Can Evolutionary Biology Help to Render Natural Law Approaches to Sexual Ethics More Affirming of Non-Heterosexual Relationships?
- Introduction and Hypothesis
- Fields of Study
1. Introduction and Hypothesis
‘Natural law’ approaches to sexual ethics appeal in part to biological information about what it means to be a flourishing mammal of the type that we are to ground normative claims about sexual relationships and behaviours. As Jean Porter argues, in order to develop a ‘plausible natural law analysis’ of sexuality and marriage, ‘we need an account of the ways in which the diverse purposes of sex and marriage fit within a general teleological account of the life and functioning of the human organism’ (2010, 91). Thus, for a natural law ethicist, sex and marriage ‘need to be seen within the context of an overall pattern of life, one that we share with the other primates to some extent, even though it both informs and is transformed by our capacities for rationality’ (Porter 2010, 91). ‘Natural law’ is an expansive category that represents a variety of different approaches to ethics, but as Stephen Pope notes, they are joined by their attempts to ‘ground ethics in a view of the human good and a normative view of human nature’ (1997, 100). This theological puzzle will not examine every variety of natural law approaches, but instead focuses on two—the New Natural Law Theory (NNLT) and the ‘revisionist’ approach. Given the partial reliance of natural law frameworks for sexual ethics upon assumptions about human biology, insights drawn from evolutionary biology about the roles that sexuality and sexual behaviours play in contributing to the flourishing of our species present a particularly crucial resource for engagement.
The insights of evolutionary biologists reveal a broad diversity of sexual characteristics and behaviours at play in the world that contribute positively or negatively to creaturely flourishing. Scientific information about sexual behaviours also sheds light on the important positive evolutionary role played by non-reproductive intimate behaviours such as cuddling, mutual grooming, and between-sex and same-sex sexuality (Roughgarden, Oishi, Akçay 2006, 968). These insights challenge simplistic narratives about the biological purpose of sexual desire and behaviours, and this has important implications for understanding and articulating sexual norms which inform Christian sexual ethics, even if biology is not totally determinative for establishing sexual norms in these frameworks. While neither traditionalist nor revisionist proponents of natural law ethics reduce the category of ‘nature’ to biology, both groups make appeals at some level to biology to partially ground their claims about human flourishing. This puzzle thus examines the intersection of biological information about sex and sexual ethics in the natural law framework. The hypothesis investigated in this puzzle is the following: insights about sexuality drawn from evolutionary biology can inform understandings of the ‘nature’ of human desire and sexual behaviours in ways that can render natural law ethics more amenable to non-heterosexual expressions of sexual life.
2. Fields of Study
2.1 ‘Natural law’ approaches to sexual ethics
Traditionalist natural law frameworks for sexual ethics, such as those promulgated by the Catholic magisterium or by proponents of the New Natural Law Theory (NNLT), describe the virtuous Christian sexual life in terms of heterosexual, monogamous, procreative sexual relationships or celibacy. The word ‘natural’ in this context appeals in part to understandings of human biology, or assessments of what kinds of sexual relationships and behaviours contribute to our flourishing given the types of creatures that we are. Advocates of NNLT argue that heterosexual marriage is a basic good, and basic goods can be known through our experience of our natural inclination toward those goods (Salzman and Lawler 2008, 58). As John Finnis, one of the advocates of NNLT explains, ‘by a simple act of non-inferential understanding one grasps that the object of the inclination which one experiences is an instance of a general form of good, for oneself (and others like one)’ (2011, 34).
