Tag Archives: domestication

The evolution of puppy dog eyes

Dogs have evolved new muscles around the eyes to better communicate with humans. New research comparing the anatomy and behavior of dogs and wolves suggests dogs’ facial anatomy has changed over thousands of years specifically to allow them to better communicate with humans.

Puppy dog eyes

In the first detailed analysis comparing the anatomy and behavior of dogs and wolves, researchers found that the facial musculature of both species was similar, except above the eyes. Dogs have a small muscle, which allows them to intensely raise their inner eyebrow, which wolves do not.

The authors suggest that the inner eyebrow raising movement triggers a nurturing response in humans because it makes the dogs’ eyes appear larger, more infant like and also resembles a movement humans produce when they are sad.

The research team, led by comparative psychologist Dr Juliane Kaminski, at the University of Portsmouth, included a team of behavioural and anatomical experts in the UK and USA.

It is published in PNAS (Proceedings of the National Academy of Sciences).

Dr Kaminski said: “The evidence is compelling that dogs developed a muscle to raise the inner eyebrow after they were domesticated from wolves.

“We also studied dogs’ and wolves’ behavior, and when exposed to a human for two minutes, dogs raised their inner eyebrows more and at higher intensities than wolves.

“The findings suggest that expressive eyebrows in dogs may be a result of humans unconscious preferences that influenced selection during domestication. When dogs make the movement, it seems to elicit a strong desire in humans to look after them. This would give dogs, that move their eyebrows more, a selection advantage over others and reinforce the ‘puppy dog eyes’ trait for future generations.”

Dr Kaminski’s previous research showed dogs moved their eyebrows significantly more when humans were looking at them compared to when they were not looking at them.

She said: “The AU101 movement is significant in the human-dog bond because it might elicit a caring response from humans but also might create the illusion of human-like communication.”

Lead anatomist Professor Anne Burrows, at Duquesne University, Pittsburgh, USA, co-author of the paper, said: “To determine whether this eyebrow movement is a result of evolution, we compared the facial anatomy and behaviour of these two species and found the muscle that allows for the eyebrow raise in dogs was, in wolves, a scant, irregular cluster of fibres.

“The raised inner eyebrow movement in dogs is driven by a muscle which doesn’t consistently exist in their closest living relative, the wolf.

“This is a striking difference for species separated only 33,000 years ago and we think that the remarkably fast facial muscular changes can be directly linked to dogs’ enhanced social interaction with humans.”

Dr Kaminski and co-author, evolutionary psychologist Professor Bridget Waller, also at the University of Portsmouth, previously mapped the facial muscular structure of dogs, naming the movement responsible for a raised inner eyebrow the Action Unit (AU) 101.

Professor Waller said: “This movement makes a dogs’ eyes appear larger, giving them a childlike appearance. It could also mimic the facial movement humans make when they’re sad.

“Our findings show how important faces can be in capturing our attention, and how powerful facial expression can be in social interaction.”

Co-author and anatomist Adam Hartstone-Rose, at North Carolina State University, USA, said: “These muscles are so thin that you can literally see through them – and yet the movement that they allow seems to have such a powerful effect that it appears to have been under substantial evolutionary pressure. It is really remarkable that these simple differences in facial expression may have helped define the relationship between early dogs and humans.”

Co-author Rui Diogo, an anatomist at Howard University, Washington DC, USA, said: “I must admit that I was surprised to see the results myself because the gross anatomy of muscles is normally very slow to change in evolution, and this happened very fast indeed, in just some dozens of thousands of years.”

Soft tissue, including muscle, doesn’t tend to survive in the fossil record, making the study of this type of evolution harder.

The only dog species in the study that did not have the muscle was the Siberian husky, which is among more ancient dog breeds.

An alternative reason for the human-dog bond could be that humans have a preference for other individuals which have whites in the eye and that intense AU 101 movements exposes the white part of the dogs eyes.

It is not known why or precisely when humans first brought wolves in from the cold and the evolution from wolf to dog began, but this research helps us understand some of the likely mechanisms underlying dog domestication.

Source:  University of Portsmouth

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Dogs were domesticated not once, but twice

The question, ‘Where do domestic dogs come from?’, has vexed scholars for a very long time. Some argue that humans first domesticated wolves in Europe, while others claim this happened in Central Asia or China. A new paper, published in Science, suggests that all these claims may be right. Supported by funding from the European Research Council and the Natural Environment Research Council, a large international team of scientists compared genetic data with existing archaeological evidence and show that man’s best friend may have emerged independently from two separate (possibly now extinct) wolf populations that lived on opposite sides of the Eurasian continent.

