Anthropologists at the University of Utah and the Natural History Museum of Utah have traced the anthropogenic spread and cultivation of a relative of the potato, Solanum jamesii (the Four Corners potato). Their findings are published in PLOS ONE. This plant has been a culinary, medicinally and culturally important food crop across the Colorado Plateau for millennia.
Until now, despite its long history, the extent to which indigenous people domesticated S. jamesii has been unknown. Genetic evidence has shown that it had been transported and cultivated far from its natural range and had acquired frost resistance, longer dormancy and sprouting resilience, all of which made it more suitable for cultivation in its anthropogenic range. The Utah team have now shown how it arrived on the Colorado Plateau from its origins in the south-west USA, probably through a trading network.
A problem which I have found impossible to get a creationist to address without them running for the bolt-hole of ‘mysterious ways’ is the fact that, with only a very few exceptions, every domesticated animal and cultivated plant has been considerably improved on the wild stock and is always the result of a human-mediated evolutionary process. The result is often almost unrecognisable as the same species as their wild ancestor.
Yet according to the Bible, all animals and plants were created for the sole benefit of humankind by a supposedly omnipotent, omniscient god. Had that been so, we could expect them to have been created fit for purpose and perfectly suited to the uses to which we put them. The fact that we have had to adapt them and change them so drastically to make them fit for purpose gives the lie to claims of intelligent design by an omniscient designer.
This relative of the potato therefore serves as an illustration of how humans, unwittingly or otherwise, have modified and changed the distribution of cultivated plants by inadvertently mimicking the process of evolution — mutation → selection → reproduction. S. jamesii is native to the Mogollon Rim, a region spanning south-central Arizona and into the Mogollon Mountains of New Mexico. The researchers were able to build a picture of how this plant was transported from there to the Four Corners region of southern Utah, south-west Colorado and north-west New Mexico by extracting the characteristic starch granules embedded in the stone tools used to process the tubers, recovered from 14 archaeological sites within and beyond the tuber’s natural range.
This research adds to the growing body of evidence that indigenous people in the south-western USA actively cultivated crops of their own and did not just acquire them from other peoples. It had previously been believed that they relied primarily on crops domesticated in Mesoamerica, such as maize, beans or squash. It also adds another species to the long list of plants and animals that have had to be modified from their wild type, and for which creationists are at a loss to explain why their supposed omniscient designer god did not do a very good job of it to begin with.
Top: Multiple views of MLP-3000-1, the newly discovered Paranthropus partial left mandible and molar crown. Bottom: MLP-3000-1 in side-by-side comparison with mandible fossils from other species — Australopithecus afarensis (A.L. 266-1), Paranthropus aethiopicus (OMO-57/4-1968-41 and OMO-18-1967-18), and early Homo (LD 350-1).
Alemseged Research Group
Two fragments of the newly discovered mandible specimen in the location they were originally found.
Research published two days ago in Nature by a team led by University of Chicago paleoanthropologist Professor Zeresenay Alemseged will dismay and delight creationists in about equal measure — especially those who manage to rationalise a fossil dating from about 2.6 million years before they believe Earth and everything on it was created — because it shows that scientists were wrong about something.
It is the news that the jawbone of an archaic hominin, Paranthropus, has been found in Ethiopia some 200 miles further north than the previously believed northern limit of these hominins.
Normally, to a binary-thinking creationist, science being wrong about even the most minor and unimportant detail is “proof” that science is wrong about everything. This childish belief probably stems from them having a single source-book which has been deemed to be inerrant, so even the slightest falsehood in it renders that claim untenable. They assume it is the same with science: that what scientists believe comes from supposedly inerrant textbooks written by “prophets” such as Charles Darwin, serving as the source-books from which all scientists get their information. So, if scientists are ever wrong, all the books from the science libraries of the world can be thrown in the waste bin, leaving creationism’s book of “inerrant” origin myths as the winner.
