Thirty years ago, genetic engineers hoped new technology would revolutionise world farming and reduce or even eliminate the need for fertilisers and pesticides. It was a noble idea that deserved success.
But only promises came. In the 1990s the public was told genetic modification would increase yields enough to feed the world. Now in an age of climate change we hear that GM can reduce climate change emissions, improve drought tolerance, stimulate growth and eliminate poverty.
Perhaps all these benefits to society will one day accrue, but my fear, after tens of billions of dollars of public and private research and development money have been spent by some of the world's most powerful companies, is that it has met a dead end.
Only a handful of GM food crops such as maize, soy and oilseed rape are grown widely and mostly in only a few countries.
Instead, the business is in the grip of a few global chemical companies who make their profits mostly from the sale of the chemicals they engineer their seeds to resist. After 30 years of public relations and backing by governments, the crops are still not trusted and food safety concerns will not go away.
Advocates say the science is settled after three trillion meals have produced little more than a few, possibly linked, allergic reactions. But critics respond that most of the foods are fed to animals, not humans, and no clinical trial of any genetically modified crop has ever been published.
Instead, the toxicity trials are designed and conducted in semi-secret by the companies themselves and the regulators have concentrated on the crops' environmental effects. Any reports of serious illnesses are routinely batted away as "bad science".
I fear much of the problem of trust stems from the chemical company Monsanto, which from the start has been the world's largest producer, researcher and distributor of the crops. Its fierce use of patents, its heavy-handed lobbying of governments to deregulate markets, and its buying up of seed companies internationally have scared the public, raised concerns among small farmers the world over and denied the public the potential benefits.
In five years' time, it is possible someone will manage to engineer GM crops to "fix" carbon and eliminate the need for pesticides. If the crops can then be seen to be without risk and be for the benefit of the public rather than for sheer corporate profit, then even organic farmers should not oppose them.
But so far the promoters of the technology have relied on political bullying to give us promises rather than better products.
In fact, advances in conventional farming have at least matched and possibly exceeded anything achieved by GM.
At a time when we desperately need new ideas to grow more food, genetic modification offers more chemicals, more expensive seeds and patents to protect corporates.
If the companies had really sought from the start to develop traits useful to people and farmers, rather than to create massive profits for themselves, it might now have become a technology to change the world.
As it is, I fear GM has proved beneficial for the few but held back the real debate on how to grow food without harming the environment or people.