狗是如何演化成人类最忠心伙伴的

我们将狗当作实用工具繁育，但最后它们成了我们最忠实的盟友。

Man and dog share a long history. In much of the world, a history as old as humanity. The latest genetic evidence now tells us that the emergence of the domestic dog lineage occurred soon after the human expansion out of Africa 50,000 years ago, in the depths of the last Ice Age. We came. We saw. And we befriended. This we knew, but now we can closely examine how. A paper out today in Science uses 27 ancient dog genomes from the past 11,000 years to construct an evolutionary history nearly as rich as that produced by human population geneticists over the last decade.

人类和狗有着悠久的共同史。在世界上许多地方，这段历史和人类自身一样久远。最近的遗传证据告诉我们，在五万年前上一次冰期正盛时，人类从非洲出走向外扩张，家犬谱系不久也跟着出现了。我们到来，我们相见，我们成为朋友，这是我们已知的，但如今我们能够详细考察这一过程。今天（指 2020 年 10 月 30 日）发表于《科学》的一篇论文中，研究小组利用过去 11000 年 27 个古代狗的基因组构建出了一段狗的演化史，它几乎和人类群体遗传学家过去十年为人类构建的演化史一样丰富。

The authors found five lineages of ancient dogs that were present at the end of the last Ice Age. These were the dogs that interacted with human migrations during the rise of agriculture and the fall of civilizations to produce the riotous dog diversity that we know today. Familiar breeds like the Pekingese and the St. Bernard, as well as stray Asian village mutts, they’re all the products of a deep shared history, which has left its imprint on the genetic variation of modern dogs.

作者发现，上一次冰期结束的时候存在五个古代狗谱系。农业兴起，文明衰落，在此期间狗与人类迁徙的互动，产生了我们如今所知的纷繁的狗种多样性。这段深远共同史在现代狗的遗传变异中刻下了印记，狮子狗、圣伯纳犬，以及亚洲流浪土狗等常见品种都是这段历史的产物。

The dog-human relationship has always been special in several ways. Our canine companions are well adapted to us, in that they can engage with humans socially in a manner no other animal seems equipped to, not even our closest relatives, the chimpanzees. This is thanks to tens of thousands of years of co-evolution. In a very real sense the evolutionary niche of the domestic dog is the human mind. Wolves may have higher IQs, and yet there are 1,500–3,000 times more dogs alive today. Perhaps it was smarter to be friendly than just smart.

在许多方面，人和狗的关系一直都是特别的。我们的犬类伙伴很好地适应了我们，它们能够与人类亲密交往，似乎没有其他动物能做到这个程度，甚至我们的近亲黑猩猩也做不到。这要归功于数万年的共同演化。甚至可以说，家犬的演化位就是人类心智。狼可能智商更高，但今天狗的数量是前者的 1500-3000 倍。也许光聪明还不行，你还得变得友善。

Dogs are the only domestic species who have been with us since the Pleistocene, which ended 11,500 years ago. Crops, cattle, and cats all came later, during the Holocene, after the Ice Age. When Siberians crossed over to the New World 15,000 years ago, they also brought their dogs. These dogs served many roles. Friend, beast of burden, and yes, even food.

狗是唯一自更新世（距今 11500 年前）就一直陪伴着我们的驯化物种。谷物、牛和猫都是在冰河时期之后的全新世才出现的。西伯利亚人 15000 年前向新世界迈进时，他们也带了自己的狗。这些狗有许多职责：朋友、役兽，没错，甚至是充当食物。

The New World dogs, who were present when the Spaniards landed in 1492, are one of the five great Pleistocene lineages from which all modern dogs descend. The authors of the Science paper call them the Neolithic Levant, Mesolithic Karelia, Mesolithic Baikal, ancient America, and the New Guinea singing dog. The last group includes Australian dingos and represents the ancient expansion of our species and its companions into Southeast Asia. Karelia is a region bordering Finland and Russia, while the Baikal dogs come from the lake of that name in east-central Siberia. These samples are termed Mesolithic because they are more recent than the Ice Age (7–11,000 years ago), but the peoples in Karelia and Baikal were still hunter-gatherers at that time. In contrast, the Neolithic Levant dogs date to 7,000 years ago, and were companions to agricultural populations.

