The Evolutionary Role of Death & Natural Evil
In addition to providing a general theological critique of the endemic—as opposed to post-hoc or intrusive—origins of death in the natural world, John Laing’s imminently fair-minded essay also takes theological aim at the role death and natural evil play in the evolutionary diversification of life. It is one thing to say that death is primordial; it is another to view it not just as an ancient byproduct, but as the central means of creation. The understandable theological uneasiness expressed by John and many others about this issue ultimately rests not just on an understanding of God’s creative activity, but also on a particular representation of evolution. In this regard John makes two important claims:
- a) “…natural selection, with its emphasis on a natural state characterized by competition for limited resources and a general struggle for survival, is the primary means by which speciation takes place…”
- b) “death actually functions as a mechanism for life. Death plays a vital role in natural selection by rooting out weakness and driving evolutionary development.”
For reasons I discussed in the previous section, it is not entirely clear that death constitutes an evil that is incommensurate with divine activity. However, the fact is that the above depiction of evolution—which is not unique to John amongst public commentators and is largely commensurate with Darwin’s own views—does not adequately portray current discussions within evolutionary biology. There are three problems with this portrayal that I’d like to address in turn—three aspects of evolutionary theory that need to be better understood.
First, while there is no uncertainty about common descent or about natural selection as a cause of evolutionary change, there is considerable discussion over the extent to which natural selection is “the primary means” by which speciation takes place. For one thing, there are manifold other agents of evolutionary change: drift, gene flow, systems of mating, mutation itself unfiltered by selection. A tremendous amount of variation may be adaptively neutral, being invisible to natural selection. For another thing, some claim that evolution proceeds most rapidly and speciation occurs most precipitously in the relaxation of selection—when ecological times are good and the culling effects of the environment are minimized. We may see this in the contingency-driven formation or colonization of a new habitat or the exploitation of a new resource that does not displace previous variants. Or, speciation events or species-level innovations may be the results of chromosomal rearrangements or symbiogenesis that are not the cumulative results of selection. Finally, there exist manifold and admittedly controversial proposals that are critical of neo-Darwinism as a whole, claiming that natural selection may be a necessary, but is neither a sufficient nor a primary cause of large-scale evolutionary change.1
Second, notwithstanding Darwin’s formulation of natural selection in terms of competitive struggle as (accurately) cited by John, the modern understanding of evolution and competition is considerably more differentiated and complicated. For one thing, competition is neither a necessary nor a sufficient condition for natural selection. Natural selection is formally defined as the differential reproduction of genotypes (or information.) Some sets of genes are replicated with greater efficiency than are others. Competition is formally defined as the negative impact of two organisms (or two species) on one another’s fitness. You can have all sorts of competition that does not result in natural selection. And importantly, you can have differential reproduction by natural selection without the negative fitness impacts of competition. Colonists to a new under-exploited habitat, or two species that are partitioned onto separate resources in a way that minimizes competition might well have some variants that leave more offspring than others without displacing them. This is natural selection.
Indeed, imagine an infinite habitat with non-limiting resources and no competition at all: as long as there were adaptively salient mutations, there would be natural selection—some of those new genotypes would reproduce more effectively than others. Competition, to whatever extent it exists in nature, is a consequence of finitude and not a necessary precondition of natural selection. And finally, the role of cooperation in evolution has itself been massively reconsidered in recent years. It would not be entirely unfair to say that on the basis of mathematical models and empirical data, the proposal that cooperation “is now seen as a primary creative force”2 and a “fundamental principle of evolution”3 has moved from being a cult-alternative to a widely accepted paradigm. Indeed, cooperation and increasing scales of cooperative interdependence are seen not only as a formative process but also as a recurring product of evolutionary change, which may even be viewed as “progress.”4 A biologically significant and theologically salient thematic trend across major evolutionary transitions, is that cooperative interdependence itself – and the wondrous properties of life mentioned in the first installment of this essay – seem to be amplified through selection.4 Through evolution, God may be seen to confer life and confer it in greater abundance.
