troublesome of all were the weeds that resembled crops. These included darnel, a toxic grass which happened to be a dead ringer for wheat, and which infested the Middle East’s earliest agricultural sites. Pastoralism only worsened the situation, as grazing and browsing livestock suppressed tree regrowth, maintaining the sort of open conditions favoured by weeds. What’s more, just like crops, many weeds were adapted to thrive on the elevated levels of soil fertility resulting from all that extra animal dung.
British farmers, like their continental antecedents, set about annihilating the wildwood with their crops and livestock. Shifting agriculture was probably practised at first, with the felling of a few trees and controlled burning of understorey, followed by successive plantings of cereals. After a few seasons, the plot’s soil nutrients were exhausted, forcing people to move on and repeat the destructive pattern. Anthropogenic deforestation was hardly a new thing – as we’ve seen, hunter-gatherers were keen on woodland openings – but its scale from the Neolithic onwards was unparalleled.
Trees were removed for reasons beyond the need for cropland: their timber was a source of both fuel and building material, while the clearances themselves may have held a symbolic value. Britain’s vanishing woodland is reflected in changes in the incidence of particular pollen species in the archaeological record. As the representation of oak, elm, lime and ash dwindled, grasses, shrubs and wildflowers came to the fore. Invertebrate communities also changed, with a decline in specialist forest insects, including those associated with old or decaying timber, their place taken by varieties adapted to open and disturbed ground; dung beetles flourished thanks to livestock. Every so often a prolonged spell of climatic deterioration – as occurred between 5,000 and 3,500 years ago – would lead to a temporary abandonment of arable farming in Britain. Forests then had a chance to recover, although pastoral farming would still have been practised.
Of course, Britain’s Neolithic farmers had their work cut out dealing with the weeds that prospered in the denuded landscape. Many unwanted plants already lurked as seeds in our soil, just waiting for their moment in the sun; others were conveyed from further afield as contaminants of grain imports. The field, or corn, poppy, well-known to early Middle Eastern civilisations, is among the more familiar of the non-natives to have debuted in Britain around this time. The ancient Egyptians were taken by the striking blood-red blooms which infested their wheat and barley fields at harvest. The poppy’s reappearance each year was a metaphor for rebirth and regeneration. The flower was woven into funerary bouquets and depicted on tombs.
Another arrival in Britain was charlock, or wild mustard, which was once described as the most troublesome annual weed of arable land. Indeed, an assortment of familiar crops including artichokes, flax, garden peas, leeks, lentils, lettuces and radishes may have started out as invaders of arable fields. Given that these are all fast-growing, short-lived species thriving on bare soil, their weedy heritage seems to fit. Even einkorn – one of the first types of wheat to be cultivated on a large scale – may have started life as a contaminant of emmer wheat crops. Furthermore, bread wheat, today’s single most important variety, thanks to its easier threshing and greater grain yield, arose in the Fertile Crescent at least 8,500 years ago as a result of hybridisation between emmer and another weed, wild goat grass.
From a British perspective, some of the most important of the arable weeds were rye and wild-oats. Although originating in the Middle East, both seemed better adapted to our miserable climate and harsh soils, and often outperformed wheat and barley. So tenacious were these grassy invaders that by the Early Bronze Age, about 4,000 years ago, central and northern European farmers stopped bothering to weed them out and instead harvested them as crops in their own right. Domesticated varieties of both rye and oats were soon cultivated for bread-making, for flavouring alcoholic drinks, and as animal feed. Wilder versions of the oat stuck around and remain intractable arable weeds to this day, in large part due to the similarities in appearance and lifecycle with those of crops. Selective herbicides are available but hand-weeding, or ‘rogueing’, of wild-oats is still practised on a small scale.
When Brits took to agriculture 6,000 years ago, the door wasn’t just opened to invasive plants. Also waved through was an assortment of animal species adapted to living among people and exploiting their way of life. The house sparrow is a case in point. Remains of this small, gregarious bird have been identified in 10,000-year-old Natufian sites, suggesting sparrows long ago learned to nest in or close to buildings, purloining stored cereals and picking through the rubbish piles. By the Late Bronze Age, about 800 BCE, sparrows are known to have been present in central Sweden, so had probably reached Britain by then too. Today, they’re one of the world’s most cosmopolitan birds, outcompeting indigenous avians and proving a serious agricultural pest. In Russia alone, they’ve been accused of consuming a third of the annual grain production. During the 1950s the Chinese leader, Mao Zedong, even declared war on the sparrow, his scientists reckoning that, for every million birds killed, 60,000 extra people could be fed for a year. Chairman Mao’s scheme backfired: the removal of sparrows resulted in plagues of locusts and other insect pests, whose populations the birds had helped suppress, which in turn led to famine. The Chinese government ended up reintroducing sparrows from the Soviet Union.
It seems therefore that house sparrows have a value in agricultural systems and in Britain, at least, we’re fond of them. The sparrow population has been falling of late: during the 1970s there were up to 12 million of them in the UK, but the population is now half that, with the worst declines in England. No one is really sure what’s killing off sparrows. Possible factors include a reduced availability of invertebrate prey, a shortage of nesting sites and increased predation by squirrels, magpies and cats. In cities, high levels of nitrogen dioxide in the air, mainly from car exhausts, also seems to be a factor, with London alone seeing a 60 per cent decline between 1994 and 2004. All this has triggered urgent conservation efforts to save the sparrow.
Such measures won’t be contemplated any time soon for the house mouse, another accomplished non-native invader, which originated up to a million years ago somewhere between the Middle East and northern India. The rodent was first drawn to the organic waste tips of hunter-gatherer settlements in the southern Levant at least 15,000 years ago and its population was primed to explode with the invention of agriculture. Recent evidence shows the house mouse sometimes shared the more mobile of the Natufian sites with a second species, the short-tailed mouse; however when people settled down for any length of time, the house mouse soon elbowed out its wilder cousin. By the Bronze Age, the rodent had scurried into western Europe but took a while to make its mark in Britain: the earliest records date from pre-Roman Iron Age settlements at Gussage All Saints in Dorset and Danebury Hillfort in Hampshire. The mouse seems to have got established after repeated introductions as a ship stowaway; by then Britain was well connected to the continent by the maritime trade and replete with granaries. Danebury alone boasted some 4,500 pits for storing crops, making it a house mouse heaven.
Along with rabbits, rats and grey squirrels, the house mouse shares the accolade of being among the few vertebrates to inflict both economic and social costs on a national scale. In addition to eating and fouling food stores, the rodent harbours a catalogue of unpalatable (and unpronounceable) diseases from tularaemia and typhus to leptospirosis and lymphocytic choriomeningitis. Humans have long waged a losing war against the species. These days baited traps and poisons tend to be used, but in times past barley cakes, spiked with black hellebore (a toxic variety of buttercup), would be placed at the entrance to their holes. Mice were also said to flee a censer of haematite stone and burning green tamarisk. But nature also provided a more elegant solution to the rodent problem.
The African wildcat’s mouse-destroying prowess, along with its skill as a bird and fish catcher, may have been what recommended the species as the perfect household pet to the Egyptians more than 4,000 years ago. If true, that would make its tame version, the domestic cat, an early agent of biological control (the use of one organism to reduce populations of another). The sacred importance of cats in ancient Egypt is the stuff of legend with the feline deity Bastet worshipped as a goddess of fertility and the moon. The Greek historian Herodotus famously