新世界的狗在 1492 年西班牙人登陆新世界时就已存在，它们属于五大更新世谱系之一，而所有现代狗的祖先都可追溯到这五大谱系。论文作者将这五大谱系命名为：新石器时代黎凡特犬、中石器时代卡累利亚犬、中石器时代贝加尔犬、古代美洲犬，以及新几内亚唱犬。最后一组中包括澳洲野犬，这表明我们这一物种及其犬类伙伴曾经扩张到了东南亚。卡累利亚位于芬兰与俄罗斯接壤处，而贝加尔犬得名于西伯利亚中东部的同名湖。由于这些样本要晚于冰河时期（距今 7 到 11000 年前），它们被归进了中石器时代，但当时生活在卡累利亚和贝加尔的人仍然是狩猎-采集者。相反，新石器时代黎凡特犬可追溯至 7000 年前，而且它们陪伴的是农业群体。

All modern dogs can be thought of as a mixture between these five early Holocene lineages. Despite their highly specific names, the Karelian and Baikal lineages represent huge geographic distributions, not just the sample sites. In this regard, they are analogous to modern humans. As David Reich has shown in his magisterial work, Who We Are and How We Got Here, the past 10,000 years have witnessed the merging of disparate hunter-gatherer tribes to form the peoples we see today, threaded together from distinct strands. This naturally leads us to the question: did human populations bring their particular dogs everywhere they went?

可以说，所有现代狗都是这五种全新世早期谱系之间的混合产物。尽管它们的名字都很具体，卡累利亚和贝加尔谱系所代表的不只是样本地点，而是广大地理分布。在这点上，它们类似于现代人类。如大卫·赖克在其巨著《人类起源的故事》中所展示的，过去一万年间不同狩猎-采集者部落的合并，形成了我们如今所见的，不同支系交错融合而成的民族。这自然让我们想到一个问题：人类群体有没有把他们各自的狗带到他们所至之处？

Comparing the relatedness of humans and relatedness of dogs, the authors of the Science paper found that there was a definite correlation. Phylogenetic trees of both dogs and humans exhibited strikingly similar shapes, indicating common underlying histories of separation and diversification. Analyses comparing the genetic data of dogs and humans revealed that they were tightly correlated. In fact, the relationship between the evolutionary trees for dogs and for humans is close enough that the tree for humans explains much of the pattern we see for dogs. There is an underlying structure which spans the two species, but also novel and curious deviations that alert us to particular stories.

论文作者比较了人类的亲缘关系与狗的亲缘关系，发现两者有着明确相关性。狗和人类的系统发生树形状惊人相似，这表明他们或许潜存共同的分化和多样化史。对人和狗的遗传数据的对比分析显示，他们之间紧密相关。实际上，狗和人类的演化树之间的联系是如此密切，人类的演化树也可以解释我们在狗身上看到的大部分模式。这两个物种的底层结构相互交叉，但也存在一些稀奇的差异，提醒我们要留意不寻常的情况。

Some of the stories are straightforward and to be expected. The dogs of ancient Europe are a mix of the Karelian and Neolithic Levant lineages. The latter clearly tagged along with the early farmers expanding out of the Near East. Further south in Europe, the dogs were more like those of the Neolithic Levant, while further north they were more like the Mesolithic Karelian dogs. American dogs were genetically closest to the Siberian dogs from Lake Baikal. Additionally, both these groups were closer to the dogs of Southeast Asia than they were to those of the Levant. This recapitulates the pattern for Eurasian peoples; East Asians are more closely related to Europeans than they are to Middle Eastern people.

