好英语网为什么人类和大熊猫有惊人相似之处
If you want to understand how humans evolved, there's a few species you obviously want to look at.
如果想了解人类如何进化，就有必要对几类物种做一番认真研究。
Chimpanzees are a good bet. After all, they're our closest relatives, so they offer clues about our ape-like ancestors. Monkeys are also worth a look, for similar reasons.
作为人类的近亲，黑猩猩就是一个很理想的研究对象，它能为人类始祖类人猿的研究提供线索。基于同样的原因，猴子也值得研究一番。
You might also want to look at unrelated animals that are noted for their intelligence and big brains. Crows or dolphins would be good.
另外，一些不相关但是以拥有智力和大体积大脑而著称的动物也值得探究，比如乌鸦和海豚。
You surely wouldn't bother studying a panda. Sure, they are cute, but they have nothing to do with us. They aren't a close relative, and they aren't packing a lot of brainpower.
你肯定不会去研究大熊猫。尽管很萌很可爱，但是它们跟人类毫不相关，因为它们既非人类近亲，而且智力水平也一般。
That's all true, but according to a new analysis, pandas might be extremely relevant to our evolution. They could help explain one of the most peculiar things about the human body: our upright posture.
这些都没错。但是一项新近研究发现，大熊猫和人类的进化可能有非常密切的相关性。这种相关性可能有助于解答关于人体结构的一个最特别之谜：人为什么直立行走？
Humans and pandas are both mammals, and the majority of mammals spend most of their time on four legs. From dogs and rats to bears and elephants, that's the norm.
人类与大熊猫均为哺乳动物，包括犬、鼠和熊在内的大多数哺乳动物在大多数时间里均依靠四肢支撑身体。
Walking around on four legs means that your back is horizontal, parallel to the ground. That in turn determines how the bones in your back are arranged, and how they join to your leg and arm bones.
动物在用四足行走时，背部沿水平方向与地面平行。这种姿势反过来决定了动物背部骨骼的排列方式，以及背部与四肢骨骼的连接方式。
Humans are different. We hold our backs and spines vertically, at right-angles to the ground. Apes often do the same thing.
人类则不同。人类的背部和脊柱直立，与地面垂直。猿类动物也常常采用这种姿势。
The question is, when and why did this upright posture evolve? To find out, Gabrielle Russo of Stony Brook University in New York and Scott Williams of New York University decided to compare humans with another species that holds its back upright.
问题在于，动物界什么时候出现了这种直立姿势，为什么会出现？为了找寻问题的答案，纽约州立大学石溪分校的加布里埃尔.罗素(Gabrielle Russo)和纽约大学的斯科特.威廉姆斯(Scott Williams)决定将人类与其他背部直立的动物进行比较研究。
They wanted something that wasn't an ape or a monkey, because those species have experienced a lot of the same evolutionary pressures as us. That makes it hard to disentangle which factors caused which evolutionary shift.
由于猿类和猴类在历史上曾经经历了与人类同样的进化压力，导致很难理清有哪些因素造成了那些特定的进化变异。因此，他们决定研究其他背部直立的动物。
That's where giant pandas come in.
这就是为什么要把大熊猫作为研究对象的原因。
In common with other bears, they spend a lot of time sitting on their bottoms, back upright.
和其他熊类动物一样，大熊猫一天内有很长时间是以背部直立的姿势端坐在地上。
Russo and Williams wanted to find out if pandas' spines had also changed shape in a similar way to ours.
罗素和威廉姆斯希望了解大熊猫的脊柱是否像人类一样曾经在远古的进化过程中改变了形状。
If they had, it would suggest that pandas and humans evolved their upright postures for similar reasons. On the other hand, if pandas' spines were not like ours, that would suggest that they evolved their upright posture for different reasons.
如果上述性状同为进化的产物，就说明大熊猫和人类出于类似的原因而进化出直立姿势。而如果大熊猫的脊柱形态与人类不同，则说明大熊猫进化出直立姿势的原因与人类不同。
They compared the shapes of individual backbones – vertebrae – from pandas and closely-related bears.
他们比较了大熊猫及其近亲——熊的椎骨形状。
Compared to their closest relatives, pandas had fewer vertebrae in their lower backs, and the vertebrae were a different shape. The same change happened when our monkey-like ancestors evolved into apes.
与其近亲相比，大熊猫脊柱下半部的椎骨数量较少，同时椎骨形状也不相同。当我们形状如猴类的祖先进化成为古猿时，也发生过同样的变化。
If pandas and apes evolved their upright posture for the same reason, what could that reason be?
如果大熊猫和灵长类动物是由于同一原因而各自进化出直立姿势，这个原因会是什么呢？
Traditionally, apes' spinal shapes have been explained by their habit of swinging below tree branches using their arms, or climbing vertical tree trunks. But pandas don't do either of those things, so Russo and Williams say they are unlikely to be the explanation.
传统研究认为，灵长类动物的特殊脊柱形状是由于其用双臂在树枝间悬挂跳跃，以及在垂直树干上攀爬的习性所造成的。但是大熊猫却没有这两种习性，因此，罗素和威廉姆斯认为上述原因站不住脚。
Instead it might all come down to something very simple: sitting upright on one's bottom.
真正的原因可能很简单：坐姿。
"Gorillas spend a significant amount of time sitting in upright posture and eating bamboo and other foliage," say Russo and Williams. Sitting upright leaves their hands free to pick and trim leaves.
“大猩猩每天花费大量时间直立坐在在地上吃竹子和其他植物的叶片，”罗素和威廉姆斯说。坐在地上能解放它们的双手，用来抓取和整理树叶。
The same might apply to giant pandas, which famously have to spend most of their time sitting around eating bamboo.
大熊猫每天也有大量时间坐在地上吃竹子，因此可能也经历了类似的进化过程。
Russo and Williams think that apes probably began evolving upright postures 15-20 million years ago.
罗素和威廉姆斯认为，大猩猩可能是在1500-2000万年前开始进化出直立坐姿的。
"There are fossil apes like Pierolapithecus that show adaptations in their lower backs to upright posture," they say.
“Pierolapithecus 等古猿化石表明，其下部椎骨已经为适应直立坐姿而改变了形状，”他们说。
The line that would lead to humans then split from the rest of the apes sometime between 13 and 7 million years ago.
人类的祖先是在1300-700万年前与其他古猿物种分道扬镳的。