The Age of Weeds: Let's declare war before it is too late

Albert the archaeology student was in the Charles Sturt University library, slumped over a heap of palynological textbooks that traced the emergence of the Emmer and the Einkorn on the Fertile Crescent some 10,000 years ago.

He was dozing gently in the spring sunshine when an early blowfly droned past, rousing him from his soporific state, in which a mischievous Morpheus had implanted a sudden question.

The books all said the same thing: That humans had, over a few thousand years or so, harvested wild grasses, brought them back to the home shelter, dropping a few seeds around the place which, over a longish period, selected themselves into a sort of crop. It was the start of agriculture, the start of civilisation, religion, literacy, computers, wars, politics, the cross-your-heart bra, Tupperware, Spandex, the space race, Teletubbies, the whole goddam thing.

And with humans came weeds. Weeds everywhere. Humans spread weeds like they spread, well, humans. They turned the whole of planetary biology topsy turvey and created a problem they couldn't even begin to handle. But Albert had the eerie sensation that he wasn’t getting the full picture. At back of his sleepy head a small question popped up. In a squeaky sort of voice it said, "I wonder if, instead of humans spreading weeds, all the time weeds have actually been spreading humans?"

Feverishly he began to thumb through botanical, palaeontological and agricultural histories. Hour by hour the sun slid down the sky and up again, he searched and cross referred till his eyes stood out on stalks. In the end it was as plain as a pikestaff. Back in good old Pangaea, the weeds had the world pretty much to themselves. They could move around at their ease and do weedy things to one another, colonising any ecosystem they chose. They weren't even much bothered by dinosaurs.

Then Terra Firma played a nasty trick on them: plate tectonics: First Gondwana and Lawrencia, then a whole mass of inferior continental fragments, each a weedy island empire unto itself. For a couple of hundred million years the weeds sat and stewed over it all. Their Garden of Weeden had been taken away and somehow - anyhow - they had to get back again. It was written in the root zone.

It took a long, long time before a misbred chimpanzee stumbled out of the enfolding shelter of the rainforest, scratched himself and took off across the savannah, rock in hand. But the weeds knew a priceless opportunity when they saw one. It took 'em a while, but in the end they managed to breed a particular sort of chimp, clad in the skins of other animals, who was prone to pick up grains and cart them around with him. Instead of humans domesticating wheat and barley, the wheat and barley had domesticated humans.

The weedy strategies for doing this were amazing. They lured humans with luscious fruits. They ravished us with head-spinning scents. They wooed us with nectar. They taught male humans to gather the brightly coloured genitals of weeds and present them to their females as a sign of their true intent.

It wasn't long before weeds began selectively breeding humans on the basis of their ability to transport weed seeds. They started by developing farmers - famed for their ability to cultivate a whole lot of other things by accident besides wheat and barley - but soon they moved on to explorers, merchants, witches and apothecaries.

In Elizabethan times they invented the gardener and seduced him with the rose. They hooked the Chinese on rice. They drove the Dutch crazy over tulips. In collectors, they launched a still-growing and slightly pornographic obsession with orchids.

Then, in the 18th Century, they invented the botanist.

The botanist, as everyone knows, is a compulsive spreader of weeds. He takes a curious plant from darkest Africa and introduces it to Kew Gardens, whence it quickly leaks out to collections, gardens, nature reserves and wildernesses all round the world, takes over and throttles them. He is a bio-terrorist “par excellence”. One highlight of this weedy campaign appears to have been a specimen called Banksia distributor.