In this view, heterosexual marriage is a basic good; sexual acts in the context of heterosexual marriages contribute to actualizing this basic good; and nonprocreative sexual relationships and nonmarital sexual acts are ‘unnatural, unreasonable, and immoral’ (Salzman and Lawler 2008, 58). Marriage is a ‘fundamental human good’ according to NNLT because it contributes to the flourishing of those who join together in marriage (a man and a woman only, in this framework), and because it is procreative, or in other words, it brings into existence and nurtures the flourishing of a new person (Finnis 2008, 389). The goals of marriage are friendship between the spouses and reproduction, and so for NNLT, a sexual act is not truly ‘marital’ unless it ‘actualizes, expresses, and enables the experiencing of a marriage’s freely chosen commitment to equality between the spouses, exclusivity, permanence, and openness to procreation’ (Finnis 2008, 393). Sexual acts should contribute to the goods of marriage (friendship and procreation), and those that do not are immoral and unreasonable—since these goods of marriage can be known through ‘practical reason’ (Finnis 2008, 393). Homosexual acts, Finnis argues, cannot be truly ‘marital’, regardless of the legal status of the couple, because those acts have no potential to generate children (Finnis 2008, 396). He claims further that homosexual relationships have ‘no structural orientation or inherent intelligible ground for either exclusivity or permanence, no deep complementarity, no connection between its sexual interactions and any children the partners may acquire, and no inherent commitment to the arduous parenting of children’ (Finnis 2008, 398). This approach to natural law ethics, then, that is expressed by Finnis and other traditionalists articulates a particular vision for the norms that will contribute to human flourishing based on what it takes to be the goals and purposes of sex, drawn from both biology (what leads to our flourishing, given the types of creatures that we are) and ‘practical reason.’
‘Revisionist’ approaches to natural law ethics, by contrast, tend to emphasize the importance of historical contingency and human experience for establishing ethical norms, even as they retain Thomistic emphases on human life as teleological and oriented towards happiness and human flourishing (Pope 2011, 79). Revisionists are less likely to make appeals to ‘nature’ to ground ethical norms, but tend more toward appeals to the ‘affective, imaginative, narrative, and interpersonal’ (Pope 2011, 79). According to Stephen Pope, revisionist approaches to natural law reject the notion that we ought to conform ourselves to an objective nature, and emphasize instead that humans should be ‘selective in our judgements about what aspects of nature contribute to the human good’ (Pope 2011, 80). In other words, an act is judged to be moral not simply because it is ‘natural’ or because it appears commonly in the behaviours of a variety of species including our own; rather, they emphasize the importance of discerning whether or not a particular act contributes to human flourishing. Regarding the purposes of sex and marriage, revisionists tend to emphasize the good of marriage as context in which to express interpersonal love more than they emphasize procreation. As Pope notes,
The will of God, in this view, requires that sexual activity be marked by generosity of spirit, personal responsibility, permanent and monogamous commitment, deep interpersonal love and fidelity, and attentiveness to relevant contextual factors. The procreative purpose of sexual intercourse is a good in general, but not necessarily in each and every concrete situation or even in each particular monogamous bond (1997, 113).
Revisionist natural law ethicists are, in general, positive about the possibilities of same-sex unions expressing the goals of Christian marriage, as expressed in the quotation above. Revisionist natural lawyers also affirm the need to develop ethical frameworks in light of the deliverances of the sciences, especially evolutionary biology and psychology, and thus also appeal in part to understandings of human biology to ground arguments about sexual ethics. As revisionists Todd Salzman and Michael Lawlor argue, ‘An ongoing dialogue with the sciences and other modern disciplines is essential for developing our understanding of the basic goods and the norms that facilitate their realization’ (2008, 101). Indeed, both approaches to natural law sexual ethics at least partially ground their arguments in understandings of what contributes to the flourishing of the types of animals that humans are on a biological level.
2.2 Insights from Evolutionary Biology
There are many potentially relevant insights from evolutionary biology for this discussion, and many debated questions within the field about sexual reproduction and behaviours in animals. Without providing a comprehensive account of everything that evolutionary biology has to offer to natural law approaches for sexual ethics, this section focusses briefly on a few insights related to animal and human sexual desire, sexual preferences, and the evolutionary purposes of intimate behaviours and sex in animals and humans from an evolutionary point of view before proceeding to the discussion portion of this puzzle.
