Why Evolution is True is a blog written by Jerry Coyne, centered on evolution and biology but also dealing with diverse topics like politics, culture, and cats.
Over at the Cornell Hawkcam, a redtailed hawk chick has finally appeared, and the snow seems to be melting. Alert reader Kevin sent me a link to a screenshot of that first chick. Here’s the little fuzzball, already with a wicked beak:
Well, Bart Ehrman has responded on his website (Christianity in Antiquity: The Bart Ehrman Blog) to Richard Carrier’s criticisms of Ehrman’s new book affirming the historicity (but not the divinity) of Jesus. Well, he’s sort of responded, because, in his reply, called “Acharyna S, Richard Carrier, and a cocky Peter (or ‘A cock and bull story'”) he takes up only one of Carrier’s assertions: that a statue of a man with a penis for a nose sits in the Vatican, a statue whose existence Ehrman previously denied. This is only one of elebenty gazillion criticisms that Carrier levelled at Ehrman, and is by far the tamest. I haven’t seen Ehrman’s original assertion that the statue did not exist, but I’ll take Carrier’s word for it.
In his response, Ehrman admits that the statue did exist, but it wasn’t a statue of Saint Peter, so it was irrelevant to the argument about Jesus. Maybe it was, but Carrier never claimed it was a statue of Peter, only that Ehrman made a factual error in claiming the statue didn’t exist. This is what Carrier said:
At the very least I would expect Ehrman to have called the Vatican museum about this, and to have checked the literature on it, before arrogantly declaring no such object existed and implying Murdock made this up. I do not assume Murdock’s interpretation of the object is correct (there is no clear evidence it has anything to do with Christianity, much less Peter).
So Carrier appears to be correct here. If Ehrman denied the statue existed, he was wrong, and that may or may not reflect on his scholarship in Did Jesus Exist? But Ehrman’s admission that he erred was backhanded, I think. At any rate, Ehrman ignores the rest of Carrier’s more serious accusations, saying only this:
He [Carrier] makes this kind of mistake routinely in his vicious assault on me and my book. The problem appears to be that he sees something that strikes him as a problem, and he isolates it, dissects it, runs with it, gets obsessed with it, and …. forgets how it was actually said in the first place. Careful reading can solve a lot of problems of misunderstanding.
To me this is a non-response; an apology without apologizing. Carrier wrote a huge critique, and Ehrman responds to just one trivial point about a penis-nosed statue, a point that may reflect on Ehrman’s carefulness. (Let me hasten to say that I haven’t read Ehrman’s book yet.) Perhaps Ehrman will write a longer response, but he notes that he reserves in-depth responsesfor the Members Only part of his site, where you have to pay to see Ehrman’s lucubrations ($3.95/month, $24.95/year). Since Ehrman is presumably reasonably compensated in his academic post, and has probably made tons of money from his book, I really do object to a scholar reserving his serious responses for a pay-only part of his site. Does he need the money that badly? And will he respond there?
At the beginning of his post, Ehrman says a few words about the responses to his book, words that I find rather defensive and a bit disingenuous:
As many readers know, Richard Carrier has written a hard-hitting, one might even say vicious, response to Did Jesus Exist. I said nothing nasty about Carrier in my book – just the contrary, I indicated that he was a smart fellow with whom I disagree on fundamental issues, including some for which he really does not seem to know what he is talking about. But I never attacked him personally. He on the other hand, appears to be showing his true colors.
Still, the one thing this bit of nastiness has shown me is that even though I seem to stir up controversy everywhere I go and with everything I write, I really don’t like conflict. I would much prefer that we all simply get along and search for truth together. But alas, the world does not appear to be made that way. And I seem to be a lightning rod for criticism. This morning I woke up to the old Stealer’s Wheel song in my head, “Clowns to the left of me, jokers to the right, here I am, stuck in the middle with you.” It’s a good place to be, stuck in the middle, when there are so many outlandish options to the left and right.
