The Problem Dogs Solved That We Couldn't

one of the most incredible biological adaptations ever discovered in mammals is one that might be right next to you or maybe in your bed or on your couch or on top of comfy mountain it's one that might even get on your nerves as your dog yanks your arm off to smell a light post or guides him to hoover every ghost of a crumb you may have ever dropped in your kitchen a dog's sense of smell is estimated to be ten thousand to one hundred thousand times better than our own this means that dogs can detect some odors in parts per trillion to put this into a simple analogy of taste we humans can detect if our coffee has a teaspoon of sugar added to it a dog could detect a teaspoon of sugar in a million gallons of water or two olympic-sized swimming pools worth it's impossible to even imagine what the experience of smell is like for a dog when we notice a smell it's because something is particularly good or particularly bad we may notice the smell of freshly baked bread in the air or the potent dumpster we're walking by but if you take a smell survey right now you would likely report that you don't really smell anything that your environment is odorless but that couldn't be farther from the truth every place object animal and person in this world is constantly giving off an explosion of odor and to a dog these odors convey a suite of rich layered and complex information dogs don't experience a sidewalk as simply a sidewalk to them it's the smell of concrete of all the foliage nearby of decaying acorns and the dead frog up ahead it's the smell of every recent footfall of every other dog's recent visit and complex scent trails of the direction that they went and time is in those details a dog can tell when another dog marked that light post how recently someone walked by with a bag of treats and how far along in the decaying process that frog is but a dog's smelling abilities go so much beyond snack detecting it's an ability that could one day save your life dogs are employed to track missing people through the woods find people buried under feet of snow and detect dangerous explosives and now dogs are even being used to detect human disease sometimes diseases that should be undetectable diseases that we have never figured out how to spot ourselves until it's too late how do dogs smell the world so much better than we do and how can we train them to detect something as invisible and intangible as disease smell is the oldest of all the senses or at least a rudimentary version of it is before sight hearing or even touch organisms evolved to respond to the chemicals around them even the most simple of bacteria can follow a chemical scent trail and with hundreds of millions of years of evolution behind it it's no surprise that smell is a sense that in some animals has evolved to be fantastically complex but what actually is a smell a smell or odor is a volatile molecule one that has shed from its source and then wasps through the air or even travels through the water until it's picked up by an animal for most animals this begins with a sniff a sniff for us is a rather clumsy affair we breathe some air into our nostril holes and then out the same holes over and over trying to make sense of the odor we've detected but a dog's sniff is much more complex it begins with muscles in the nostrils drawing a current of air and any scent chemicals into them then on the exhale instead of going straight back out the air exits through slits in the sides of the nose and backwards in this way inhaled odors don't get mixed with the air already in the nose allowing each new inhale to be pure and undiluted and on top of this the direction of the exhaled air does more than just get out of the way of new air it actually helps to pull more of the new scent in by creating a current of air that pulls the odor from the object being scented towards the nose when a dog is investigating a scent it repeats this inspiration expiration cycle very quickly about five times per second from here the scent travels up the dog's nasal passage into the nasal turbinates this is a labyrinth of bony ridges that are covered with mucous membranes which provides a large surface area for the air breathed in to be warmed and cleaned before entering the ethmoid turbinates here is where the dog's super ability begins to shine lining the ethmoid turbinates is the olfactory epithelium the membrane which contains millions of scent receptors the olfactory receptor neurons each covered in cilia the neurons are activated when ascent binds to the olfactory receptors on the cilia some of these receptors are shaped to pair with only a few select molecules in a hyperspecific lock and key fashion but most olfactory receptors will bind to a large number of different molecules the brain can decipher specific smells based on the combinations of receptors that are activated and the sheer number of these olfactory receptor neurons and their cilia in dogs is part of what gives dogs their super ability we have around 6 million olfactory receptor neurons each with about 25 cilia dogs have as many as 300 million olfactory receptor neurons each with hundreds of cilia dogs have more genes dedicated to creating olfactory cells more cells and more types of cells and when these things work in unison when combinations of sites fire together to send information to the brain dogs can detect significantly more types of smells and in smaller concentrations once the scent is picked up by the neuron a signal is sent to the olfactory bulb the olfactory bulb is a bulb of neural tissue within the dog's brain and is responsible for processing smells it's approximately 40 times larger in dogs than in humans relative to total brain size from the olfactory bulb the sense information then travels to the cortex where it's finally recognized as a smell to the dog this part of a dog's sense of smell is enough to outperform us to an extraordinary degree but on top of all of this dogs have a second way to smell the world an entire olfactory ability that we don't even have in the roof of a dog's mouth is the vomeronasal organ an organ that picks up pheromones pheromones are talked about a lot but what they actually are is kind of crazy their chemicals an animal produces that act much like hormones do except for that they act outside of the body affecting the behavior of other animals dogs will purposely leave pheromones behind in their urine to tell other dogs about their gender and sexual receptivity and the closer the sniffing dog can get to these chemicals the better other animals have this organ too when you see a lizard darting its tongue out to touch an object it's not tasting it or smelling it it's sampling chemicals and bringing them closer to the vomeronasal organ it's deeply contested whether or not humans have this organ but even if we do have some version of it our pheromone detecting abilities are basically non-existent compared to a dog's hounds in particular are a type of dog with one of the strongest senses of smell not only do they have the highest number of olfactory receptors in their noses but other features of their body also enable them to smell extra strongly their ears are ridiculously long not to hear better but to waft more scented air up towards their nose basset hounds even have short legs to keep their head close to the ground at scent level and their seemingly constant drooling helps bring extra liquids up to the vomeronasal organ naturally these dogs have an incredible sense of smell but with some training what they can do is incredible in one study researchers took five clean glass