What they find hard to comprehend, apparently, is that scientific knowledge is cumulative, with current thinking always provisional, pending further confirmation or in need of revision in the light of new information, and that facts are neutral in any dispute, so can be objective referees. They fail to realise that because science works this way, scientists from all over the world will eventually converge on a single answer. Religions, by contrast, because they are not based on evidence but on the tenuous thread of interpretation of an ancient book which itself presents no evidence for its claims, continue to diversify into ever smaller sects, each claiming to have the one true answer but having no evidence to referee the dispute.
But of course, in the best scientific tradition, this jawbone simply adds richness to the hominin evolutionary story and raises the possibility that Paranthropus, like Australopithecus and Homo, was present in the Afar region of Ethiopia. And that opens up the intriguing possibility — given the propensity of hominins to diverge and then hybridise — that modern Homo sapiens could have some Paranthropus ancestry.
Paranthropus^ the “robust” hominins.
Paranthropus is an extinct genus of hominins that lived in eastern and southern Africa between about 2.7 and 1.2 million years ago. It is best known for its so-called “robust” anatomy — not in the sense of being especially large or powerful overall, but because of its massively built jaws, large molar teeth, thick enamel, and prominent cheekbones. Many species also had a sagittal crest (a ridge along the top of the skull) for the attachment of powerful chewing muscles.
These hominins were specialised for processing tough, fibrous, or gritty foods such as roots, tubers, sedges, and possibly hard seeds. Stable-isotope and microwear studies show that different species exploited different diets, but all appear adapted for heavy chewing.
Despite their imposing jaws, Paranthropus species had relatively small brains (roughly 400–550 cm³), similar to or only slightly larger than those of Australopithecus.
Where Paranthropus sits in the hominin family tree
Paranthropus is generally regarded as a specialised side-branch of the hominin lineage rather than a direct ancestor of modern humans. Most palaeoanthropologists think it diverged from an australopithecine-like ancestor sometime after about 3 million years ago, around the same time that the genus Homo was emerging.
In simplified terms:
An australopithecine ancestor gave rise to at least two major lineages:
one leading to Homo (eventually Homo sapiens),
another leading to the robust, chewing-adapted Paranthropus.
This makes Paranthropus a cousin lineage rather than a direct ancestor of modern humans.
However, the family tree is not a neat, branching diagram. The early hominin record shows multiple contemporaneous species living side by side, sometimes in the same regions. Genetic evidence from later hominins (such as Neanderthals and Denisovans) shows that hybridisation between hominin lineages did occur. Although no ancient DNA has yet been recovered from Paranthropus fossils, the possibility that early hominin species occasionally interbred cannot be ruled out.
Why Paranthropus matters
The existence of Paranthropus shows that human evolution was not a straight line from “ape” to “human”, but a bushy, experimental process with multiple lineages trying different ecological strategies. While the robust hominins ultimately went extinct, they represent a successful and long-lived adaptation that coexisted with early members of the genus Homo for over a million years.
Their story underlines a central point of evolutionary biology: most evolutionary experiments fail — not because they were “badly designed”, but because changing environments favour some adaptations over others.
The discovery of the jawbone and what it means for our understanding of the history of the hominins is explained in a University of Chicago news item:
New 2.6-million-year-old Paranthropus fossil reshapes understanding of early homininsA partial lower jaw discovered in Afar, Ethiopia expands the known geographic distribution of Paranthropus northward by 1000 km, revealing the genus to be more widespread and adaptively versatile than previously thought.
In a new paper published in Nature, a team led by University of Chicago paleoanthropologist Professor Zeresenay Alemseged reports the discovery of the first Paranthropus specimen from the Afar region of Ethiopia, 1000 km north of the genus’ previous northernmost occurrence. This finding offers significant new information about when and where Paranthropus existed, its adaptation to diverse environmental conditions, and how it may have interacted with other ancient relatives of modern humans including our genus Homo.
If we are to understand our own evolutionary trajectory as a genus and species, we need to understand the environmental, ecological, and competitive factors that shaped our evolution. This discovery is so much more than a simple snapshot of Paranthropus’ occurrence: It sheds fresh light on the driving forces behind the evolution of the genus.
