14 Jan 2015 How the sense of taste has shaped who we are
Our current cultural obsession with food is undeniable. But, while the advent of the foodie may be a 21st century phenomenon, from an evolutionary standpoint, flavour has long helped define who we are as a species, a new book, Tasty, argues. Written by Pulitzer prize-winning US journalist, John McQuaid, it weaves a fascinating story with a beginning some half a billion years ago.
McQuaid (right) was interviewed for Scientific American… read on!
What made you decide to write a book about taste?
I have two kids, a boy and a girl born two years apart – now teens – and a few years ago, I became fascinated with how their tastes and preferences in food differed. My son liked extremes, especially super-hot chili peppers and whole lemons and limes. My daughter hated that stuff. She preferred bland comfort foods such as mashed potatoes, pasta, cheese and rice. White foods. Both kids were also picky eaters. They liked what they liked, and it didn’t overlap (except for pizza). Speaking as a parent, this was maddening.
So I wondered where these differences came from. Were they genetic? The kids had mostly the same genes. Environment? They lived in the same place. And yet clearly both genes and environment were in play somehow. So I began to look into the question, and a whole world opened up.
And the basic answer to my original question is: kids are, biologically speaking, weird creatures. Pickiness seems to be programmed by evolution: it would have protected small children from eating strange, possibly poisonous items. Certain preferences, meanwhile, can develop arbitrarily and become very strong, then suddenly fade – every kid goes through phases as the brain matures and the neural networks that shape perception and behavior grow. Each person’s sense of flavour is like a snowflake or a fingerprint, in this way, shaped by partly by genes, but largely by experience. And always changing as more meals are eaten.
What is known about the earliest origins of the sense of taste?
The sense of taste – or let’s say taste and smell, the two big components of flavour – is impossibly ancient, dating back more than a billion years to the earliest cells, which needed to sense chemicals in the seawater around them – stuff to avoid, or stuff that was beneficial. So over time natural selection crafted receptor proteins. These are coiled molecules in cell walls that respond to specific kinds of chemical signatures (and also to light, vibration and other stimuli).
The really interesting thing is, as more complex life evolves – that is, multicellular life with mouths, brains, and internal organs – taste and smell play a central role. They are linchpins of survival, of winning the game of natural selection. They allow an animal to sense prey is nearby, and to derive some satisfaction from devouring it. The more acute they are, the better. And the more acute they become, the more brainpower is needed to process them. So the emergence of more sophisticated brains and behavior are, in evolutionary history, very often tied to sharpening senses of smell and taste. You can see this in anatomy: our systems for taste and smell are tied into the oldest, most “primitive” parts of the brain.
You also draw connections between the sense of taste and the earliest humans. What did you find most interesting about this?
Flavour plays an underappreciated role the evolution of Homo sapiens, and in the invention of culture. How the human body evolved – the big brain, small gut, upright posture – is a hotly-debated topic. But a big driver is a series of dietary revolutions: from vegetarian to omnivore, from raw to cooked food. These go hand-in-hand with the use of tools, which were all about food: killing it, cutting it up, preparing it. And as tools improve, so does the food. Cutting and pounding meat or tubers tenderizes them. Cooking fires make everything more palatable and easier to digest. A positive feedback loop emerges between tastier food, better food, better tools, and changing bodies and brains.
Cooked game, for example, tastes vastly better than raw game. It’s also a bigger challenge to obtain and to prepare than, say, jungle fruits. The hunt requires the ability to run, the right weapons, a complex strategy, cooperation. Meal prep requires the ability to render the meat, make a fire, roast and serve communally. As with earlier life forms, flavour is the crux of big evolutionary changes.
You also see one legacy of these changes in the shape of the human head. The retronasal passage running from the mouth up to the nasal cavity – where the aromatic component of flavour arises as food is chewed – shortened as human jaws shrank and faces flattened. The shorter distance supercharged flavours. So, although we have a weaker sense of smell than many other mammals, for us, smell plays a much more powerful role in flavour. Our big brains, meanwhile, allow flavour to tap into a range memories, thoughts, emotions and associations. This is what allows us to appreciate the fine flavours of braised meats, wines or cheeses…..