Right-Handedness and Evolving Jaws

At least one Homo habilis was right-handed, about 1,800,000 years ago. It’s the earliest evidence of handedness in humanity’s history. So far.

Our jaws may have started out as armor plate, not gill arches. Paleontologists found a second Silurian placoderm species with surprisingly familiar jaws.

  1. Using Our Brains: Also Teeth
  2. Jaw Evolution, 2016
  3. 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.


Evolution

“Christian” bookstores where I grew up generally sold quite a few books attacking evolution, along with grim warnings against the Catholic Church and other threats to their preferred reality.

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.

Taking the Bible seriously isn’t an option for me. It’s a requirement. (Catechism of the Catholic Church, 101133)

So is “frequent reading of the divine Scriptures” and using my brain. (Catechism, 35, 133, 154)

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.”
(Isaiah 40:15)

4 Indeed, before you the whole universe is as a grain from a balance, or a drop of morning dew come down upon the earth.”
(Wisdom 11:22)

Truth and Questions

Truth is very important. (Catechism, Prologue, 27, 74, more under Truth in the index)

“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.”
(Catechism, 2505)

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)

We can learn a bit about God by noticing “the world’s order and beauty,” which reflects God’s infinite beauty. (Catechism, 3132, 341)

A thirst for truth and happiness is written into each of us, which should lead us to God. (Catechism, 27)

Faith, the Catholic version, is a willing and conscious “assent to the whole truth that God has revealed.” (Catechism, 142150)

Using the brains God gave us, seeking the Almighty and studying this wonder-filled universe, is fine. It’s what we’re supposed to do. (Catechism, 35, 50, 159, 22922296)

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

Knowable Physical Laws

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, 302305)

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.

For starters, God really is “the Almighty.” But God’s power isn’t arbitrary in the sense of capricious. (Catechism, 270271)

Everything we observe reflects some facet of the Creator’s truth, according to its nature. (Catechism, 300310)

Natural processes, like fire and gravity, involve secondary causes: creatures changing in knowable ways, following laws woven into this creation. (Catechism, 301308, 339)

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.

Emerging From a Mist


(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.

Anaximander lived around the time of Sappho, Psamtik I, and Zhou Kuang Wang.

His “Περὶ φύσεως,” “On Nature,” poem suggested that life emerged from a mist; and that animals — humans included — developed from fish.

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.

Charles Darwin and Alfred Russel Wallace published another evolutionary theory in 1858. Darwin’s “On the Origin of Species” explained the theory in more detail, and that’s where it gets interesting.

“The Contest Must Not be Abandoned”

I don’t think it helps that Darwin’s theory got mixed up in 19th century English politics.

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

I’m forgetting something. Make that someone: James Ussher, England’s Calvinist boss of Ireland from 1625 to 1656.

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.

And I’m certainly not afraid of honest research. Since I believe that God is Truth,5 and is creating the universe, fearing knowledge of God’s world would be — illogical.

“…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])


1. Using Our Brains: Also Teeth


(From David W. Frayer, et al, via Journal of Human Evolution, used w/o permission.)
(“…Depicted here is a right-hander pulling with the left and cutting with the right….”
(David W. Frayer, et al))

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


2. Jaw Evolution, 2016


(From Dinghua Yang, via Nature, used w/o permission.)
(“An artist’s impression of the newly described ancient fish Qilinyu rostrata.”
(Nature))

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….”

This research is a big deal, but it’s hardly a “Shocking Discovery,” as Nature World News put it. Interesting, certainly, but not “shocking” in the “causing intense surprise” sense.

Surprising news about jaws came about three years back, when scientists found Entelognathus.

Up to that point, many scientists figured that vertebrate jaws evolved from the first two pharyngeal arches; starting as gill arches and getting re-purposed as supports for the mouth.7

It made sense, and the first two pharangeal arches in vertebrate embryos do morph into our jaws; among other things. Except for Agnatha, vertebrates without jaws, and that’s still another topic.

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.

Numbers, Science, and Admiration

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.

Oddly, the Wikipedia Qilinyu page says it’s 419,000,000 years old — and from the Ludlow epoch of the Silurian, 427,400,000 to 423,000,000 years back, give or take two or three million.

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)


3. Fish Face, 2013


(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.”
(Nature))

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….”

Qilinyu and Entelognathus were both placoderms, a class of armored fish that lived between 430,000,000 and 360,000,000 years ago.

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.

Puzzle Pieces

Placoderms didn’t survive the Late Devonian extinction, one of Earth’s five biggest known extinction events.

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.

Potpourri and Phyaryngeal Jaws

Jaws in mammals are fairly simple: a lower jaw fitting into what’s left of the upper set with little or no cranial kinesis — a five-dollar term for what snakes and some other critters do.

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.

Giant morays are also the only fish to cooperate with another species in hunting. They team up with roving coralgroupers.

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.

The Wikipedia page on phyaryngeal jaws say that the moray’s phyaryngeal mobility was discovered in 2007 by UC Davis scientists. That seems to be based on a 2007 piece in The New York Times.

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:


1 I’m a Christian. I accept Jesus as our Lord. (John 1:15; Catechism, 430451)

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!’

18 Jesus said to him, ‘Have you come to believe because you have seen me? Blessed are those who have not seen and have believed.’ ”
(John 20:2729)

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.

4 A little more about creationism, evolution, and getting a grip:

5 Among other attributes, God is truth. (Catechism, 214217)

“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.

“If you know me, then you will also know my Father. 6 From now on you do know him and have seen him.’ ”
(John 13:57)

6 Teeth and brains:

7 About jaws, mostly:

About Brian H. Gill

I'm a sixty-something married guy with six kids, four surviving, in a small central Minnesota town. I mostly write and make digital art. I'm only interested in three things: that which exists within the universe; that which exists beyond; and that which might exist.
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10 Responses to Right-Handedness and Evolving Jaws

  1. Naomi Gill says:

    You already said that a couple paragraphs up: “Faith, the Catholic version, is a willing and conscious “assent to the whole truth that God has revealed.””

    This sounds awkward, but I’m not sure if it’s incorrect: “Homo habilis is what scientists call a particular sort of folks who lived”

    The Friendly Neighborhood Proofreader

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