Domestication photo

Man’s best friend. Dogs were domesticated not once, but twice… in different parts of the world. Credit: © lenaivanova2311 / Fotolia

This means that dogs may have been domesticated not once, as widely believed, but twice.

A major international research project on dog domestication, led by the University of Oxford, has reconstructed the evolutionary history of dogs by first sequencing the genome (at Trinity College Dublin) of a 4,800-year old medium-sized dog from bone excavated at the Neolithic Passage Tomb of Newgrange, Ireland. The team (including French researchers based in Lyon and at the National Museum of Natural History in Paris) also obtained mitochondrial DNA from 59 ancient dogs living between 14,000 to 3,000 years ago and then compared them with the genetic signatures of more than 2,500 previously studied modern dogs.

The results of their analyses demonstrate a genetic separation between modern dog populations currently living in East Asia and Europe. Curiously, this population split seems to have taken place after the earliest archaeological evidence for dogs in Europe. The new genetic evidence also shows a population turnover in Europe that appears to have mostly replaced the earliest domestic dog population there, which supports the evidence that there was a later arrival of dogs from elsewhere. Lastly, a review of the archaeological record shows that early dogs appear in both the East and West more than 12,000 years ago, but in Central Asia no earlier than 8,000 years ago.

Combined, these new findings suggest that dogs were first domesticated from geographically separated wolf populations on opposite sides of the Eurasian continent. At some point after their domestication, the eastern dogs dispersed with migrating humans into Europe where they mixed with and mostly replaced the earliest European dogs. Most dogs today are a mixture of both Eastern and Western dogs — one reason why previous genetic studies have been difficult to interpret.

The international project (which is combining ancient and modern genetic data with detailed morphological and archaeological research) is currently analysing thousands of ancient dogs and wolves to test this new perspective, and to establish the timing and location of the origins of our oldest pet.

Senior author and Director of Palaeo-BARN (the Wellcome Trust Palaeogenomics & Bio-Archaeology Research Network) at Oxford University, Professor Greger Larson, said: ‘Animal domestication is a rare thing and a lot of evidence is required to overturn the assumption that it happened just once in any species. Our ancient DNA evidence, combined with the archaeological record of early dogs, suggests that we need to reconsider the number of times dogs were domesticated independently. Maybe the reason there hasn’t yet been a consensus about where dogs were domesticated is because everyone has been a little bit right.’

Lead author Dr Laurent Frantz, from the Palaeo-BARN, commented: ‘Reconstructing the past from modern DNA is a bit like looking into the history books: you never know whether crucial parts have been erased. Ancient DNA, on the other hand, is like a time machine, and allows us to observe the past directly.’

Senior author Professor Dan Bradley, from Trinity College Dublin, commented: ‘The Newgrange dog bone had the best preserved ancient DNA we have ever encountered, giving us prehistoric genome of rare high quality. It is not just a postcard from the past, rather a full package special delivery.’

Professor Keith Dobney, co-author and co-director of the dog domestication project from Liverpool University’s Department of Archaeology, Classics and Egyptology, is heartened by these first significant results. ‘With the generous collaboration of many colleagues from across the world-sharing ideas, key specimens and their own data — the genetic and archaeological evidence are now beginning to tell a new coherent story. With so much new and exciting data to come, we will finally be able to uncover the true history of man’s best friend.’

Source:  Science Daily

A bond that goes way back

The special relationship between humans and dogs may go back 27,000 to 40,000 years, according to genomic analysis of an ancient Taimyr wolf bone reported in the Cell Press journal Current Biology on May 21. Earlier genome-based estimates have suggested that the ancestors of modern-day dogs diverged from wolves no more than 16,000 years ago, after the last Ice Age.

The genome from this ancient specimen, which has been radiocarbon dated to 35,000 years ago, reveals that the Taimyr wolf represents the most recent common ancestor of modern wolves and dogs.

his image compares an ancient Taimyr Wolf bone from the lower jaw to a modern pipette.  Photo by Love Dalén

This image compares an ancient Taimyr Wolf bone from the lower jaw to a modern pipette. Photo by Love Dalén

“Dogs may have been domesticated much earlier than is generally believed,” says Love Dalén of the Swedish Museum of Natural History. “The only other explanation is that there was a major divergence between two wolf populations at that time, and one of these populations subsequently gave rise to all modern wolves.” Dalén considers this second explanation less likely, since it would require that the second wolf population subsequently became extinct in the wild.

