Survival of the fittest is science, but it's not predictable

One very Newtonian definition of science (popular with economists):

Science is about theories that make testable predictions. 

This is obviously true of physics: the theory of gravity predicts that an object falling to Earth will accelerate at a rate of 9.8 meters per second, squared. 

This is true in biology, too. The theory of evolution by natural selection predicts that if we look into the past we will find species that change over time.  It predicts that over long periods of time we will see the species around us change in the future.

Notice that the physics example predicts the specific events while the biology example explains the events without being able to make specific predictions. Biology explains the future, but unlike physics, it doesn't  predict the future. 

For example, an exciting area of study in biology is called "the microbiome". Basically every big living thing in the world is itself home to a whole world of smaller living things. Humans live on the surface of the earth. That's our biome. But a ton of bacteria live on our skin and in our stomach. Those bacteria inhabit our microbiome. Obesity seems to be tied to something wrong with our microbiome. Turns our coral reefs have microbiomes, too, and sick or "stressed" coral have microbiomes that are out of whack. From A Grand Unifying Theory Of Unhealthy Microbiomes:

Scientists have conducted hundreds of similar studies in humans. They compare healthy and sick people and look for differences in their microbiomes—the vast community of bacteria and other microbes that share our bodies. They aren’t looking for a specific disease-causing bug, like the ones behind classic infections like plague, leprosy, or tuberculosis. Instead, they’re looking for imbalances, where certain species rise to the fore, others slink into obscurity, and the entire community changes for the worse.

That’s what Vega Thurber expected to find in the corals. But that’s not what her postdoc Jesse Zaneveld found when he analyzed the results. The extra nutrients and the missing fish both changed the coral microbiomes—but not in any consistent ways. “It was a pretty dark day after three years of work,” says Vega Thurber. “A lot of students would have thrown up their hands and cried a bit. But Jesse said: You know what, I think I see something strange. It’s a pattern but one we didn’t predict.”

The microbiomes of the stressed corals had become more varied. They didn’t shift in any particular direction—they changed in every direction. And shortly after Zaneveld realized this, he spotted the same pattern—but this time in chimpanzees. Researchers at Yale University had studied the gut microbiomes of chimps that were infected with an HIV-like virus, and found that their microbiomes had also become more variable.

Zaneveld and Vega Thurber now think that this trend applies to all kinds of microbiomes, whether in corals, chimps, or humans. All of these hosts use a range of tactics to control which species and strains get to share their bodies. When the hosts are stressed or diseased, their control breaks down, and their microbiomes start to change. But they change randomly, rather than predictably. They don’t shift to any one specific unhealthy state. Rather, they veer off in unpredictable directions and enter a wide range of new states.

When people say economics is a failure because it did not predict the crash of 2007-08 they are confused. Economics is a disaster because the entire field thinks that predicting the future is a thing that you can do. In life science, predicting the future is simply not possible the way it is in physics.  



In June 1918, we knew that on August 21, 2017, the moon would once again block the sun in a total eclipse. But no amount of science, not even an infinite amount of understanding of the world in 1918, would have been able to predict that on August 24, 2017, the President of the United States would do this: