Comparing Apples and Pears

I have two pear trees in my garden. In the middle of August, the grass is suddenly covered in rotting pears. Why do pears rot faster than apples? 

People have long observed that pears sink in water, while apples float. The pear is more dense, and has a higher water content. Apples continue to breathe (absorb oxygen) after they are picked, which keeps them fresh, but pears get out of breath (don't absorb much oxygen) and can decay fairly quickly. 

From a human point of view, apples are more well-behaved than pears, and fruit growers and supermarkets would like pears to behave more like apples. Belgian scientists have now discovered differences in the cell structure that explain why apples can breathe better than pears. 

But what does better mean? The apple is more efficient at staying fresh. But the pear is more efficient at rotting. Why is staying fresh better than decaying? The biological purpose of the pear is to grow a new pear tree, not to get wrapped in plastic and put onto a supermarket shelf. For the pear, staying fresh is a bad idea because it delays the fulfilment of its biological purpose. 

Of course, that's not to say that the pear is superior to the apple in terms of producing new trees - it has merely evolved a slightly different method. But both methods seem to work, even in the absence of human intervention. If we try to understand botanical behaviour in terms of human purpose, we may get curious results. 

Jonathan Amos, Apples beat pears on crunch issue, BBC News 11 July 2008

Related posts: Redesigning the Banana (July 2009), Is this really as nature intended? (November 2011)