Why the Durian Smells So Strong

The story

In Singapore, and in many cities nearby, there is one fruit that is not allowed on the trains. There are signs about it. Hotels turn it away at the door. And yet, in the markets, people queue up happily to buy it, calling it the king of fruits and paying royal prices for the best ones.

It is the durian: big as a football, heavy, and armoured all over with sharp spikes. But it is not the spikes that get it banned from trains. It is the SMELL. A ripe durian's smell is famous around the world. It rolls through a room and fills a whole train carriage. Some people say it smells terrible, like old socks and rubbish bins. Others breathe in the very same smell and sigh with happiness, because to them it means custard-sweet, creamy golden fruit inside. Same fruit, same air, completely different noses.

Now, some might call this a design flaw. Why on earth would a fruit want to stink?

Turn the question around and you find the wonder: scientists think the durian's mighty smell is not really written for us at all. It works like an advertisement, and the audience is the animals of the rainforest.

Here is the durian tree's problem. A tree is rooted to its spot. It cannot walk its children to a new patch of forest, yet its seeds must travel, because a seed that just drops by its parent's feet has to grow up in its parent's shadow. So the tree does what clever companies do: it advertises. It wraps its seeds in rich, sweet, creamy flesh, the reward, and then it broadcasts an announcement that carries far through the thick, tangled forest, where eyes cannot see far but noses work wonderfully. That announcement is the smell. Scientists who studied the durian's odour found it is built from dozens of smelly ingredients mixed together, a chemical shout of an advertisement.

And the forest answers. Wild pigs come trotting. Orangutans climb for it, for durian is one of their favourite feasts. Civets, elephants where there are elephants, all kinds of hungry neighbours follow the smell to the fruit and feast on the creamy insides. Not every guest helps the tree. Some freeloaders chew up the very seeds. But some animals, especially big ones that swallow seeds whole or carry fruit away, leave seeds behind far from the parent tree, sometimes with a helpful dollop of natural fertiliser. Enough seeds catch their ride that the smell keeps earning its keep: the tree's children travel across the forest.

So the durian is not badly designed. It is PERFECTLY designed, just not for train carriages. Its smell seems to be a message for the fruit-loving animals of the forest, and human noses are only eavesdropping. Our tastes and experiences differ, so no wonder people disagree about what the message smells like.

The next time a powerful smell finds your nose, from a durian stall or anywhere else, remember: you may be overhearing a conversation, an invitation written on the air, sent from one living thing to another.