Mothers and Others

by Sarah Blaffer Hrdy

  No one doubts that organisms like fish benefit from being able to see. That is why they have eyes. When reared in total darkness, however, fish like the small cave-dwelling characin fish of Mexico cease to develop their capacity for vision. Even when reintroduced to sunlight and reared outside, populations of characin fry long isolated in the dark fail to regain sight. As a simple matter of somatic economy, unused traits no longer favored by natural selection are lost, while somatic or neurological resources are diverted for uses elsewhere.

  Viewed from the perspective of some evolutionary theorist surveying humans 20,000 years hence, our powerful impulses to empathize with others, to give, share, and seek reciprocation, might seem like nothing more than transient phases in the ongoing evolution of the species. Although there is a widely held assumption (known as Dollo’s Law) that evolutionary processes are irreversible, don’t count on it. Dollo’s Law is more nearly a description of the deep history of some organisms than a universally applicable natural law like gravity.38 A far more basic and universal tenet of evolutionary biology states that “the removal of an agent of selection can sometimes bring about rapid evolutionary consequences.”39

  To all the reasons people might have to worry about the future of our species—including the usual depressing litany of nuclear proliferation, global warming, emerging infectious diseases, or crashing meteorites—add one more having to do with just what sort of species our descendants millennia hence might belong to. If empathy and understanding develop only under particular rearing conditions, and if an ever-increasing proportion of the species fails to encounter those conditions but nevertheless survives to reproduce, it won’t matter how valuable the underpinnings for collaboration were in the past. Compassion and the quest for emotional connection will fade away as surely as sight in cave-dwelling fish.

  I have no doubt that our descendants thousands of years from now (whether on this planet or some other) will be bipedal, symbol-generating apes. They will probably be technologically proficient in realms we do not even dream of yet, as well as every bit as competitive and Machiavellian as chimpanzees are now, and probably even more intelligent than people today. What is not certain is whether they will still be human in ways we now think of as distinguishing our species—that is, empathic and curious about the emotions of others, shaped by our ancient heritage of communal care.

  NOTES

  REFERENCES

  ACKNOWLEDGMENTS

  INDEX

  NOTES

  1. APES ON A PLANE

  1. The study of theory of mind dates from Premack and Woodruff 1978. For an update on the literature, begin with Penn and Povinelli 2007 and references therein.

  2. Psychiatrists Daniel Stern (2002) and Peter Hobson (2004) and developmental psychologists Karlen Lyons-Ruth (Hennighausen and Lyons-Ruth 2005) and Colwyn Trevarthen (2005; Trevarthen and Aitken 2001) prefer to talk about “intersubjectivity” or “affective sharing,” terms which encompass both the sharing of attitudes about the world and the affective components of the relationship between the individuals involved. Eager questing for such emotional sharing is thought to emerge very early in human infant development (Reddy 2003, 2007) and to precede and guide later theories of mind and inferences about what others know or believe.

  3. This account appeared in 1884 in the Proceedings of the Asiatic Society of Bengal and is cited in full in Hrdy 1977a:5–6.

  4. Neuroimaging studies by Jean Decety, Perrine Ruby, and others are reviewed in Decety and Jackson 2004, see esp. pp. 86–87.

  5. Rilling et al. 2004a:1695; Fehr and Fischbacher 2003.

  6. Cosmides and Tooby 1994; Ostrom 1998; Trivers 1971.

  7. Wiessner 1977, 1982; Thomas 2006.

  8. Trivers 1971; Burnham and Johnson 2005; Nesse 2007.

  9. Trivers 2006; Warneken and Tomasello 2006; Hamlin et al. 2007.

  10. Rilling, Gutman, Zeh, et al. 2002.

  11. For quotation about “wired to cooperate” see Damasio 2003:172–173. For an economist’s perspective, see Ostrom 1998:7. For experimental evidence that our brains work differently when we are making decisions based on what other people, as opposed to computers, are doing, see Rilling et al. 2002; Rilling, Sanfey, et al. 2004a.

