By Jim Provan
I suppose I should start this review with a double-disclaimer. Firstly, I have a background in crop plant genetics, a fact only marginally less embarrassing than possessing a degree in biochemistry! I did my PhD at the quondam Scottish Crop Research Institute (latterly the James Hutton Institute) on the genetics of cultivated potatoes. I also carried out work on aspects of the domestication of wheat, rice and maize – that makes the top four crop plants consumed by humans, but more on that later. Secondly, the author is a mate of mine, but, unlike having a degree in biochemistry, I wouldn’t expect you to hold that against anybody.
Producing enough food to feed an ever-expanding population is one of the great challenges in global food security. Around half of the total calories consumed by humans come from just three crops – wheat, maize and rice. With that in mind, we have to ask the corollary question based on the subtitle of the book, namely that out of the almost half-a-million plant species thought to exist on the planet, why don’t we eat the plants that we don’t? This, in fact, is one of the key underlying themes of the book, and the author quickly debunks the key popular misconception that we don’t eat plants because they are poisonous or harmful. Quite the opposite – years of experimentation have shown that we have succeeded in domesticating many crops that have high levels of toxins (e.g. potatoes) or that ripening or sufficient cooking can ameliorate the effects of other toxins. Cassava, fifth on the list of plants consumed by Homo sapiens, contains enough cyanide to kill us if eaten raw, and the akee –staple of the Jamaican national dish of salt fish and akee – can kill impatient locals who can’t wait for the fruit to ripen. Indeed, the toxins in many plant species are just what makes them so attractive to (at least some) humans – habañero chillies weigh in at around 400,000 – 500,000 on the Scoville scale, but how many of us would fancy tacking the naga chilli (923,000 units)? And forget eating – what about the pharmacologically active compounds in legal (e.g. tobacco) and not-so-legal (e.g. cannabis) crops?
As it turns out, one of the most important concepts of what makes a good crop is that of reproduction – sex, or lack thereof. Vegetative propagation is key to the production of many crops, and reproductive isolation of the putative crop plant from its wild progenitors is often an important step in the domestication process. A complete chapter is devoted to the weird and wonderful sex lives of plants and – not surprisingly – we very often find ourselves in “Carry On” territory. Sections of Chapter 3 entitled “Behind the fig leaf”, “Papaya – the sex-change king, queen and more besides” and “Avocado – the flasher” (Ooooh – Matron!!) are fascinatingly funny. And surely if it was good enough for the Big L.*, who could rarely see beyond sex and sexual-bitties in his classifications of plants, then it’s good enough for us!
The book is littered throughout with many anecdotes on historical reasons why we do and don’t eat various plants. Again, the section on the domestication of beans for consumption in a polite society will appeal to the schoolboy humour in all of us, and the tale of the serendipitous early insights into plant genetics gained from trying to cultivate strawberries are wonderful. When it all comes down to it, though, we still have the very real and possibly very important question of why we eat the plants that we do, and not others. The author’s answer is a simple one – ourselves. He argues that we are conservative and / or complacent in our choice of foods, but does acknowledge that very often, necessity (i.e. famine) has been the mother of invention. In another recent book, The Third Plate: Field Notes On The Future Of Food, author Dan Barber also argues that a change of mentality is needed, and that we should change our diets to accommodate better what nature can provide for us, instead of vice-versa. Food for thought indeed!
* Carl Linneaus: Swedish Botanist who laid the foundations of modern taxonomy.
The Nature Of Crops: How We Came To Eat The Plants We Do by John M Warren and published by CABI Press