I do not plan on spending my next three months going back and forth with Carrier over his criticisms. This is a problem I have with many of the mythicists: they are often so prolix and make point after point after point, that it is impossible to deal with them in short order. One of the things Carrier laments is that I don’t deal with the various mythicists all at length – even (this is a special point he presses) those who cannot be taken seriously (he names Freke and Gandy). My view is that there is no reason to take seriously people who cannot be taken seriously: a few indications of general incompetence is good enough.
Well, I’m not sure whether a general attack on mythicists—of which Carrier is one—shouldn’t be taken personally. Regardless, though, Ehrman should stick to the factual issues at hand, which is the veracity and accuracy of his scholarship. As for not liking controversy, I’m not sure I believe Ehrman. If he doesn’t like conflict, why did he go after not only mythicists but atheists so strongly in his books, talks, and interviews. In fact, controversy is what brought Ehrman popularity and makes him money, and he knows that full well. The very subjects he tackles, and the titles of his books, are calculated and guaranteed to promote controversy. His “I am a poor beleaguered man” stance doesn’t sit well. And, finally, I’m distressed that Ehrman and Carrier can’t have a debate over this: Ehrman doesn’t seem inclined to respond. Well, Carrier is someone who needs to be taken seriously, and he’s taken the time to level a long critique at Ehrman. The least Carrier deserves is to be taken seriously; and he certainly deserves an in-depth reply. Ehrman doesn’t realize that he’ll lose credibility as a scholar if he can’t produce one.
Here, from the Guardian via Matthew Cobb, is some nice footage of the first white orca (“killer whale,” Orcinus orca) seen in the wild. As the article notes:
Scientists have filmed what is believed to be the first sighting of an adult white killer whale in the wild. The marine mammal, nicknamed Iceberg and believed to be at least 16 years old, was swimming with its mother and siblings in waters off the Kamchatka peninsula off the far eastern coast of Russia. Fully albino orcas can have weak immune systems and die young, but partial albinos can live into adulthood.
It’s not clear to me whether this is a true albino or a case of genetic leucism. And I wonder if its pod-mates shun it, or even notice anything different? Surely they must.
Oh, and read my narwhal post, for crying out loud! It took hours.
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Most of you surely know of Victor Stenger, a physicist who has written several books on science and atheism, including God: The Failed Hypothesis and The New Atheism, both of which I liked. His main thrust is, like Dawkins, to regard the notion of God as a scientific hypothesis, and then apply the tools of science to show that the hypothesis is falsified. (Dawkins may be backing off on that view: lately he’s floated the idea that the notion of God is intrinsically incoherent). Stenger has also written eloquently, and at length, about the failure of the “fine tuning” argument for God from the nature of physical constants.
At any rate, I’ve just finished Victor’s new book, which you’ll see from the title has a particular interest for me: God and the Folly of Faith: The Incompatibility of Science and Religion (only $13.43 on Amazon). I can recommend this as well, particularly if you haven’t read many of Stenger’s books.
Despite its title, the book doesn’t deal at great length with the nature of the incompatibility of science and faith, although he mentions it tangentially. What he sees as the “incompatibility” is both the difference in methodology that the disciplines use to find out stuff, and the difference in outcomes: i.e., religion has made predictions that science has falsified. Most of the book is taken up with religious assertions that science has disproven, like the existence of ESP, intercessory prayer, divine fine-tuning, the existence of human morality as a proof of God, and so on. If you’ve read Stenger’s previous books, there’s some overlap between what he writes about here and what he covered in those earlier books (fine tuning, for instance), so the book is most appropriate for those who haven’t read a lot of Stenger.
But there is also much that is new, including his discussion of free will, whether determinism reigns on a macro scale in the universe, and especially about the history of science. Did Christianity, for example, have a hand in producing science? What contribution did non-European countries, or ancient Greece, make to our understanding of science, commonly thought to have really begun in 16th-century Europe? There’s also new stuff on the evolution of consciousness and morality that repays reading. And the references are extensive and up to date. Do buy it, especially for the discussion of fine-tuning if you’re not acquainted with Stenger’s rebuttals. Fine-tuning is probably the most superficially convincing of recent science-based arguments for God.