One way of understanding the purposes of sexual desires and behaviours in animals suggested by many evolutionary biologists is in terms of their function to achieve the goals of reproduction and perpetuating high-quality genes. Proponents of the ‘good genes’ school of thought argue that ‘mate choice evolves under selection for females to mate with ecologically adaptive genotypes’ (Kirkpatrick 1987, 44). In this view, sexual desires and behaviours are oriented towards reproducing the best genes in a species, so female animals, they argue, will in general be attracted to the most well adapted males. This model also typically understands homosexuality in animals to be ‘an inadvertent mistake, a deception, or a deleterious trait maintained through particular inheritance’ (Roughgarden 2009, 244). Evolutionary biologists Angela M. Achorn and Gil G. Rosenthal, argue further that “few studies in fact test the key predictions of ‘good genes’ models, and as predicted by theory, they show scant evidence for additive effects of mating decisions on offspring viability” (2020, 206). There is a darker side to this model as well. The ‘good genes’ model of understanding mate choice endures with such persistence, Rosenthal suggests, because ‘it most appeals to our folk eugenic sensibilities’ (Rosenthal 2017, 406). Biologist and ecologist Joan Roughgarden argues similarly that the standard ‘good genes’ model of sexual selection “underwrites ‘genetic classism’ by naturalizing a mythical urge on the part of females to locate and sleep with males who have the best genes” (Roughgarden 2009, 4). Roughgarden characterizes this view as a ‘narrative of genetic entitlement’ (Roughgarden 2009, 4).
Achorn and Rosenthal support a movement away from a narrow focus on genes in thinking about organism preferences and mating decisions. Rosenthal, in his monograph entitled, Mate Choice: The Evolution of Sexual Decision Making From Microbes to Humans, explores at length the contextual influences on the evolution of preferences. Mate choice, Rosenthal argues, ‘is by definition a social interaction’, and so it can be shaped by other individuals in a chooser’s life (2017, 306). As he notes, ‘Even before birth, parents impart epigenetic markings, hormones, and resources that can affect preferences’ (Rosenthal 2017, 312). Preferences for particular types of mates, even in humans, are ‘hypervariable, within individuals, among individuals, and among populations’ (Rosenthal 2017, 473). Humans express massive amounts of variation in what arouses and attracts them (Rosenthal 2017, 481). He explores at length the roles played by epigenetics, social context, environmental niches, life histories, early experiences of nutritional and social stress, and other contextual factors that play roles in shaping mating decisions and sexual selection. He summarizes these factors with his use of the phrase ‘the importance of the nest’ (Rosenthal 2017, 338). In other words, early experiences in life with parents and other adults, levels of nutrition, and the presence or absence of social and ecological stress play major roles in shaping desires and preferences. Preferences have a history, and they can also flip in response to social experiences (Rosenthal 2017, 29). What was once repulsive to an organism can become attractive, and vice-versa, based on social experiences.
As Rosenthal argues, our intuition tells us that ‘desire is complicated and strange and unpredictable, and this intuition holds true broadly across sexually reproducing organisms’ (2017, 492). So while empirical reflection such as that offered by Rosenthal affirms that concerns about survival and fecundity in part determine mate choices and sexual behaviours, this is counterbalanced by the persistent ‘exuberance’ of preferences found in humans and other animals that don’t always map onto utilitarian purposes such as procreation or coupling with the highest quality mate to reproduce their genes (Rosenthal 2017, 492). Regarding same-sex desires and behaviours, Rosenthal argues that while it is most common for animals to prefer heterosexual coupling, nevertheless, ‘same-sex sexual behavior is ubiquitous in animals’ (2017, 260). Something akin to what we would describe as sexual orientation (i.e. a stable preference for sexual activity with one sex over another) is not found in animals other than humans and sheep. Instances of same-sex sexual behaviour in many cases seem to play an important role in strengthening the ‘social glue’ tying together various groups (Rosenthal 2017, 261). Some species even form same-sex pair bonds that jointly care for offspring (such as humans, Laysan albatrosses, and female red squirrels). Rosenthal argues regarding non-human animals in a same-sex pair bond who care for offspring together, ‘as in humans, there was no measurable difference in the outcome of parental care between same and opposite-sex parents’ (Rosenthal 2017, 224).
