Francisco J. Ayala1
-Author Affiliations
Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697
Abstract
In The Descent of Man, and Selection in Relation to Sex, published in 1871, Charles Darwin wrote: “I fully … subscribe to the judgment of those writers who maintain that of all the differences between man and the lower animals the moral sense or conscience is by far the most important.” I raise the question of whether morality is biologically or culturally determined. The question of whether the moral sense is biologically determined may refer either to the capacity for ethics (i.e., the proclivity to judge human actions as either right or wrong), or to the moral norms accepted by human beings for guiding their actions. I propose that the capacity for ethics is a necessary attribute of human nature, whereas moral codes are products of cultural evolution. Humans have a moral sense because their biological makeup determines the presence of three necessary conditions for ethical behavior: (i) the ability to anticipate the consequences of one's own actions; (ii) the ability to make value judgments; and (iii) the ability to choose between alternative courses of action. Ethical behavior came about in evolution not because it is adaptive in itself but as a necessary consequence of man's eminent intellectual abilities, which are an attribute directly promoted by natural selection. That is, morality evolved as an exaptation, not as an adaptation. Moral codes, however, are outcomes of cultural evolution, which accounts for the diversity of cultural norms among populations and for their evolution through time.
biological evolution cultural evolution human uniqueness moral norms moral sense
Footnotes
1E-mail: fjayala@uci.edu.
Author contributions: F.J.A. wrote the paper.
The author declares no conflict of interest.
This paper results from the Arthur M. Sackler Colloquium of the National Academy of Sciences, “In the Light of Evolution IV: The Human Condition,” held December 10–12, 2009, at the Arnold and Mabel Beckman Center of the National Academies of Sciences and Engineering in Irvine, CA. The complete program and audio files of most presentations are available on the NAS Web site at www.nasonline.org/SACKLER_Human_Condition.
In this essay, the author draws extensively from his work, “What the Biological Sciences Can and Cannot Contribute to Ethics,” chap. 18, pp. 316–336, in Ayala FJ and Arp R, eds. Contemporary Debates in Philosophy of Biology (Wiley-Blackwell, Malden, MA, 2010).
This article is a PNAS Direct Submission.
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