Think Humans Invented Agriculture? Think Again

A fungus-farming ant trapped in amber a la Han Solo. Hongjie Li.

Humans like to brag about how we invented agriculture around 12,000 years ago, perhaps somewhere in the fertile crescent of Southwest Asia. We also like to boast about how we pioneered antibiotics some 80 years ago. However, like most things, nature beat us to the punch millions of years ago.

A new study, published in the journal Proceedings of the National Academy of Sciences, has revealed that ants have been cultivating fungus for some 60 million years. This is no easy feat, however. The ants' "mushroom crops" are at risk of fungal parasites, which have the potential to wipe out an entire colony. To ward off any unwanted infestation, the ants cake themselves in a white symbiotic bacterium, called actinobacteria, in order to protect their harvest (pictured below).

The world is currently home to around 250-some ant farming species, and this new research reveals how their impressive agricultural skills evolved independently three times, a phenomenon known as convergent evolution.

“Less than a century ago, humans learned to employ antibiotics for medicinal purposes, whereas ants have been using antibiotic secretions from bacteria to manage their fungus gardens for millions of years,” Christian Rabeling, an assistant professor in the School of Life Sciences within Arizona State University’s College of Liberal Arts and Sciences, said in a statement.

A fungus-farming ant is covered in white symbiotic bacteria. Alex Wild 

Perhaps coolest of all, the discovery was made thanks to ants trapped in amber found in the Dominican Republic. A couple of these specimens had deep pockets, known as crypts, which modern-day ants use to contain their doses of actinobacteria. Another ant was covered in tiny gas bubbles that were most likely produced by respiration from the actinobacteria.

The amber dates back to between 15 million and 20 million years ago; however, the scientists have strong reason to believe that ants took up this hobby long, long before this. They gathered the genetic data of 69 ant species and pieced together a large portion of their evolutionary tree. This suggested that the use of actinobacteria among ants originated 50 to 60 million years ago and evolved independently on as many as three separate occasions.

The research also brings to light another particularly interesting idea. Ant colonies never show signs of antibiotic-resistance, despite using the same old method for millions of years. It seems that somewhere within this strange web of ants, fungus, and actinobacteria, we might be able to find a way to ward off antibiotic resistance – among one of the biggest challenges the world will encounter within the coming century.

"I strongly believe there are mechanisms here that reduce the emergence of antibiotic resistance," added Professor of Bacteriology Cameron Currie from the University of Wisconsin-Madison.

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