhat. One of the most intriguing findings of the last half-century of biology was the discovery of archaebacteria (also called archaea)- a whole new kingdom of bacteria characterized by their tendency to occupy extreme habitats, their clear separation from bacteria by chemical and genetic criteria, and also their close relationship to eukaryotes, especially what is presumed to be the original host genome. Many proposals have been made, (including that archaea are the original cell, preceding other bacteria), but the best one currently is that archaea split from the rest of bacteria rather late, after which eukaryotes split off from archaea, thus making the latter two sister groups. This explains the many common traits they share, while allowing significant divergence, plus the incorporation of many bacterial features into eukaryotes, either through the original lineage, or by later transfer from the proto-mitochondrion. So here at last is one lineage that survived out of the gradual development of eukaryotes- the archaea, though one wouldn't guess it from looking at them. It took analysis at the molecular level to even know that archaea existed, let alone that they are the last extant eukaryotic sister group.

comically overstuffed figure from an argument for the late development of archaebacteria out of pre-existing bacteria (prokaryotes), with subsequent split and diversification of eukaryotes out of a proto-archaeal lineage. Many key molecular and physiological characters are mentioned.

Lastly, surveying the various outlying protist lineages for clues about which might hearken back to primitive eukaryotic forms, one research group suggests that the collodictyonids might fit the bill. Being an ancient lineage means that it is lonesome, without a large family of evolutionary development to show diversification and change. It also means that in molecular terms, it is highly distinct, branching deeply from all other groups. Whether that all means that it resembles an ancient / early form of the eukaryotic cell, or went its own way on a unique evolutionary trajectory, is difficult to say. For each trait, (including sequence traits), a phylogenetic analysis is done to figure out whether it is differential- shared with some other lineages but not all- whether those without the trait lost it at some later point, or whether it was gained by a sub-group. After analyzing enough such traits, one can make a statement about the overall picture, and thus the "ancient-ness", of an organism.

Is anything special about collodictyon? Not really. It is predatory, and has four flagella and a feeding groove, which functions as a sort of mouth. It can make pseudopods, has normal microtubule organizing centers for its flagella, and generally all the accoutrements of a eukaryotic cell. It lacks nothing, and thus may be an early branching eukaryote, but is not in any way a transitional form.

An unassuming protist (collodictyon) as possible representative of early eukaryotes. Its cilia are numbered.


At this point, we are left still peering darkly into the past, though obscure living protists and their molecular fossils, trying to figure out what happened when they split from the bacteria and archaea. A tremendous amount happened, but little record survives of the path along the way. That tends to be characteristic of the most momentous evolutionary events, which cause internal and external cataclysms, (including the opening of whole new lifestyles to exploit), that necessitate a rapid dynamic of further adaptation before their descendents achieve a stable and successful state sufficient to ride out the ensuing billion or more years ... before we come on the scene with the ability and interest to contemplate what went before.


  • Red regions have three times the death rates from Covid as blue regions. Will that change electoral math?
  • Annals of secession, cont.
  • Sad spectacle at the court.
  • Analysis of how the energy transition might go. Again, a carbon tax would help.

Saturday, October 27, 2018

Native Americans and Genetics

A fraught story.

The recent profusion of DNA studies of human lineages have clarified a lot about human history- where we came from and where we have travelled over the millennia. All this depends on samples from native populations- the ones we came from. It is only apparent that we came out of Africa if there are stable African populations that constitute the source and retain the vast diversity of our oldest homeland. But what if the natives do not want to be sampled? What if they are woke to the colonialist and genocidal legacy of the science / scientists doing the sampling, and want no part of it?

That is what happened, in part, in the recent flap over Elizabeth Warren's announcement of Native American heritage. Native South or Central American, that is. As told by a couple of experts, the lab that performed the analysis could not get permission to use North American samples, so used DNA from populations elsewhere in the Americas. Since Warren is herself from North America, indeed Oklahoma, and since the history of native peoples throughout the Americas is known to be relatively recent, expanding over last 15,000 years at the outside, the method is clearly valid in inferring, indirectly, some North American native ancestry for Warren.


So why the guff she caught from the Native American community? It was quite puzzling to hear their representatives trying their hardest to pour cold water on her claim, as though they were getting talking points from the FOX propaganda channel. Despite her not claiming to be a tribal member or wanting to be, they trotted out their arcane rules for membership, which certainly wouldn't accept anything so white as DNA testing. But lo and behold the tribe- the Cherokee in this case- use fractional blood relations determined from a list compiled by white people of the US government back in 1902. There are no good answers here, after half a millenium of disposession, destruction and abuse, but denying the obvious is not one of them.

The deeper issue is the appropriation and objectification of Native Americans and their culture by others, from here to Germany and beyond. Playing cowboys and indians, putting on Karl May dramas, naming sports franchises ... we have a very fraught relationship of romanticization and trivialization, little of which has anything to do with real Native Americans, particularly those living today who wish to be custodians of their own culture even while still suffering under the various debilities of their treatment by the dominant culture. I was part of this myself, in the Boy Scouts, which still play at being Indians, mortifyingly enough. Then the history of eugenics, and the plundering of native treasures, archeology, and burials, etc. has put so-called scientists in a particularly bad light.

