Evolution, Hiccups And Impacted Molars

[FSTargetDrone]

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Posted on Mon, Apr. 21, 2008

We're not finished yet

Mankind is no perfect work. As a product of evolution, the design is haphazard, part fish and part monkey.

By Faye Flam

Inquirer Staff Writer

'Oh what a piece of work is man," wrote Shakespeare, long before Darwin suggested just how little work went into us. Somehow, that same process that gave us reason, language and art also left us with hernias, male nipples, impacted wisdom teeth, flatulence and hiccups.

One argument scientists often make against so-called intelligent design - the idea that evolution cannot by itself explain life - is that on closer inspection, we look like we've been put together by someone who didn't read the manual, or at least did a somewhat sloppy job of things.

Viewed as products of evolution, however, our anatomical quirks start to make sense, says University of Chicago fossil hunter and anatomy professor Neil Shubin, author of the recent book Your Inner Fish (Pantheon Books). And by focusing on our less lofty traits, evolutionary biology can help dispel one of the most egregious and even tragic fallacies surrounding Darwinian evolution - that it moves toward perfection, with man at the apex of some towering ladder.

That misreading of evolution has been connected to the eugenics movement of the early 20th century, with the Nazis extending the man-as-ideal notion to blue-eyed blond German-man-as-ideal notion.

"Darwin didn't believe it, but some, who saw it through a more religious light, tended to want to interpret evolution as a steady march toward the pinnacle of humanity," says Penn (University of Pennsylvania) ethicist Art Caplan, who has written extensively on the eugenics movement.

By today's understanding, evolution by natural selection doesn't march toward anything - it just modifies existing creatures to better compete in ever-shifting environments.

Understanding something as seemingly trivial as the evolution of hiccups can help clear up some profound misperceptions on the nature of life and humanity.

The sound of a hiccup echoes back to our very distant past as fish and amphibians some 375 million years ago, says Shubin. It's really just a spasm that causes a sharp intake of breath followed by a quick partial closing of our upper airway with that flap of skin known as the glottis. It's best if you can nip it in the first couple of hics, he says.

It's much harder to stop once you've let yourself get up to 10. By that point you've reverted to an ancient breathing pattern orchestrated by the brain stem that once helped amphibians breath, letting water pass the gills without leaking into the lungs. "Tadpoles normally breathe with something like a hiccup," Shubin says.

The theme of his book is that we owe much of our anatomy to our animal ancestors. "Parts that evolved in one setting are now jury-rigged to work in another," he says. "When you look at the human body, you see layer after layer of history inside of us." The first layer is what we share with chimpanzees and gorillas. The next goes back to mice and cows, while further down, you get to the relatively underappreciated layers we share with fish - which include the backbone and basic layout of the body.

Our descent from fish explains why men are so much more prone to hernias than women. In fish, Shubin explains, the testicles lie up near the heart. (Had they remained there, he said, it would give a whole new meaning to the pledge of allegiance.)

The budding gonads still form up high in a human embryo, but male mammals reproduce better with their sperm kept a bit cooler than body temperature. And so during gestation, human testicles take an incredible journey down through the body to their destination in the scrotum. The trip downward puts a loop in the cord that connects the testes to the penis, leaving a weakness in the body wall where the cord attaches that never quite repairs itself.

Hence the trouble with hernias down the road.

Biologist Sean B. Carroll of the University of Wisconsin-Madison, author of The Making of the Fittest (W.W. Norton & Co.) and other popular books on evolution, says evolutionary leftovers are born of a "use it or lose it" system.

For example, he says, we carry damaged versions of genes for dozens of smell receptors that give mice and other mammals far sharper noses. "Our repertoire of smell-receptor genes has gone to pot," Carroll says.

Why couldn't we keep our ancestors' scent-tracking ability and lose, say, male nipples and wisdom teeth? The nipple issue is complicated, say biologists, by the fact that females need them to reproduce - or at least did for most of our existence. It may be hard to erase the trait in males without compromising it in females, especially since nipples form very early in a human embryo.