  12. Trevarthen and Logotheti 1989:43. Although controversial when first proposed, Trevarthen’s views have since gained considerable support (Draghi-Lorenz et al. 2001).

  13. Marci et al. 2007.

  14. We are “hardwired, it appears, to feel each other’s happiness and pain—more deeply than we ever knew,” cautions psychotherapist Babette Rothschild in her warning to fellow therapists (2004).

  15. Sober and Wilson 1998; Tomasello 1999; Hammerstein, ed. 2003; Fehr and Fischbacher 2003; Boyd 2006. I know of no better introduction to the evolution of cooperation and altruism than Matt Ridley’s beautiful 1996 book on The Origins of Virtue.

  16. Bowles and Gintis 2003:433.

  17. For excellent overviews see McGrew 1992; Whiten et al. 1999; van Schaik et al. 2003. As early as 1874, Darwin was describing observations of chimpanzees cracking nuts with stones (1974:78–79).

  18. For chimpanzees see McGrew 1992; Boesch and Boesch-Achermann 2000; Pruetz and Bertolani 2007; Matsuzawa 1996. For captive bonobos see Savage-Rumbaugh and McDonald 1988; Parish and de Waal 1992. For captive gorillas see Gomez 2004. For wild orangutans see van Schaik et al. 2000.

  19. Mercader et al. 2007.

  20. Mulcahy and Call 2006; Raby et al. 2007.

  21. Inoue and Matsuzawa 2007.

  22. Matsuzawa 2001; Herrmann, Call, et al. 2007.

  23. For an overview of the role of bipedalism in human evolution, see Stanford 2003.

  24. Herrmann, Call, et al. 2007.

  25. Tomasello et al. 2005:675

  26. Tomasello et al. 2005:676.

  27. Tomasello et al. 2005.

  28. Tomasello 1999:59; Boyd and Richerson 1996.

  29. Tomasello et al. (2005) review arguments for considering humans as “hypersocial,” in line with Tomasello’s 1999 proposal. They also update earlier comparisons between humans and other apes to take into account more recent findings in what is a rapidly developing field of inquiry.

  30. According to the taxonomy now preferred by many geneticists, the super-family Hominoidae is composed of the so-called Lesser Apes (gibbons and siamangs) plus what are commonly known as the Great Apes (orangutans, gorillas, chimpanzees, and bonobos) plus humans. But unlike the old days when the term “hominid” was used to distinguish humans and their various bipedal ape ancestors (such as Australopithecus) from the “Great Apes,” current phylogenies include the Great Apes as well as humans among the creatures called hominids. Thus, many specialists now divide hominoid apes into two families, the Hylobatidae (gibbons and apes) and the Hominidae, with these hominid apes in turn divided into two subfamilies, Ponginae for the orangutan and its fossil relatives and Homininae for African apes and humans. All members of our lineage subsequent to their divergence from chimpanzees are placed in the tribe Hominini. Hominins include Australopithecus, Homo habilis, Homo erectus, Homo heidelbergensis, and Homo sapiens.

  31. Darwin 1890:240.

  32. Rilling, Gutman, et al. 2002; Rilling, Sanfey, et al. 2004a.

  33. Ingman et al. 2000; Wade 2006:52–60; Behar et al. 2008.

  34. Kaplan et al. 1990; see also Cashdan 1990; Hawkes 2001, esp. Table 4; Smith 2003.

  35. See esp. Kelly 2005.

  36. Wiessner 1977, 1996, 2002b.

  37. Wiessner, personal communication, March 5, 2007, elaborating on her written account; see also Marshall 1976: 310–311.

