Mann titled his talk “The Edge of the Petri Dish.”  He explained, “If you drop 
a couple protozoa in a Petri dish filled with nutrient goo, they will multiply 
until they run out of resources or drown in their own wastes.”  Humans in the 
world Petri dish appear to be similarly doomed, judging by our exponential 
increases in population, energy use, water use, income, and greenhouse gases.  

How to save humanity?  Opposing grand approaches emerged from two remarkable 
scientists in the mid-20th century who fought each other their entire lives.  
Their solutions were so persuasive that their impassioned argument continues 70 
years later to dominate how we think about dealing with our still-exacerbating 
exponential impacts .

Norman Borlaug, the one Mann calls “the Wizard,” was a farm kid trained as a 
forester.  In 1944 he found himself in impoverished Mexico with an impossible 
task—solve the ancient fungal killer of wheat, rust.  First he invented 
high-volume crossbreeding, then shuttle breeding (between winter wheat and 
spring wheat), and then semi-dwarf wheat.  The resulting package of hybrid 
seeds, synthetic fertilizer, and irrigation became the Green Revolution that 
ended most of hunger throughout the world for the first time in history.

There were costs.  The diversity of crops went down.  Excess fertilizer became 
a pollutant.  Agriculture industrialized at increasing scale, and displaced 
smallhold farmers fled to urban slums.

William Vogt, who Mann calls “the Prophet,” was a poor city kid who followed 
his interest in birds to become an isolated researcher on the revolting guano 
islands of Peru.  He discovered that periodic massive bird die-offs on the 
islands were caused by the El Niño cycle pushing the Humboldt Current with its 
huge load of anchovetas away from the coast and starving the birds.  The birds 
were, Vogt declared, subject to an inescapable “carrying capacity.“  That 
became the foundational idea of the environmental movement, later expressed in 
terms such as “limits to growth,” “ecological overshoot,” and “planetary 
boundaries.”  Vogt spelled out the worldview in his powerful 1948 book, The 
Road to Survival.  

The Prophets-versus-Wizards debate keeps on raging—artisanal organic farming 
versus factory-like mega-farms; distributed solar energy versus centralized 
fossil fuel refineries and nuclear power plants; dealing with climate change by 
planting a zillion trees versus geoengineering with aerosols in the 
stratosphere.  The question continues: How do we best manage our world Petri 
dish?  Restraint?  Or innovation?

Can humanity change its behavior at planet scale?  Mann ended by pointing out 
that in 1800 slavery was universal in the world and had been throughout 
history.  Then it ended.  How?  Prophets say that morally committed 
abolitionists did it.  Wizards say that clever labor-saving machinery did it.  

Maybe it was the combination.

—Stewart Brand <>

[The video and podcast versions of Mann’s talk are here 
<>   For a 
linkable, illustrated version of this summary, go to Medium, here 
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