Dogs roamed with bands of humans 10,000 years ago and came in all shapes and sizes

From village dogs to toy poodles to mastiffs, dogs come in an amazing array of shapes, colors and sizes. Today it is estimated that about 700 million dogs live with or near humans.

For many of us, dogs are loyal companions, work partners and beloved family members. And the histories of our species are woven together. But how did this incredible diversity happen – and how far back does this relationship with humans go?

Two new studies were published today Science Provide some answers. One, led by Avon from the University of Montpellier, attracts ancient skeletal remains. The other, led by Shao Ji Zhang from the Kunming Institute of Zoology, is based on studies of DNA from ancient East Eurasian dogs.

Together, these studies tell the story of dogs and their relationship with humans being older and more complex than once thought.

Origins of modern dog diversity

The study by Evan and his colleagues used 643 dog and wolf skulls spanning the past 50,000 years to trace the origins of modern dog diversity.

His team’s analysis shows that the skull shape first arose around 11,000 years ago during the Holocene Epoch, the time since the most recent Ice Age. They also found considerable anatomical diversity in the skulls of dogs from the same period.

This means that today’s wide range of dog shapes and sizes is not a product of the intensive selective breeding programs that have become popular over the past few centuries. Some of these variations appeared thousands of years ago.

The team reanalyzed the skull shapes of all 17 known dog or wolf skulls, dating from the Late Pleistocene, a geological period from 129,000 to 11,700 years ago. Some skulls were 50,000 years old.

They found that all of these Pleistocene skulls were primarily wolf-like in shape, with some previously identified as early dogs.

Importantly, it shows that while the split between wolves and dogs likely occurred during the Pleistocene, the skull shape of early dogs didn’t begin to change until closer to the Holocene—that is, 11,000 years ago. However, some Holocene dog skulls also retain wolf-like features.

The research suggests that early dogs were more diverse than previously thought. This diversity may have laid the foundation for the extreme variation in size and shape of the dogs we have today.

Traveling companions

Previous genomic studies have revealed four major dog lineages that probably began around 20,000 years ago: Eastern (East Asian and Arctic) and Western (Europe and the Near East) dogs.

The origins of these ancient dog breeds are still elusive. However, studying changes in dog ancestry over time and between different regions can help us better understand the origins of dogs and the movements of Neolithic (New Stone Age) humans.

The new study by Zhang and his colleagues used the genomes of 73 ancient dogs over the past 10,000 years to trace how humans and dogs moved across eastern Eurasia over time.

Analysis of these ancient dogs has sometimes indicated multiple changes in dog lineages in eastern Eurasia associated with the movement of specific human groups (hunter-gatherers, farmers, and pastoralists). This suggests that as different human cultural groups migrated across Eurasia, their dogs often migrated with them, carrying their unique genetic signatures.

In some parts of Asia there was some contrast between the ancestry of human and dog populations. For example, the Eastern hunter-gatherers of Verti and Botai, who were more closely related to West Eurasian humans, had largely Eastern (Arctic) dogs, rather than the Western dogs observed with West Eurasian cultures at the time.

This means that dogs have been an important part of cultural exchange or trade between different human cultures or communities. It may also explain complexities in dog evolution that we have yet to understand.

Zhang and his team’s work provides compelling evidence that thousands of years ago in eastern Eurasia, dogs played an indispensable role in human societies as important “biocultural packages” that moved with humans. In other words, humans took their companions with them on their travels (and perhaps traded them), rather than acquiring new dogs after they moved.

The findings highlight a long-term, complex and interconnected relationship between dogs and humans that spans more than 10,000 years.

The genetic ancestry of dogs can serve as a living record of ancient human migrations, trade networks, and cultural exchanges. Studies of ancient dogs can also help us understand the environmental factors that contributed to the evolution of dogs and their relationship with humans.

Changing our understanding of dogs

Together, these new studies profoundly reshape our understanding of how dogs became so diverse and how they related to humans along the way.

Both studies indicate that the incredible diversity in modern dogs is not entirely a recent phenomenon. The genetic and moral foundations for this variation were laid thousands of years ago, in the form of natural selection, human selection and diverse environments, long before the structured breeding of the last few centuries.

Future studies investigating the anatomical diversity and ancestry of dogs over time may deepen our understanding of the complex origins and spread of dogs throughout the world. Whatever their origins, this research deepens our appreciation for the unique and ancient relationship between humans and dogs that was as diverse as the Kenyans themselves.

This article is reprinted from The Conversation under a Creative Commons license. Read the original article.