The evolution of puppy dog eyes

宠物狗狗的眼睛进化

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上海译锐翻译          2019-6-20               14:17p.m.

Dogs have evolved new muscles around the eyes to better communicate with humans.

为了能够更好地与人类交流，宠物狗的眼部进化出了新的肌肉。

New research comparing the anatomy and behavior of dogs and wolves suggests dogs' facial anatomy has changed over thousands of years specifically to allow them to better communicate with humans.

在一项对比狗和狼解剖构造和行为的新研究中，人们发现狗狗的脸部解剖构造在数千年来已经发生了特定的改变。这一特定改变可以使狗狗更好的与人类进行交流。

In the first detailed analysis comparing the anatomy and behavior of dogs and wolves, researchers found that the facial musculature of both species was similar, except above the eyes. Dogs have a small muscle, which allows them to intensely raise their inner eyebrow, which wolves do not.

在第一项细节分析中，研究人员对比了狗和狼的解剖结构和行为。研究人员在对比中发现，除了眼部上方的区域，两个物种的脸部肌肉组织类似。狗狗的眼部上方有小肌肉，小肌肉可以让狗狗大幅抬起内眉，而狼却无法做到这一点。

The authors suggest that the inner eyebrow raising movement triggers a nurturing response in humans because it makes the dogs' eyes appear larger, more infant like and also resembles a movement humans produce when they are sad.

研究作者表示，内眉的抬起动作会激发人类的呵护反应，因为抬起内眉会让狗狗的眼睛看上去更大，更像婴儿，同时也像人类悲伤时的表情。

The research team, led by comparative psychologist Dr Juliane Kaminski, at the University of Portsmouth, included a team of behavioural and anatomical experts in the UK and USA.

朴次茅斯大学比较心理学家Juliane Kaminski博士所带领的研究团队包括英美两国的行为学和解剖学专家。

It is published in the journal Proceedings of the National Academy of Sciences (PNAS).

研究结果被刊登在《美国科学院院报》上。

Dr Kaminski said: "The evidence is compelling that dogs developed a muscle to raise the inner eyebrow after they were domesticated from wolves.

Kaminski博士表示：“有充分的证据证明，当狼被驯养成为狗后，狗狗进化出一种可以抬起内眉的肌肉。”

"We also studied dogs' and wolves' behavior, and when exposed to a human for two minutes, dogs raised their inner eyebrows more and at higher intensities than wolves.

“我们还研究了狗和狼在2分钟内面对人类时的行为。与狼相比，狗抬起内眉的频率和幅度都比狼要大。”

"The findings suggest that expressive eyebrows in dogs may be a result of humans unconscious preferences that influenced selection during domestication. When dogs make the movement, it seems to elicit a strong desire in humans to look after them. This would give dogs, that move their eyebrows more, a selection advantage over others and reinforce the 'puppy dog eyes' trait for future generations."

“研究结果表明，狗狗具有表现力的眉毛可能是人类无意识偏好的结果。在狗狗被驯化的过程中，被偏爱的狗狗会受到人类这种无意识偏好的影响。当狗狗抬起眉毛时，这一动作似乎能够唤起人类强烈的照顾欲望。而这也会让更多抬起眉毛的狗狗比其他狗狗更受到偏爱并在未来的后代中强化了这一‘眼部特征’。”

Dr Kaminski's previous research showed dogs moved their eyebrows significantly more when humans were looking at them compared to when they were not looking at them.

Kaminski博士此前的研究证明，与人类不注视狗狗相比，当人类注视着狗狗时，狗狗抬起眉毛的次数会更加频繁。

She said: "The AU101 movement is significant in the human-dog bond because it might elicit a caring response from humans but also might create the illusion of human-like communication."

她表示：“AU101动作对于狗狗和人类之间的关系意义重大，因此这一动作可能会唤起人类的呵护反应，并同时让人产生一种类似于人与人类沟通的感觉。”

Lead anatomist Professor Anne Burrows, at Duquesne University, Pittsburgh, USA, co-author of the paper, said: "To determine whether this eyebrow movement is a result of evolution, we compared the facial anatomy and behaviour of these two species and found the muscle that allows for the eyebrow raise in dogs was, in wolves, a scant, irregular cluster of fibres.

来自美国匹兹堡迪尤肯大学的教授、首席解剖学家以及论文的合著者Anne Burrow表示：“为了判断眉毛动作是否为进化的结果，我们对比了这两个物种的面部解剖结构和行为并发现可以让狗狗眉毛抬起的肌肉在狼的面部解剖结构中只是一丁点且不规则的纤维束。”

"The raised inner eyebrow movement in dogs is driven by a muscle which doesn't consistently exist in their closest living relative, the wolf.