I want to briefly reprise two of Stenger’s ideas here.
1. Free will. Stenger is a compatibilist, and says this, which, I think, is similar to what Dennett said in Freedom Evolves:
While “conscious will may be an illusion, it can be argued that our material selves do still possess a kind of free will. Every decision we make is the result of a complex calculation made by our individual conscious and unconscious brains working together. That calculation relies on input from our immediate circumstances and our past experiences. So the decision is uniquely ours, based on our specific knowledge, experience, and abilities. That seems pretty free to me. While others can influence us, no one has access to all the data that went into the calculation except our unique selves. Another brain operating according to the same decision algorithms as ours would not necessarily come up with the same final decision, since the lifetime experiences leading up to that point would be different.(p. 269)
This is a common compatibilist argument, which of course applies not just to humans, but to nearly every evolved creature that can modify its behavior according to past experience. It also applies to computers that have different software. If you take a computer program that “learns” from experience, like one that plays chess, and then give it different “experiences,” it will produce a different output. Is that free will? What Stenger is saying here is that each individual’s behavior is determined by its genetic and developmental (hence molecular) constitution as well as by how its past experience has modified its wiring. Here Vic and I agree. But because each individual’s wiring is different—because our “algorithms” are “unique”—then different inputs will regard in different outputs among different individuals. Yes, of course that’s true. But where is the “freedom” in all this? What Stenger is doing is equating the complexity of input and processing to “free will”, even though the output is completely determined by the input. I submit that there is no “freedom” in that, even though I’m sure that others can wring a tortured notion of “freedom” out of that.
2. Determinism. Lou Jost and other readers on this site have argued that behavior (and evolution) might not be deterministic because they’re affected by quantum-mechanical considerations. When I used the word “determinism” in the past, I suppose I was a bit inaccurate: what I meant was that behavior is determined by physical processes, both deterministic and quantum-mechanical, i.e., that there is nothing to our behavior beyond physics. I should have used “materialism” rather than “determinism”!
Now I’m not quite convinced that quantum mechanics plays a real role in both our decision-making or in the course of evolution. Can our “choices” really be affected by nondeterministic motions of molecules? And is mutation, a crucial factor in setting the course of evolution, really affected by quantum mechanics? I remain agnostic on these issues and am doing some reading to get up to speed.
Stenger does some interesting calculations to show that neurotransmission in the brain cannot be affected by quantum-mechanical events, and so in that respect the operation of our brain is truly deterministic (he also takes up and rejects the “microtubule hypothesis for quantum effects in the brain). But he admits the possibility of another way the actions of the brain might not be physically determined:
However, quantum effects can still involve brain processes by another route. The brain is bathed in electrically charged particles from cosmic rays (muons) that reach Earth and beta-rays (electrons fro the radioactive potassium isotope K40 in our blood. These are energetic enough to break atomic and molecular bonds, unlike the radio waves from power lines and cell phones that people worry about so much. And they are ultimately quantum mechanical. . . . We can imagine someone’s brain carrying out a classical algorithm, like a computer, bit a high-energy muon or electron breaks up a bit or two in either the code or the data and changes the outcome. This would result in the person making a random decision. But it would give the appearance of free will. (p. 272).
Now if this is the case, then we would have free will under my own definition, which is “given that all the initial molecular conditions obtaining at the moment of a decision remain the same when rerunning the ‘tape of that decision,’ you could have decided otherwise.” If there are unpredictable and non-deterministic quantum effects of the sort Stenger decides, then, yes, one could get two different “decisions” in exactly the same situation, and I would have to call that free will. Of course, there is no dualism here, for the quantum indeterminacy has nothing to do with consciousness, but under my definition that doesn’t matter. In fact, if one could replay the tape of a decision and find a different outcome, I don’t see any way to distinguish quantum effects from real spooky free will, except that we know there’s nothing other than material effects in the brain.
