Domestication History of Fig Trees - What Archaeology Tells Us

What is the Oldest Domesticated Plant? The Weird and Wonderful Fig!

Figs on a Tree in northern Israel
Figs on a Tree in northern Israel. Yaniv Yaakubovich

The fig tree, long a symbol of Western culture, may also be one of the earliest domesticated plants in the world. In an article in the June 2, 2006 issue of Science magazine, a research team led by Mordechai Kislev at Bar-Ilan University in Israel reports evidence for parthenocarpic figs from six sites in the greater Mediterranean Sea region dated between 11,700 and 10,500 years ago. This evidence of domestication at the Pre Pottery Neolithic A (PPNA 8300-7300 BC) sites of Gilgal, Jericho, Netiv Hagdud and Gesher in the Jordan Valley and Mureybet in the Euphrates Valley, occurs at roughly the same time as rice domestication in Asia, but fully five thousand years earlier than millet or wheat or any other seed plant in the middle east.

To explain why the recovery of this particular fruit almost certainly means they were from domesticated fig trees involves a dip into the biology of this weird and fascinating plant.

Fig Trees: Weird and Wonderful

The fig tree (Ficus carica) is a plant native to the Mediterranean region. The edible part of the fig, called the 'fruit' is not really a fruit at all, it's a synconium. A synconium, in the fig's case anyway, is a green globe with an opening on one end. Inside the synconium are a cluster of hundreds of flowers. If pollinated, these flowers produce drupelets, tiny bubbles of fruit material with a seed in the center.

Each species of fig tree in the wild comes in two types: the hermaphrodite fig, that produces pollen but does not produce seeds to generate a new tree; and the female, that produces no pollen but does produce three crops of figs throughout the year, one of which if pollinated, produces a seed that can make a new tree.

One important physical difference between a hermaphrodite and female fig, believe it or not, is the length of the flower.

Symbiosis and the Fig Tree

Fig trees are symbiotic--that is to say, they can only survive to reproduce with the assistance of another creature, in this case a fig wasp. Without the fig wasp's pollinating activities, the tree would never produce a germinated seed for the next generation; alternatively, the fig wasp would never survive without the fig tree's food and shelter.

At the proper time, female fig wasps enter the opening of the synconium, and attempt to inject their progeny (eggs) into the flowers. If fig wasp eggs are injected into the short hermaphrodite fig flowers by their mothers, the new fig wasps feed on the developing fruit and spend most of their lives within the synconium until they reach adulthood. Still inside the syncomium, the females are fertilized by the males and then the females gnaw their way out of the synconium. On the way out, their bodies are dusted with pollen. Their sole remaining job in life is to find another synconium, enter it, inject their eggs, dust the pollen off their bodies and die.

However, if a wasp enters a female fig, the flowers are too long for the eggs to be successfully placed; the wasp then spreads pollen but no next generation of fig wasps, and the female fig can produce unconsumed fruit and seeds for the next generation. If a synconium from this kind of fig is never pollinated at all, the fruit does not form at all, and the synconiums dry up and drop off the tree. In other words, to bear fruit and produce seeds for the next generation of trees, a fig tree flower must be both exposed to pollen and be left unpierced by a mother wasp.

Therefore, all fruit of a regular fig tree have fig wasp embryos in them; whether the fruit is consumed by the wasp embryo or not determines whether the fruit survives to adulthood.

What is a Parthenocarpic Fig Tree?

But somewhere along the way, a mutation of the fig tree occurred that doesn't require pollination to bear fruit. In this case, no fig wasp needs to make its way into the synconium and you don't find any embryos in among the completed fruit. This kind of fig is called parthenocarpic, because it produces edible fruit without pollination. Since these trees are not fertile (even if you can produce fruit you can't produce a working seed without pollination), the only way a parthenocarpic fig tree can reproduce is with the assistance of another symbiote--a human being. It's not difficult to propagate parthenocarpic figs: all you have to do is cut a branch and root it. But that takes human intervention.

And without human intervention, we would have no fig trees that bear fruit without wasp embryos today.

Human Intervention and the Fig

All plants and animals evolved originally irrespective of what humans wanted. The fig doesn't care if its fruit is tasty; neither does the wasp. But humans care, and when we are looking for figs and find a tree that produces good and tasty fruit, we pick that tree to propagate.

In this way, humans subvert the natural selection processes, and instead create new forms of plants or animals: this we call domestication.

The archaeological evidence recovered from the early Neolithic sites of Gilgal, Netiv Haghdad, Jericho and Gesher in the Jordan Valley and from Mureybet in the Euphrates Valley are of parthenocarpic figs, figs undisturbed by wasp embryos, and therefore, figs which had to be propagated by human beings. On that basis, say the authors, incipient horticulture of fig trees by humans began in the greater Mediterranean region by at least 11,400 years ago.

References

Mordechai E. Kislev, Anat Hartmann, and Ofer Bar-Yosef. 2006. Early domesticated fig in the Jordan Valley. Science 312:1372-1374.

This article on Fig Trees is part of the About.com Guide to Plant Domestications, and part of the Dictionary of Archaeology.

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Hirst, K. Kris. "Domestication History of Fig Trees - What Archaeology Tells Us." ThoughtCo, Nov. 10, 2015, thoughtco.com/domestication-history-of-fig-trees-170637. Hirst, K. Kris. (2015, November 10). Domestication History of Fig Trees - What Archaeology Tells Us. Retrieved from https://www.thoughtco.com/domestication-history-of-fig-trees-170637 Hirst, K. Kris. "Domestication History of Fig Trees - What Archaeology Tells Us." ThoughtCo. https://www.thoughtco.com/domestication-history-of-fig-trees-170637 (accessed November 20, 2017).