The Evolution of Coupling - Social Sciences

1 The Evolution of CouplingElizabeth G. Pillsworth and Martie G. HaseltonCenter for Behavior, Evolution , and CultureUniversity of California, Los AngelesA cult, as the term is commonly used, denotes aset of unorthodox or spurious beliefs and the peoplewho adhere to them. DePaulo and Morris (this issue)propose thatthe cult of the coupleleads members of so-ciety in general and Social scientists in particular toview the conjugal pair as the single most important so-cial relationship, encompassing the roles of sexualpartner, best friend, primary Social partner, fundamen-tal kin relation, and economic partner.

2 One outcome ofthis cultish view is singlism: singles are cast a suspi-cious gaze and they experience discrimination rangingfrom Social ostracism to economic taxation in a worldof 2-for-1 specials and family-size portions. Why is be-ing coupled so crucial, seeming to outweigh othermarkers of Social value?DePaulo and Morris (this issue) place some of theblame on scientific theories, stating, The evolutionaryperspective, attachment theory, and the cult of the cou-ple all seem to share the assumption that the best out-comes occur when the most important roles or func-tions are all invested in just one person.

3 We werepuzzled by this claim about evolutionary we explain later, it is certainly true that sex and mat-ing are central in the Evolution of species like humans,but we see nothing in evolutionary theory leading tothe prediction that the reproductive pairbond is theonly relationship of importance, or even the this article, we review the evolutionary psychol-ogy of Coupling and discuss why we should expectmateship status to be important to the self and whypeople seem to have an obsessive interest in the mate-ship status of others.

4 Our perspective suggests thatthese Social foci spring from universal human motiva-tions with a deep evolutionary history, and therefore itis misleading to think of them as elements of a modernideology as thecultview Coupling Important?Natural selection has been erroneously associatedwith the phrase survival of the fittest (a phrase Dar-win himself did not coin), leading many people to thinkof differences in abilities to survive as the central com-ponent in Evolution . However, survival has an evolu-tionary impact only inasmuch as it leads to reproduc-tion.

5 Adaptations may serve the proximate function ofincreasing survival, such as a particular beak morphol-ogy that allows some finches to obtain more food thanothers or a tendency for some gazelles to startle moreeasily than others, giving them a head start when thereis a predator afoot. But without adaptations that pro-mote successful mating, such as the basic desire to finda mate and have sex, even the finch with the most per-fect beak for her environment or the fastest and mostalert gazelle of his herd will meet an evolutionary deadend.

6 From the perspective of the gene, reproduction isquite literally the meaning of life, and for sexually re-producing species, the mateship is indeed Offspring and theImportance of Fathers InvestmentThe evolutionary path leading to human intelli-gence and bipedal locomotion has produced a suite ofreproductive challenges unique to humans, requiringunique solutions. Human offspring, compared to thoseof other primates, are born weak and dependent and re-quire an extended period of juvenile development(Martin, 2003).

7 Chimpanzee offspring, who gamboland climb with playmates at an age when human in-fants are only able to roll over for the first time, are ca-pable of providing nearly their entire nutritional needsby the time they are weaned at 5 years of age (Lancas-ter, Kaplan, Hill, & Hurtado, 2000; Silk, 1978).Children in modern hunter gatherer populations donot begin to produce as much food as they consume un-til they are around 15 years old (Hill & Kaplan, 1999).During this time, children are incapable of caring forthemselves and are fully dependent on the care of adultkin to provide food, protection, and opportunities the slow growth and lengthy juvenile de-pendency of human children, we wean our offspringmuchearlierthandochimpanzees(mo dernhunter gatherers wean their children at about years)and consequently have much shorter interbirth intervals(Lancaster et al.)

8 , 2000). In chimps and most other pri-mates, the interbirth interval is slightly longer than thetime it takes to raise a single offspring to independ-ence about years for chimpanzees and mothersrarely need to care for more than one dependent off-spring at a time. In rare cases in which there are multipledependents, such as in the birth of twins, only one willusually survive (Dixson, 1999). Yet the interbirth inter-val among modern hunter gatherers ranges from only 3to 5 years, approximately 10 years less than the time re-quired to raise a single child to possible independence(Lancaster et al.

9 , 2000). Thus, humans not only have98 COMMENTARIES atypically helpless infants but also regularly care formultiple dependent offspring adaptation for raising dependent, slowly devel-oping children is biparental care. Studies of modernhunter gatherers demonstrate that paternal care can becritical to child survival (Hill & Hurtado, 1996;Hurtado & Hill, 1992; Marlowe, 2003). For example,Ach children between 1 and 5 years of age are more likely to die if their fathers are dead than iftheir fathers are living, and times more likely to dieif their parents are divorced than if they are together(Hurtado & Hill, 1992).

10 The resources provided by pa-ternal investment in offspring are many: fathers pro-vide nutritional resources, protection against predatorsor unfriendly conspecifics, models for learning, andsocial resources (Marlowe, 1999a, 1999b, 2001).When paternity certainty is low, however, as it is inchimpanzees, males have little incentive to invest inoffspring. In mating systems in which only one malemates with several females, as in gorillas, paternitycertainty is close to 100%, but any investment the malemight provide will be divided among many monogamous mating systems, in contrast,serve to increase a male s paternity certainty, evenwhen there is some level of sexual infidelity, whileconcentrating his parental efforts on fewer offspring(Birkhead, 1998; Daly & Wilson, 1983).