Scientists have discovered the oldest fossil evidence of agriculture — not by humans, but by insects.The team, led by Eric Roberts of James Cook University along with researchers from Ohio University, discovered the oldest known examples of "fungus gardens" in 25 million-year-old fossil termite nests in East Africa.The results are published today in the journal PLOS ONE.Some termite species cultivate fungi in "gardens" in subterranean nests or chambers, helping to convert plant material into a more easily digestible termite food source.