The big question, of course, is this: do the kind of effects Stenger describes here really happen in our brains, and can they really affect our behavior? Note that he says “we can imagine” that scenario, but what we can imagine doesn’t necessarily happen.
I doubt, however, whether any compatibilist will agree with Stenger that quantum effects of this sort play a role in free will, for they assert that our will is free even if there were no such effects. What I still don’t get is what part of the “free will” is “free”?
Anyway, read Vic’s book.
It’s snowing in Ithaca, and the Cornell Hawk Cam shows the female red-tailed hawk, “Big Red” sitting on her brood while covered with snow. One chick has hatched already and is vocalizing, and there are two more to go (perhaps one of those has hatched as well).
No worries: even though it’s snowing, it’s warm under the mother.
A screenshot:
Of course the birds have evolved to sit on their eggs regardless of weather or their own personal discomfort (those who didn’t left no offspring), but somehow the endurance of this bird invokes in me feelings of solicitude towards Big Red.
I’ve sorely neglected animal cams this spring, but alert reader M. May has called my attention to Cornell University’s red-tailed hawk cam sponsored by their Laboratory of Ornithology. It’s live, it’s in color, the female has laid three eggs, and . . . one is hatching right now! If you keep watching, you’ll see it hatch (assuming that mom gets off the egg, which she surely will).
GET OVER THERE NOW!
A Red-tailed Hawk pair has been nesting on a light pole 80 feet above Cornell University’s athletic fields on Tower Road for at least the past four years. In 2012, we installed a camera to get a better look at these majestic birds as they raise their young amid the bustle of a busy campus. So far, we’ve seen the birds bringing prey such as voles, squirrels, and pigeons to the nest.
Big Red and Her Mate
The female, nicknamed “Big Red” in honor of her alma mater, is slightly larger, with a darker head, nape and throat, and is banded on her right leg. From banding records we know she was banded in nearby Brooktondale, New York, during her first autumn in 2003, making her nearly nine years old.
The male, nicknamed “Ezra” after the co-founder of Cornell University, is banded on his left leg. He’s a bit smaller and has golden-tawny feathers on his face and head, and a paler neck than the female. He is at least seven years old and was first banded in 2006 as an adult bird on Judd Falls Road near the Cornell campus.
The Achilles heel of all theistic religion is the existence of evil. The ludicrous ways that theologians bob and weave in their theodicean attempts to explain it convince nobody but the already deluded—and gives the rest of us a good laugh
But Islam and conservative Christianity have a second Achilles heel: the existence of Hell. Can any thinking person really believe that a beneficent God would send people to eternal torment for sins like masturbation or adultery? Think of what it’s like to burn your hand badly on a stove; now imagine that torment, all over your body, for eternity. (And let’s not mention purgatory, which Catholics are jettisoning as fast as they can.) Such a notion is wicked and insupportable, and only someone who’s delusional, or who believes that God is a fiend, could accept something like that. The notion of hell, though, is not as damaging to religion as is evil, for it’s easy for believers and theologians to see hell as metaphorical. Evil, however, is real.
Well, theologian William Lane Craig does see hell as real—as an eternal torture chamber for sinners.
The anonymous writer of the website Evangelical Realism has been taking on, in successive posts, the chapters of William Lane Craig’s 2010 book, On Guard: Defending Your Faith with Reason and Precision. A week ago he dissected Craig’s Chapter 10: “Is Jesus the only way to God?”, in a post called “The Hell with Christianity.” It’s about Craig’s ridiculous (and literal) notion of hell, and the blog writer has a unique style that is at once sarcastic, funny, mildly obscene, and absolutely on the mark. Since it behooves all of us to consider the possibility that we’ll be boiled in molten sulphur for eternity, I’ve put two excerpts below.
In this section I’ve renumbered Craig’s “inconsistencies” because there are others preceding this discussion. Craig’s words are in quotes and italics.