Joan Roughgarden, an ecologist and evolutionary biologist, has specialized in (among other things) the study of the diversity of sexual behaviours in the animal kingdom. In contrast to some biological accounts that describe the purpose of mating in terms of reproducing high quality genes, Roughgarden argues that the goal of mating is for organisms to produce and successfully raise the greatest number of offspring they can because, ‘offspring are investments held in common’ (2006, 965). Reproductive social behaviours of animals, then, should be understood in terms of cooperative ‘teamwork’ (Roughgarden 2009, 13). Cooperative teamwork involves animals sharing a common interest and they work together to achieve evolutionary ‘payoffs’ or benefits. The work of the team is cooperative not only in the sense that it results in a mutually beneficial outcome, but also in the ‘way the game is played,’ or in other words, the ‘process of perceiving and playing the game’ is also by its nature cooperative (Roughgarden, Oishi, and Akçay 2006, 966-967). Cooperation can, of course, sometimes fail, in which case conflict and competition may arise, but according to Roughgarden et al., these are derivative of the fundamental cooperation that motivates most animal reproductive social behaviour.
Roughgarden also provides an evolutionary explanation for the pervasive presence of non-reproductive intimate behaviours among animals such as same-sex copulation, mutual grooming, co-sleeping, and interlocking vocalizations. The purpose of these non-reproductive intimate behaviours, either same-sex or opposite-sex, are, according to Roughgarden, to ‘coordinate actions and tacitly to sense one another’s welfare’ (2009, 243). These behaviours also have an evolutionary payoff—pleasure and bonding. Pleasure in physical intimacy deepens relational bonds and strengthens connections. In other words, she argues, same-sex sexual behaviour ‘promotes friendship’ (Roughgarden 2004, 155). It also contributes to effective teamwork, Roughgarden argues. Thus, pleasurable sexual behaviours are evolutionarily useful in promoting more effective teamwork to achieve shared goals. The more deeply bonded the pair is, the more successful they will be in working together to rear their offspring. Pleasure is an evolutionarily useful experience that makes the ultimate goal of reproduction—successfully raising offspring—much more likely to be achieved.
As we have seen, all natural law ethicists agree that biological facts are not sufficient on their own to determine the morality of sexual behaviours. Certainly in the case of humans; culture, religion, and moral reasoning will play influential roles in shaping understandings of sexual norms. However, natural law ethicists would also agree that there should not be a contradiction between our moral norms and what insights from evolutionary biology reveal about what contributes to our species flourishing, because our moral reasoning should be informed and circumscribed by the kinds of organisms that we are, including reference to what is true about us as biological creatures. As Stephen Pope argues, ‘scientists from various disciplines can shed light on human flourishing. Science can assist our understanding of the descriptively human, the base from which the normatively human is derived’ (1997, 120). So what can the insights from the scientists discussed above tell us about human flourishing as it relates to sexual behaviour?
The first insight to take into consideration in terms of its relevance for natural law sexual ethics is the argument from Rosenthal about the complexity of creaturely desires, inclinations, and preferences. Finnis and other NNLT thinkers appeal to the category of ‘natural inclination’ as a means of determining what qualifies as a ‘basic human good.’ If by ‘natural inclination,’ Finnis et al. mean something akin to instinctual preference, attraction, or desire, Rosenthal helps appreciate the complex matrices of influences that contribute to the production of an organism’s desires, and the explosive variety and unpredictability of those desires, such that it becomes difficult to straightforwardly determine what humans are ‘naturally’ inclined to. As we discussed above, early experiences in life with parents and other adults, peer pressures and other social influences, nutritional deficiencies, and the presence or absence of social and ecological stress play major roles in shaping desires and preferences. There is reason to think that Finnis, at least, does mean by ‘natural inclination’ something like ‘instinctual desire.’ In speaking of the mating of non-human animals, Finnis describes their behaviour as ‘sheerly instinctual,’ while regarding human marital intercourse he argues that, in its commitment to express friendship and openness to procreation through sex, a married couple ‘illuminates, integrates, extends, and deepens all that is instinctual and passionate in their motivation to make the commitment’ (2008, 390). By referring to human married sex as deepening and extending that which is instinctual, Finnis appeals to an understanding of biological instinct or desire. Evolutionary biologists like Rosenthal or Roughgarden would likely agree with Finnis that sexually reproducing animals are instinctually drawn to sexual pleasure, mating, and (often) reproduction, and that this is often heterosexual in expression. However, they would also at the same time emphasize the diversity and unpredictability of sexual inclinations and instincts, and their plasticity to environmental or cultural influences (especially in the case of humans).