Professor Zeresenay Alemseged, lead author
Department of Organismal Biology and Anatomy
University of Chicago
Chicago, IL, USA.
Alemseged sifts through unidentified fossil fragments in the field to find parts of a Paranthropus specimen.
Alemseged Research Group.
Paranthropus previously “missing” among hominins in the Afar and northeast Africa.
Since the human and chimpanzee lineages diverged around 7 million years ago, human ancestors went through a dramatic evolutionary process that ultimately led to the emergence of Homo sapiens around 300,000 years ago.
We strive to understand who we are and how we became to be human, and that has implications for how we behave and how we are going to impact the environment around us, and how that, in turn, is going to impact us.
Professor Zeresenay Alemseged.
In the fossil record, the human lineage is represented by over 15 hominin species that generally fit into four groups:
Facultative bipeds, e.g. Ardipithecus — Occasionally bipedal but mostly living in trees and walking on all four limbs.
Habitual bipeds: Australopithecus — Retained arboreality to some degree but mostly practiced upright walking and experimented with stone tools.
Obligate bipeds: Homo— The genus to which modern humans belong, characterized by a larger brain, sophisticated tools and obligate bipedalism.
Robust hominins: Paranthropus (also known as robust australopithecines) — Habitually bipedal like Australopithecus but distinguished by extremely large molars capped by thick enamel and facial and muscular configurations that suggest a powerful chewing apparatus.
Hundreds of fossils representing over a dozen species of Ardipithecus, Australopithecus, and Homo had been found in the Afar region of northern Ethiopia, so the apparent absence of Paranthropus was conspicuous and puzzling to paleoanthropologists, many of whom had concluded the genus simply never ventured that far north. While some experts suggested that dietary specialization restricted Paranthropus to southern regions, others hypothesized that this could have been the result of Paranthropus’ inability to compete with the more versatile Homo, [however] neither was the case: Paranthropus was as widespread and versatile as Homo and the new find shows that its absence in the Afar was an artifact of the fossil record.
Professor Zeresenay Alemseged.
Professor Zeresenay Alemseged demonstrates how fragments of the newly discovered mandible specimen fit together.
Alemseged Research Group.
Rethinking hominin biogeography, adaptation, and competition.
The 2.6-million-year-old partial jaw reported in Nature comes from the Mille-Logya research area in the Afar and is one of the oldest Paranthropus specimens unearthed to date. After recovering as many fragments as possible from the field site, the team brought them back to Chicago to analyze internal anatomy and morphology with powerful micro-CT scanning.
It’s a remarkable nexus: an ultra-modern technology being applied to a 2.6-million-year-old fossil to tell a story that is common to us all.
Professor Zeresenay Alemseged.
This new find shows that Paranthropus was as widespread and versatile as Homo and was not necessarily outcompeted by Homo.
Paranthropus was previously nicknamed the “nutcracker” genus, highlighting the very large molars, thick enamel, and heavy jaws and reflecting assumptions that this chewing apparatus caused Paranthropus to occupy a highly specialized and narrower dietary niche. But the new Paranthropus from Afar reveals that starting from its earliest origins, Paranthropus was widespread, versatile, and able to crack more than just nuts.
The new discovery gives us insight into the competitive edges that each group had, the type of diet they were consuming, the type of muscular and skeletal adaptations that they had, whether they were using stone tools or not — all parts of their adaptation and behavior that we are trying to figure out. Discoveries like this really trigger interesting questions in terms of reviewing, revising, and then coming up with new hypotheses as to what the key differences were between the main hominin groups.
Professor Zeresenay Alemseged.
Two fragments of the newly discovered mandible specimen in the location they were originally found.