Craig has a real problem here, and that is that he himself cannot stomach what the Bible really says about Hell. Read Matthew 25. Read Jesus’ description of God’s attitude towards the unsaved. It’s not, “Oh dear, you’re going to Hell, if only there were something I could do to save you.” God’s attitude can be summed up by two words: “Fuck you.” You pissed Me off, and I am throwing your ass in Hell, and you can stay there. No apologies, no regrets. The God of the Bible absolutely does throw people in Hell, and doesn’t ask for Craig’s approval or consent. Call that Inconsistency #3: Craig has to reinvent damnation before he can defend it.
“Our eternal destiny thus lies in our own hands. It’s a matter of our free choice where we shall spend eternity. Those who are lost, therefore, are self-condemned; they separate themselves from God despite God’s will and every effort to save them, and God grieves over their loss.”
Let’s count the inconsistencies in these three brief sentences. Inconsistency [#1]: a misinformed choice is not really free. God does not show up in real life, which limits us to the kind of choices where you either gullibly embrace whatever men tell you about God (and let’s face it, that could be almost anything) or else you stick to the facts, which ends up making you an atheist. If God is real and is hiding from us, His absence is denying us the opportunity to know what our real choices are, and thereby denying us the opportunity to make a truly free choice.
Inconsistency [#2]: separation. We have not separated ourselves from God. We’re here; God isn’t. It wasn’t skeptics who ascended into Heaven and left Jesus all alone here on the earth. We have no control over God’s willingness and ability to show up in real life. The gap created by His absence is not one we can bridge (not even by credulity and superstition). If God wants to eliminate the separation, it’s up to Him to show up.
Inconsistency [#3]: every effort to save us? Get real. The most fundamental, trivial, and obvious “effort” would be to show up in real life, tell us that He loves us, and offer us a relationship with Himself. Notice I say “in real life” and “tell us,” not “show up in an ancient legend” and “tell a few guys who died 2,000 years ago.” Does He want to save us, or did He stop caring once the apostles were gone? Show me a tangible effort happening in the real world (as opposed to happening in the superstitious worldview of a self-convincing Christian), and then we’ll talk.
Inconsistency [#4] God grieves? Not in the Bible. It makes believers sad because it’s so obviously inconsistent with the idea of God as a genuinely loving Father who really cares whether or not the vast majority of His children suffer for all eternity. But time and again, in the parables of Jesus, the “guilty” are dispatched to their eternal judgment with nary a particle of remorse or regret on the Lord’s part.
Here’s a piece explaining exactly how Craig rationalizes God’s imposition of infinite punishment for finite sins (again, Craig’s words are in italics):
“We could agree that every individual sin that a person commits deserves only a finite punishment. But it doesn’t follow from this that all of a person’s sins taken together as a whole deserve only a finite punishment. If a person commits an infinite number of sins, then the sum total of all such sins deserves infinite punishment.
Now, of course, nobody commits an infinite number of sins in the earthly life. But what about in the afterlife? Insofar as the inhabitants of hell continue to hate God and reject Him, they continue to sin and so accrue to themselves more guilt and more punishment. In a real sense, then, hell is self-perpetuating. In such a case, every sin has a finite punishment, but because sinning goes on forever, so does the punishment.”
Assuming God is merciless, of course. Otherwise, since He’s the ultimate arbiter of how much punishment each sin deserves, He could, for example, arrange for the punishment earned to be slightly less than the punishment received, and thus allow His beloved children to eventually escape from the torments of Hell. Or He could simply pardon them—it’s not like He’s going to be impeached for showing too much mercy as Judge. Or, to take it in a different direction, He could simply make them unconscious, or even non-existent. They might not be saved, but at least they’re not being tortured for all eternity, or racking up more punishment. Or again, He could not send them to Hell in the first place. The Bible does say that the wages of sin is death, and the people at the Last Judgment are pretty much all dead, so they’ve paid the penalty already.
Now, lest you think that only a small number of Americans accept the idea of a literal hell where sinners are actually tormented, have a look at this Pew report, “Religion among the millennials” (download pdf at link; “millennials” are those born around 1980 who came of age at the turn of the millennium). The data below are based on a huge survey—over 35,000 Americans 18 years of age or older—conducted in 2007.
