摩洛哥马拉喀什的两只乡村狗。

“狗”（CC By 2.0）L.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.

With the advent of modern genomics technology, a number of approaches have been used to search for the precise genetic changes that turned wolves into dogs.

Village dogs are essential genetic resources that help us understand dog evolution

We recently participated in a study that that used来自古狗的DNA这生活在人类中，以解决与狗驯化时间有关的杰出问题。古代DNA技术是一种遗传时间机，使研究人员可以直接看到过去存在的遗传变异。

When we assessed the genetic makeup of three新石器时代的欧洲狗（（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.

为了解释这个难题，在我们的新出版物中BMC生物学，，，，我们转向乡村狗，这代表了地球上绝大多数狗。这些狗是半铁，沿着我们的街道和城市漫游，主要是在人类垃圾中生存，但最重要的是，它们是驯化的。

实际上，these dogs are descended from the same ancestors as our favorite breed dogs today，自从驯化时就可能与人类或附近生活在一起，这发生在大约40，000年前。自由放养的乡村狗是丰富的遗传资源，使科学家瞥见了一系列遗传多样性以及成为狗的真正含义。

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, a研究人员小组noticed 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.

Changes in the number or activity of neural crest cells in any of these final body locations can subsequently alter the size, shape, or level of expression of the corresponding trait.

狗和狼的基因组可以告诉我们有关驯化的知识？

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

通过比较乡村狗和狼的遗传多样性，我们确定了246个基因组区域，这些区域可能在驯化过程中已经改变。通过使用乡村狗，由于人类的指向近亲繁殖，最近没有丧失多样性，我们能够发现活着的狗和新石器时代的古老样本中共享的旧事件，这表明我们确定了与驯化过程相关的变化。

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.

The precise details surrounding the process of domestication remain a mystery, but researchers can link archeological evidence with the patterns observed in genomes to help evaluate possible theories. One scenario suggests that in ancient times wolves lived near early human settlements, as they were attracted by trash or remains of hunted animals. Over time, some wolves may have become less fearful of humans, as these may have had more success in obtaining food.

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

在这个渐进过程中，称为自我理解,研究人员假设基因the neural crest pathway were slowly changing, leading to a wide range of different appearances relative to wild wolves and leaving signatures in the dog genome that we can detect today. At some point, humans began their active involvement in domesticating these “less wild” wolves, who already likely had a head start on the process, and other physical traits may have continued to accompany the behavioral changes.

辩论仍是阿布t when humans became directly involved 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.