But at least male nipples don't cause men any major pain, unlike wisdom teeth, which can get impacted and then infected. That's a puzzle addressed in an exhibit called "Surviving: The Body of Evidence," which opened last weekend at the University of Pennsylvania Museum of Archaeology and Anthropology.

Fossils show that our ancestors had bigger jaws than we do, to fit all those teeth that they may have needed to chew uncooked meat and plants. But as our diet changed, our jaws got smaller.

Why did our jaws get smaller at the expense of our dental health? Several years ago, Penn medical researcher Hansell Stedman proposed a genetic explanation. He found that all humans share a mutation in a gene that remains in working order in our ape relatives. That mutation caused a degeneration of our jaws, rendering them much less powerful. It also allowed more room in our heads for the brain.

Using a technique known as a molecular clock, he counted the number of random changes in the gene to estimate that this new mutation took over about 2.4 million years ago, just as our ancestors were revolutionizing the use of stone tools.

We humans have the capacity to evolve away our wisdom teeth, according to geneticist Pragna Patel of the University of Southern California. As many as 25 percent of us are lucky enough to be missing these teeth, also known as third molars. A very few have mutations in a gene called Pax-9 which leads to other missing teeth.

No good story about human design flaws can pass up a discussion of flatulence - and science has addressed the kind that would occur if everyone in the world drank a tall glass of milk at the same time.

Patel said one of her favorite examples of evolution in progress involves the gene that determines who can digest the sugars in milk and who cannot. From genetic studies it appears that so-called lactose intolerance was our ancestral state.

A few people, however, were genetically gifted with an enzyme called lactase, which breaks down lactose, and in groups that started drinking lots of milk around 10,000 years ago, that version of the gene started to take over.

Scientists recently sequenced the lactase gene and found 43 different variations that allow adults to drink the milk of other animals. "It's the first clear evidence of convergent evolution," Patel said, though it's not known whether those lacking this innovation failed to pass on their genes because they suffered from lack of nutrition or just didn't get invited to any parties.

As for design, intelligent or otherwise, Shubin says the body only makes sense if viewed as a product of evolution. If it was designed, the designer could have done away with some of our relics of the past.

"This designer, if there was one, liked history, and he really liked fish."

Nothing really earth-shattering or new to most of the crowd here, I imagine, but what the hell, thought I'd share.

[cosmicalstorm]

Well i've tried using that argument against bible-thumpers, but they usually resort to some rambling about the sins of man making us imperfect or something like that.

[Qwerty 42]

I actually never knew about the hiccup thing, that was fascinating.

[Kanastrous]

Well i've tried using that argument against bible-thumpers, but they usually resort to some rambling about the sins of man making us imperfect or something like that.

It's this weird composite of stupid and crazy, that works like intellectual reactive armor...

[The Vortex Empire]

Ahh, so that's why we hiccup. Fascinating.

[Red Star]

I was watching Daily Planet on the Discovery channel and the host said that it is believed that hiccups occur when there is an uneven amount of air in the lungs (more in one side than the other) and that hiccupping is the bodies way to try and even out the amount of air.

Though I cant find anything to back it up there are also two other explanations for it

[Andrew_Fireborn]

An interesting read, and indeed... a facinating reason behind hiccups...

But seriously... male nipples? What the hell?... Flatulence I can understand being a fault, but who the bloody fuck thinks male nipples are a design flaw?... (some -variations- on nipples, yes... but really?)

[The Vortex Empire]

An interesting read, and indeed... a facinating reason behind hiccups...

But seriously... male nipples? What the hell?... Flatulence I can understand being a fault, but who the bloody fuck thinks male nipples are a design flaw?... (some -variations- on nipples, yes... but really?)

Do they serve any purpose? No. So they're unnecessary.

[Eulogy]

Evolution is also responsible for shit like the uterus needing to pass through the pelvis (thus limiting crainial growth) and big bellies making us hungier (thus starting a vicious cycle that eventually kills the afflicted).

Nature is either a shitty engineer, or an evil one, to introduce so many flaws that eventually kill us.

[Andrew_Fireborn]

Ah, but you're thinking in the standard fashion, IE males are a seperate and distinct product as opposed to a slightly different package deal. The accounts for why they exist...