On page 19 of the report we find a list of questions asked, and the answers given by the respondents:
Question wording:
The responses?
Now perhaps not all of the 60-odd percent of American who believe in Hell see it as a place where you’re licked by flames ad infinitum—some see the torment of Hell as “separation from god”—but I’m willing to bet that a substantial proportion of these envision fire, brimstone, and pitchforks (after all, around 70% of Americans believe in demons, and 60% in Satan). Once again we find that Americans’ religious beliefs are far stranger than most of us think.
For some reason, atheists are obsessed with narwhals, a fascination that I can’t quite understand. I mean, I do like them, but why do they come up so often, invariably accompanied by incredibly annoying narwhal songs? At any rate, let us leave this persiflage behind and deal with some real narwhal science, reported in a new journal paper. It’s an investigation of the nature of their tusks, and gives some fascinating results.
But first, a bit about the beasts. The species is Monodon monoceros (Greek for “one tooth, one horn—a clue to what its “horn” is), and its closest relative is the beluga whale (Delphinapterus leucas), with these two species constituting the entire family Monodontidae. Narwhals are small, with males growing up to only sixteen feet long, but they’re heavy: although three times as long as a human, they can weigh up to 4,000 pounds!
Their signal attribute is, of course, their “tusk,” which is really an upper tooth that protrudes not from the mouth, but from a hole in the upper “lip”. We’ll talk about this tooth in a minute:
The narwhal lives in the Arctic; here’s its range:
They subsist on squid, fish, and shrimp, which they swallow whole. Why? Because, with the exception of its tusk, the narwhal has no teeth. Here’s a shot of an adult narwhal mouth, as toothless as that of a newborn baby, taken from a Smithsonian Science report on this week’s paper (reference below). Credit for all remaining images: Narwhal Discoveries and http://www.narwhal.org
There has never been a single observation of narwhals feeding in the sea; all dietary information comes from analyzing stomach contents. They’re really a largely unstudied species.
It’s also one of the deepest-diving whales: the Narwhal FAQ from the University of Washington says this:
Narwhals typically dive to at least 800 meters between 18 and 25 times per day every day for 6 months. Many of these dives go even deeper than 800 meters: over half reach at least 1,500 meters (4,500 feet). Dives to these depths last around 25 minutes, including the time spent at the bottom and the transit down and back from the surface. In addition to making remarkably deep dives, narwhals also spend a large amount of their time below 800 meters (>3 hours per day). This is an incredible amount of time at a depth where the pressure can exceed 2200 PSI (150 atmospheres) and life exists in complete darkness.
Finally, they can live up to 90 years in the wild, are the only whales that overwinter in the Arctic pack ice (making them vulnerable to entrapment; see below), and there are about 80,000 of them worldwide.
On to the “tusk”. Wikipedia says this:
The most conspicuous characteristic of the male narwhal is its single 2–3 meter (7–10 ft) long tusk, an incisor tooth that projects from the left side of the upper jaw and forms a left-handed helix. The tusk can be up to 3 meters (9.8 ft) long—compared with a body length of 4–5 meters (13–16 ft)—and weigh up to 10 kilograms (22 lb). About one in 500 males has two tusks, which occurs when the right incisor [JAC: as we’ll see below, it’s really a canine tooth, so some Wikipedia editor should correct this], normally small, also grows out. A female narwhal has a shorter, and straighter tusk. She may also produce a second tusk, but this occurs rarely, and there is a single recorded case of a female with dual tusks.
The most broadly accepted theory for the role of the tusk is as a secondary sexual characteristic, similar to the mane of a lion or the tail feathers of a peacock. This hypothesis was notably discussed and defended at length by Charles Darwin, in The Descent of Man, and Selection in Relation to Sex (1871). It may help determine social rank, maintain dominance hierarchies, or help young males develop skills necessary for performance in adult sexual roles. Narwhals have rarely been observed using their tusk for fighting, other aggressive behavior or for breaking sea ice in their Arctic habitat.