有些情况是直观和意料之内的。古代欧洲地区的狗是卡累利亚谱系和新石器时代黎凡特谱系的混合产物，后者显然是跟随早期农民从近东扩张而来的。欧洲往南地区的狗更像新石器时代黎凡特犬，往北地区的狗则更像中石器时代卡累利亚犬。美洲地区的狗在基因上最接近贝加尔湖的西伯利亚犬。此外，这两个种群与东南亚地区的狗的关系都比与黎凡特犬的关系更近。这重演了欧亚民族的模式；东亚人与欧洲人的关系比他们与中东人的关系更近。

But a few surprising findings confound our expectations. Four thousand years ago on the Volga steppe of Russia, on the cusp between Europe and Asia, the Srubna people flourished as part of a broad continuum of Indo-European peoples that stretched far to the west. While the Indo-European relatives of the Srubna came to dominate much of Europe, their dogs did not. The burials of early Indo-Europeans in Europe yield dogs whose heritage connected them to the Eurasian steppe and the Srubna, but this was a fleeting affair. The dogs of Northern Europe were not replaced by the dogs of the steppe, though the people largely were.

但一些出人意料的发现打乱了我们的预期。四千年前，在欧洲和亚洲交界的俄罗斯伏尔加大草原上，斯鲁布纳人作为一直延伸至西方的印欧连续体的一支兴旺起来。虽然斯鲁布纳人的印欧近亲后来主宰了欧洲大部分地区，他们的狗却没有。欧洲早期印欧人的坟地中发现了狗的遗骸，使得它们与欧亚草原和斯鲁布纳人产生了联系，但这不过是短暂情缘。北欧地区的狗并没有被草原上的狗取代，尽管人基本上是被取代了。

Instead, the heritage of the Srubna dog persists far to the east. Chinese dogs are mostly a mixture of ancient Southeast Asian dogs, related to the New Guinea singing dog and the dingo, plus the Srubna steppe dogs. While half the ancestry of modern Europeans comes from people related to the Srubna, very little of that ancestry is to be found in modern Chinese. And yet dogs are not the only evidence of the influence of steppe people in ancient China. In 1200 BC, chariots became prominent during the Bronze Age Shang dynasty, chariots whose design indicates borrowing from the Iranian peoples of Central Asia, direct descendants of the Srubna. It seems entirely likely that if chariots were brought to China during the Bronze Age, then so were dogs. While the dogs of the steppe found no welcome in Europe, the Chinese adopted them as their own.

然而，斯鲁布纳狗后代的身影却不断出现在更遥远的东方。中国地区的狗基本是古代东南亚地区的狗的混合产物，与新几内亚唱犬、野犬，以及斯鲁布纳草原狗有亲缘。尽管现代欧洲人一半的血统来自与斯鲁布纳人有亲缘的人，但在现代中国人中很少能发现这一血统。不过，狗并不是古中国受草原牧民影响的唯一证据。公元前 1200 年，在青铜时代的商朝，战车变得重要起来，这些战车的设计表明它们借鉴自中亚的伊朗人，即斯鲁布纳人的直系后裔。如果战车在青铜时代被带到了中国，那么狗也完全有可能。尽管草原狗在欧洲没有受到欢迎，但中国人接纳了它们，当成了自己的狗。

It also sometimes happens that the migration of dogs runs counter to the migration of peoples. While humanity evolved in Africa and spread to the rest of the world through the Middle East, the origin of African domestic dogs reflects the reverse. Indigenous African breeds such as the Basenji descend from dogs of the Neolithic Levant. These dogs were likely brought south and west by the Near Eastern pastoralists who also brought cattle to the continent. Meanwhile, the ancient canine populations of the prehistoric Levant have been totally replaced by groups from Iran and Europe, so the primary legacy of the dogs that were associated with the first human cities is to be found today in Africa.

而且有时候，狗的迁徙和人的迁徙是背道而驰的。尽管人类在非洲进化并经中东扩散到世界各地，非洲家犬的起源却反映出相反情况。非洲本土犬种，如贝生吉犬，是新石器时代黎凡特犬的后裔。这些狗可能是近东牧民带到南方和西方的，他们也把牛带到了非洲大陆。同时，史前黎凡特的古代犬类种群完全被来自伊朗和欧洲的种群取代了。因此，与第一批人类城市相关的狗的主要遗迹今天可以在非洲找到。

But perhaps the biggest twist of the great canine diasporas is that their recent history is obscured and dominated by the phenomenon which has overshadowed our own species’ history: the rise, expansion, and domination of the world by Europe.

