Two village dogs in Marrakech, Morocco.

“Dogs” (CC BY 2.0) byL.Wi.

The dog has been man’s best friend for thousands of years, forming a relationship that pre-dates the establishment of agriculture. Domesticated animals, including dogs, share a distinctive collection of traits that distinguish them from their wild ancestors.

Changes in fur color and texture, the shape of ears, tail length and its curvature, eye color, and alterations in facial structure are some traits distinguishing dogs from wolves. Yet, the trait that most importantly differs is behavior. Thousands of years ago, dogs were tamed and domesticated from wolves, which over time yielded animals that were more and more friendly with humans, transforming the once wild creatures into the domestic dogs of today.

随着现代基因组技术的出现，已经使用了许多方法来寻找将狼变成狗的精确遗传变化。

乡村狗是必不可少的遗传资源，可以帮助我们了解狗的进化

We recently participated in a study that that usedDNA from ancient dogsthat lived among humans to address outstanding questions related to the timing of dog domestication. Ancient DNA technology is a genetic time machine, allowing researchers to directly see genetic variants that existed in the past.

当我们评估三个的基因组成从新石器时代欧洲的狗(five and seven thousand years old), we found something surprising: although genetics indicated that the three samples were clearly dogs, they carried the wild wolf sequence at many parts of the genome that were previously thought to be associated with domestication.

To explain this conundrum,in our new publication inBMC Biology,we turned to village dogs, which represent the vast majority of dogs on earth. These dogs are semi-feral, roam along our streets and cities, survive mostly off human trash, but most importantly, they are domesticated.

In fact,these dogs are descended from the same ancestors as our favorite breed dogs today, and have been likely living with or near humans since the time of domestication, which occurred as long as ~40,000 years ago. Free-ranging village dogs serve as rich genetic resources, giving scientists a glimpse at the full range of genetic diversity and what it really means to be a dog.

Many dog-specific traits are determined by the neural crest

Much of what makes dogs look and behave the way they do is determined during their early development as an embryo. By the time dog puppies are born, their appearance and behaviors are already different than wolf puppies.

These changes reflect the outcomes of complex and intricate processes during embryonic development and involve the movement and coordination of many cells that serve unique purposes. A few years ago, agroup of researchersnoticed that the diverse phenotypes of domesticated animals can be explained by differences in neural crest cells, which are stem cells that travel from their starting location, in what will become the spinal cord, along defined routes to their final destinations.

Neural crest cells play a major role in defining the forms and functions of multiple tissues in all animals with backbones including most of the skull, face, cartilaginous tissues (such as dogs’ infamously charming floppy ears), and even pigmentation of the skin and fur. In addition to changing the outward appearance, these cells ultimately contribute to the development of the brain, nervous system, and adrenal systems, all of which can influence behavior.

这些最终身体位置中任何一个中神经纹细胞的数量或活性的变化都会随后改变相应特征的大小，形状或表达水平。

What can the genomes of dogs and wolves tell us about domestication?

Free-ranging village dogs serve as rich genetic resources, giving scientists a glimpse at the full range of genetic diversity and what it really means to be a dog

By comparing the genetic diversity of village dogs and wolves we identified 246 regions of the genome which may have been altered during domestication. By using village dogs, which have not had a recent loss of diversity due to human directed inbreeding, we were able to find old events shared among living dogs and the ancient samples from the Neolithic, suggesting that we identified changes associated with the domestication process.

Interestingly, these changes were found near genes that perform critical functions in the developing dog, including many genes that are associated with the neural crest, nervous system function, and circadian rhythms. These findings offer clues to the genetic changes associated with domestication, and support the hypothesized role of alterations in neural crest cell function in this process.

围绕驯化过程的确切细节仍然是一个谜，但是研究人员可以将考古证据与基因组中观察到的模式联系起来，以帮助评估可能的理论。一种情况表明，在古代，狼生活在早期的人类定居点附近，因为它们被垃圾或猎物的遗体吸引。随着时间的流逝，一些狼可能会变得不太害怕人类，因为这些狼在获取食物方面可能取得了更大的成功。

These findings offer clues to the genetic changes associated with domestication, and support the hypothesized role of alterations in neural crest cell function in this process

During this gradual process, referred to asself-domestication研究人员假设参与神经rest途径的基因正在缓慢变化，从而导致相对于野狼的各种外观，并在我们今天可以检测到的狗基因组中留下了特征。在某个时候，人类开始积极参与驯化这些“野生”的狼，他们已经在这一过程中有了一个遥遥领先，其他身体特征可能会继续伴随着行为的改变。

辩论仍直接当人类变成了我nvolved in this process, but linked morphological and behavior changes can rapidly occur, as was found in theselective breeding of silver foxes.

Unraveling the mysteries of when wolves became dogs, how and why this happened, and how the domestication process affected modern dogs will not only help us understand the history of our furry companions, but also identify genes that may be pivotal to dog development and behavior. As more ancient dog and wolf samples are discovered and analyzed, we may soon be able to answer the many remaining questions regarding how dogs came to be.