If Finnis merely argued that humans experience a ‘natural inclination’ to sexual coupling, and from this he built his philosophy of marriage by expanding upon the foundation of this minimal claim about biology, then the insights expressed by contemporary evolutionary biology would largely support his project, or at least they would not contradict it, even if Finnis then used the tools of practical reason and philosophy to express some normative claims about the proper nature of this sexual coupling. Indeed, for a variety of reasons such as protecting stability in society or providing stable foundations for the care and protection of children, ethicists will want to establish frameworks for ensuring that sexual coupling is (at least relatively) stable and proscribed within certain boundaries. But this important work goes well beyond claims about human biology. However, the claim from Finnis about biology is stronger in asserting that humans experience a ‘natural inclination’ to heterosexual and procreative marriage as a basic good, and here the insights provided above from evolutionary biology have some bearing. As argued above, the work of Rosenthal and Roughgarden demonstrates the persistent ‘exuberance’ of sexual inclinations in humans and other animals that don’t always map onto utilitarian purposes such as procreation, and it shows that homosexual behaviours are ubiquitous among all types of animals. So, the move to invoke the concept of ‘natural inclination’ to ground heterosexual and procreative marriages, and to delegitimize same-sex marriages or non-procreative sexual behaviours, is not supported by contemporary evolutionary biology. Thus, while it is clear that natural law ethicists of all stripes, including those within NNLT, do not wholly ground their claims about human sexual norms in biology, this example of Finnis’s argument from ‘natural inclination’ to heterosexual, procreative marriage shows that appeals to biological instinct are at play, even if they are subtle. And to the extent that assumptions about human biology are invoked in defences of human sexual norms, natural law ethicists should ensure that they are equipped with the most up-to-date information from evolutionary biology.
There are two other categories frequently discussed in natural law approaches to sexual ethics that may benefit from the insights of evolutionary biology, and these are the goods of marriage expressed in terms of friendship (or love) and procreation. In order to be truly ‘marital’, Finnis argues that sexual activities must contribute to friendship and procreation. Revisionist natural law ethicists in general retain a value for both of these goods, but tend to speak more in terms of ‘interpersonal love’ rather than friendship, and they also tend to prioritize the goal of expressing interpersonal love as more important for marriage than procreation, and even acknowledge that procreation may not be a good for every marriage. Here the work of Rosenthal and Roughgarden can offer some insight. As they suggest, in both humans and non-human animals, same-sex and opposite-sex non-reproductive intimate behaviours (cuddling, mutual grooming, oral sex, co-sleeping, etc.) can serve important evolutionary functions in deepening affective bonds, strengthening the social glue in various groups, and in the case of humans, non-reproductive sexual acts are important for deepening and expressing interpersonal love. From the point of view of Christian natural law ethics, there would need to be other factors also present alongside these sexual acts to make them truly virtuous (such as respect, permanent and monogamous commitment, generosity, and fidelity). Yet these acts are far from being at odds with the goals of friendship and love in marriage, and can indeed support their flourishing. As Porter argues, ‘such acts can serve as an expression of deep interpersonal love and deserve respect to the extent that they do’ (2010, 94).
