Today I watched as a young East Asian family with a small child wandered carefully, heads bowed, through the bracken (Pteridium aquilinum), picking young not-yet-unrolled shoots known as fiddleheads — they do look rather like the curled ends of violins — for use as a vegetable. It is commonly eaten in Japan, China and Korea.

Bracken, including young shoots, is carcinogenic in animals, and herbivores like horses generally avoid it if they can. The main toxin is ptaquiloside. Richard Mabey’s Food for Free mentions bracken only once, to say that it is carcinogenic, and omits it from the main text. Some scientists suspect that the high incidence of stomach cancer in Japan is connected to the consumption of bracken.

It was chilling, on a fine hot day, to consider the danger that family were putting themselves in. On the other hand, if they select only young shoots, the dose is as low as possible — the plants have not had time to accumulate toxins in newly-grown parts. And all of us consume substances — sugar, salt, nitrates in ham and sausages, … — not to mention alcohol, which are certainly not good for us. Can you have a natural history of human beings? I can’t see why not.