The reason why less than 1% of the population can work on agriculture is because the 1% that work on agriculture are supported by highly specialized individuals that provide advanced farming equipment, weather modeling, genetically engineered seeds, financial products that help forecast demand and supply capital, etc. In a world where only 1% work, the supply chains for those things fall apart, and it then takes more than 1% of the population to feed the rest.
This is true but some of the technology needs to be done only once - the same way you only need to make a firmware once and sell thousands of devices. So a farmer today by him- or herself alone, does feed a lot more people than two centuries ago.