能够让狗狗抬起内眉的肌肉并没有在狗狗最为接近的现存物种-即狼身上发现。

"This is a striking difference for species separated only 33,000 years ago and we think that the remarkably fast facial muscular changes can be directly linked to dogs' enhanced social interaction with humans."

“对于这两个在3万3千年前分离的物种而言，这是最为显著的区别。我们认为这一快速的面部肌肉变化与狗狗不断提升的、与人类之间的社交互动有直接关系。”

Dr Kaminski and co-author, evolutionary psychologist Professor Bridget Waller, also at the University of Portsmouth, previously mapped the facial muscular structure of dogs, naming the movement responsible for a raised inner eyebrow the Action Unit (AU) 101.

Kaminski博士和论文合著者、朴茨茅斯大学的教授及进化心理学家Bridget Waller在早些时候绘制出了狗狗的面部肌肉结构，并将负责抬起内眉毛的运动命名为AU101.

Professor Waller said: "This movement makes a dogs' eyes appear larger, giving them a childlike appearance. It could also mimic the facial movement humans make when they're sad.

Waller教授表示：“这一动作让狗狗的眼睛看上去更大并让狗狗有一种孩童般的外观。此外，狗狗还能模拟人类在伤心时的面部表情。”

"Our findings show how important faces can be in capturing our attention, and how powerful facial expression can be in social interaction."

“我们的研究结果表明，脸在吸引我们的注意力方面非常重要，同时面部表情在社交方面也发挥着非常重要的作用。”

Co-author and anatomist Adam Hartstone-Rose, at North Carolina State University, USA, said: "These muscles are so thin that you can literally see through them -- and yet the movement that they allow seems to have such a powerful effect that it appears to have been under substantial evolutionary pressure. It is really remarkable that these simple differences in facial expression may have helped define the relationship between early dogs and humans."

论文的合著者、解剖学家以及来自美国北卡罗莱纳州立大学的Adam Hartstone-Rose表示：“这些肌肉非常薄，以至于你几乎可以透过肌肉看到对面的东西--但是这些肌肉所实现的动作似乎具有如此有力的影响，以至于它似乎经历了巨大的进化压力。让人无法忽略的是，这些简单的面部表情区别似乎已经帮助我们定义了早期犬类和人类之间的关系。”

Co-author Rui Diogo, an anatomist at Howard University, Washington DC, USA, said: "I must admit that I was surprised to see the results myself because the gross anatomy of muscles is normally very slow to change in evolution, and this happened very fast indeed, in just some dozens of thousands of years."

论文的合著者、美国华盛顿特区霍华德大学的解剖学家Rui Diogo表示：“我必须承认，当我亲眼看到这一结果时，我很吃惊。因为，肌肉的大体解剖进化过程中发生改变的速度通常很慢。而狗狗的这一肌肉变化却如此迅速，仅用了大概几万年的时间。”

Soft tissue, including muscle, doesn't tend to survive in the fossil record, making the study of this type of evolution harder.

包括肌肉在内的软组织无法在化石记录中保留，因而导致这一进化类型的研究更为困难。

The only dog species in the study that did not have the muscle was the Siberian husky, which is among more ancient dog breeds.

研究中唯一没有这种肌肉的狗狗物种是西伯利亚的哈士奇。哈士奇是最为古老的犬类之一。

An alternative reason for the human-dog bond could be that humans have a preference for other individuals which have whites in the eye and that intense AU 101 movements exposes the white part of the dogs eyes.

另一个解释人类和狗狗联系的原因是人类对另一些眼部带有白色眼球的人类有偏好，而AU101动作则会显示出狗狗眼睛中的白色部分。

It is not known why or precisely when humans first brought wolves in from the cold and the evolution from wolf to dog began, but this research helps us understand some of the likely mechanisms underlying dog domestication.

人类为什么会将狼驯化或人类具体从何时开始驯化狼以及狼从狗的进化从何时开始，目前这些都尚未知晓。但是这一研究可以帮助我们理解狗狗驯化所隐含的部分类似机理。

要了解的词汇：

Musculature：肌肉系统/组织

Domesticate:驯化

Closest living relative：最为接近的现存物种

striking difference：显著不同

Capture attention:吸引注意力

文章来源：科学日报    编辑：上海译锐翻译Susan