PARIS – Biology and economics face similar challenges: both seek to explain survival and innovation in an unpredictable world. For example, Nassim Taleb, famous for his prescient identification of rare “black swan” events that are correlated with economic catastrophes, recently proposed the notion of “anti-fragility” as a way to conceptualize the reproduction of markets and output in the face of such events. In fact, anti-fragile structures and processes are all around us – suffusing life itself.

To define anti-fragility, Taleb asks what would be the true opposite of “fragile.” Starting with the Sword of Damocles, he chooses as its opposite not the robustness of the Phoenix rising from the ashes, but the inventiveness of the Hydra, who sprouts two heads whenever one is cut off. Can we think of entities that not only resist the ravages of time, but that, through the creation and recombination of novel components, become able to cope with an unpredictable future?

The inevitability of death might seem to suggest that life is not constructed to be anti-fragile. But consider King Mithridates VI of Pontus, who took a tiny daily dose of poison to protect himself from poisoning by his enemies. The idea that better fitness results when systems are challenged by a low level of toxic or other dangerous influences is at the root of an ongoing heated debate about whether low-level radiation benefits, rather than harms, humans.

The problem is the lack of unambiguous evidence of Mithridatism. We know that exercise, for example, will change muscle strength and bone mass and structure, but is this what we are looking for when seeking anti-fragility’s essence?

Anti-fragility, as defined by Taleb, seems less biologically disputable than Mithridatism. Indeed, anti-fragility appears to be a general quality of evolving systems. It does not correspond to isolated objects, but to populations. And here we do indeed observe Hydra-like behavior in the evolution of living beings: in the course of time, natural selection will use genetic mutations in populations to split their progeny into two or more distinct species.

Living organisms are always composite. They are made of populations of molecules, cells, or individuals that are not identical, but that are similar to one another. When we think of anti-fragility in living organisms, we do not think that specific aging structures improve when confronted with low-level challenges, but rather that there is an in-built genetically-encoded process that uses time-dependent accidents to make the organism as a whole better adapted to its environment. While the components of the organism keep aging, as an ensemble they improve over time, forming a collection of specific individual instances, before they suffer the inevitable decay of senescence.

This implies that, as it ages, the organism extracts and uses information from its environment in order to respond to that environment’s unpredictable challenges. Life measures and memorizes: it uses the built-in variety in its otherwise similar components to store memory of past events so that they can be used to react to a novel situation.

The basic memory of an organism’s heredity is not composed of identical components, but rather is what the physicist Erwin Schrödinger in his famous book What is Life called an “aperiodic crystal” – a concept that gave rise to molecular biology. The concept, most importantly, implies a lack of permanent accurate identity: the organism reproduces (it keeps being similar to itself), rather than replicating (its progeny are not an exact copy of itself). This means that no general grand design or unique hierarchy, but rather a collection of smaller entities of similar design, cooperate to generate the global behavior of the organism.

Much of the memory in our brain, for example, is dispersed among a huge number of contacts between many neurons. These contacts are not identical in different individuals or in different memories. Before the catastrophic decline of real senescence occurs, the way these contacts evolve improves over time: the capacity for collecting new memories may be slowly declining as a process, but memory as a whole increases. This is the paradox of what scientists call the “growth advantage in stationary phase”: when old and young microbial cultures are forced to compete, the old one, contrary to intuition, wins the contest.

By allowing some individual entities to stand out from the crowd, anti-fragility improves the fate of a population under a challenging situation. The number of candidates for anti-fragile behavior among biological structures is enormous. Cells are essentially made of macromolecules, which, even when coded from the same gene, are never entirely identical to one another. The very process of macromolecular biosynthesis is tied to the structure of the environment. No two cells are the same.

This remarkable variety, deployed within a strict genetic envelope that limits its range, roots life in anti-fragility. This is an essential point that biology should retain. And, as the global economy responds to the unpredictable challenges of economy crisis and recovery, it is a point that economists, too, should bear in mind.