“It is [still] possible that a population of wolves remained relatively untamed but tracked human groups to a large degree, for a long time,” adds first author of the study Pontus Skoglund of Harvard Medical School and the Broad Institute.

The researchers made these discoveries based on a small piece of bone picked up during an expedition to the Taimyr Peninsula in Siberia. Initially, they didn’t realize the bone fragment came from a wolf at all; this was only determined using a genetic test back in the laboratory. But wolves are common on the Taimyr Peninsula, and the bone could have easily belonged to a modern-day wolf. On a hunch, the researchers decided to radiocarbon date the bone anyway. It was only then that they realized what they had: a 35,000-year-old bone from an ancient Taimyr wolf.

The DNA evidence also shows that modern-day Siberian Huskies and Greenland sled dogs share an unusually large number of genes with the ancient Taimyr wolf.

“The power of DNA can provide direct evidence that a Siberian Husky you see walking down the street shares ancestry with a wolf that roamed Northern Siberia 35,000 years ago,” Skoglund says. To put that in perspective, “this wolf lived just a few thousand years after Neandertals disappeared from Europe and modern humans started populating Europe and Asia.”

Source:  EurekAlert! media statement

Dog-human cooperation is based on social skills of wolves

Dogs are man’s best friend and partner. The origins of this dog-human relationship were subject of a study, published recently in the journal Frontiers in Psychology,  by behavioural scientists from the Messerli Research Institute at the Vetmeduni Vienna and the Wolf Science Center.

They showed that the ancestors of dogs, the wolves, are at least as attentive to members of their species and to humans as dogs are. This social skill did not emerge during domestication, as has been suggested previously, but was already present in wolves. 

Photo by the Wolf Science Center

Photo by the Wolf Science Center

Commonly accepted hypotheses about domestication suggest: “Dogs have become tolerant and attentive as a result of humans actively selecting for these skills during the domestication process in order to make dogs cooperative partners.”

Friederike Range and Zsófia Virányi from the Unit of Comparative Cognition at the Messerli Research Institute question the validity of this view and have developed the “Canine Cooperation Hypothesis”. Their hypothesis states that since wolves already are tolerant, attentive and cooperative, the relationship of wolves to their pack mates could have provided the basis for today’s human-dog relationship. An additional selection, at least for social attentiveness and tolerance, was not necessary during canine domestication.

The researchers believe that wolves are not less socially attentive than dogs. Dogs however cooperate more easily with humans because they more readily accept people as social partners and more easily lose their fear of humans. To test their hypothesis, Range and Virányi examined the social attentiveness and tolerance of wolves and dogs within their packs and toward humans.

Various behavioural tests showed that wolves and dogs have quite similar social skills. Among other things, the researchers tested how well wolves and dogs can find food that has been hidden. Both wolves and dogs used information provided by a human to find the hidden food.

In another study, they showed that wolves followed the gaze of humans. To solve the task, the animals may need to be capable of making a mental representation of the “looker’s” perspective. Wolves can do this quite well. 

Another experiment gave dogs and wolves the chance to observe conspecifics as they opened a box. When it was the observer’s turn to do the same, the wolves proved to be the better imitators, successfully opening the box more often than dogs. “Overall, the tests showed that wolves are very attentive to humans and to each other. Hypotheses which claim that wolves have limited social skills in this respect in comparison to dogs are therefore incorrect,” Range points out. 

At the Wolf Science Center in Ernstbrunn in Lower Austria, Range and Virányi investigated the social behaviour of dogs and wolves that grew up with members of their species and with humans. “The animals are socialized both with conspecifics and with humans. To be able to compare the behaviour of dogs and wolves and to investigate the effects of domestication, it is important that the animals live in the same conditions,” Virányi explains.

Source:  Vetmeduni Vienna media release

Read my other post about the Institute’s research with wolves here

Kathleen Crisley, specialist in dog massage, rehabilitation and nutrition/food therapy, Canine Catering Ltd, Christchurch, New Zealand

Domestication of dogs and the culling of mammoths

Adjunct Professor at Penn State, Pat Shipman, believes that the abrupt appearance of large numbers of dead mammoths may have been caused by early humans hunting with the first domesticated dogs.

