Humans have five senses – sight, hearing, smell, taste and touch. The popular theory is that we are really not good at any of these. Birds such as eagles can see far better than we do, dogs and cats have exceptional hearing (a cat can detect the distance of a sound in just one hundredth of a second, and can hear five times farther than we can hear), catfish have far more taste buds (100,000) than we do (10,000), many creatures have far superior touch mechanisms (manatees’ tactile sense is so finely tuned that the animals may experience “touch at a distance”—an ability to “feel” objects and events in the water from relatively far away) and dogs and rats are masters at sniffing, putting out olfactory capabilities to shame.
This conventional wisdom on smelling is about to be shattered as new research suggests that the human sense of smell may be equal to or even superior than that of dogs and rodents, the champions of smell. Aristotle wrote, “Man smells poorly,” but he could be proved wrong.
John McGann, a neuroscientist at Rutgers University in New Jersey and the new research paper’s author, reached this unexpected conclusion after spending 14 years studying the human olfactory system. McGann said he was alerted to the “big myth” after trying to translate rodent experiments to humans. He realized that even when mice could not tell two smells apart, humans correctly identified two distinct smells.
McGann identifies a 19th century brain surgeon, Paul Broca, as the primary culprit for introducing the notion of inferior human olfaction into the scientific literature. Broca noted that the olfactory bulb – the brain region that processes odour detection – is smaller, relative to total brain volume, in people compared with dogs or rats.
McGann points out that in absolute terms the human olfactory bulb is bigger than those of many mammals and a search revealed that the absolute number of olfactory neurons is remarkably consistent across mammals.
Humans have approximately 1,000 odour receptor genes, for instance, compared to 1,100 in mice, which some had taken as confirmation of mouse superiority. The genes code for different “flavours” of odour receptor in the nose, is attuned to selectively detect different volatile chemicals in the air.
Initially, only about one third of human olfactory genes were thought to be functional and the rest appeared to be evolutionary relics. However, recent research suggests otherwise.
This is not the only study that has recently debunked the “humans are poor smellers” theory. A study published last year found that humans are able to distinguish between one trillion different smells and another study showed that people are able to track a scent across a grassy field. Having the required anatomical features for smelling a trillion different smells is quite different from the question as to whether we need all that olfactory information. It is all part of the great mystery of evolution.
The one human sense responsible for relegating the others to second place is sight. While some animals can indeed see far better than we do, our vision is quite good.
When you can see something so well, there usually is no need for the other senses to meddle. But, if you are temporarily or permanently deprived of sight, the other senses really come into play.
This you can experience for yourself by closing your eyes for a few minutes and trying to hear what is going on around you. Yes, you will hear sounds that were always around you, but never really heard earlier. Indeed, blind people, especially, those blind from birth, often have exceptionally good hearing.
Another factor is that the five senses rarely work in isolation. The best example is a good cup of coffee. First, you see the coffee swirling in the cup, then you experience the sheer aroma and finally you get that heavenly taste.
The senses work with each other to give us an overall feeling or sensation. Of course, there are occasions when one sense is enough – close your eyes, put on the headphones and let Gustav Holst’s The Planets take you on a journey across the Solar System.
Smell is a vital sense, but you only feel its loss when it is gone. We all know that food is not all that alluring when our nose is blocked by a cold.
People generally tend to be miserable when their sense of smell is permanently affected by injury. We also do have an uncanny ability to remember smells and tastes, which often go together, at least when it comes to food.
There are so-called multiple-dimension cinemas where fragrances are disseminated during particular scenes (for example, a field of flowers) which most people will remember even 20 years later. And smells are important for our personal relationships – which is why perfumes and body odour fighting fragrances exist.
But are these five senses the only ones we have ? Do we have a so-called “Sixth Sense” (which incidentally was the title of a famous Night Shyamalan movie) or more formally, Extra Sensory Perception (ESP) ? One theory is that we had a sixth sense of intuition which we have lost in the evolutionary process, mainly due to the superior vision and hearing. Others say we still have the facility, but it is dormant.
A US scientist recently claimed to have found evidence of a “sixth sense” in humans that can detect the Earth’s magnetic fields. Joe Kirschvink, from the California Institute of Technology, says, his experiment can also be “repeated and verified”, something research on magneto reception has never been able to do before.
It is generally believed that most animals have a sixth sense that warns them of impending danger. Hours before the 2004 Boxing Day Tsunami, many wild and domestic animals ran inland.
No animals perished in the Yala National Park, which was pounded by huge tsunami waves. There are also reports that no dogs, except those chained, were killed in the Meethotamulla garbage dump collapse because they had fled earlier.
There are many examples of animals using their sixth sense for everything from hunting down prey to navigating vast distances. Scientists have found that eels can feel changes in the earth’s magnetic field to find their way up to 5,000 Km in a featureless expanse of ocean even if it means swimming away from their ultimate destination at first, researchers report in the April 13 Current Biology. Many birds also use a similar tactic for their annual migrations, some of which can exceed 10,000 Km.
But, can anyone develop a sixth sense ? There is a raging debate on this issue, whether meditation and other such activities can eventually give us an extra mental dimension. In the meantime, enjoy the senses that you already have and drink that coffee before it loses that aroma.