Friday, November 23, 2018

Science Story of the Year So Far

I was reading other people's blogs today, and both Bayou Renaissance Man and Borepatch had stories that made me want to do a serious blog post about important things.

And then I got an email today about a scientific fact and exploration of how it works that are without a doubt the biggest science story of the year.

Wombats poop little cubes, about 3/4" on a side.  I did not know that.  You Aussies can laugh at me now, but I've never seen a wombat in person before, and certainly never seen their poop.  The story is about a group that researched and discovered exactly how cubical poop is formed.  As the friend who sent me the email said, "when you read this, you'll shit a brick".  Well, the wombats will.

Derek the wombat at 8 months old.  Derek was rescued from his mother's pouch after she was hit by a car in December 2015.  It doesn't say if Derek is still alive, or what the life expectancy of a wombat is.
The wombat, native to Australia, produces about 80 to 100 cubes of poop each night. It is known to deposit piles of dung outside burrows and on top of rocks and logs, most likely to communicate with other wombats, researchers believe.

"Wombats have really strong sense of smell that they use probably for communication," said University of Tasmania wildlife ecologist Scott Carver, who co-authored the study. "We don't know what that information they're sharing is, but it might be something about mating, it might be something about general advertising about who's in the area."

It is thought that the cubed shape of the poop means it is less likely that it will roll away, and is prominent for other individuals to notice and smell, Carver added.
Less likely to roll away?  Do wombats only poop on steep inclines or hills?  I suppose it's a plausible explanation, but exactly how they could extrude cubical poop when every other species ever observed extrudes more or less cylindrical poop was never understood.  Then the article runs what I think is my favorite sentence of the last year, or more:
Researchers, led by the Georgia Institute of Technology's Patricia Yang, said they have uncovered the digestive processes behind the mystery and presented their findings at the 71st Annual Meeting of the American Physical Society's Division of Fluid Dynamics in Atlanta on Sunday.
The American Physical Society is about as prestigious an academic society as there is.  I bet nobody there had another APS paper on poop formation, though. 
To solve the puzzle, the team examined the digestive tracts of wombats that had to be euthanized following vehicle collisions in Tasmania, Australia.

The wombat takes about two weeks to digest its food and researchers found that as faeces move into the final 8% of the intestine, it changes from a liquid-like state into solid matter. At that stage the dung takes on the shape of separated cubes measuring about two centimeters in length.

"The weird thing is that if you open up a wombat you actually find that the cubes become formed in the lower part of the intestine, before they exit the body," Carver said.

By inflating the intestine with a long balloon, the researchers found that the wombats' intestine walls stretch unevenly, allowing for the formation of the cube shapes.

"The local strain varies from 20% at the cube's corners to 75% at its edges," the team said.

"Basically around the circumference [of the intestine], there are some parts that are more stretchy and some parts that are more stiff," Carver said. "And that is what creates the edges and the cubing."
There ya go, if you'll pardon the expression.  The wombats' intestinal walls are stretchier in some place and stiffer and others; exactly what you'd need if you were trying to design a system to extrude cubes. 

As I understand natural selection and evolutionary theory, a trait survives to become dominant in a species if it offers survival advantage - or comes along with other genes that do offer survival advantage.  That means the cubical poop must be important to the wombat - not in the sense of wildlife bar bets like saying "I bet you can't poop a cube like I can"; it has to increase the chance of surviving and mating.  Perhaps, at some point, some proto-wombat ancestor dude got to mate more because the proto-wombat ancestor babes were impressed with their cubical poop.  "I was going to pair up with Jeffy, but Todd poops these beautiful little cubes!"  Maybe cubical poop was thought to be so cute that the wombats who could produce it got all the girls and the ability spread through the wombat population like wildfire.  Or you could say God has a sense of humor.


  1. Cubical Poop......the mind boggles at the implications....

  2. There were always euphemisms in the military about 'stacking shit'. You can't stack that high, etc. Now it might be possible for science to arrange surgery that would allow shit to be stacked. Imagine that. It is the science story of the year...that and the coming ice age.

  3. Well, I'll throw out a wild-ass posit out there: if the material becomes solid in the last bit of the intestine, unless it is broken up into pieces it won't be able to exit the intestine and the animal will die. There is probably a mathematical reason why cubical shapes are more likely than chunks of cylindrical shapes when you start randomly changing the stretchiness of the mold form.

  4. And a supporting observation: a long chunk of hard material can only be pressured by contracting the upstream bit of the intestine it sits in, but small chunks are each pushed by a contraction. Thus you are comparing pushing mass M with force F, or mass M/n with n forces F.

  5. That is some interesting s**t there.
    I wonder if the famous Play-Doh press was designed after an engineer returned from a trip to the land down under.
    And it puts a different spin on "Be there, or be square."

  6. It's all perfectly obvious:
    The wombat co-evolved with a castle-building species that needed bricks for construction material; the castles would shelter both the builder and the wombat.
    Alas, the wombat, having been the low bidder on the brick-supply contract, only evolved as far as producing cubes, never attaining the proper oblong brick format.
    Lacking the promised supply of bricks, the builder species went extinct.
    The wombat retains its partially-evolved poopforming capability just in case of renewed war against the Turk, for which square sh*t might be in demand.

  7. Correct me if I am wrong, but if their doody is cubical, does it really measure 2cm in length? Or is it 2cm on a side? If not, how is it cubical? Asking for a friend.

    1. B. 2cm on a side. Or it's at least lots more cubical than any other species' poop