In Dog We Trust – The Case For Man’s Best Friend
According to a recent survey about 36% of households in the USA have at least one dog. According to the Pet Food Institute this totals to around 57.6 million dogs, meaning there are nearly 3 times the amount of dogs in America as there are humans in Australia. Americans spend around $5.6 billion on food for their dogs and the American Veterinary Medical Association estimates around $7 billion dollars are spent annually on keeping dogs healthy. Why and how are humans so connected to an entirely separate and distantly related species like Canis familiaris? What makes dogs stand out from other domesticated animals and what can the study of human-canine co-habitation tell us about our own evolutionary history?
Let’s start with a very brief look at the ancestry of both dogs and humans. The canine group has its origins in North America and were originally small forest dwelling carnivores around the size of a fox. When open herd grazing ungulates like horse and antelope began to dominate the vast plains of North America the ancient canines radiated out from the forest onto the open ground. This created a canine ancestor that began evolving into a swift pack hunter in order to tackle the ungulate herds. It is thought that some of these ancestors migrated over the Bering straight into Asia, Europe and Africa around 10 million years ago. Over the next few million years these canids formed into the wolves, jackals, coyotes and painted dogs (not actually ‘dogs’) that we are familiar with today. The grey wolf (Canis lupus), the species from which domestic dogs arose evolved at the end of the Late Pleistocene around 300,000 years ago.
Meanwhile in Africa the ancestors of humans had been evolving steadily. The earliest member of the homo genus is currently identified as Homo habilis who lived from around 2.4-1.4 million years ago. Homo habilis was already using stone tools though it’s leg structure was more suited to tree dwelling than plains walking. After (and alongside) habilis arose Homo ergaster, who later gave rise to Homo erectus and Homo antecessor. Erectus and Antecessor were the first human ancestors to move far out of Africa and into Asia and Europe, both around 1.2 million years ago. Then from Antecessor came Rhodesiensis which finally evolved into Homo sapiens and Homo neanderthalensis. Homo sapiens have lived from around 250,000 years ago till present while poor old neanderthalensis disappeared around 30,000 years ago. So while canid ancestors beat us into Europe and Asia by a good margin the grey wolf from which dogs evolved arose at around the same time as modern humans.
The exact circumstances surrounding the first co-habitations of wolf and man are not known but evidence suggests the earliest interactions took place more than 100,000 years ago. Even before this time it is thought that humans may have been observing and learning from the wolves about how to hunt large ungulates on the tundra. What is known is that by 30,000 years ago dogs had split from wolves and were living alongside humans. The earliest clearly identified dog skeleton was found in Belgium and dates to 31,000 years ago. The March 2010 edition of the Journal Nature published a study that looked at tracing the geographic origins of the domestic dog using genetic markers. The genetic evidence shows that the domestic dog originated in the Middle-East, rather than East Asia as previously thought. It is logical to assume therefore that if the oldest dog remains we have are from Western Europe but dogs evolved in the Mid-East then the split must have taken placed many thousands of years before our oldest skeleton.
But how exactly did we domesticate wild wolves in the first place? Unfortunately the exact circumstances will likely never be known, the great tragedy of all historical sciences. It is thought though that initially wolves began hanging around human campsites, picking off refuse and scraps of food. This would have created a selective pressure where those wolves who were less frightened and spent more time alongside humans would be favoured. This evolutionary pressure would have resulted in a combination of increased fitness in some wolves through extra nutrition and a mixing of the genes of those wolves who remained in the locale of humans over time. In no time at all geologically speaking, (perhaps 5,000 years) wolves were fully integrating into the societies of Paleolithic man in Asia and Europe.
What occurred at this important moment in human history is an event perhaps unparalleled in todays natural world. Man and dog became linked in a far more meaningful way than other examples of symbiosis or co-evolution. We gained in dogs a valuable hunting partner, effective guardians, a pest controller and later a shepherd. We also gained a close emotional companion and the social worlds of humans and dogs enveloped each other in a near seamless way, humans became part of their packs and dogs became part of our tribe. Evidence for the emotional bond between human and dog is informative and at times quite touching.
In both Eurasia and North America, archaeologists have found 10-15,000 year old dogs that have been buried beneath the floors of huts or tent-camps, curled in sleeping postures, and covered with the red ochre that people of the time used in human burials. In some cases the dogs are interred directly with humans, as at one Middle-Eastern site where a puppy was found curled in the arms of a buried human. Think about, for more than 20,000 years before agriculture began, before the first written language, before the earliest philosophers or world monuments, before the first organized religion or civilization nearly every pocket of mankind had formed a psychological, emotional and practical bond with dogs that lasts until today.
