It's an impossible question to answer without a lot of guesswork and speculation. Scientists have low confidence in any of the answers.

The reasons are that:

• Domestication is hard to detect. You are looking for physical changes in a plant that make it differ from the wild ancestor in a way useful to man.

• The farther back you go, the fewer the differences. At the very beginning of domestication the changes are so small you may overlook them or misidentify them.

• It's hard to tell if minor changes were natural or artificially selected.

• In some cases the wild ancestor is unknown or unavailable for comparison.

• Tiny amounts of plant remains don't survive very long, so we have very sparse sampling that gives a patchy picture. Especially true in warm humid climates like Indochina.

Right now, figs are believed to be the oldest domesticated plant. How sure are we of this? Not very, because the difference between figs, barley, wheat and rice is of the order of a thousand years, much too short a time to establish precedence. Maybe wheat is the oldest but we can find older figs because figs are much bigger than cereal grains and preserve better. Maybe rice is oldest but older samples are hard to find because of the humid climate of southeast Asia versus the dry climate of the middle east that preserved figs and wheat.

If the difference were a few thousand years we could be more certain, but at 1,000 years the situation is ambiguous.

It's also important to remember that domestication does not equal farming. Domestication is only about 12,000 years old, but farming goes back at least 20 or 25,000 years. The difference is because you need millennia of continuous farming to produce domestication, but such continuity was not possible before climate stabilized in the holocene.

Also, keep in mind that our very first domestication wasn't a plant at all - it was an animal. There is some controversy about exactly when dogs were domesticated, but for sure it was long before figs or wheat.