This forms the backdrop of the notorious fate of the Kennewick man, an archeological find that led to bitter, drawn-out controversy. The almost complete skeleton, found in Washington state at the Columbia river, was 9,000 years old, and by morphology was more similar to other peoples such as the Jomon aboriginal people of Japan than native Americans. Ironically, it was DNA testing that confirmed affinity with Native Americans after all, after which the remains were given to the local Native American nations, including the Umatilla, which buried them at an unpublished location. From the native perspective, this fed into the narrative that their history is eternal and static, meaning that any pre-Columbian artifacts or remains found on what is currently their land is associated with their culture in some way, despite the thousands of years that may have passed and migrations that may have happened, and thus presents the right of possession and cultural use. One gets the distinct impression that Native Americans do not really want to know their own deep history, preferring a religious narrative of having been forever in the Americas, instead of having wandered in a few thousand years before the Europeans did.

From a scientific perspective, the episode was a travesty of political correctness, as a 9,000 year old skeleton could have no imaginable cultural connection to the current inhabitants of the area, while being an inestimably rich source of knowlege about this early post-glacial time of North American settlement. This antiscience attitude is perhaps a fair harvest for all the harms and hurts inflicted over the last few centuries, science being one of the most domineering and distinctive expressions of Western culture. Still, the loss to general knowledge rankles.

One Cherokee representative spoke of how irritating it is to repeatedly meet people who claimed to be part Cherokee, expecting some positive pat on the head. But those people wouldn't dream of moving back to the reservation, or taking part in Cherokee culture, as is undoubtedly true of Elizabeth Warren as well. It is a "heritage" without practice and of dubious significance. Nor may they be alive to the sense of loss and injury this represents, as such blood mixing may not have been voluntary, but the result of rape and rapine of various sorts.

Nevertheless, it would seem advisable for Native Americans to get off their metaphorical high horses and be more welcoming to the diversity that exists in the US. Even if the pride that Warren feels in her minuscule Native American ancestry is somewhat false, romaticized, and lacking in practice/practical effect, it is still pride, unmistakably, rather than its opposite. Citizens of the US generally take pride in vibrant Native American cultures and take steps through the government to help them, via direct aid, educational assistance, gambling concessions, and other benefits, after and in compensation for, the deeper history of genocide, reservation confinement, ethnic cleansing, and cultural extermination. The relationship is surely a difficult, guilty one. No one wants to alter the definitions that American Indian nations have developed for their formal membership. But their wider membership of genetic descendants is also a positive asset, in pursuit, not of assimilation, but of friendly relations with the wider, shared culture.

Saturday, December 23, 2017

Pterosaurs

Yes, they really did fly- the amazing world of pterosaurs.

National Geographic recently had a beautiful spread on pterosaurs- those ungainly creatures that nobody thought could fly, until, apparently, we realized they really did fly. Indeed, they ruled the skies for over 160 million years- far longer than birds have. They operated a good deal like bats, with wings of membrane spread between modified fingers, which also stretched back to their legs. But a crucial difference is that, unlike bats, pterosaurs used only a modified fifth finger to carry the outside of the wing. The other fingers made up a strong hand about mid-wing that could be used for walking and lifting off. Thus pterosaurs were much better walkers than bats, and could also lift off from a standstill more effectively.
Reconstruction of the largest known pterosaur, Quetzalcoatlus, as tall as a giraffe, from the late Cretaceous.

What remains astonishing is how much apparent weight these animals carried, especially in front. The largest known pterosaur, Quetzalcoatlus, weighed about 440 pounds and had an enormous head. The head may have been quite thin, but, with neck, takes up roughly half its length. All pterosaurs tended to have large heads, and frequently added remarkable crests or horns, as if snubbing their beaks at aerodynamics. But looks are deceiving, since, like the toucan's bill, pterosaur crests and bones are hollow, very thin (1 mm), and thus were very light. The classic Pteranodon, with a crest almost as long as its enormous bill, is estimated to have weighed only 25 pounds, easily carried by a wingspan of 25 feet. Whether they could have carried off the hapless Zara Young is another matter.

Beautiful specimen of Rhamphorhynchus, from the Jurassic, with impressions of wing and tail membranes.

What is almost as compelling as the fossils of pterosaur bones are fossilized trackways, which show them in action. Over thirty walking tracks have been found, and one paper even describes what the authors interpret as a landing track. Typical pterosaur walking tracks show the heavier hind feet on the inside, and the wing/hands much more lightly on the outside. At each stride, the rear feet pull up roughly parallel to where the wing/hands have just left (b, in the figure). In these novel tracks, which begin abruptly, there are only hind feet for two strides, before the wing/hands appear. Secondly, the first hind feet tracks have elongated claw marks. Thirdly, the first two or three hind foot track sets are parallel and show a very short stride, different from typical walking gaits, of which the rest of this track is an example. These characteristics all lead to the idea that this pterosaur was landing, and hopped a couple of times with both feet before transitioning to a walking gait.

150 million year-old tracks from France. Top is an interpretation of the middle tracks, as evidence of landing. Below is a typical walking sequence and interpretation from the same location / source. The scale bar at bottom is 10 cm, so this pterosaur was relatively small.

This is not new work, dating from 2009, but the message is still a little hard to wrap one's head around- that tens of millions of years went by with these incredible creatures carrying on the battle for survival, with great success, and high style as well.

Nyctosaurus gracilis, reconstructed, from the late Cretaceous.


  • A dumber nation- Thanks, Scott Pruitt!
  • Xmas notes on another flying life form.