What about the good of procreation in marriage? NNLT ethicists argue that sexual acts in marriage must be undertaken in the context of openness to procreation in order to be truly marital, and that same-sex copulation can thus never be truly ‘marital’ because it is impossible for it to generate children. In the same vein, they argue that non-reproductive sexual acts in heterosexual couples also fail to be truly ‘marital’ for this same reason. From the context of evolutionary biology, it can be argued that non-reproductive sexual acts (either same-sex or opposite-sex) do in fact contribute to procreation, if procreation is understood more broadly than simply conceiving a child. Returning to the insights of Roughgarden, she argues that the goal of sex from a biological point of view is not simply to reproduce, but also to successfully raise offspring. In the case of humans, caring for offspring (particularly in their early years when they are especially vulnerable) requires extensive teamwork between the parents, and teams work better together when the team members are in sync with one another. The purposes of non-reproductive intimate behaviours are, then, to ‘coordinate actions and tacitly to sense one another’s welfare’ (Roughgarden 2009, 243). The more deeply bonded the pair is, the more successful they will be in working together to rear their offspring, and so if the definition of procreation is expanded beyond simply ‘conceiving a child,’ then evolutionary biology helps to demonstrate how non-reproductive sexual behaviours actually do contribute to procreation broadly understood.
Same-sex pairs might also be seen to demonstrate ‘openness to procreation,’ again if procreation can be broadened beyond conception. Several species (including humans) demonstrate same-sex joint parenting. For example, though only one of them is the biological mother, female red squirrels occasionally form same-sex pair bonds and together raise a litter, with both females contributing to nursing the offspring (Roughgarden 2004, 141). Certainly in humans, it is obvious that same-sex couples often work together to raise children from previous relationships, to adopt, or to become pregnant via artificial insemination. If procreation is understood broadly as ‘successfully raising offspring,’ same-sex couples also achieve this good of marriage, even if the offspring they successfully raise are not their biological children. The question of whether or not same-sex couples achieve the goods of marriage is easier to answer in the context of revisionist natural law ethics because procreation is not required for a marriage to be virtuous, as long as the marriage expresses fidelity, monogamy, interpersonal love, generosity, and personal responsibility.
This puzzle sought to investigate the hypothesis that insights about sexuality drawn from evolutionary biology can inform understandings of the ‘nature’ of human desire and sexual behaviours in ways that can render natural law ethics more amenable to non-heterosexual expressions of sexual life. To begin, the essay reviewed two versions of natural law ethics expressed in NNLT and ‘revisionist’ approaches. Both forms of natural law ethics make appeals at some level to biology to ground their claims, though this is seen more overtly in NNLT. John Finnis, one NNLT ethicist, argues that in order for sexual acts to be ‘marital’ they must express and support the goods of marriage, namely, friendship and procreation. Based on how Finnis and other NNLT ethicists define friendship and procreation, they argue that homosexual sexual acts are always unnatural, unreasonable, and immoral. Revisionist approaches to natural law ethics tend to describe the goods of marriage more in terms of expressing interpersonal love in permanent, monogamous relationships, with procreation being a potential but not necessary good of the marriage.
From this overview of approaches to marriage in natural law ethics, the essay moved to consider insights from evolutionary biology. This section emphasized the broad diversity and unpredictability of sexual desires and behaviours among humans and non-human animals. It illuminated the complex webs of influences that contribute to an organism’s sexual desires and preferences, and it noted the ubiquity of same-sex sexual activity among humans and non-human animals, even if statistically heterosexual coupling is more common. It highlighted the important evolutionary role played by non-reproductive sexual behaviours (same-sex or opposite-sex) in strengthening bonds of affection and facilitating more effective teamwork. The insights provided by evolutionary biology also enabled a view of the goal of sex as broader than merely reproduction to include the successful raising of the offspring.
