Altruism in Cells

It is commonly held that evolution teaches the “survival of the fittest,” as Herbert Spencer (1820-1903) put it. Life forms at all levels compete until the best mutation in each species prevails. Many advocates of conservative politics and free market economics project a blueprint for human society from this summary formulation: the fittest will rule; the others should conform or die off. But Darwin’s own formulation, “natural selection,” is far subtler than Spencer’s.

Adaptive mutations within species lead them to outdo themselves —in many different ways—to the point where wholly new species emerge. But how does that actually happen?

Competition is not the only adaptive strategy; cooperation also aids both survival and reproduction. Cooperation is vital to the way cells form groups and groups evolve into new kinds of individuals. Simple cells became complex. Complex cells, in turn, cooperate to form multicellular organisms. Anthills or bee colonies thrive as superorganisms because many specialized individuals work together. In other cases, separate cells unite to form wholly new individuals. These combinations can be compared to human cooperation.

For example, Richard E. Michod describes the evolution of a type of multicellular alga called the volvox as an example of altruism between the constituent cells. Whatever our personal reaction to algae, whether as seaweed decking a shore or the nasty green stuff that besmirches a pond, it’s vital to understand how it evolved. One answer lies in the evolution of multicellular individuals from unicellular ancestors. Michod explains this as the “cooperation” of cells with very different characteristics. The extent of their difference made them good matches to form a new superorganism, but they had to give up their individuality to become a part of a multicellular unit. Why would they do that?

By plotting key traits of individual volvox cells, Michod discovered a kind of division of labor—specialization. Some cells, at one extreme,  specialized in one component of fitness, reproductive capacity, and others, at the opposite extreme, specialized in another aspect of fitness, viability (longevity). Alone, these differently specialized cells don’t have a complete fitness, but together, the group does. Because reproduction requires much energy, highly reproductive cells have short lives. Conversely, cells that conserve reproductive energy live longer. Thus, when mapping for reproductive strength and viability, the statistical curve resembles not a bell but a U, with either the reproductive or the long-lived champions attaining the heights. And, Michod found, it is these specialized cells that combined their outstanding traits, over generations, to form a new individual, complex group that combines both strengths. The reproductive cell sacrifices longevity, and the long-lived cell sacrifices reproductive power to create a combined, complex individual that is more fit overall. This relationship of covariance shows that, although specialization requires a sacrifice on both sides, the pay off for both types of cell can be enhanced when they are together in a group. In both reproductive capability and length of life, later generations of the new, complex organism, the multicellular group, outperformed either of the two old types.

The synergy produced by the evolution of this kind of cooperation does not mean that human life should mimic nature. Like the cell in the volvox, we humans have evolved to build societies that contain individuals who benefit from living well together.  Cooperation is in our nature as much as aggression and competition. Though there will always be tensions, there is a spectrum of arrangements that allow harmony between the individual and society. In well tempered communities, debate, compromise, and consensus will achieve this balance. Just as no one wishes to submerge the individual in the collective, neither do we wish to sacrifice pro-social cooperation (families, clans, villages, towns, states) to the individualist extreme.

(Professor Michod kindly reviewed a draft of this post and suggested improvements. Any confusion that remains is my own.)