If you want to understand how humans evolved, there's a few species you obviously want to look at.
如果想了解人類如何進化，就有必要對幾類物種做一番認真研究。
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.
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，一些不相關但是以擁有智力和大體積大腦而著稱的動物也值得探究，比如烏鴉和海豚。
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.
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.
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.
人類與大熊貓均為哺乳動物，包括犬、鼠和熊在內的大多數哺乳動物在大多數時間裡均依靠四肢支撐身體。
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.
Humans are different. We hold our backs and spines vertically, at right-angles to the ground. Apes often do the same thing.
人類則不同。人類的背部和脊柱直立，與地面垂直。猿類動物也常常採用這種姿勢。
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.
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.
In common with other bears, they spend a lot of time sitting on their bottoms, back upright.
和其他熊類動物一樣，大熊貓一天內有很長時間是以背部直立的姿勢端坐在地上。
Russo and Williams wanted to find out if pandas' spines had also changed shape in a similar way to ours.
羅素和威廉姆斯希望了解大熊貓的脊柱是否像人類一樣曾經在遠古的進化過程中改變了形狀。
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.
They compared the shapes of individual backbones – vertebrae – from pandas and closely-related bears.
他們比較了大熊貓及其近親——熊的椎骨形狀。
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.
If pandas and apes evolved their upright posture for the same reason, what could that reason be?
如果大熊貓和靈長類動物是由於同一原因而各自進化出直立姿勢，這個原因會是什麼呢？
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.
Instead it might all come down to something very simple: sitting upright on one's bottom.
真正的原因可能很簡單：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.
giant pandas
為什麼人類和大熊貓有驚人相似之處
If you want to understand how humans evolved, there's a few species you obviously want to look at.
如果想了解人類如何進化，就有必要對幾類物種做一番認真研究。
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.
作為人類的近親，黑猩猩就是一個很理想的研究對象，它能為人類始祖類人猿的研究提供線索。基於同樣的原因，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，一些不相關但是以擁有智力和大體積大腦而著稱的動物也值得探究，比如烏鴉和海豚。
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.
你肯定不會去研究大熊貓。儘管很萌很可愛，但是它們跟人類毫不相關，因為它們既非人類近親，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.
這些都沒錯。但是一項新近研究發現，大熊貓和人類的進化可能有非常密切的相關性。這種相關性可能有助於解答關於人體結構的一個最特別之謎：人為什麼直立行走？
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.
人類與大熊貓均為哺乳動物，包括犬、鼠和熊在內的大多數哺乳動物在大多數時間裡均依靠四肢支撐身體。
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.
動物在用四足行走時，背部沿水平方向與地面平行。這種姿勢反過來決定了動物背部骨骼的排列方式，以及背部與四肢骨骼的連接方式。
Humans are different. We hold our backs and spines vertically, at right-angles to the ground. Apes often do the same thing.
人類則不同。人類的背部和脊柱直立，與地面垂直。猿類動物也常常採用這種姿勢。
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.
問題在於，動物界什麼時候出現了這種直立姿勢，為什麼會出現？為了找尋問題的答案，紐約州立大學石溪分校的加布裡埃爾.羅素(Gabrielle Russo)和紐約大學的斯科特.威廉姆斯(Scott Williams)決定將人類與其他背部直立的動物進行比較研究。
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.
由於猿類和猴類在歷史上曾經經歷了與人類同樣的進化壓力，導致很難理清有哪些因素造成了那些特定的進化變異。因此，他們決定研究其他背部直立的動物。
That's where giant pandas come in.
這就是為什麼要把大熊貓作為研究對象的原因。
In common with other bears, they spend a lot of time sitting on their bottoms, back upright.
和其他熊類動物一樣，大熊貓一天內有很長時間是以背部直立的姿勢端坐在地上。
Russo and Williams wanted to find out if pandas' spines had also changed shape in a similar way to ours.
羅素和威廉姆斯希望了解大熊貓的脊柱是否像人類一樣曾經在遠古的進化過程中改變了形狀。
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.
如果上述性狀同為進化的產物，就說明大熊貓和人類出於類似的原因而進化出直立姿勢。而如果大熊貓的脊柱形態與人類不同，則說明大熊貓進化出直立姿勢的原因與人類不同。
They compared the shapes of individual backbones – vertebrae – from pandas and closely-related bears.
他們比較了大熊貓及其近親——熊的椎骨形狀。
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.
與其近親相比，大熊貓脊柱下半部的椎骨數量較少，同時椎骨形狀也不相同。當我們形狀如猴類的祖先進化成為古猿時，也發生過同樣的變化。
If pandas and apes evolved their upright posture for the same reason, what could that reason be?
如果大熊貓和靈長類動物是由於同一原因而各自進化出直立姿勢，這個原因會是什麼呢？
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.
傳統研究認為，靈長類動物的特殊脊柱形狀是由於其用雙臂在樹枝間懸掛跳躍，以及在垂直樹幹上攀爬的習性所造成的。但是大熊貓卻沒有這兩種習性，因此，羅素和威廉姆斯認為上述原因站不住腳。
Instead it might all come down to something very simple: sitting upright on one's bottom.
真正的原因可能很簡單：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.
“大猩猩每天花費大量時間直立坐在在地上吃竹子和其他植物的葉片，”羅素和威廉姆斯說。坐在地上能解放它們的雙手，用來抓取和整理樹葉。
The same might apply to giant pandas, which famously have to spend most of their time sitting around eating bamboo.
大熊貓每天也有大量時間坐在地上吃竹子，因此可能也經歷了類似的進化過程。
Russo and Williams think that apes probably began evolving upright postures 15-20 million years ago.
羅素和威廉姆斯認為，大猩猩可能是在1500-2000萬年前開始進化出直立坐姿的。
"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，其下部椎骨已經為適應直立坐姿而改變了形狀，”他們說。
The line that would lead to humans then split from the rest of the apes sometime between 13 and 7 million years ago.
人類的祖先是在1300-700萬年前與其他古猿物種分道揚鑣的。