但也许犬类大散居的最大意外转折是，它们近来的历史和我们这一物种的历史一样，变得模糊不清，这主要是因为一个现象：欧洲的崛起、扩张，以及对世界的统治。

Modern European dogs do not descend from the full diversity of the continent. Rather, almost all European breeds today derive from a population best represented by a 5,000-year-old sample discovered in southern Sweden, an individual who was equally descended from Karelian and Levantine populations. The authors could not pinpoint the time or place that this replacement of the ancient lineages occurred, but by the time of the rise of European colonialism this single population had swept aside all the other ancient populations of the continent.

现代欧洲地区的狗并非没有把大陆的多样性都继承下来。反而，今天几乎所有欧洲犬种都衍生自一个种群，其最佳代表是瑞典南部发现的一个 5000 年前的样本，这一个体同样也是卡累利亚种群和黎凡特种群的后裔。作者无法确定这种古代谱系更替发生的时间或地点，但到欧洲殖民主义兴起时，这一种群已经将欧洲大陆的所有其他古代种群彻底取代。

Today the majority of the ancestry of dogs across the world is from this single European population that flourished 5,000 years ago. In the New World almost all the ancestry is now European, with the exception of the Arctic dogs. The venerable chihuahua has less than five percent of its ancestry from the dogs of the Aztecs. In Africa and the Middle East, most canine ancestry is now European, while European ancestry is often the majority in many Asian dog populations, and is substantial even in the dingo. Decolonization may have occurred politically, but the evolutionary history and genetic variation of dogs illustrate how powerful the hand of history can be and how long its shadow persists.

今天，世界上大多数的狗的血统都来自 5000 年前兴旺的这一欧洲种群。除北极地区的狗以外，新世界几乎所有狗的祖先如今都是欧洲种。历史悠久的吉娃娃犬只有不到 5% 的血统来自阿兹特克的狗。在非洲和中东，大部分犬类的祖先如今都是欧洲种，欧洲血统在许多亚洲狗种群中往往占多数，甚至在野犬中也占相当大比例。去殖民化或许已经在政治层面上发生，但狗的演化史和遗传变异展现了历史之手的威力，以及其影响之久远。

Ancient DNA is like a genetic time capsule. We’ve spent these first decades honing our extraordinary new tools as we examine our own ancient human ancestry. But ours is hardly the only species with a history worth unpacking in such fascinatingly granular detail. Rather, we can look forward to the recent history of life on Earth being thoroughly illuminated via the evidence left behind by hardy fragments of DNA from creatures long gone.

古代 DNA 就像一颗遗传时间胶囊。我们在研究自己的古人类祖先时把最初几十年时间花在了磨练这一非凡的新工具上。不过，我们并不是唯一值得如此细致入微剖析其历史的物种。反而，我们可以期待，透过这些早已消逝的生物的 DNA 片段留下的证据，地球生物的近代史将得到全面解释。

The past 40,000 years has seen the transformation of our planet’s ecosystems due to humans. We live in the “Anthropocene” because our species has reshaped the planet to our ends. The evolutionary history of the domestic dog reflects humanity’s first, and longest, bioengineering experiment. We took a pack of wolves and transmuted it into a new species to walk alongside us. We bred dogs to be useful tools, but eventually they became our most loyal allies. We owe it to them to understand how they came to be as they are. And in the process we’ll inevitably continue to learn about ourselves.

由于人类，我们星球的生态系统在过去四万年里发生了大幅转变。我们这一物种为自己的目的重塑了这个星球，可以说，我们生活在「人类世」。家犬的演化史反映了人类第一次，也是最长的一次生物工程实验。我们把一群狼改造成了一个新物种，陪伴我们左右。我们将狗当作实用工具繁育，但最后它们成了我们最忠实的盟友。我们有必要了解它们是如何变成今天这个样子的。在此过程中，我们也必将不断了解我们自己。