Very few of us would argue against the notion that spices (and to a lesser extent, their leafy cousins, herbs) play an important role in our culinary preferences. These days it would be almost unthinkable to make a dish that is completely devoid of our standard 鈥榞o-tos鈥� from the aptly named spice cabinet in the kitchen, such as a spaghetti sauce without oregano and thyme or a cauliflower soup without some cumin鈥� or just about any prepared dish for that matter, without the omnipresence of pepper, garlic and onion. Well it wasn鈥檛 that long ago that these key ingredients were less of a flavouring agent and were more like conservation agents, protecting us from eating rotting food.
However, the true origin of the story of herbs and spices spans back to the earliest terrestrial environments when aquatic plants first colonized the empty landscape during the Silurian Period over 440 million years ago. These first land plants, simple vegetation like mosses and ferns enjoyed the plentiful sunshine and oxygen for photosynthesis and the complete absence of natural enemies, whom had yet to also make the trek out of the seas to colonize the new terrestrial environment. It wasn鈥檛 long though that other organisms began to emerge from the seas in order to take advantage of the bountiful supply of plant matter that had colonized the terrestrial environment before them.
By as early on as 380 million years ago, we have direct evidence of this from fossilized plant tissue showing damage from herbivores, first from bacteria and other microbes and followed not long thereafter by insects. This began the longest antagonistic relationship in the terrestrial history of life on earth, that of plants fighting to avoid being eaten. Because of the small size of these early natural enemies, physical defenses in plants would have been of little use, as the microbes and insects could just move about freely around the spines and thorns.
The best defensive option against the mini-enemies is a chemical one, for two reasons: firstly because microbes and insects have metabolisms that are governed by the same or very similar enzymes and neurotransmitters as one another, meaning that a chemical that works on one will likely work on the other as well, and secondly, because plants already have a series of internal biochemical pathways that make their own plant chemicals for growth, reproduction and metabolism of their own physiologies. Conveniently, it did not require much tweaking of these pre-existing pathways to make them produced substances that were biologically active against their newfound natural enemies on land.
And so began the historical production of herbs and spices, known as defensive phytochemicals, which allowed plants to protect themselves against their natural enemies millions of years ago, and that we now enjoy as a regular part of our daily diet. The fact that these phytochemicals have inhibitory effects against microbes and insects is well established in the field of biochemistry. In fact, when added to a petri dish teeming with bacteria, the following plant extracts are capable of suppressing the microbial growth with over 75% effectiveness: garlic, onion, thyme, allspice, oregano, cinnamon, cumin, cloves, chillies, rosemary and the list goes on.
If these so-called herbs and spices evolved to protect plants against microbial attack, could it be that early humans also began adding them to their food in order to prevent sickness from microbial rot? This would have been especially important in pre-industrial times when no-one had a fridge or a freezer and food conservation would have represented a great advantage to early humans otherwise susceptible to the nasty effects of food-borne illnesses.
Were this to be the case, we should expect that the historical use of herbs and spices in food would be largely associated with parts of the world where microbial and insect attack would be more likely, namely the highly biodiverse tropics and sub-tropics, which also have consistently warm and humid environments, where rot is more likely. Incidentally, when ethnobotanists trace the historical use of herbs and spices to pre-industrial and pre-colonist societies, that there is a strong correlation between their use and people living in hot and humid environments, such as India, Thailand, and Central America among others. Sound familiar? Those cultures are renowned for their spicy food even nowadays.
It appears that pre-industrial humans certainly did use herbs and spices adaptively in order to protect themselves against food-borne illness and this fact was certainly not lost on the first European explorers looking to reap the resources of the new lands they were colonizing during the 18th and 19th centuries. Remember that at the time, the journey from Europe to the Orient involved the longest boat ride possible, from England down around the southern tip of South Africa and back up into the Indian Ocean. Although this was an arduous journey at the time, it was still deemed worthwhile in order to bring back some of those precious herbs and spices for the dishes of the aristocracy back home.
Also, it was because of the great long duration of the sea route and later the perilous dangers of the land route through what is now Russia (plagued by bad weather and marauding bands of looters) that inspired Christopher Columbus to sail west from Europe, hoping to find a shorter route to the East Indies. Unfortunately, he did not account for there to be a whole new continent in the way and accidentally (re-)discovered the Americas. However, it was because he thought that he鈥檇 made land-fall on the eastern tip of India that the Indigenous people of our continent are still erroneously called Indians by some.
The human use of phytochemistry is an evolutionary and historical tale that has enriched the biodiversity of our planet as well as our human culture and history. It is therefore not just our food that would appear bland without it, but also perhaps our whole recent story of human civilization and we should be thankful for having spiced things up a little.
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