This specimen clearly shows the spiral nature of the “tusk”:
According to one source, the narwhal’s “tusk” is the only straight tusk in the world, and one of the only spiral teeth. It’s also flexible, can bend a foot either way. The placement of the tusk on the left side of the body is a case of directional asymmetry: an animal asymmetry that goes in only one direction, as opposed to “fluctuating asymmetry” in which the asymmetry is random with respect to side. The lobster claw is an example of the latter: the claws are asymmetrical (a “grinder” and a “crusher”), but random with respect to side. Many species show directional asymmetries, including humans. Our heart, for example, tilts over to our left side, which is why we put our hands there to feel our heartbeat, and our right clavicle (“shoulder bone”) tends to be shorter than our left.
Here’s a double-tusked narwhal skull from the Smithsonian piece:
A brief digression: directional asymmetry has fascinated me because it implies that a gene somehow “knows’ whether it’s on the right or left side of the body. Once evolution has established a dorsoventral and an anterior-posterior body axis, then left and right are completely specified, and presumably in the ancestral animal the developmental cues were the same on both sides of the body. For a directional asymmetry to evolve, then, the gene for such a trait has to be activated consistently on the same side of the body, and hence be activated by some developmental “cue” that differs consistently between left and right. But the ancestor wouldn’t seem to have such cues! How this happens is a mystery, though work on mice has shown that it may all stem from the direction in which the cilia of the embryo beat. And, of course, once you’ve evolved one directional asymmetry, that sets up a left-right difference that can serve as a developmental cue for the evolution of further directional asymmetries.
But let’s proceed to the new data, given in a new paper in The Anatomical Record (reference below; free download; see also http://www.narwhal.org)) by M. T. Nweeia et al. Martin Nweeia is a New England dentist who also has appointments at the Smithsonian, Harvard’s Museum of Comparative Zoology,and the Harvard School of Dental Medicine; and his dentistry training plays a big role in the paper. The authors examined 131 narwhal skulls (110 from museums, the rest from kills), and did fine-structure dissection of the skull and “tusk” as well as CT imaging. And they found some cool things:
The next photo shows two vestigial teeth embedded in the bone horizontally, along with enlargements:
And here are some of these vestigial teeth, with a scale to show size. Note that although the teeth are deformed, they have roots and crowns. Their status as “teeth” is also confirmed by histological studies showing a pulp chamber inside that is surrounded by dentin and cementum.
These are true vestigial features, testifying to the descent of narwhals from toothed ancestors. And they’re clearly nonfunctional. Let some creationist come out of the woodwork and explain how they’re really useful after all (though a vestigial trait doesn’t have to be nonfunctional, viz., the ostrich’s wings). I’m sure one will. Nweeia et al. say this:
The small size of some vestigial teeth, 3 mm by 1 mm, makes them difficult to locate during dissection, even with good imaging aids. Their location in subadult and adult maxillae is posteroventral and lateral to the tusks and their varied expressions in root (Fig. 13) and crown (Fig. 14) morphology suggest a lack of any defined functional significance.
“As the erupted tusk of Monodon monoceros is distinguished by unique morphology and expression (Arvy, 1978; Hay and Mansfield, 1989) including an extreme example of dental asymmetry (Arvy and Pilleri, 1977; MacLeod et al., 2007) and sexual dimorphism in mammalian teeth, horizontal impaction in the maxilla, eruption through the upper lip, and a cementum covering over its entire exposed length, it can be considered a novel innovation (Nitecki, 1990; Muller and Wagner, 1991). As there is no ancestral condition that accounts for this expression, conventional mechanisms of evolution do not help explain this organ system. Behavioral observations are also difficult to collect and piece together in a conclusive discussion of functional significance (Silverman, 1979; Best, 1981). Such a phenotypic novelty is more likely explained as an epigenetic byproduct of selection.”
I’m not sure what the authors mean by saying “conventional mechanisms of evolution do not help explain this organ system.” Do they mean that the tusk was not subject to selection for its presence as a large protruding tooth, but for some other reason? Or that there are other mechanisms of evolution (genetic drift?) that are involved?