Third, the claim that “death drives evolutionary development” turns out to be problematic. Recent discussions of death and senescence (organismic decay) between various branches of the biosciences are spirited and fascinating. One of the vexing characteristics of living creatures is the internalization of death and senescence: even if an individual is not killed by external forces, it will die from the inside out—virtually no species is immortal.6 One account of this—the rate of living theory of senescence—understands it not in terms of selection for reduced mortality but in terms of biophysical or allometric constraints relating rate of metabolism to rate of wearing out. Though it views senescence differently, the prevailing evolutionary theory of senescence, with several variants, does not affirm death or decay—at least the kind of death and decay that is intrinsic to organismic development—as a prerequisite to evolution by natural selection either.7
Indeed, internalized death is viewed not as driving but as deriving from, not as a necessary requirement for but as a byproduct of, natural selection. Specifically, mutations or traits with detrimental impacts later in life may not be eliminated by or may even be favored by selection if their contribution to reproduction early in life is sufficient. Now, neither theory completely dismisses the shaping role of death. Under certain but not all conditions, differential mortality may have adaptive import (and it is not even the longer-lived organisms that always have adaptive advantage). Extrinsic sources of death may also shape the internalization of death.8 But the view that death drives evolution does not adequately represent emerging scientific understanding of the relationship between natural selection and senescence.
Scientifically death does not “drive” evolution. And theologically, although neither evolutionary change nor ecological interaction “solve” the ultimate puzzle of human death, they may nevertheless mitigate the proximal existence of creaturely death by amplifying the complexity and vibrant abundance of living forms.
Darwin famously closed The Origin by observing “There is a grandeur in this view of life, with its several powers, having been originally breathed by the Creator into a few forms or into one…from so simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved.”9 Unlike John, I do not see anything in evolutionary theory to reduce, and I see much to augment the sense of grandeur and (for that matter) the appreciation of sheer goodness—both earthly and divine—evoked by the wonders of the living world.
Yet grandeur and goodness are not perfection. My Dad is still dying. I still wince at the suffering of clearly sentient animals. And, truth be told, I tremble at the biblical images of universal herbivory: even metaphors are metaphors of something, and in the case of biblical revelation, that something can be taken to be real and important. So like John, I confess to profound gratitude tempered with a lingering unease at the state of nature. Though I believe in a Fall, this unease is not rationally relieved by attributing to an Adam the present state of all nature. Nor is it resolved by the various alternative considerations I’ve described and which, taken together, seem to have considerable merit but not sufficiency. Notwithstanding, I thankfully affirm that “I have known the goodness of the Lord in the land of the living.” And I look to the day when we may say together, “My ears had heard of You, but now my eyes have seen You.” (Job 42:5)
1. E.g., Salthe, S. 2008. “An Anti-Neo-Darwinian View of Evolution.” Artificial Life. 14:231-233; David Depew and Bruce Weber (eds). Darwinism Evolving: Systems Dynamics and the Genealogy of Natural Selection. 2004. MIT Press
2. Michod, Richard and Denis Roze. 2001. “Cooperation and Conflict in the Evolution of Multicellularity.” Heredity. 86:1-7. Page 2
3. Nowak, Martin. Evolution, Games, and God: The Principle of Cooperation. Martin Nowak & Sarah Coakley, eds. Forthcoming from Harvard University Press.
4. Sigmund, Karl and Eörs Szathmáry. 1998. “Merging Lines and Emerging Levels.” Nature. 392: 439-441.
5. John Maynard Smith and Eörs Szathmáry. 1998. The Major Transitions in Evolution. Oxford University Press. Brett Calcott & Kim Sterelny (eds). 2011. The Major Transitions in Evolution Revisited. MIT Press.
6. “Virtually” is an important qualifier: while senescence has been documented in nearly all organisms examined, there are some cell lines and species in which this may not be the case.
7. Williams, George. 1957. “Pleiotropy, Natural Selection, and the Evolution of Senescence.” Evolution. 11:398-411.
8. This relationship is complex and not invariant. E.g., Williams, Paul and Day, Troy. 2003. “Antagonistic Pleiotropy, Mortality Source Interactions, and the Evolutionary Theory of Senescence.” Evolution. 57(7): 1478-1488.
9. Darwin, Charles. 1876. The Origin of Species By Means of Natural Selection, or the Preservation of Favored Races in the Struggle for Life. 6th Edition. John Murray. p. 429.