Sunday, November 1, 2020

Single Dog Ancestry Distinct From Modern Wolves Says Ancient DNA Study, Man Walking with Dogs before Ice Age Ended, "Substantial Dog-to-Wolf Gene Flow

Wolves were the first animal with which humans formed a mutualistic relationship, eventually giving rise to dogs. Although there is little consensus regarding when, where and how many times domestication may have taken place. 

A global study of ancient dog DNA, led by scientists at the Francis Crick Institute, University of Oxford, University of Vienna and archaeologists from more than 10 countries, presents evidence that there were different types of dogs more than 11,000 years ago in the period immediately following the Ice Age.

Researchers "sequenced 27 ancient dog genomes and found that all dogs share a common ancestry distinct from present-day wolves, with limited gene flow from wolves since domestication but substantial dog-to-wolf gene flow" 

Dogs are thought to have originated sometime during the The Pleistocene, often referred to as the Ice Age, is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the world's most recent period of repeated glaciations. The end of the Pleistocene corresponds with the end of the last glacial period and also with the end of the Paleolithic age used in archaeology.



Credit: E.E. Antipina

In their study, published in Science, the research team sequenced ancient DNA from 27 dogs, some of which lived up to nearly 11,000 years ago, across Europe, the Near East and Siberia.* They found that by this point in history, just after the Ice Age and before any other animal had been domesticated, there were already at least five different types of dog with distinct genetic ancestries.

Pontus Skoglund

This finding reveals that the diversity observed between dogs in different parts of the world today originated when all humans were still hunters and gatherers. 

Pontus Skoglund

Pontus Skoglund, author and group leader of the Crick’s Ancient Genomics laboratory, says: “Some of the variation you see between dogs walking down the street today originated in the Ice Age. By the end of this period, dogs were already widespread across the northern hemisphere."

This study of ancient genomics involves extracting and analysing DNA from skeletal material. It provides a window into the past, allowing researchers to uncover evolutionary changes that occurred many thousands of years ago.

. Anders Bergström

The team showed that over the last 10,000 years, these early dog lineages mixed and moved to give rise to the dogs we know today. For example, early European dogs were initially diverse, appearing to originate from two highly distinct populations, one related to Near Eastern dogs and another to Siberian dogs. However, at some point this diversity was lost, as it is not present in European dogs today.

Anders Bergström, lead author and post-doctoral researcher in the Ancient Genomics laboratory at the Crick, says: “If we look back more than four or five thousand years ago, we can see that Europe was a very diverse place when it came to dogs. Although the European dogs we see today come in such an extraordinary array of shapes and forms, genetically they derive from only a very narrow subset of the diversity that used to exist.”

The researchers also compared the evolution in dog history to changes in human evolution, lifestyles and migrations. In many cases comparable changes took place, likely reflecting how humans would bring their dogs with them as they migrated across the world.

But there are also cases when human and dog histories do not mirror each other. For example, the loss of diversity that existed in dogs in early Europe was caused by the spread of a single dog ancestry that replaced other populations. This dramatic event is not mirrored in human populations, and it remains to be determined what caused this turnover in European dog ancestry.

Greger Larson, author and Director of the Palaeogenomics and Bio-Archaeology Research Network at the University of Oxford, says: “Dogs are our oldest and closest animal partner. Using DNA from ancient dogs is showing us just how far back our shared history goes and will ultimately help us understand when and where this deep relationship began."

Ron Pinhasi, author and group leader at the University of Vienna, says: "Just as ancient DNA has revolutionised the study of our own ancestors, it’s now starting to do the same for dogs and other domesticated animals. Studying our animal companions adds another layer to our understanding of human history."

While this study provides major new insights into the early history of dog populations and their relationships with humans and each other, many questions still remain. In particular, research teams are still trying to uncover where and in which human cultural context, dogs were first domesticated. 

Their study revealed by 11,000 years ago, at least five major ancestry lineages had diversified, demonstrating a deep genetic history of dogs during the Paleolithic. Coanalysis with human genomes reveals aspects of dog population history that mirror humans, including Levant-related ancestry in Africa and early agricultural Europe. Other aspects differ, including the impacts of steppe pastoralist expansions in West and East Eurasia and a near-complete turnover of Neolithic European dog ancestry." 

*The researchers sequenced ancient DNA from 27 dogs. Their analysis also included previously sequenced genomic data from a further 5 dogs.


Contacts and sources:
The Francis Crick Institute


Publication: Origins and genetic legacy of prehistoric dogs.
Anders Bergström, et al.Science, 2020 DOI: 10.1126/science.aba9572

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