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Why Apples

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Cristy Meiners
/
KUER

The other day, as I lugged home 300 pounds of apples from my neighbor’s yard, I thought about the purpose of … fruit.

Flowering plants — like apple trees — have evolved so that their seeds will land in the best place to flourish, the very definition of biological fitness. If tree seeds remain in their own shade, the seedlings would compete for resources with their parent, a bad outcome for both generations.

So, how can a tree that’s rooted in the ground send its seeds out into the world? Marketers of any product — be that a box of cereal or an apple — know that it’s all about packaging.

Take a walk along the cereal aisle of a grocery store. Corporations design cereal boxes so kids will clamor for the package with the brightest colors and the best prizes. Similarly, the bigger and brighter the apple, the more inclined a potential disperser is to choose it.

Archeological records reveal that the ancestors of apples were very small, more like the modern crabapple. Their seeds were spread by birds.

Other fossil evidence shows that as apples evolved, they were dispersed by the now-extinct megafauna that roamed the northern hemisphere 12,000 years ago. Those woolly mammoths and bear-sized beavers were well-suited to gathering and distributing larger apple fruits.

But fruit dispersal is useless if seeds are chewed up or destroyed.

So, many trees have evolved seeds that contain distasteful or poisonous compounds. Each apple seed contains amygdalin, a chemical that, when chewed, changes into cyanide, one of the deadliest of human poisons. But don't worry. You'd have to consume the seeds of 40 apple cores before suffering ill effects.

Over the centuries, horticulturists have deliberately selected trees that favor certain traits, creating the 7,000 apple varieties grown today.

So, next time you choose a big juicy apple and toss the core out the car window – with unchewed seeds — you’re playing right into evolution’s hands.

Dr. Nalini Nadkarni is an emeritus professor of both The Evergreen State College and the University of Utah, one of the world’s leading ecologists and a popular science communicator. Dr. Nadkarni’s research and public engagement work is supported by the National Geographic Society and the National Science Foundation. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation. @nalininadkarni
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