Abstract
The Afar depression in northeastern Ethiopia contains a rich palaeontological and archaeological record, which documents 6 million years of human evolution. Abundant faunal evidence links evolutionary patterns with palaeoenvironmental change as a principal underlying force1. Many of the earlier hominin taxa recognized today are found in the Afar, but Paranthropus has been conspicuously absent from the region. Here we report on the discovery, in the Mille-Logya research area, of a partial mandible that we attribute to Paranthropus, dated to between 2.5 and 2.9 million years ago and found in a well-understood chronological and faunal context. The find is among the oldest fossils attributable to Paranthropus and indicates that this genus, from its earliest known appearance, had a greater geographic distribution than previously documented2. Often seen as a dietary specialist feeding on tough food, the range of diverse habitats with which eastern African Paranthropus can now be associated shows that this suggested adaptive niche did not restrict its ability to disperse as widely as species of Australopithecus and early Homo. The discovery of Paranthropus in the Afar emphasizes how little is known about hominin evolution in eastern Africa during the crucial period between 3 and 2.5 million years ago, when this genus and the Homo lineage presumably emerged.
For creationists, then, this discovery is a double embarrassment. On the one hand, it further extends the fossil record of hominins into yet another inconvenient corner of deep time and geography, while on the other it neatly illustrates how science actually works: hypotheses are refined, boundaries are adjusted, and understanding improves as new evidence comes in. What it does *not* do is undermine the entire enterprise of palaeoanthropology or cast doubt on the reality of human evolution, despite the fevered hopes of those who imagine that any minor correction is a fatal blow to all of science.
Notably, the authors themselves show no difficulty whatsoever in fitting this new find into an evolutionary framework. There is no hand-wringing, no talk of “crisis” or “collapse” of evolutionary theory, and no appeal to supernatural intervention to plug a supposed gap. Instead, the jawbone is treated exactly as it should be: as a new data point that enriches our picture of early hominin diversity, biogeography, and ecological flexibility. It refines our understanding of where Paranthropus lived, how widely it ranged, and how complex the early hominin landscape really was.
In other words, this is not a problem for evolution at all — it is a routine success story for it. The fossil record continues to grow, predictions continue to be borne out, and the messy, branching, occasionally hybridising reality of human evolution becomes ever clearer. What remains conspicuously absent, as ever, is any comparable explanatory framework from creationism — only a set of immovable dogmas that must be defended by denial, distortion, or special pleading whenever the evidence refuses to cooperate.
Once again, the facts turn out to be neutral referees in the dispute. And once again, they come down firmly on the side of an evidence-based, evolutionary account of our origins rather than on a handful of ancient origin myths that cannot be updated, tested, or corrected when they are shown to be wrong.
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You might expect an intelligently designed system, created by an omnibenevolent designer, to work just as effectively for everybody and not badly for some and only just adequately for others. And yet, as so often with creationism, the facts are not at all what the theory predicts. In science this would be called falsification, but for creationists it is just another inconvenient fact to be ignored or blamed on ‘the Fall’ — or even on the victim.
According to a paper just published in Cell Press Blue, the reason some people suffer more from a cold caused by a rhinovirus is not so much because of differences in the virus, but because their bodies react differently. Some take control and prevent the spread of viruses to adjacent cells of the mucous membrane lining the nasal passages, whereas other people’s bodies fail to prevent the virus spreading.
The paper is by a team at Yale School of Medicine, New Haven, CT, USA, led by Associate Professor Dr Ellen F. Foxman, PhD.
By growing organoids in vitro and infecting them with rhinoviruses, the team were able to show that whether the infection spreads depends on how quickly the infected cells are able to mount an interferon response. A good response limits the infection to just a few cells and the cold does not develop beyond a ‘sniffle’. Where the response is weak, the infection spreads and, in cases where the victim has an underlying respiratory condition such as asthma or COPD, the cold can develop into a serious illness.
Why the interferon response differs between individuals is not known with any certainty, but it could be due to a number of factors, including genetics. However, it is known that in patients with pre-existing respiratory conditions, the interferon response is inhibited.
That, of course, begs the question for ID creationists: why a system supposedly designed to protect us gets downgraded when it is most needed, and, if the difference is due to underlying genetics, why some people got better genes in this respect than others. Under the ID creationist paradigm, genes that produce any given output are deemed to hold ‘complex specified genetic information’ and, as such, are evidence for intelligent design.
Leaving aside the question of why any omnibenevolent designer would design viruses to make us sick and then design an immune response to prevent them doing so, we are left with the question of why this immune system does not always work very well and why some people have a worse version than others. If an omnibenevolent designer can design an effective immune system, why did it not give it to everyone? Does it actually want those people to suffer more from the viruses it supposedly designed?
The evolutionary explanation is, of course, straightforward, with none of the theological conundrums that plague creationism. Evolution does not seek out perfection and has no interest in equity. In the environment of an evolutionary arms race with viruses, the results are inevitably suboptimal and unevenly distributed throughout the population unless there is particularly strong selection pressure to drive the ‘best’ solution to fixation. It is also in the survival interests of viruses to tone down their victim’s responses, thereby reducing that selection pressure. The resulting trade-off and compromise is what we see today in the different responses to the same virus.
The problems for creationists deepened today with news that two scientists, Simon Parfitt of the UCL Institute of Archaeology and a Scientific Associate at the Natural History Museum, London, and Silvia M. Bello of the Natural History Museum, have discovered an elephant bone tool dating from roughly half a million years ago — the oldest such tool discovered in Europe, from a time before anatomically modern hominins had left Africa. They published their findings in Science Advances.
Of course, most creationists will be blissfully unaware of this discovery, as with all such archaeology, because there is no point in being a creationist if you are going to read the latest scientific discoveries. How is that going to help you cling to patently absurd beliefs despite all the evidence against you? Best just ignore it and dismiss it all as some sort of Satanic conspiracy aimed at making you show weakness and change your mind.
Nevertheless, the fact is that this elephant bone tool exists and has been dated to about 490,000 years before creationism’s favourite book of Bronze Age superstitions says Earth existed. It was used by archaic hominins, probably to sharpen dulled flint tools by gently knapping the cutting edges. It was discovered at Boxgrove, Kent, England, in the early 1990s but was not recognised as a tool until recently, when finds from the Boxgrove site were studied in detail using new technology such as 3D scans and scanning electron microscopy, which revealed impact notches with embedded flint fragments.
Bone, being softer than flint, would have been the material of choice for work where precision was important, and elephant bone, with its hard outer layer of compact bone making it more durable, would have been the bone of choice. However, elephants and mammoths were rare in what is now southern England 500,000 years ago, so these tools would have been valuable objects.
It is not clear which archaic hominins used these tools in southern England, but at 500,000 years ago it was probably one of the ancestors of Neanderthals and Denisovans, which form the “muddle in the middle” of the human evolutionary story. Here the problem is not a lack of fossils but an abundance of them, showing varying mixtures of primitive and derived features typical of transitional species, coming somewhere between Homo erectus and Neanderthals. Candidates are H. heidelbergensis and H. antecessor.
The stone tools from Boxgrove are part of the widespread Acheulean technology, which originated in East Africa about 1.95 million years ago and spread across Africa and into western Eurasia after about 1.5 million years ago, persisting until between 200,000 and 100,000 years ago.
A recent paper in Proceedings of the National Academy of Sciences of the USA (PNAS) reports the discovery that an ancestor of mammals, a cynodont called Thrinaxodon liorhinus, had ear structures derived from redundant jaw bones that probably gave it an acute sense of hearing some 250 million years ago — around 50 million years earlier than previously believed. As nocturnal animals, a well-developed sense of hearing would have been hugely advantageous.
The research, by palaeontologists from the University of Chicago, used CT scans of the skull and jawbones of Thrinaxodon to simulate the effects of different sound pressures and frequencies on its anatomy.
Transitional fossils such as this are a major source of embarrassment to creationists because their Bronze Age mythology insists that all species were created fully formed, without ancestry, so there should never be any examples of species evolving or of existing structures being exapted over time for new functions.