Spectacular archaeological sites yielding stone tools and extraordinary numbers of dead mammoths — some containing the remains of hundreds of individuals — suddenly became common in central and eastern Eurasia between about 45,000 and 15,000 years ago, although mammoths previously had been hunted by humans and their extinct relatives and ancestors for at least a million years.

A fragment of a large bone, probably from a mammoth, Pat Shipman reports, was placed in this dog's mouth shortly after death. This finding suggests the animal was according special mortuary treatment, perhaps acknowledging its role in mammoth hunting. The fossil comes from the site of Predmosti, in the Czech republic, and is about 27,000 years B.P. old. This object is one of three canid skulls from Predmosti that were identified as dogs based on analysis of their morphology. Photo credit: Anthropos Museum, Brno, the Czech Republic, courtesy of Mietje Germonpre.

A fragment of a large bone, probably from a mammoth, Pat Shipman reports, was placed in this dog’s mouth shortly after death. This finding suggests the animal was according special mortuary treatment, perhaps acknowledging its role in mammoth hunting. The fossil comes from the site of Predmosti, in the Czech republic, and is about 27,000 years B.P. old. This object is one of three canid skulls from Predmosti that were identified as dogs based on analysis of their morphology. Photo credit: Anthropos Museum, Brno, the Czech Republic, courtesy of Mietje Germonpre.

“One of the greatest puzzles about these sites is how such large numbers of mammoths could have been killed with the weapons available during that time,” Shipman said.

Surprisingly, Shipman said, she found that “few of the mortality patterns from these mammoth deaths matched either those from natural deaths among modern elephants killed by droughts or by culling operations with modern weapons that kill entire family herds of modern elephants at once.” This discovery suggested to Shipman that a successful new technique for killing such large animals had been developed and its repeated use over time could explain the mysterious, massive collections of mammoth bones in Europe.

The key to Shipman’s new hypothesis is recent work by a team led by Mietje Germonpré of the Royal Belgian Institute of Natural Sciences, which has uncovered evidence that some of the large carnivores at these sites were early domesticated dogs, not wolves as generally had been assumed. Then, with this evidence as a clue, Shipman used information about how humans hunt with dogs to formulate a series of testable predictions about these mammoth sites.

Shipman’s research has been published in the journal Quaternary International and is entitled “How do you kill 86 mammoths?”

For more information about this research and related studies, read the full Penn State media statement.

One of the first domestic dogs revealed

DNA technology is being used to refine our understanding of when the domestic dog became a separate genetic line from wolves.

Wolf

In latest research, published in the open access journal PLoS ONE, DNA analysis on a 33,000-year old dog is reported.  DNA was extracted from a tooth.

The analyses show that the dog, from the Altai region which is east of Kazakhstan and north of China and Mongolia, is more closely related to modern dogs than contemporary wolves.  The research team, led by Anna Druzhkova from the Institute of Molecular and Cellular Biology in the Russian Federation, report that genetic analyses of ancient canids may help to reveal a more exact date and centre of domestication for the dog.

While it is widely accepted that the dog domestication predates the beginning of agriculture (about 10,000 years ago), no one can be sure when the genetics of wolves and domestic dogs began to diverge.

Source:  PLoS ONE

Re-thinking dog domestication

A research team led by the University of Durham has published a study in the Proceedings of the National Academy of Sciences (USA).  This study shows that today’s modern breeds of dog have little in common genetically with their ancient ancestors. 

Dog domestication occurred over 15,000 years ago – and there is still much to learn!

Years of cross-breeding are the major influence on the genetic differences, although the researchers are quick to add that other effects on genetic diversity will include patterns of human movement and the impact on dog population sizes caused by major events such as World War I and World War II.

The research team analysed genetic data from 1,375 dogs representing 35 breeds. They also looked at data showing genetic samples of wolves because other research studies have concluded that the dog descended directly from the gray wolf.

Lead author Dr Greger Larson, an evolutionary biologist, says the study demonstrated just how much there is still to understand about the early history of dog domestication.  “We really love our dogs and they have accompanied us across every continent.  Ironically, the ubiquity of dogs combined with their deep history has obscured their origins and made it difficult for us to know how dogs became man’s best friend.”

The study also refutes claims of previous researchers that genetic differences in breeds such as the Basenji, Saluki and Dingo were evidence of an ancient heritage.  The Durham team’s study shows that these dogs are genetically different because they were geographically isolated and were not part of the 19th Century Victorian-initiated kennel clubs that blended lineages to create most of today’s breeds.

A Saluki (copyright Keith Dobney)

Source:  University of Durham press release