Altruism, Infectious Disease, and the Future

This essay should be of great interest during the coronavirus pandemic. But I wrote it before the pandemic began, based on reading a book written in 1965.

I first discovered the scientific principles of the evolution of disease by reading the René Dubos classic Man Adapting. Even though I was a professor, I still had never heard of balanced pathogenicity. And it was even later that I began to read some of the many wonderful books about altruism. But it was only recently that I noticed the connection between the two.

Altruism has evolved by at least three mechanisms: kin selection, and direct and indirect reciprocity. Kin selection (Blood is thicker than water) is widespread in animal societies, and direct reciprocity (Let’s help each other) is common among intelligent animals. Indirect reciprocity (A good reputation is worth more than money in the bank) is nearly absent outside of human society.

In human tribal societies, altruism was extremely important. The best way, perhaps the only way, for a person to rise to the top was with help from friends and supporters (direct reciprocity), and with a good reputation (indirect reciprocity). Trustworthiness was rewarded, and cheaters were hated. At least one scientist, Robin Dunbar, speculated that human language evolved largely as a facilitation of reciprocity.

Balanced pathogenicity is where a virulent disease, so long as it is transmitted by direct contact, usually evolves into a milder form over time. This is because even in prehistoric times everyone around the victim knew that the victim was sick—whether from demons or bad air—and stayed away from him or her. A successful germ was one that had mild effects on the victim, who could then get up out of bed and go around spreading the germs. In this way, an acute disease can evolve into a chronic disease or even all the way to commensalism: Dubos speculated that some diseases evolved themselves out of recognized existence. This has been my experience. Like many people who grew up in Tulare County, California, I had tularemia. I did not know it, however, until a skin test revealed it. The doctor told me I had just felt bad one day, and that was it. In earlier decades, it was often a serious ailment.

The first parallel between altruism and the transmission of infectious disease is this. Just as everyone knows who it is that has an acute disease, everyone knows whom you can trust and whom you cannot, in traditional society.

Today, however, massive corporations conduct much of their business in a way that their practices are shielded from public scrutiny. Even corporations that had infamous practices, as many did during the 2008 recession, remain in business and are profitable, since most customers nationwide do not remember what they did. Reciprocity and reputation have not eliminated them or even, in some cases, reformed them. In modern corporations, oppressive decisions are made in boardrooms, decisions that a CEO might not normally make if he actually looked the customer in the eye.

The second parallel between altruism and infectious disease is this. There are many diseases in which balanced reciprocity does not evolve. Cholera is an example. Potential victims cannot know where the cholera germs in the water came from. Did they come from an acutely sick, or a mildly sick, person? Virulent and mild germs spread equally well. This is how Paul Ewald succeeded in getting cholera to evolve into milder form in some locations: if cholera could not spread through water, it had to spread through direct contact, and by doing so it evolved into a milder form.

In the mass of online information about corporations, a customer is unlikely to be able to determine which banks, for example, have a good reputation and which ones have a bad one. They choose banks the way people drink contaminated water. I certainly did, and regret it.

It can get worse. Some diseases spread more effectively if their victim is very ill. This is often the case with diseases that spread by insect vectors. Mosquitoes prefer to bite victims who are too sick to move around or to swat them. Such diseases can evolve to become worse.

In a similar fashion, some corporations actually benefit from social disruption that they and other corporations create. Consumers who are suffering from inadequate sleep, debt, and job insecurity seek pleasures and entertainment that many corporations are only too happy to provide to them.

In traditional societies, anti-altruistic people were ineffective for the same reason that virulent diseases were. But in modern societies, anti-altruistic corporations can equal the profitability of altruistic ones, the same way cholera spreads, or even exceed the profitability of altruists, the same way that insect-transmitted diseases spread.

If I am right about this, altruism faces significant challenges in the immediate future, even after the current pandemic abates.

This may be no more than an analogy. If so, it is a useful concept for teaching the principles of evolution—principles that show up in such seemingly unrelated fields as epidemiology and altruism. As a result, students may be forced to realize that they cannot consign evolution into an easily-ignored little box in the warehouse of knowledge.

Balanced Pathogenicity in Shangri-La

When I first learned about balanced pathogenicity back in the 1980s, it made me feel good about the world. This is the process in which germs evolve into milder forms over time. Natural selection favors the milder strains of germs because they can spread more readily. Any germ that kills its host is at a disadvantage. There are many examples in which diseases used to be very virulent, but today they are milder even without vaccination or medication. Examples include smallpox, which in Europe and North America evolved into a mild disease; leprosy, which today is a slow skin disease but used to kill people quickly. There are even diseases such as the “sweating sickness” that had major outbreaks in Europe in past centuries but appears to have evolved itself out of existence (it persists only in very mild forms): there are no diseases today that have exactly those symptoms. Balanced pathogenicity was part of the balance of nature in a blessed world.

Or so I thought. That’s what I wanted to believe.

Then I started learning about the exceptions. Waterborne diseases such as cholera do not evolve into milder forms. Insect-borne diseases may evolve into even worse forms. So I had to change what I taught and wrote: balanced pathogenicity applies to diseases that spread to a new host by close proximity to the victim. My main example was ebola, which, I thought, will evolve into a milder form since the worst forms of it keep healthy people from coming in close proximity to the victims.

But it turns out that even ebola can evolve into a worse form, as explained in this article by Carl Zimmer. I suppose that this evolution of worse forms of ebola is a temporary reversal of the overall trend of balanced pathogenicity. But I am now having to make so many “exceptions to the rule” that I am beginning to wonder how much of a pattern balanced pathogenicity really is.

My original feeling about balanced pathogenicity came about because I wanted to believe that there was a fundamental goodness to the world. Bad things happen, but within them is the seed of a better world. This was partly because I got my optimism from the same source that I got my original information: Rene Dubos. I learned about balanced pathogenicity by reading his Man Adapting and Celebrations of Life. He was a scientist and informal philosopher in the same mold as Lewis Thomas. A great thinker. But his “gospel” was that evolution ultimately produces a better world. I wanted very badly to believe that evolution was a good process that God incorporated into a good world. But the world in which evolution works for the Greater Good is more of a Shangri-La than a real world.

Balanced pathogenicity happens, except when it doesn’t. Evolution makes the world better, except when it doesn’t. Creationists look for scientific reasons to believe God is good. Theistic evolutionists look for scientific reasons to believe that evolution produces goodness that God intended. In this particular sense, I am not sure that theistic evolution is much of an improvement over creationism.