Sadly for creationists, the fossil evidence paints an entirely different picture. It is a record of everything creationism predicts should not be there and everything evolution predicts will be. To most normal people, that sort of evidence should strongly suggest that creationism is wrong and that the Theory of Evolution is right.
It is rather like someone who does not believe in gravity stating that if you throw a stone into the air it will stay there and never fall back to Earth. A simple demonstration will establish the falsehood of that claim, just as the fossil record establishes the falsehood of creationist claims.
Background^ Cynodonts and the Evolution of the Mammalian Middle Ear.
Cynodonts were a group of synapsid reptiles that lived from the Late Permian to the Early Jurassic and include the direct ancestors of mammals. Unlike true reptiles, cynodonts already showed many mammal-like features, including differentiated teeth, a more upright posture, a secondary palate, and increasingly complex jaw and skull anatomy. Fossils such as Thrinaxodon, Cynognathus, and later forms like Morganucodon document a clear, step-by-step transition from reptile-like synapsids to early mammals.
One of the most striking evolutionary changes recorded in this lineage is the origin of the mammalian middle ear. In reptiles, several small bones at the back of the lower jaw — notably the articular and quadrate — form part of the jaw joint. In mammals, these same bones are repurposed as the malleus and incus of the middle ear, joining the stapes to form the familiar three-bone hearing apparatus. This transformation did not occur suddenly; it unfolded gradually over tens of millions of years.
Fossil cynodonts preserve intermediate stages in which these jaw bones became progressively smaller, less involved in chewing, and increasingly specialised for sound transmission. Some transitional species even show a “double jaw joint,” with both the old reptilian joint and the new mammalian joint functioning simultaneously. This provides direct, physical evidence for exaptation — the evolutionary process in which structures originally evolved for one function are co-opted for a new one.
The result of this long transition was the highly sensitive mammalian middle ear, capable of detecting higher-frequency sounds far better than that of reptiles. This would have been particularly advantageous for small, nocturnal early mammals, allowing them to detect predators and prey in low-light conditions. Far from being a problem for evolutionary theory, the cynodont fossil record is one of its clearest and most elegant confirmations — and one of the most awkward facts for creationism to explain away.
Creationist Claim vs Reality: The Mammalian Middle Ear
Claim:
The mammalian middle ear is “irreducibly complex” and could not have evolved because all three bones — the malleus, incus, and stapes — must be present and perfectly arranged for hearing to work.
Reality:
The fossil record preserves multiple transitional stages showing exactly how the mammalian middle ear evolved from reptile-like jaw bones. In early synapsids and cynodonts, the articular and quadrate bones formed part of the jaw joint. Over time, these bones became progressively smaller and less involved in chewing, while increasingly specialised for transmitting sound.
Claim:
There are no transitional fossils showing this transformation.
Reality:
There are many. Fossils such as Thrinaxodon, Cynognathus, Diarthrognathus, and Morganucodon preserve intermediate anatomies, including species with a functioning “double jaw joint” — one reptilian and one mammalian — operating at the same time. This is exactly what gradual evolution predicts.
Claim:
Repurposing jaw bones for hearing would destroy their original function.
Reality:
It did not. For millions of years, both functions co-existed. As the new mammalian jaw joint (between the dentary and squamosal bones) took over the role of chewing, the old jaw joint bones were freed to specialise for sound transmission. This is a textbook example of exaptation, not a paradox.
Reality:
They do not. The step-by-step transformation of jaw bones into middle ear bones is one of the best-documented transitions in the entire fossil record. It is exactly the opposite of what creationism predicts — and exactly what evolutionary theory predicts.
Fossil study rewrites timeline of evolution of hearing in mammalsUChicago paleontologists use CT scanning and simulations to show how a 250-million-year-old mammal predecessor could hear like us
One of the most important steps in the evolution of modern mammals was the development of highly sensitive hearing.
The middle ear of mammals, with an eardrum and several small bones, allows us to hear a broad range of frequencies and volumes, which was a big help to early, mostly nocturnal mammal ancestors as they tried to survive alongside dinosaurs.
