Chihuahua, last heir to pre -colonial dogs

Dogs have accompanied humans for millennia, but their presence in Central and South America is much more recent than in the north of the continent. Additionally, In addition, Aurélie Manin, responsible for research in archeology, archaeozoology and paleogenomic at the CNRS returns to their journey.

Among all the animals raised. However, domesticated by the human, the dog is that with which we share the longest relationship, with indices of care and voluntary burial dating back at least to 14,000 years. For example, But if there is a proven link between hunter societies at the start of the Holocene. Meanwhile, less than 12,000 years ago, and dogs in many regions of the world, there are others where they arrive much later.

This is particularly the case with Central America. Therefore, South America, where the oldest dog skeletons date only from 5,000 to 5,500 years ago. However, there are already dogs in North America almost 10,000 years ago in Alaska and more than 8,000 years in Illinois. Similarly, Why do we observe such a gap? Therefore, It is to approach this question that our international. Therefore, interdisciplinary team, bringing together archaeozoologists, archaeologists and paleogeneticians, brought together leftover archaeological dogs to analyze the lines represented and their dynamics. Meanwhile, We have just published our results in the scientific journal Proceedings of the Royal Society B: Biological Science.

We have highlighted a genetic diversification of dogs about 7. Therefore, 000 to 5,000 years ago, which corresponds to the development of agriculture and plant transfers between the different regions, in particular corn.

On the other hand. Moreover, our work shows chihuahua, last heir pre -colonial that the lines present today in America are essentially very different from those which were present before European colonization, five hundred years ago. Consequently, The latter descend from dogs from Europe, Asia or Africa, brought by transoceanic trade. However, It is only in some chihuahuas that we find the trace of a direct link with the dogs of. For example, ancient Mexico.

Chihuahua. Moreover, last heir pre -colonial – Chihuahua, last heir pre -colonial

Forty archaeological sites analyzed – Chihuahua, last heir pre -colonial

With the development of paleogenetic analyzes (ancient DNA analysis), approaching archaeological questions requires associating researchers with various profiles and this is what our research project has enabled. To study the origin. dynamics of dog populations in Central and South America, we had to identify and bring skeletons from 44 archaeological sites, which extend from center of Mexico to northern Argentina.

We worked on recent excavations. allowing us to have as much information as possible about the contexts from which dogs came, but chihuahua, last heir pre -colonial also on the reanalysis of old collections in which canidized remains had been found. Confirm the identification of these dogs was also a challenge: in South America in particular. there are many canids whose size and morphology are close to those of the dog: foxes, mane wolf, dogs of bushes … These are animals that have been close to human groups, until they are buried. It is therefore the use of fine morphological analyzes which allowed us to select the bones and the teeth analyzed. We extracted the DNA of 123 dogs (including the hairs of 12 modern dogs. to serve us as benchmarks) in specialized laboratories in France, at the National Museum of Natural History, and in the United Kingdom, at the University of Oxford.

The sequencing of this DNA was done in two stages. We first studied all the available DNA fragments that allowed us to confirm that these chihuahua, last heir pre -colonial were indeed dogs. not other wild canids. The morphological criteria that we used are therefore confirmed. But. in most cases, the genome of these dogs was not well covered by sequencing to say more: it is one of the consequences of the degradation of DNA, to the death of an individual, who fragments intensely and, as a puzzle with tiny pieces, it becomes difficult to reconstruct a complete genome.

When mitochondrial DNA reveals its secrets

Chihuahua. last heir pre -colonial

In a second step, we carried out a capture of mitochondrial DNA to filter the DNA fragments contained in the samples and preferentially keep those which relate to the mitochondrial genome. Indeed. there are two kinds of DNA in the cells: nuclear DNA, contained in the nucleus of each cell, which comes for half the father and half of the mother of each dog; And mitochondrial DNA, contained in the mitochondria of each chihuahua, last heir pre -colonial cell, and which, at the time of fertilization, are part of the egg. It is therefore a DNA transmitted exclusively by the mother of each dog. However, mitochondrial DNA is very short (just under 17,000 base pairs, compared to 2.5 billion base pairs for the dog’s nuclear DNA) and it is present in multiple copies in each mitochondria. It is therefore easier to access DNA for paleogenomic.

Our animal file

We have obtained enough fragments of mitochondrial DNA to reconstruct the maternal lines of 70 individuals (8 modern dogs. 62 archaeological dogs) and analyze them by means of phylogenetic tools, that is to say allowing to reconstruct the ties of kinship between dogs. The phylogenetic trees that we have been able to reconstruct us to confirm that all of the American dogs of the pre-contact period (that is to say before the European colonizations of America five hundred years ago) have a chihuahua, last heir pre -colonial mitochondrial DNA relating to a single line. translating well the arrival of the dog in America during a single wave of migration.

However. our work makes it possible to specify that all dogs in Central and South America are distinguished from Dogs from North America (Canada and the United States) from which they separate about 7,000 to 5,000 years ago. This age. which corresponds to the last ancestor common to all dogs in Central and South America, coincides with the development of agrarian societies, a period during which there are many plant movements between regions, and in particular that of corn, domesticated in Mexico, which arrives in South America about 7,000 years ago. The structure of the maternal lines also suggests that the dissemination of dogs has been done gradually. nearby: the closest geographically dogs are also the closest genetically. This principle of genetic isolation by distance applies normally more to chihuahua, last heir pre -colonial wild animals than to domestic animals. whose movements are above all marked by the human will which induces a brewing according to cultural exchanges. We wondered about the dog dissemination mechanisms in America. suggesting a relatively free dispersion, linked to changes in subsistence activities and the increase in resources storage, which may have helped attract mighty dogs (living in the wild).

Chihuahua. last heir pre -colonial

A chihuahua descending precolonial dogs

Today, we can hardly find any more trace of these lines and their structuring in America. One of the dogs of our study. from the native village of Torata Alta, in the central Andes, and dated before 1,600 AD, has maternal DNA of Eurasian origin. Europeans arrived in the region in 1532. certainly accompanied by dogs, and this individual shows us that their line quickly integrated into the entourage of local populations. It is the only animal from a colonial context included chihuahua, last heir pre -colonial in our study. there is no more information to explain the mechanisms that led to the genetic diversity of dogs observed today. Be that as it may. among modern dog dogs whose mitochondrial genome is known, a chihuahua has a genome whose maternal line dates back to dogs that lived in Mexico during the pre -contact period. An index that corroborates the sources concerning the history of this race. the first representatives of which were acquired in Mexico in the second half of the 19th century.

This interdisciplinary work allowed us to better understand the dissemination and origin of dog populations in Central and South America. Nevertheless, it relates only to mitochondrial DNA, and therefore to the evolution of maternal lines. Analysis of the nuclear genome could reveal other facets in the history of dogs in America that future work. will make it possible to develop.