The discussion portion of the essay highlighted several key areas where evolutionary biology can provide relevant information about human flourishing in relation to sexuality. The first point was to use evolutionary biology to critique Finnis’s use of the term ‘natural inclination’ to ground his argument that only heterosexual, procreative relationships can be truly ‘marital.’ Next, the insights from evolutionary biology were used to expand and clarify the ways in which non-reproductive sexual acts (in same-sex or opposite-sex pairs) can contribute to the goods of marriage understood as friendship, love, and procreation. Same-sex couples can achieve and express friendship, love, and even procreation in marriage, if procreation is defined more broadly than biological conception to include the successful raising of offspring, who may or may not be biologically related to one of the parents. At the end of this investigation, the initial hypothesis was confirmed, with one caveat. Evolutionary biology can be used to critique and/or expand understandings of the purposes of sex expressed in natural law theory in order to enable them to become more amenable to same-sex relationships, but this has the most traction when brought into conversation specifically with NNLT. Revisionist natural law ethics, while still engaged with developments in the natural and social sciences to understand what can contribute to human flourishing, is less dependent upon claims about the biology of sexual difference and procreation to ground its claims. Indeed, revisionist natural law ethicists have, in many ways, already developed their own philosophical arguments for the goods of marriage that can be achieved in same-sex unions, and many of these arguments would be supported by insights from evolutionary biology.
Achorn, Angela M. and Gil G. Rosenthal. 2020. “It’s not about him: mismeasuring ‘good genes’ in sexual selection.” Trends in Ecology & Evolution 35: 206-219.
Adams, J. and Light, R. 2015. ‘Scientific consensus, the law, and same sex parenting outcomes.’ Social Science Research 53: 300-310.
Finnis, John. 2008. ‘Marriage: A Basic and Exigent Good.’ The Monist 91: 388-406.
Finnis, John. 2011. Natural Law and Natural Rights. Oxford: Oxford University Press.
Grisez, Germain and Russell Shaw. 1991. Fulfilment in Christ: Summary of Christian Moral Principles. Notre Dame: Notre Dame University Press.
Kirkpatrick, Mark. 1987. ‘Sexual Selection by Female Choice in Polygynous Animals.’ Annual Review of Ecology and Systematics 18: 43-70.
Pope, Stephen J. 2011. ‘Natural Law and Christian Ethics.’ In The Cambridge Companion to Christian Ethics, edited by Robin Gill, 65-86. Cambridge: Cambridge University Press.
Pope, Stephen J. 1997. ‘Scientific and Natural Law Analyses of Homosexuality: A Methodological Study.’ Journal of Religious Ethics 25: 89-126.
Porter, Jean. 2010. ‘The Natural Law and Innovative Forms of Marriage: A Reconsideration.’ Journal of the Society of Christian Ethics 30: 79-97.
Rosenthal, Gil G. 2017. Mate Choice: The Evolution of Sexual Decision-Making From Microbes to Humans. Princeton: Princeton University Press.
Roughgarden, Joan. 2009. The Genial Gene: Deconstructing Darwinian Selfishness. Berkeley and Los Angeles: University of California Press.
Roughgarden, Joan. 2004. Evolution’s Rainbow: Diversity, Gender, and Sexuality in Nature and People. Berkeley and Los Angeles: University of California Press.
Roughgarden, Joan, Meeko Oishi, and Erol Akçay. 2006. ‘Reproductive Social Behavior: Cooperative Games to Replace Sexual Selection.’ Science 311: 965-969.
Salzman, Todd A. and Michael Lawler. 2008. The Sexual Person: Toward a Renewed Catholic Anthropology. Washington DC: Georgetown University Press.
 C.f. Germain Grisez and Russell Shaw, Fulfilment in Christ: Summary of Christian Moral Principles, Notre Dame: Notre Dame University Press (1991).
 To make this point, Rosenthal cites the following study: Adams, J., & Light, R. (2015). ‘Scientific consensus, the law, and same sex parenting outcomes.’ Social Science Research 53: 300-310.
Cite this article
Loumagne Ulishney, Megan. 2022. “Can Evolutionary Biology Help to Render Natural Law Approaches to Sexual Ethics More Affirming of Non-Heterosexual Relationships?” Theological Puzzles (Issue 8). https://www.theo-puzzles.ac.uk/2022/06/14/ulishney/.
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