Conventional wisdom would suggest that we should solve all problems with targeted solutions that tackle the root cause of the problem. In complex adaptive systems, this conventional wisdom is wrong. Attribution of failures to root causes is fundamentally inapplicable to complex systems where all failures and problems are systemic and multi-causal. But there is another fundamental reason why magic bullets don’t work in complex systems. In complex adaptive systems, targeted solutions elicit a stronger adaptive response that neutralises the solution (after an initial period of success).
Instead, complex adaptive systems need combination therapy rather than targeted therapy. The best example of this dynamic comes from the field of cancer treatment where:
large tumors are genetically diverse. This means that for any given treatment, there is likely to be a small population of cells within the tumor that is resistant to the effects of the drug. When the drug is given to a patient, these cells will survive and multiply and this will lead ultimately to treatment failure. Given that a single drug is therefore highly unlikely to eradicate a tumor, combinations of two or more drugs may offer a higher chance of cure. This approach has been effective in the treatment of HIV as well as certain forms of leukemia.
As Raymond Chang notes1, “the best example of a successful combination approach in Western medicine is the case of HIV treatment, which evolved from monotherapy to cocktail therapy over the course of two decades”. There are many other examples of this principle which explains why “cinchona bark is still effective [as a treatment for malaria] after hundreds of years even though chloroquine (a derivative) is not”. It also explains why faecal transplants work even though a more precise approach that excludes any one of the seventeen species of bacteria in the faeces does not work.
The same principle also explains why exercise, diet and lifestyle changes are a more robust way to deal with many illnesses rather than using drugs (that cause side effects that need more drugs and so on). In complex systems, one intervention requires another and so on, until we have a fragile state of ‘normalcy’ that must be constantly defended by external interventions. Peter Sterling explains this cycle with respect to treating hypertension:
In treating hypertension medicine commonly targets the lowest level mechanisms. Since one cause of high blood pressure is excessive fluid for the vascular reservoir, hypertension is often treated with a diuretic to shrink blood volume. But then the brain, predicting a need for high pressure, compensates by shrinking the reservoir. To prevent that, a calcium antagonist is added to relax vascular smooth muscle. Still the brain insists that pressure should be high, and again it compensates by increasing cardiac output. To prevent that, a beta blocker is added, thus antagonizing the last pathway capable of raising the pressure. Unfortunately, this also renders the patient unable to exercise – a core need for every aspect of physical, emotional, and cognitive health.
The same principle has also been learnt at great cost in agriculture, where integrated pest management has proven to be a much more resilient method of pest control than the use of pesticides such as DDT. As Ruth DeFries explains2,
Strategies to employ natural predators of pests, mixed crops rather than monocultures, and locally successful strategies, such as those of the Guatemalan and African farmers, are all part of this approach. Integrated pest management is far from the dominant mode for farms in the industrialized world, but the approach has made it back from the sidelines since the DDT bonanza went bust. The South American cassava mealybug that created such devastation in Africa, for example, came under control with the introduction of a tiny wasp that preys on the unwelcome bug. Screwworm flies that lay eggs in animal wounds no longer trouble cattle producers in the southeastern United States following a program to release millions of radiated, sterilized males so that the females would not produce viable offspring.
Combination therapy and a fuzzier, messier approach also work better in complex human systems. In an earlier essay, I explained how Amazon found out that a more complex, precise control regime does not work better than a looser, more fuzzy control regime precisely because of the adaptation of the agents within the system to the control, i.e. Goodhart’s Law. The same is true of macroeconomic and monetary policy, which would be more effective if it utilised a less predictable approach and a varying and unpredictable combination of tools rather than the current approach where one predictable intervention is followed by another, each with a short half-life of effectiveness as the agents within the economic system rapidly adapt to each intervention and render them ineffective.
Raymond Chang in ‘Beyond The Magic Bullet’
Ruth DeFries in ‘The Big Ratchet’