Our jaws may have started out as armor plate, not gill arches. Paleontologists found a second Silurian placoderm species with surprisingly familiar jaws.
- Using Our Brains: Also Teeth
- Jaw Evolution, 2016
- Fish Face, 2013
Before talking about Homo habilis, and new evidence showing how jaws evolved, I’ll do my usual explanation of why science doesn’t upset me.
I’m a Christian, and a Catholic, and that’s another topic.1
Since a remarkable number of folks, including some Catholics, seem to think someone can either be Christian or acknowledge that we live in a vast, ancient, and changing, cosmos; I’ll be talking about Darwin, Ussher, and Anaximander.
Also the Bible, science, and getting a grip.
That’s not even close to believing that the universe is literally a dewdrop:
“Behold, the nations count as a drop in the bucket, as dust on the scales; the coastlands weigh no more than powder.”
“Truth or truthfulness is the virtue which consists in showing oneself true in deeds and truthful in words, and guarding against duplicity, dissimulation, and hypocrisy.”
Truth is beautiful: whether it’s expressed in words, “the rational expression of the knowledge of created and uncreated reality;” or “the order and harmony of the cosmos;” or in other ways. (Catechism, 2500)
A thirst for truth and happiness is written into each of us, which should lead us to God. (Catechism, 27)
That’s one reason I like Thomas. He asked questions, and wanted evidence, which earned him the “doubting Thomas” nickname. But he knew when to accept reality.2
Seeing human evolution as a “march of progress” made more sense when when Time-Life published “Early Man.”
But despite what’s occasionally in the news, evolution isn’t “random.” Unpredictable, maybe.3
I see no problem with believing that God is creating a universe that’s following knowable physical laws. That’s just as well, since it’s what we’re told to believe. (Catechism, 268, 279, 299, 301, 302–305)
I enjoy understanding things, and learning how to understand more. But fully understanding God is beyond me. The Almighty is “…incomprehensible, almighty and ineffable … a mystery beyond words.” (Catechism, 202, 230)
We have, however, been learning a bit about God over the millennia.
Scientists are assuming that evolution is like fire and gravity: something that’s real, and follows knowable rules. I think they’re right.
A big difference between evolution and gravity is that we we weren’t sure that evolution was real until quite recently. And that brings me to Anaximander.
(From Thomas Hawkins; via The Online Books Page, University of Pennsylvania; used w/o permission.)
(Front piece of “The Book of the Great Sea-Dragons, Ichthyosauri and Plesiosauri…,” Thomas Hawkins (1840))
Thomas Hawkins’ florid prose may have influenced H. P. Lovecraft, and that’s yet another topic. Where was I? Book stores, truth, secondary causes. Right.
He wasn’t a scientist. That branch of natural philosophy wouldn’t take off until about four centuries back.
Carl Linnaeus wasn’t the first natural philosopher to sort out differences and similarities between critters.
Aristotle wasn’t, either, but his idea that species don’t change had a lot of fans; and still does. Various folks had figured species could change, no matter what Aristotle thought. Jean-Baptiste Lamarck published his evolutionary theory in the early 1800s.
Inheritors of Henry VIII’s Church of England attacked ideas they hadn’t invented. Liberal Anglicans attacked the establishment’s position, and folks like Thomas Huxley defended Darwin’s theory — in part, maybe — because it helped pry England’s schools out of the religious establishment’s grip.
I’m oversimplifying things a lot, but I think you get the idea.4
His “Annales veteris testamenti, a prima mundi origine deducti” was pretty good scholarship in 1650.
But I’m quite sure he was wrong about the universe starting at nightfall on Saturday, October 22, 4004 BC.
I don’t think Ussher was wrong about 4004 BC because he was a Calvinist. I think he’s wrong because data gathered and analyzed in the following centuries shows that the universe is a whole lot older. (August 28, 2016)
I’m not upset that the world is older than some folks thought, or that we didn’t have all the answers in the 17th century.
“…God, the Creator and Ruler of all things, is also the Author of the Scriptures – and that therefore nothing can be proved either by physical science or archaeology which can really contradict the Scriptures. … Even if the difficulty is after all not cleared up and the discrepancy seems to remain, the contest must not be abandoned; truth cannot contradict truth….”
(“Providentissimus Deus,” Pope Leo XIII (November 18, 1893) [emphasis mine])
“Scientists find evidence that human ancestors were right-handed”
Jayson MacLean, cantech letter (October 21, 2016)
“New research published in the Journal of Human Evolution has found that an ancestral relative of modern-day humans may have been right-handed, providing further evidence that the division of cognitive labour between the two halves of the brain, otherwise known as brain lateralization, likely occurred early on in human evolution, at least 1.8 million years ago.
“Researchers studying the fossil remains of OH-65, a specimen of Homo habilis retrieved from the Olduvai Gorge in Tanzania, discovered minute cuts and ridges in the ancient human relative’s upper front teeth which were likely produced from OH-65’s use of a stone tool to cut meat….”