Nweeia said something similar in his interview in the Smithsonian piece:
“The whole thing that is great about the teeth of the narwhal is that nothing makes sense,” Nweeia adds. “The tusks are an extreme example of dental asymmetry. They exhibit uncharacteristic dimorphic or sexual expressions since females do not exhibit erupted tusks as commonly as males. Also, the tusk has a straight axis and a spiraled morphology. Conventional mechanisms of evolution do not help explain these expressions of teeth.”
It seems likely to me that a form of selection was involved here: sexual selection. And that’s because the “tusk” is found only in males. When one sees an ornament or excrescence like this that’s limited to males, the immediate hypothesis is sexual selection, often based on female choice. Now it’s not clear whether in this case the males actually joust with their tusks to win females, or that females use the size or presence of tusks as a way to judge mates, or whether some other form of sexual selection is going on, but I think that sexual selection is ultimately responsible. That could be tested in principle: by seeing whether females prefer tusked over untusked males, two-tusked over one-tusked males, or males with longer rather than shorter tusks. We can’t do this of course, but perhaps there are indirect ways to test for sexual selectin.
To me the real mystery is how the toothed ancestor developed into the narwhal: how all the teeth but one canine tooth disappeared, and how that tooth changed its development from erupting from the gums to erupting through the upper lip. It’s hard to imagine the intermediate stages of that transformation, yet if it was impelled by sexual selection, each step in this process must have incurred a selective advantage over its predecessor. I have no clue here, as I haven’t thought about it deeply and at any rate don’t have the dental expertise. Perhaps one clue is that the vestigial teeth are, like the tusk, oriented horizontally: perhaps this is a sign of how it might have happened developmentally.
Intelligent design advocates may see this as some kind of “irreducible complexity,” in which the intermediate stages weren’t adaptive and hence required the hand of God. Readers may want to weigh in below with their scenarios of how evolution produced the tusk. But when the authors say, “Such a phenotypic novelty is more likely explained as an epigenetic byproduct of selection,” they should provide some clues about what they mean. What kind of selection: sexual or natural? What is the real trait that was subject to selection? And how can such a bizarre malformation of a tooth be a mere “epigenetic byproduct”? This is all fertile ground for evolutionary biologists, but my guess, again, is sexual selection, which has caused the evolution of many bizarre traits in male animals (have a look at the New Guinea birds of paradise, for instance).
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Finally, here’s a National Geographic video I found of a narwhal pod (they travel is groups of variable size), including an “ice entrapment,” which the narwhal FAQ describes this way:
Q. What is an ice entrapment?
Although narwhals spend much of their time in heavy ice, they are vulnerable to unique events called ice entrapments or ‘sassats’. During an ice entrapment, hundreds of whales might become trapped in a small opening in the sea ice and they often die. This occurs when sudden changes in weather conditions (such as shifts in wind or quick drops in temperature) freeze the open water and the leads and cracks are sealed shut. Narwhals occupy dense pack ice for half of the year and are incapable of breaking holes in dense ice. There have been no direct observations of narwhal ice entrapments in central Baffin Bay because the area they routinely occupy is hundreds of kilometers from shore and is rarely visited by humans. There are, however, reports of large coastal ice entrapments in areas near where humans live.
Note the highly misleading statement in the video: “They use it for jousting, but it doesn’t seem to serve any evolutionary purpose.” Well, I don’t know what the term “evolutionary purpose” means, but I think they mean it doesn’t have any obvious function. My own guess is that it’s a sexually selected ornament, and thus does have a function: to attract female narwhals.
h/t: Michael
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M. T. Nweeia. F. C. Eichmiller, P. V. Hauschka, E. Tyler, J. G. Mead, C. W. Potter, D. P. Angnatsiak, P. R. Richard, J. R. Orr, and S. R. Black. 2012 Vestigial tooth anatomy and tusk nomeclature for Monodon monoceros. Anat. Rec. online: DOI: 10.1002/ar.22449
