1 Introduction
Whole books , and sections of books, have been dedicated to reviewing the intellectual history of multilevel selection, some small swath of which are considered in this first chapter. Readers are then made aware of other pertinent publications, acquiring something of their substance in this condensed review. For example, readers will certainly gain knowledge of multilevel selection’s prototypical origins as they are present in Darwin’s Descent of Man, while also being introduced to its reformulation a century later as a measure of population regulation. In addition to preferring main ideas to tortuous detail, we here take such content’s subsequent relevance as our litmus test for inclusion. We also review recent bouts of controversy between adherents and detractors. Where historical review is the end of other books, we use the history of multilevel selection instrumentally, with the end of contrasting its original formulation with its present instantiation. Having drawn these distinctions, one can clearly see that most controversies and objections no longer apply, as they do not pertain to modern manifestations of multilevel selection. Even as naysayers continue to criticize it for something it either never was or no longer is, the modern formulation of multilevel selection is becoming known to, and accepted among, most evolutionists. Nevertheless, this is only the first act in the two-part drama, taking us to the lowest ebb of multilevel selection’s reputation. The astute reader may notice that we use the expression multilevel selection when referring to the more general theoretical framework that is the subject matter of the present volume, while reserving the term group selection for describing the positions of past commentators that directed their reflections specifically to this particular component of multilevel selection theory, especially as more narrowly defined by past formulations of this principle. Multilevel selection theory is a more inclusive term that recognizes the operation of selection at multiple levels of biological organization, including both solitary individuals and social groups, as exemplified but never explicitly named by Charles Darwin’s thinking on the matter.
2 Darwin and the Descent of Man
Let us begin at the beginning. Charles Darwin marks our beginning. Only after Darwin’s lifetime of thinking, collecting, traveling, and writing does a modern world unfold wherein blind, bottom-up processes are known to outstrip, in the creation of wonder and complexity, even the most ingenious top-down design. Too many pass by this epoch with a nod and a glance, satisfying themselves with Herbert Spencer’s oversimplified characterization: The Survival of the Fittest. Yes, evolution is elegantly simple. From a few basic premises, operative over geologic time, come marvelous variation and staggering creation. Still, the natural products of evolution are not invariably “red in tooth and claw” (Tennyson, 1850, In Memoriam A. H. H., Canto 56) and cannot be reduced to Spencer’s aphoristic formulation, or to any single phrase whatsoever. From the start, within the original writings of Darwin, much of the complexity of evolution was extant. By contrast, brilliant and capable though he was, Alfred Russel Wallace intuited his understanding of natural selection suddenly in a malarial fever dream and thereafter developed it less fully, whereas Darwin’s understanding of natural selection was better elaborated, as well as being better theoretically and empirically supported by the time he published it in 1859. In the process of critically viewing his own theory, with bravery overcoming trepidation, Darwin catalogued potentially contrary facts and held out possible mechanisms by which his theory of evolution could be disproven. It was through this process that Darwin expanded his vision of evolution from a purely organismic view of selfish competition to one encompassing the evolution of groups in altruistic cooperation.1
The most pointed examples of apparent evolutionary paradoxes considered by Darwin, which were only solved by transitioning from an individual to a multilevel selectionist paradigm, are found among Darwin’s writings on social insects and human tribes. For instance, Darwin understood worker sterility as advantageous to the community. Even as he understood that sterile workers were born capable of work, but not of procreation, Darwin remarked, “I can see no very great difficulty in this being effected by natural selection.” The reasoning behind this judgment is explained more fully in the fourth edition of On the Origin of Species:
Thus I believe it has been with social insects: a slight modification of structure, or instinct, correlated with the sterile condition of certain members of the community, has been advantageous to the community: consequently the fertile males and females of the same community flourished, and transmitted to their fertile offspring a tendency to produce sterile members having the same modification. And I believe that this process has been repeated, until that prodigious amount of difference between the fertile and sterile females of the same species has been produced, which we see in many social insects.
With respect to human evolution, Darwin noted that self-sacrifice is necessary for the welfare of a tribe. As Darwin (1871, p. 166) realized long ago, “at all times throughout the world tribes have supplanted other tribes.” Or as Steven Mirsky notes, Darwin is thought to have said that tribes of moral men have an immense advantage over fractious bands of pirates. Embryonic sympathies with multilevel selection are manifest in Darwin’s passages concerning the evolution of altruism, self-sacrifice, intelligence, and obedience. Also evident are considerations as to how outgroup competition and ingroup pressures simultaneously select for group cohesion in opposition to individual self-interest.
Selfishness was punished by death and displacement at the hands of outsiders, while being punished by shame and ostracism at the hands of one’s own group. Thus, notwithstanding some few dissenting opinions, Darwin did recognize that multilevel selection was possible and could furthermore result in directional change. In other words, if tribes could supplant other tribes, this recognizes that groups can compete; in turn competition can change gene frequencies even up to the replacement of one group by another.
Obedience, as Mr. Bagehot has well shewn, is of the highest value, for any form of government is better than none. Selfish and contentious people will not cohere, and without coherence nothing can be effected. A tribe possessing the above qualities in a high degree would spread and be victorious over other tribes; but in the course of time it would, judging from all past history, be in its turn overcome by some other.
Without irresponsibly extrapolating from the direct quotation above, one can infer a positive feedback effect, wherein between-group competition ratchets up cooperation and cohesion over millennia. This is then combined with an acknowledgment that specific traits, in this case cooperation and altruism, decide the contest, with the result that those traits become more common in aggregate. In short, cooperation and altruism are under directional selection within groups due to competition between groups. However, cooperation and altruism only extend to the ingroup, with quite a different standard of behavior applicable to relations with outgroups:
No tribe could hold together if murder, robbery, treachery, &c., were common; consequently such crimes within the limits of the same tribe ‘are branded with everlasting infamy;’ but excite no such sentiment beyond these limits. A North American Indian is well pleased with himself, and is honoured by others, when he scalps a man of another tribe; and a Dyak cuts off the head of an unoffending person and dries it as a trophy. The murder of infants has prevailed on the largest scale throughout the world, and has met with no reproach...
We also see passages more distinctly detailing how altruism might have been selected for within the group via sexual selection and status seeking:
We may therefore conclude that primeval man, at a very remote period, would have been influenced by the praise and blame of his fellows. It is obvious, that the members of the same tribe would approve of conduct which appeared to them to be for the general good, and would reprobate that which appeared evil. To do good unto others—to do unto others as ye would they should do unto you,—is the foundation-stone of morality. It is, therefore, hardly possible to exaggerate the importance during rude times of the love of praise and the dread of blame. A man who was not impelled by any deep, instinctive feeling, to sacrif...