我们终于知道为什么袋熊会拉完美的立方体了

Like other herbivores, wombats poop a lot, but unlike any other known species, their droppings are almost cubic, the size and shape of dice. Biologists have long had an explanation for why this is, but have now mostly explained the how.

和其他食草动物一样，袋熊也会大量排便，但与其他已知物种不同的是，它们的粪便几乎是立方体的，大小和形状都像骰子。长期以来，生物学家们一直对这一现象有一个解释，但现在主要解释的是如何发生的。

Anything practiced by one animal species alone among all the millions on Earth is interesting, and biologists have long been intrigued by wombats' distinctive droppings. Moreover, even world leaders in animal preservation recognize wombats' special excellence. The shape is thought to help wombats mark their territory, by allowing them to produce tall piles that don't roll down the often steep hillsides of their habitat.

在地球上数百万种动物中，只有一种动物的行为是有趣的，生物学家长期以来一直对袋熊独特的粪便感兴趣。此外，即使是世界动物保护领袖也承认袋熊的特殊优点。人们认为，这个形状可以帮助袋熊标记自己的领地，因为它们可以堆出高高的堆，而不会从栖息地陡峭的山坡上滚下来。

However, many other species use dung to mark their territory, and have never come up with this useful innovation, for the simple reason it isn't easy to construct a digestive system that produces cubic, rather than broadly cylindrical, shapes. Now the wombat's secret has finally been revealed and published in the journal Soft Matter.

然而，许多其他物种用粪便来标记自己的领地，而且从来没有发明过这种有用的创新，原因很简单，要构建一个只能产生立方体而不是圆柱形的消化系统并不容易。现在袋熊的秘密终于被揭开，并发表在《软物质》杂志上。

Stephen Luntz

The work was led by Dr Patricia Yang of the Georgia Institute of Technology, proving wombat-love is truly a universal language. "The first thing that drove me to this is that I have never seen anything this weird in biology. That was a mystery," Yang said in a statement. "I didn't even believe it was true at the beginning. I Googled it and saw a lot about cube-shaped wombat poop, but I was skeptical."

这项工作由乔治亚理工学院的Patricia Yang博士领导，证明了袋熊的爱确实是一种通用语言。“驱使我这么做的第一件事是，我在生物学上从未见过这么奇怪的事情。这是一个谜，”杨在一份声明中说。“一开始我甚至不相信这是真的。我在谷歌上搜索了一下，看到了很多关于袋熊的方形粪便的信息，但我对此持怀疑态度。”

So Yang, who studies fluid dynamics within the body, did the appropriately scientific thing. She obtained digestive systems of wombats tragically killed by cars and inflated their intestines. The widespread assumption wombat anuses must be square has long been debunked, and Yang also contradicted the previous theory that the cubic shape is formed at the top of the intestine.

所以，研究人体流体动力学的杨做了一件恰当的科学事情。她获得了不幸被汽车撞死的袋熊的消化系统，并使它们的肠道充气。人们普遍认为袋熊的肛门一定是方形的，但这一假设早已被推翻，杨教授也反驳了先前的立方体是在肠道顶部形成的理论。

Instead, the digested wombat food comes down the gut in a semi-liquid state, only to solidify in the last 8 percent of the intestine, something Yang and colleagues attribute to alternating rigid and flexible stretches of the intestine walls. These apply very different strains to the cubes' corners and edges to produce the cubic shapes.

相反，袋熊消化后的食物会以半液态的状态进入肠道，只会在最后8%的肠道中凝固，杨及其同事认为这是由于肠道壁的刚性和柔性交替拉伸造成的。它们对立方体的边角施加了非常不同的张力，从而产生了立方体的形状。

Because you'd probably rather look at wombats than their droppings. Paul Looyen/Shutterstock

Curiosity-inspired research always attracts allegations of wasting tax-payer funds, but Yang thinks there could be practical outcomes besides the satisfaction the results bring. "We currently have only two methods to manufacture cubes: We mold it, or we cut it. Now we have this third method," she said. Whether replica wombat intestines will prove advantageous in producing industrial parts remains to be seen, but it's possible future manufacturing revolutions could be inspired by the wombat's gut.

出于好奇的研究总是会引来浪费纳税人资金的指控，但杨认为，除了结果带来的满足感外，还可能有实际的结果。“我们目前只有两种制造立方体的方法:模塑或切割。现在我们有了第三种方法，”她说。仿制袋熊肠子在生产工业部件方面是否有优势还有待观察，但未来的制造业革命可能会受到袋熊肠子的启发。

One thing Yang hasn't solved, however, is the old question of how painful it is for wombats to be constantly shitting (small) bricks.

然而，杨还没有解决的一个老问题是，袋熊不断拉小砖块有多痛苦。

A version of this article was first published on 19 November 2018.

本文首次发表于2018年11月19日。