Male and female ligers (a liger is a cross-breed of a male lion and a female tiger) taken at Everland amusement park, South Korea.

What causes biological evolution? 

For over a century, scientists have focused on natural selection as  the driving force of evolution.  Darwin noted that just as important as selection is variation.  So where does all this variation come from?

With DNA sequencing technology, scientists are learning more and more about how variation comes about.  And one of the most important sources of variation is hybridization.

Hybridization is the  interbreeding between animals or plants of different species that results in a novel offspring. Though infrequent, hybridization is a powerful driver of evolution.

Famous hybrid animals include mules (horse/donkeys), zeedonks  (zebra/donkey), beefalo (bison/cow); liger (lion/tiger); killer bees (European bee and African bee.) Hybrid plants include wheat (three wild grasses  ) and grapefruit (pomelo/orange).  Hybridization is the  interbreeding between animals or plants of different species that results in a novel offspring. Hybridization, though infrequent, is a powerful driver of evolution.

Hybrid Chocolate

Hybrids plants are important not only to understand evolution, but also in economic terms. Hybrid plants give us high quality chocolate.   Cocoa is a $73 billion dollar cash crop industry.  One of the most important species is a hybrid, the Trinitario variety of Theobroma cacao. Thanks to genomic sequencing, we now know that a rare hybridation event gave us this delicious and important hybrid (Yang, et al, 2010)


“Rare events have huge consequences.” ~ Nolan Kane, genomicist at CU Boulder

While hybridization is an extremely rare event, it’s consequences are huge.   Because hybridization can create a tremendously successful variant, it can quickly sweep through an ecosystem and become a dominant variety.  Now, thanks to genome sequencing, we can see this selective sweep.  

Some biologists dismiss the importance of  rare events. Others, like Nolan Kane and his colleagues present convincing evidence that rare events, when useful to the organism, spread quickly throughout vast geographical regions.  A single rare hybridization event quickly takes over an entire region. Some of these hybridization events allow organisms to inhabit new new places.

Hybridization as Cultural Driver

Hybridization is bigger than biology.  Just as organisms share genes, so too do people share memes. The ability to hybridize ideas is foundational for cultural evolution. Today, successful corporate leaders design their companies to promote the hybridization of ideas. Steve Jobs fascilitated idea hybridization by encouraging frequent meetings and by designing buildings to facilitate face to face communication.  Zappos CEO Tony Hsieh encourages sharing of ideas by discouraging people from working at home.


For More Information 

The Kane Lab, University of Colorado at Boulder.

Complex origin of Trinitario-typeTheobroma cacao (Malvaceae) from Trinidad and Tobago revealed using plastid genomicsJi Yong YangMoira ScascitelliLambert A. MotilalSaemundur SveinssonJohannes M. M. Engels,Nolan C. KaneHannes DempewolfDapeng ZhangKamaldeo MaharajQuentin C. B. Cronk

“Hybridization as a stimulus for the evolution of invasiveness in plants?” by  Norman C. Ellstrand and Kristina A. Schierenbeck


Hybrid Wikipedia