Still, I know, I was basically venting over that silliness. Small pointless details tend to get under my skin. In the end, it's a big point for only one reason, it's a major, easily observed point for evolution. (What with the coccyx being, like most other obsolete parts, buried under all the meaty parts.)

But it always strikes me a little like why wondering why a car without AC has air vents. >_>

[Andrew_Fireborn]

Nature is either a shitty engineer, or an evil one, to introduce so many flaws that eventually kill us.

It's pretty much established at this point that nature is a very shitty engineer, because it never set out to be an engineer.

[Eulogy]

Nature is either a shitty engineer, or an evil one, to introduce so many flaws that eventually kill us.

It's pretty much established at this point that nature is a very shitty engineer, because it never set out to be an engineer.

Then nature clearly needs to go to university.

Seriously though, this means that even a mechanic can very well do a much better job designing a human. Which means that all those idiots screeching at us not to play god can go fuck themselves.

[Andrew_Fireborn]

Did you never wonder why everyone here is so, to steal the word, righteously indignant about the whole evolution debate?

Yeah, I'm not sure it would even take a trained mechanic to not make some of the mistakes. And the "Play god" people always amuse me, because that's all humanity's ever tried to do. Combine with the fact that most of them hail from a splinter faction of a religeon that has a man specifically chosen to play god...

[Eulogy]

Did you never wonder why everyone here is so, to steal the word, righteously indignant about the whole evolution debate?

Of course. After all, why teach fairy tales as fact?
Yeah, I know that doesn't stop some fucktards from trying anyway.

Yeah, I'm not sure it would even take a trained mechanic to not make some of the mistakes. And the "Play god" people always amuse me, because that's all humanity's ever tried to do. Combine with the fact that most of them hail from a splinter faction of a religeon that has a man specifically chosen to play god...

The irony and hypocrisy is delicious, is it not?

[LadyTevar]

Evolution is also responsible for shit like the uterus needing to pass through the pelvis (thus limiting crainial growth) and big bellies making us hungier (thus starting a vicious cycle that eventually kills the afflicted).

Nature is either a shitty engineer, or an evil one, to introduce so many flaws that eventually kill us.

If the Uterus is passing through the Pelvis, something is really fucking wrong with you, and it's got nothing to do with a cranium.

[FSTargetDrone]

But it always strikes me a little like why wondering why a car without AC has air vents. >_>

Because even cars without air conditioning generally still have heaters (and fresh air routed to the vents inside) as standard equipment.

[kc8tbe]

I was under the impression that lactose tolerance in adults is the result of a mutation that inactivates the gene that is supposed to shut down lactase production after infancy (infants produce lactase so that they can digest breast milk), not some new gene that codes for lactase production. Presumably our ancestors, who did not drink milk beyond infancy, would have benefited from not wasting energy producing lactase in adulthood.

[Dargos]

Evolution is also responsible for shit like the uterus needing to pass through the pelvis (thus limiting crainial growth) and big bellies making us hungier (thus starting a vicious cycle that eventually kills the afflicted).

Nature is either a shitty engineer, or an evil one, to introduce so many flaws that eventually kill us.

If the Uterus is passing through the Pelvis, something is really fucking wrong with you, and it's got nothing to do with a cranium.

I think Eulogy is talking about the passing of the baby through the pelvic brim and under the pubic arch during child birth.

The pelvis is made up of four bones, which support the growing baby during pregnancy and form a tunnel through which the baby passes during birth.

The two large hip bones join together in the front at the pubic arch, which is held together by a pad of cartilage. The sacrum and the coccyx together form the back part of the pelvis, which is connected to the hipbones on either side. The shape and position of these joints enables the bones to move in ways that increase the size and capacity of the pelvis as the baby grows

Cephalopelvic disproportion, in which the baby's head is deemed too big for the mother's pelvis can obviously cause problems for mothers, but doctors really won't be able to tell until the woman has had a chance for a normal labor because measurements obtained through ultrasound will not give an indication of the true capacity of the pelvis during labour.