Many people today fail to understand just how in tune humans and dogs are with each other, without the need of any real behavioural learning. Anthropologist Brian Hare of the Max Planck Institute for Evolutionary Anthropology in Germany has reported that domesticated dogs are better at reading human communication signals, such as glances or pointing, than chimpanzees, which have long been thought to be closer to humans than any other primate. We are also acoustically in-tune with dogs, a study of dogs owners reports than on average each dog understands 30 different human utterances, 21 percent of which were synonyms. Understood utterances range in purpose over the following: Disallowance, Posture, Invitation, Referring to object or person, Unique, Information giving, Permission and Question. Owners believed that dogs executed 31 % of commands “every time”, 53 % “in contextually adequate situations”, and 16% only “occasionally”. Age of the owners or dogs, breed of dogs, and the educational status of owners did not strongly affect the utterance structure. These findings are also supported neurologically, with evidence showing that similar brain genes have changed in the same ways in humans and dogs since our co-mingling. With these sorts of findings it is important to keep in mind that this evidence shows that not only have dogs evolved to be more in tune with us, but we have evolved to be more in tune with them.
A hypothesis which is unfortunately hard to test but is fascinating and slowly gaining ground is that a great deal of what we consider very ‘human’ may in fact be very ‘wolf’ instead. When we see a dog demonstrating a novel or familiar behaviour we often marvel at how similar to humans it seems, but it may well be that they were doing it first and we copied them. There is no closer analog in nature to humanities familial and ethical system than in wolves. In the absence of our direct ancestors we often turn to our cousins the chimpanzees, but what we see there is a frightening reflection of our most egotistical side. The pioneering work of primatologist Jane Goodall gave us a fascinating insight into the sociality of chimpanzees. Unlike humans and wolves their social structure is highly individualistic, with a strong maternal bond but limited care for others. Co-operation in chimps is limited to the violent persecution of other chimps, always to the advantage of the individual. Wolves on the other hand play and raise their young in an extended family structure, take care of their old and wounded and demonstrate emotional distress at the loss of those not related to them by blood. We must not draw too many conclusions from these differences and similarities however as humanity underwent around 5 million years of evolution separate from both chimps and wolves.
Nonetheless it is fascinating to speculate about just how much our humanity has been shaped by our early encounters with wolves. Regardless of who learnt which traits from who the bond between man and dog is undeniably real and powerful. This is extends into the medical world where a good deal of study has been undertaken to examine the medical benefits of living with dogs. There are weaknesses in many studies but arising from the noise we can see decent evidence which suggests that dogs can have a prophylactic and therapeutic value in people. Research has been done to examine if dogs can prevent us from coming ill (unlikely), facilitate our recovery from ill-health (good evidence) and even serve as an early warning system for certain ailments including cancer (unlikely) and oncoming seizures (good evidence). Studies also show reduced systolic blood pressure in dog owners as well as lower concentrations of triglycirides and cholesterol.
In “The domestic dog: its evolution, behaviour, and interactions with people” James Serpell makes the argument that as the utilitarian uses of dogs diminish in the modern age we are beginning to lose sight of the fact that dogs are a truly special and real species of carnivore uniquely adapted for a mutualistic life with humans. We are beginning to see dogs increasingly more like toys and objects of pure affection instead of what they can and used to be, our companions and equals. We force on dogs an unhealthy regime of breeding in order to maintain the idea of purity which results in a wide range of painful and crippling genetic bone disorders. We buy and trade dogs like commodities and give them as presents. In the process we are losing the closest ally in the animal world that we have. Sure, dogs will likely be with us for many thousands of years to come but they are seeming to lose their right to be regarded as a true animal.
I’ll finish with this quote from primatologist Jane Goodall.
“Dogs have been domesticated for a very long time. They have descended from wolves who were pack animals. They survive as a result of teamwork. They hunt together, den together, raise pups together. This ancient social order has been helpful in the domestication of the dog. Chimpanzees are individualists. They are boisterous and volatile in the wild. They are always on the lookout for opportunities to get the better of each other. They are not pack animals. If you watch wolves within a pack, nuzzling each other, wagging their tails in greeting, licking and protecting the pups, you see all the characteristics we love in dogs, including loyalty. If you watch wild chimps, you see the love between mother and offspring, and the bonds between siblings. Other relationships tend to be opportunistic. And even between family members, disputes often rise that may even lead to fights… even after hundreds of years of selective breeding, it would be hard if not impossible to produce a chimpanzee who could live with humans and have anything like such a good relationship as we have with our dogs. It is not related to intelligence, but the desire to help, to be obedient, to gain our approval.”
Wolfgang M. Schleidt/Michael D. Shalter, pg.60 (2003)
Hall MJ, Ng A, Ursano RJ, Holloway H, Fullerton C, Casper J. (2004). Psychological impact of the animal-human bond in disaster preparedness and response. Journal of Psychiatric Practice
Wells DL. (2007). Domestic dogs and human health: an overview. British Journal of Health Psychology
Wolfgang M. Schleidt/Michael D. Shalter (2003). Co-evolution of Humans and Canids, Evolution and Cognition
Soohyun Lee1,3* and Simon Kasif (2006). The complete genome sequence of a dog: a perspective. BioEssays
A. PLUSKOWSKI (2006). Where are the Wolves? Investigating the Scarcity of European Grey Wolf. International Journal of Osteoarchaeology