OH 65 stands for Olduvai Hominid specimen 65. The specimen’s mentioned in the Spanish Wikipedia page on Homo habilis, but not the English one. Not yet, anyway. It’s an upper jaw with most of the teeth, found by Amy Cushing and Agustino Venance in 1995.
Homo habilis is the current name for folks who lived from about 2,100,000 to 1,500,000 years back.
I’m strongly inclined to call them “folks,” since the human ‘brain gene,’ SRGAP2, showed up about 3,200,000 years ago: 1,600,000 years before whoever OH 65 comes from lived. I talked about that last month. (September 23, 2016)
I gather that there’s still discussion about what Homo habilis should be called, and exactly how they fit into our family tree, and that’s yet again another topic. I am not going to get sidetracked by taxonomy if I can help it. Not today.
The Homo habilis version of humanity looked more like us than Australopithecus afarensis, “Lucy’s” immediate kin, but they were still on the short side: 1.3 meters, four feet three inches, tall on average. Their heads had more room for brains than Australopithecus afarensis, very roughly half as much as ours.
Like “Lucy,” they’d have a terrible time blending into a crowd these days.
The Homo habilis hand, though, was probably about as good as ours for making and using tools. A strong precision grip showed up in Australopithecus afarensis.
Research published last year ran existing data through a new sort of analysis, looking at trabecular bone in a new way. That’s spongy bone that changes quickly: sometimes responding to what the individual does.
“…The distinctly human ability for forceful precision (e.g. when turning a key) and power ‘squeeze’ gripping (e.g. when using a hammer) is linked to two key evolutionary transitions in hand use: a reduction in arboreal climbing and the manufacture and use of stone tools….”
(University of Kent, via ScienceDaily (January 22, 2015))
On the whole, I think it was a good trade-off. Scrambling around in trees, or jungle gyms, is fun: and arguably an important part of childhood. But making and using tools? That’s important, too.6
“Fish fossil upends scientists’ view of jaw evolution”
“Specimen suggests that people and ancient fish have more in common than previously thought.”
Anna Nowogrodzki, Nature (October 20, 2016)
“A fossil fish found in Yunnan, China, has filled in a gaping hole in how researchers thought the vertebrate jaw evolved.
The 423-million-year-old specimen, dubbed Qilinyu rostrata, is part of an ancient group of armoured fish called placoderms. The fossil is the oldest ever found with a modern three-part jaw, which includes two bones in the upper jaw and one in the lower jaw. Researchers reported their find on 20 October in Science.
Scientists had thought that placoderm jaws were only very distantly related to the three-part jaw found in modern bony fish and land vertebrates, including people. This was because the bones in placoderm jaws generally sit further inside the animals’ mouths than do human jawbones, and they don’t contribute to the outer structure of the face, says Per Ahlberg, a palaeontologist at Uppsala University in Sweden and a co-author of the study….”
Surprising news about jaws came about three years back, when scientists found Entelognathus.
The point is that we’d figured jaws started as part of an internal structure. Now it looks like they may have started on the outside.
About the critter’s age: I don’t have access to the original Science paper, published October 21, 2016, but just about everyone’s saying it’s around 423,000,000 years old.
The fish, I mean. Not the paper.
Something doesn’t add up here. My guess is that we’re looking at a typo in the (quite new) Qilinyu page.
About geochronology, scientists are getting pretty good at determining the age of rocks.
And folks who don’t like science are still pretty good at not believing facts they don’t like.
Me? I see scientific discoveries as opportunities for “even greater admiration for the greatness of the Creator.” (Catechism, 283)
(From asdfasdf, via asdfasdf, used w/o permission.)
(“The newly described armoured fish showed in this reconstruction lived 419 million years ago but already had the bony jaw seen in modern fish and most other vertebrates.”
“Ancient fish face shows roots of modern jaw”
“Primitive vertebrate’s sophisticated mandible rewrites evolutionary tree.”
Eliot Barford, Nature (September 25, 2013)
“It may be hard to see, but you seem to share a family resemblance with Entelognathus primordialis. The fish, which lived 419 million years ago in an area that is now part of China, is the earliest known species with a modern jaw.
“Entelognathus primordialis is a new addition to the placoderms, a class of armour-plated fishes that lived from about 430 million to 360 million years ago. Like most vertebrates, including mammals, placoderms had a bony skull and jaw, but most of them had simple beak-like jaws built out of bone plates. Palaeontologists have traditionally believed that the fishes’ features bore no relation to ours….”
Most were predators, including the Dunkleosteus — a genus that included D. terrelli, a one-ton, six meter, 20 foot, fish. Size isn’t everything, but it’s impressive. Another placoderm, Materpiscis, is the oldest known viviparous vertebrate.
Lindsay Hatcher found the first, and so far only, fossil Materpiscis in 2005: a female with a probably-near-full-term embryo/juvenile inside, complete with umbilical cord.
