Being friendly is in dogs' nature and could be key to how they came to share our lives, say US scientists.

据美国科学家表示，狗狗友善的天性可能是它们能与人类一起生活的关键因素。

Dogs evolved from wolves tens of thousands of years ago. During this time, certain genes¹ that make dogs particularly gregarious² have been selected for, according to research.

狗是在几万年前从狼进化而来的。研究显示，在这段时间里，某些使狗变得特别温顺合群的基因留了下来。

This may give dogs their distinctive³ personalities⁴, including a craving⁵ for human company.

这可能使得狗狗具备一些特别的个性，包括非常喜欢和人类待在一起。

"Our finding of genetic⁶ variation in both dogs and wolves provides a possible insight into animal personality, and may even suggest similar genes may have roles in other domestic species (maybe cats even)," said Dr Bridgett of Princeton University.

普林斯顿大学的布里奇特博士表示：“我们在狗和狼身上发现了一定程度的遗传变异，这有助于了解动物的性格，甚至类似的基因可能在其他的物种(甚至是猫)中也有作用。”

The researchers studied the behaviour of domestic dogs, and grey wolves living in captivity⁷. They carried out a number of tests of the animals' skills at problem-solving and sociability⁸.

研究人员研究了家养狗和圈养的灰狼的行为特点。同时，他们对动物的解决问题的能力和社交能力进行了一系列测试。

These showed that wolves were as good as dogs at solving problems, such as retrieving⁹ pieces of sausage from a plastic lunchbox.

这些研究表明，狼和狗一样善于解决问题，比如从一个塑料午餐盒里取出一些香肠。

Dogs, however, were much more friendly. They spent more time greeting human strangers and gazing at them, while wolves were somewhat aloof¹⁰.

但是，狗更友好，他们会更愿意向陌生人问好，并看着他们，而狼则有些冷漠。

DNA¹¹ tests found a link between certain genetic changes and behaviours such as attentiveness¹² to strangers or picking up on social cues.

DNA测试发现，某些基因与行为有一定联系，如对陌生人的注意力，或对一些暗示的反应。

Dr Elaine Ostrander of the National Institutes of Health, who was a co-researcher on the study, said the information would be useful in studying human disease.

美国卫生研究院的伊莱恩·奥斯特兰德博士也是研究人员之一，他表示，这些信息对研究人类疾病很有用。