New research by paleontologists from the University of Chicago shows that this modern mode of hearing evolved much earlier than previously thought. Working with detailed CT scans of the skull and jawbones of Thrinaxodon liorhinus, a 250-million-year-old mammal predecessor, they used engineering methods to simulate the effects of different sound pressures and frequencies on its anatomy.
Their models show the creature likely had an eardrum large enough to hear airborne sound effectively, nearly 50 million years before scientists previously thought this evolved in early mammals.
For almost a century, scientists have been trying to figure out how these animals could hear. These ideas have captivated the imagination of paleontologists who work in mammal evolution, but until now we haven’t had very strong biomechanical tests. Now, with our advances in computational biomechanics, we can start to say smart things about what the anatomy means for how this animal could hear.
Alec T. Wilken, lead author
Department of Organismal Biology and Anatomy
The University of Chicago
Chicago, IL, USA.
Fossil specimen of the Thrinaxodon skull and jaw used for the study.
Photo by Matt Wood.
Testing a 50-year-old hypothesis
Thrinaxodon was a cynodont, a group of animals from the early Triassic period with features beginning to transition from reptiles to mammals. They had specialized teeth, changes to the palate and diaphragm to improve breathing and metabolism, and probably warm-bloodedness and fur.
In early cynodonts, including Thrinaxodon, the ear bones—malleus, incus, stapes—were attached to their jawbones. Later, these bones separated from the jaw to form a distinct middle ear, considered a key development in the evolution of modern mammals.
Simulations showed that sound waves applied to the eardrum of "Thrinaxodon" (top) would have enabled it to hear much more effectively than through bone conduction alone (bottom).
Infographic courtesy of April I. Neander, Alec Wilken
Fifty years ago, Edgar Allin, a paleontologist at the University of Illinois Chicago, first speculated that cynodonts like Thrinaxodon had a membrane suspended across a hooked structure on the jawbone that was a precursor to the modern eardrum. Until then, scientists who studied mammal evolution mostly believed that early cynodonts heard through bone conduction, or via so-called “jaw listening” where they set their mandibles on the ground to pick up vibrations.
While the eardrum idea was fascinating, there was no way to definitively test if such a structure could work to hear airborne sounds.
Turning fossils into an engineering problem
Modern imaging tools like CT scanning have revolutionized the field of paleontology, allowing scientists to unlock a wealth of information that wouldn’t have been possible through studying physical specimens alone.
Wilken and his advisors, Zhe-Xi Luo and Callum Ross, both professors of organismal biology and anatomy, took a well-known Thrinaxodon specimen from the Museum of Paleontology at the University of California, Berkeley, and scanned it in UChicago’s PaleoCT Laboratory. The resulting 3D model gave them a highly detailed reconstruction of its skull and jawbones, with all the dimensions, shapes, angles and curves they needed to determine how a potential eardrum might function.
Next, they used a software tool called Strand7 to perform finite element analysis, an approach that breaks down a system into smaller parts with different physical characteristics. Such tools are usually used for complex engineering problems, like predicting stresses on bridges, aircraft and buildings, or analyzing heat distribution in engines. The team used the software to simulate how the anatomy of Thrinaxodon would respond to different sound pressures and frequencies, using a library of known properties about the thickness, density and flexibility of bones, ligaments, muscles and skin from living animals.
The results were loud and clear: Thrinaxodon, with an eardrum tucked into a crook on its jawbone, could definitely hear that way much more effectively than through bone conduction. The size and shape of its eardrum would have produced the right vibrations to move the ear bones and generate enough pressure to stimulate its auditory nerves and detect sound frequencies. While it still would have relied on some jaw listening, the eardrum was already responsible for most of its hearing.
Once we have the CT model from the fossil, we can take material properties from extant animals and make it as if our Thrinaxodon came alive. That hasn’t been possible before, and this software simulation showed us that vibration through sound is essentially the way this animal could hear.
Professor Zhe-Xi Luo, corresponding author.
Department of Organismal Biology and Anatomy
The University of Chicago
Chicago, IL, USA.