Scientists are still sorting out what caused it. Several extinction pulses hit over a span of a few million years, how many and exactly when isn’t certain yet.
Discovering two placoderm species with jaws that look like today’s vertebrate jaws doesn’t, I think, “upend” what scientists thought about jaw evolution.
Not the way evidence that jaws started as, say, vertebrae would.
It’s fascinating, though. We have more pieces to the puzzle of how life has been developing, and they’re not quite what was expected.
It’s a bit like discovering that the pieces of a jigsaw puzzle we thought were part of a sailboat actually go on the captain’s cap.
The 2013 article ends on a sensibly-cautious note:
“…the authors revise the family tree of jawed vertebrates, showing that there is a serious possibility that the modern bony visage originated with E. primordialis’s ancestors. This would mean that humans look more like the last common ancestor of living jawed vertebrates than we thought, and that sharks are less primitive than palaeontologists assumed, having done away with their bones as an adaptation.
However, the rearranged family tree is not yet quite conclusive, write the authors of a related News & Views article. There remains a chance that E. primordialis evolved its jaw independently from the bony fish, so that we did not inherit it, and the resemblance is an illusion.”
(Eliot Barford, Nature (September 25, 2013))
Both E. primordialis and Qilinyu rostrata might ‘just happen’ to have jaws like ours. But it’s looking more like we’ll need to revise our ideas of how vertebrates developed. Again.
About 30,000 fish species have another variation: phyaryngeal jaws, a ‘second set’ of jaws, sometimes complete with teeth, in the throat.
Moray eels feature phyaryngeal jaws with a difference. Theirs are rigged to move into the mouth, grasp food, and pull it back into the throat.
That’s good for morays, since their heads are too narrow to manage the usual piscine ‘suck and swallow’ routine.
I suspect that their reputation for viciousness comes in part from how they react to anything entering their burrows — and the human habit of sticking hands into burrows.
It’s likely enough. But I suspect that someone, possibly a non-scientist who spent time around morays, had noticed them earlier; and passed that knowledge on to folks designing the feature creature in “Alien.”
Have a safe and happy Halloween, and use caution while exploring deserted alien spaceships.
More about science, faith, and getting a grip:
- Alchemy, Science, Life, and Health”
(October 16, 2016)
- Trusting Feelings: Within Reason”
(October 5, 2016)
- The Minden Monster, What Killed Lucy”
(September 23, 2016)
- Faith, the Universe, and Wisdom”
(August 28, 2016)
- Brogdar, Öetzi, and Piltdown Man”
(August 26, 2016)
I’m a Catholic because I insist that what I believe must make sense, no matter how I’m feeling. As John C. Wright said, “… If Vulcans had a church, they’d be Catholics.” (johncwright.livejournal.com (March 21 2008))
2 After our Lord stopped being dead, Thomas wouldn’t believe what other disciples were telling him. (John 20:25)
I can’t say that I blame him.
“Then he said to Thomas, ‘Put your finger here and see my hands, and bring your hand and put it into my side, and do not be unbelieving, but believe.’
“17 Thomas answered and said to him, ‘My Lord and my God!’
I didn’t demand that sort of proof. But nearly two millennia later, I had a whole lot more evidence than hearsay from a few badly-rattled folks to work with.
3 Evolution is not random: not in the sense of having no specific pattern. I suspect that quite a few folks say or write “random” when they mean “complex,” or “not fully understood.” In math, “random” is a probability distribution where all outcomes are equally likely.
If evolution had no specific pattern, scientists who study it wouldn’t be scientists. They’d be scorekeepers, recording meaningless trivia about “random” events.
- History of the creation-evolution controversy
- History of evolutionary thought
- Reactions to On the Origin of Species
Pope Leo XIII (November 18, 1893)
“Thomas said to him, ‘Master, we do not know where you are going; how can we know the way?’
“Jesus said to him, ‘I am the way and the truth 5 and the life. No one comes to the Father except through me.
- “OH-65: The earliest evidence for right-handedness in the fossil record”
David W. Frayera, Ronald J. Clarkeb, Ivana Fiorec, Robert J. Blumenschined, Alejandro Pérez-Péreze, Laura M. Martineze, Ferran Estebaranze, Ralph Hollowayf, Luca Bondiolic; Journal of Human Evolution (November 2016)
- “Early human ancestors used their hands like modern humans”
University of Kent, via ScienceDaily (January 22, 2015)
- “A Silurian maxillate placoderm illuminates jaw evolution”
Min Zhu, Per E. Ahlberg, Zhaohui Pan, Youan Zhu3, Tuo Qiao1, Wenjin Zhao, Liantao Jia, Jing Lu; Science (October 21, 2016)
- “A Silurian placoderm with osteichthyan-like marginal jaw bones”
Min Zhu, iaobo Yu, Per Erik Ahlberg, Brian Choo, Jing Lu, Tuo Qiao, Qingming Qu, Wenjin Zhao, Liantao Jia, Henning Blom, You’an Zhu; Nature (October 10, 2013)