slides and added a single fingerprint to one of them the slides were then put away for up to three weeks when presented with the slides again one dog was able to detect the slide touched by a human correctly 99 out of a hundred trials when the five slides were then placed outside for a week exposed to sun rain wind and debris the dog was still able to select the correct slide over 50 of the time a trained dog can even smell a cadaver under cement at least 15 feet or 4.5 meters down or on a lighter note they can stand at the front of a boat and sniff the water to help researchers locate whales since dogs can smell whale poop from over a mile away and incredibly dogs don't just notice smells they notice very small changes in those smells in one study a human participant walked in a straight line on a trail a dog was then brought in perpendicularly to that trail the dog could of course smell that someone had recently walked by but they could also smell the direction the person was traveling in as few as five steps this is because the dog can sense the change and smell over time in this way a dog can reconstruct the path taken and dogs can smell things even more intangible than steps they've been shown to be the earliest most accurate disease detectors that researchers have ever seen even better than the best current lab tests when looking for cancer in a human patient doctors can test for a lot of different things in the body that indicate cancer might be present things like tumor markers such as calcitonin for thyroid cancer or prostate-specific antigen for prostate cancer immunoglobulins circulating the blood when cancer is present and even tumor cells themselves or their genetic material circulating the body these tests can help detect some cancers early but certain cancers like lung cancer don't show up in its early stages in any of these tests in fact there's not a single blood test available that can accurately detect lung cancer it's usually only found once it's spread wildly throughout the body which is a huge contributing reason that lung cancer is the most common type of cancer death in the western world so researchers put a sniffer dog to the test to see if it could detect some indicator of lung cancer that we can't the experiment began when a golden retriever was conditioned through classical conditioning the dog was presented with lung cancer samples and control samples and a correct indication of a lung cancer sample was rewarded with food this process took around one year then 42 lung cancer patients with tumors in various stages along with healthy controls provided urine and breath samples and with a combination of these samples the dog correctly detected 40 out of 41 cancer samples a success rate of 97.6 for a cancer that can normally only be detected with a ct scan this is incredible other studies have found that dogs can also detect other cancers with similar accuracy such as bladder or breast cancer along with other diseases like diabetes covid19 malaria and parkinson's disease and every once in a while during one of these studies something strange happens sometimes a dog will keep misidentifying a member of the control group as being positive for the disease even though that person had been selected specifically because a hospital test confirmed them to be disease free researchers marked these as false positives this kept happening for one patient in a bladder cancer study so the person decided to have more testing done and sure enough a few months later a hospital test found the disease at a very early stage disease detecting dogs are now being used to provide early screening for firefighters in california who are at high risk of developing cancer due to the toxins they're exposed to in their line of work and once the fda figures out how to regulate animal-based diagnostics this could be a part of regular healthcare for everyone so when the dogs detect cancer what compound are they actually smelling the answer is we don't exactly know a person's breath in a test tube or urine in a cup contains millions of volatile organic compounds we've never been able to distill ourselves which compounds or combination of compounds a dog is picking up on when it detects a disease however researchers at mit are working to recreate a dog's sniffing abilities in an automated odor detection system they designed a machine that mimics mammalian olfactory receptors that act as sensors the problem is even if the machine can detect many different chemical signatures researchers are still unable to parse this data which combination of thousands out of millions of compounds indicate cancer this is where machine learning comes in by applying a machine learning program researchers could tease out any similarities and differences between disease samples that can help the system identify the disease and when tested with confirmed cases of prostate cancer along with disease-free controls the artificial system was able to match the success rates of dogs with both methods scoring more than 70 percent researchers hope that one day such smell detecting bots will be available to everyone maybe even built into your smartphone however the combination of compounds that smell like cancer remains a secret known only to the dogs and the robots so when you tell your dog to get a job as i often do you might have a point there are many dogs out there actually saving lives my dog is very notably unemployed her nine to five activity is sleeping in a bean bag next to me while i work but i still wonder how much she can really pick up on she isn't trained to detect disease but can she smell my emotions can she sense differences in my body can she smell when i'm happy stressed agitated how i lose 100 brain cells every time i turn on the news or read something about donald trump on reddit this i don't know but i do know that the news cycle and the overall state of this country is distracting i do my best to tune it out but inevitably i get sucked back in through social media it's a tricky balance between staying informed and ending up doom-scrolling and wasting time while also feeling like crap so i recently decided to get my news in a different way with morningbrew a daily newsletter delivered to my inbox every morning that gets me up to speed on business finance tech and politics in just five minutes it's both witty and concise and gives me the gist of all the important headlines without the fluff and sensationalism morning brew can't make the news better but it can make it understandable and digestible and the best part about it is it's completely free if you've ever thought about supporting this channel here is your easiest chance all it takes is 15 seconds and an email address signing up is the best way to support us so thank you to anyone who has so to get a new and improved morning news routine click the link in the description to get started with morning brew today and if you're looking for something else to watch right now you can watch our most recent video about the insane biology of the electric eel or you can watch real engineering's latest video about a fascinating attempt to fling a satellite into space [Music] you

Channel: Real Science

Views: 573,189

Keywords:

Id: gx2l5cu5NmM

Length: 17min 6sec (1026 seconds)

Published: Sun Aug 21 2022

Reddit Comments

[u/GentleLion2Tigress]

A woman was able to smell Parkinson’s.

[u/fluentindothraki]

I liked that, and I really liked the music

[u/Fordeelynx4]

Thanks for posting this! Amazing documentary

[u/brazeau466]

Ya, amazing. Dogs have such power in that nose.

[u/kittykrunk]

Commenting so I can watch later