Wilken said the new technology allowed them to answer an old question by turning it into an engineering problem.
That’s why this is such a cool problem to study. We took a high concept problem—that is, ‘how do ear bones wiggle in a 250-million-year-old fossil?’—and tested a simple hypothesis using these sophisticated tools. And it turns out in Thrinaxodon, the eardrum does just fine all by itself.
Significance
The middle ear of modern mammals is detached from the mandible and has a soft-tissue eardrum, which allows airborne sound to be heard across a wide range of frequencies. A rich fossil record shows that the middle ear bones of mammals evolved from the jaw bones of their synapsid predecessors, but how this transformation was associated with changes in hearing function is unknown. Our finite element analysis (FEA) of the harmonic response of the mandibular ear bones and soft-tissue eardrum of the synapsid Thrinaxodon suggests that this 250-Mya-old mammal precursor was already capable of tympanic hearing similar to extant mammals and provides evidence that this functional transition occurred very early in mammal evolutionary history.
Abstract
The middle ear of mammals is a major functional innovation, distinctive in that it is detached from the mandible and has a tympanic membrane supported by a ring-like ectotympanic. These novelties of the middle ear have enabled modern mammals to develop more sensitive hearing than all other tetrapods, especially at higher frequencies. Fossils from recent decades have clarified the evolution of the detached middle ear from the jaw bones of Paleozoic therapsids and Mesozoic cynodonts, and the evolution of the tympanum. These discoveries make it possible to answer important questions about the functional significance of these features. Here, we evaluate the relative hearing efficacy of a well-known cynodont precursor to mammals, Thrinaxodon liorhinus. Using finite element analysis (FEA), we calculated the harmonic response of the Thrinaxodon ear to bone-conducted and airborne sound and estimated the sound pressure level (SPL) at the stapedial footplate across a broad range of frequencies. We provide evidence that airborne sound received at the tympanum was the most effective mode of sound reception in Thrinaxodon. In contrast, bone conducted sound through the mandibular bones barely met our estimated hearing threshold. Our findings suggest that, like modern mammals, cynodonts were already reliant on a soft tissue tympanum to receive airborne sound, albeit with limited sensitivity to high frequencies. This is a detailed biomechanical evaluation of tympanum function in the cynodont predecessors of mammals and yields insight into the sequence of functional innovations during the evolution of mammal hearing.
For creationists, this discovery is yet another reminder of how badly their Bronze Age mythology fails when confronted with real-world evidence. The evolutionary origin of the mammalian middle ear is no longer a theoretical reconstruction inferred from comparative anatomy; it is a physical, fossil-documented transition preserved in stone. The fact that Thrinaxodon already shows mammal-like hearing structures 250 million years ago simply pushes that transition even further back in time and fills in yet another gap that creationists like to pretend does not exist.
It also underlines a point that creationists have been trying to evade for decades: evolution does not require sudden leaps or the magical appearance of fully formed organs. What it requires is exactly what the fossil record shows — incremental modifications of existing structures, shaped by selection, and repurposed for new functions as circumstances change. Jaw bones that once transmitted bite forces gradually became exquisitely tuned instruments for transmitting sound. That is not a problem for evolutionary theory; it is one of its strongest empirical confirmations.
Worse still for Intelligent Design advocates, the researchers show no hesitation whatsoever in interpreting what they found within the framework of evolutionary biology. There is no hint of mystery, no appeal to unknown designers, and no suggestion that natural processes are inadequate to explain what is observed. Instead, the anatomy of Thrinaxodon fits neatly into a well-established evolutionary sequence that has been mapped out for decades and is now being refined in ever greater detail as new fossils and new technologies come to light.
So once again, we are left with a familiar contrast. Evolutionary biology makes clear, testable predictions about what we should find in the fossil record — and those predictions keep being confirmed. Creationism, by contrast, predicts that none of this should exist at all. When one worldview consistently matches the evidence and the other consistently fails, there is no honest ambiguity about which one is right.
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