Since their emergence over 200,000 years ago, modern humans have established homes and communities all over the planet.
自从他们在20万年前出现，现代人类逐渐在这个星球上建立起了自己的家园。
But they didn't do it alone.
然而他们并非是独自完成这项壮举的。
Whatever corner of the globe you find homo sapiens in today,
如今不管你在地球的哪个角落找到人类，
you're likely to find another species nearby: Canis lupus familiaris.
你极有可能找到另外一个物种：狗。
Whether they're herding, hunting, sledding, or slouching the sheer variety of domestic dogs is staggering.
不管它们是在放牧、打猎、拉雪橇或是偷懒坐着，狗的多样性是令人震惊的。
But what makes the story of man's best friend so surprising is that
但让人类最好的朋友最神奇的是
they all evolved from a creature often seen as one of our oldest rivals: Canis lupus, or the gray wolf.
它们都从一个物种进化而来，而这个物种经常被认为是我们最古老的敌人之一：狼，或者说灰狼。
When our Paleolithic ancestors first settled Eurasia roughly 100,000 years ago,
10万年前，当我们旧石器时代的祖先在第一次在欧洲定居时，
wolves were one of their main rivals at the top of the food chain.
狼是人在食物链顶端的几个主要敌人之一。
Able to exert over 300 lbs. of pressure in one bone-crushing bite and sniff out prey more than a mile away,
在一次足以碎骨的咬合中，它能够施加超过300磅的压力，并在一英里以外嗅到猎物，
these formidable predators didn't have much competition.
这些强大的捕食者没有太多的竞争者。
Much like human hunter-gatherers, they lived and hunted in complex social groups consisting of a few nuclear families,
就像人类猎人们一样，它们以一个复杂的团体来生活，捕猎，
and used their social skills to cooperatively take down larger creatures.
其中有一些核心家庭组成，一起合作互助捕到更大的猎物。
Using these group tactics, they operated as effective persistence hunters,
使用这些团队策略，它们作为持久型的猎人，
relying not on outrunning their prey, but pursuing it to the point of exhaustion.
不依靠跑过猎物，而是追到它们筋疲力尽。
But when pitted against the similar strengths of their invasive new neighbors, wolves found themselves at a crossroads.
但当遇到有相似能力并具有侵略性的新邻居时，狼就处于了一个两难的情况。
For most packs, these bourgeoning bipeds represented a serious threat to their territory.
对于大多数狼来说，这些不断发展的两脚兽意味着对它们领地的严重威胁。
But for some wolves, especially those without a pack, human camps offered new opportunities.
但对有些狼来说，特别是那些远离族群的，人类营地提供了新的机会。
Wolves that showed less aggression towards humans could come closer to their encampments, feeding on leftovers.
那些对人类不那么有攻击性的狼，能够接近人类的营地，吃一些剩菜剩饭。
And as these more docile scavengers outlasted their aggressive brethren,
这些更温顺的食腐者比它们的暴躁老哥活得更久，
their genetic traits were passed on, gradually breeding tamer wolves in areas near human populations.
它们的基因特征遗传了下去，于是在人类附近逐渐繁衍出更温顺的狼。
Over time humans found a multitude of uses for these docile wolves.
久而久之，人们发现了这些温顺的狼的很多用处。
They helped to track and hunt prey, and might have served as sentinels to guard camps and warn of approaching enemies.
它们可以追踪和捕捉猎物，并且能作为哨兵来守卫营地，还能警告接近的敌人。

Their similar social structure made it easy to integrate with human families and learn to understand their commands.
它们与人类接近的社会结构让它们能轻易融入人类家庭，并学会理解收到的指令。
Eventually they moved from the fringes of our communities into our homes, becoming humanity's first domesticated animal.
最终它们从社会边缘进到我们家里，成为第一种被人类驯服的动物。
The earliest of these Proto-Dogs or Wolf-Dogs, seem to have appeared around 33,000 years ago,
这些原始狗或者狼狗最早出现于约三万三千年前，
and would not have looked all that different from their wild cousins.
而且不会和它们的野生同胞有太大差异。
They were primarily distinguished by their smaller size and a shorter snout full of comparatively smaller teeth.
它们的主要差异就是它们更小的体型，和更短的嘴里更小的牙齿。
But as human cultures and occupations became more diverse and specialized, so did our friends.
然而随着人类文明和领地变得多样化、特殊化，我们的伙伴也变了。
Short stocky dogs to herd livestock by nipping their heels; elongated dogs to flush badgers and foxes out of burrows;
矮壮结实的可以通过咬牲畜的后脚跟来放牧，身体长的可以把獾和狐狸赶出洞来，
thin and sleek dogs for racing; and large, muscular dogs for guard duty.
精瘦圆滑的可以赛跑，大的强壮的可以当守卫。
With the emergence of kennel clubs and dog shows during England's Victorian era,
随着在维多利亚时期的养狗俱乐部和狗展，
these dog types were standardized into breeds, with many new ones bred purely for appearance.
这些不同的狗被分为不同的犬种，还有很多只是为了外观产生的犬种。
Sadly, while all dog breeds are the product of artificial selection, some are healthier than others.
可怜的是，当所有犬种都成了人工育种的结果，有些犬种比其他的要更健康。
Many of these aesthetic characteristics come with congenital health problems,
很多这些可爱的特征伴随着一些先天健康问题，
such as difficulty breathing or being prone to spinal injuries.
比如说呼吸困难或是容易受脊椎损伤。
Humanity's longest experiment in controlled evolution has had other side effects as well.
作为人类史上耗时最长的人工育种实验，伴随着很多副作用。
Generations of selection for tameness have favored more juvenile and submissive traits that were pleasing to humans.
一代一代地为了驯化的选择，保留了很多幼嫩而温顺的特征来取悦人们。
This phenomenon of selecting traits associated with youth is known as neoteny, and can be seen in many domestic animals.
这种选择幼小特征的现象叫幼态延续，很多驯养的动物都有这种情况。
Thousands of years of co-evolution may even have bonded us chemically.
几千年来的共同地进化甚至把我们在化学层面上连结在一起。
Not only can canines understand our emotions and body language,
不只是狗们能理解我们的感情和肢体语言，
but when dogs and humans interact, both our bodies release oxytocin;
而且当人和狗互动时，我们的身体都会释放催产素，
a hormone commonly associated with feelings of love and protectiveness.
一种跟爱和保护欲有关的荷尔蒙。
It might be difficult to fathom how every Pomeranian, Chihuahua, and Poodle are descended from fierce wolves.
也许很难相信每一个博美犬、吉娃娃和贵宾犬都是凶狠的狼的子孙。
But the diversity of breeds today is the result of a relationship that precedes cities, agriculture,
但是造成这种多样性的特殊关系，超越了聚落，农作，
and even the disappearance of our Neanderthal cousins.
甚至高于我们的近亲尼安德特人的消失。
And it's heartening to know that given enough time, even our most dangerous rivals can become our fiercest friends.
这实在是振奋人心：只要有足够的时间，即使是我们最危险的敌人也会变成我们最好的朋友。