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Key points
- Dogs' original role in hunter-gatherer societies was as a sensory aid in finding prey animals.
- Some dogs have been trained to alert if they detect cancer based on volatile organic compounds emitted by cancerous tissues.
- Dogs' thermal sense may explain why dogs that are blind and hearing-impaired may continue to hunt successfully.
Dogs help humans in many tasks, but their original role in hunter-gatherer societies was as a sensory aid in finding prey animals. Newly found sensory abilities include heat mapping by the nose, as well as detecting cancer and predicting the onset of seizures.
Dog Domestication and Super Senses
Dogs have been associated with humans for around 30,000 years—three times longer than any other domesticate.1 The big positive that dogs brought to this association was their fantastically sensitive sensory systems. These were, and still are, used by hunter-gatherers to detect prey from a distance.
There are two key pieces of evidence indicating that dogs were domesticated for their sensory services to people. The first is that some of their senses are so good. Their hearing is much more sensitive than ours to high-frequency sounds, and their sense of smell is a hundred thousand times better. The second piece of evidence is that during the period of our association, human sensory capacity declined. This change meant that the human thalamus—a central station for sensory information—shrank. This shrinkage was detectable in terms of changes in the structure of the skull.2
Just two years ago, scientists reported on a new sensory system that detects heat and is analogous to the heat-detecting organ through which some snakes detect their warm-blooded prey.
The Temperature Sense
Dogs have colder noses than other mammals. This provides a background against which heat radiation registers. Born blind and without hearing ability, pups use their thermal sense to remain close to their mother who registers the warmest heat signature in their vicinity.
The thermal sense is useful to dogs in hunting. It helps to explain why dogs that are blind and hearing-impaired may continue to hunt successfully.
Dog domestication coincides with the period of declining availability of large game animals, probably due to over-hunting by humans. The surviving prey animals were smaller, and many hid from humans behind dense cover in forests and brush.
Dogs are not very helpful in hunting large prey on open ground because potential prey spots them from a distance. They were, and are, much more useful to human hunters for hunting animals concealed by cover.3 Neanderthals did not have dogs and switched to a largely vegetarian diet. These factors may have contributed to their inability to compete with sapiens.
The thermal sense was established in scientific tests. It explains why dogs have the uncanny ability to enter a room and select a recently occupied chair that still sends out weak thermal radiation. (Dogs can also detect the earth's magnetic field—magnetoreception—using receptors in the visual system).
Being able to see the heat image of an animal concealed in cover allowed dogs to help their human partners find food, but dogs could also sense prey from great distances using their remarkably sensitive hearing and an even more developed olfactory system. Olfactory sensitivity is particularly acute in specialists like beagles that were selectively bred for following scent trails.
This super sense has a variety of applications in modern medicine
Detecting Cancer and Predicting Seizures
Explosive-sniffing dogs are a common sight at airports, but dogs can also sniff out medical threats. Some dogs have been trained to alert if they detect cancer based on volatile organic compounds emitted by cancerous tissues. Their accuracy is in a similar range to scientific tests. Their use obviates invasive procedures for obtaining samples.
People who suffer from epileptic seizures also give off a chemical signature in minutes, or even hours, before an attack. Their dogs often become noticeably upset by this symptom and alert them so that they can remain safe until the attack passes.
Conclusion
Scientists are learning a great deal about the exotic sensory systems of other animals, including dogs, and we are constantly developing new applications for these sensory superpowers.
Many different animals develop close associations with their human companions. In the case of dogs, these connections form with incredible ease, reflecting our long collaboration that extends for some 30 millennia. This is a case of mutual reliance (or inquilinism). By relying on the dog's ability to spot prey, human sensory capacity declined. For their part, dogs relied on humans for food—Australia's dingoes feed on garbage dumps rather than hunting for their own food.
Dogs are highly responsive to the moods of their owners. This helped them to keep in our good books and ensure that they were well fed and cared for. One way that they monitor our mood is by listening to our heartbeat using their super-sensitive hearing.
References
1. Dugatkin, L. A., and Trut, L. (2017). How to tame a fox (and build a dog). Chicago, IL: University of Chicago Press.
2. Groves, C. P. (1999). The advantages and disadvantages of being domesticated. Perspectives in Human Biology, 4, 1-12.
3. Barber, N. (2020). Evolution in the here and now: How adaptation and social learning explain humanity. Lanham, MD: Rowman and Littlefield/Prometheus Books.