  38. Rodseth and Wrangham 2004:393ff and references therein.

  39. Dunn et al. 2008.

  40. Wiessner 2002b:421.

  41. Forty-six percent of the partnerships in her sample were with partners related as closely as first cousins. Yet in spite of the tendency to favor kin, many partnerships were with fairly distant relatives; Wiessner 2002a:31.

  42. Wiessner 2002a.
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  43. Richard Lee, who originally explained this system, learned that the elder in any “namesake” dyad gets to determine which kinship term is to be used, adding to its flexibility over a person’s lifetime (2003:64–76).

  44. Wiessner 2002b.

  45. See Marlowe 2004 for a comparison using 36 foraging societies.

  46. Sealy 2006; Johnson and Earle 2000:54ff.

  47. McHenry 2009, with thanks to John Fleagle.

  48. Cohen 1995:29; Stiner et al. 1999; Johnson and Earle 2000, esp. ch. 1; Behar et al. 2008.

  49. Choi and Bowles 2007; cited and discussed in Jones 2008:514 and references therein.

  50. Kelly 2005 and esp. Wiessner 2006. For the logic of “behavioral scaling” that explains the link between population density and human aggression, see Wilson 1971b or 1975:20ff.

  51. Washburn and Lancaster 1968; Wrangham and Peterson 1996:199; Wrangham 1999:1; Jones 2008 and references therein.

  52. See Kelly 2005 for “Paleolithic warlessness” and esp. Fry 2007 for recent overview and Johnson and Earle 2000 for general introduction. Even ar chaeologists who stress the prevalence of “prehistoric war” acknowledge that there is no evidence for warfare from the Pleistocene (e.g., Keeley 1996).

  53. Marshall 1976; Lee 1979, esp. pp. 24, 244–248, 343–346, 390–400, 458; Johnson and Earle 2000; Hewlett 2001:52; Kelly 2005; Wiessner 2006, discussed at length in Boehm 1999. See esp. Boehm’s discussion of how fiercely egalitarian hunter-gatherers can be.

  54. See esp. Lee 1979:390–400. Even though this monograph on the !Kung San is often cited to support the claim that Paleolithic people were more violent than modern people, with homicide rates comparable to those of America’s most violent cities (see Jones 2008 and references therein), Lee is explicit that the !Kung San do not engage in warfare, and if American deaths due to warfare are included, !Kung homicide rates would be far lower than those in America (1979:398).

  55. Take a look at the index to one of the best and most widely adopted textbooks on Evolution and Human Behavior by John Cartwright (2000). Terms like “sharing” and “childrearing” do not appear. There are no references to “maternal,” “paternal,” or “allomaternal care,” but there are two to “maternal-fetal conflict” and ten to “paternity confidence”; no mention of “infants” or “infant care” but two to “infanticide.” This same criticism could be applied to many of my own earlier publications.

  56. This bias can be found in some of the best books in the field, e.g., Wade 2006:148–150, n. 189. A 2000 essay by Parish and de Waal discusses the bias and suggests some antidotes.

  57. See, for example, experiments demonstrating the role of interindividual tolerance in cooperation among chimpanzees (Melis et al. 2006a) along with research documenting the more relaxed temperaments of bonobos relative to chimpanzees (Hare et al. 2007).

  58. Parish and de Waal 2000; Höhmann 2001. It is not known whether this is a species-typical difference between bonobos and chimpanzees, an artifact of bonobos having been studied less, or a consequence of habitat differences. What we do know from studying other primates, such as langur monkeys, is that behaviors such as territorial encounters, male-male aggression, and infanticide by adult males are highly variable, reported in some populations but not others. More often than not, population density is the key variable (Hrdy 1979).

  59. De Waal 1997. On the significance of semicontinuous receptivity and “concealed” (or, more precisely, inconspicuously advertised) ovulation see Hrdy 1981a, ch. 7; 1997.

  60. Silk 1978; Parish 1998; White 1994; de Waal 1997; Kano 1992:74, 166–170. A chimpanzee or orangutan baby may beg for food but would be likely to get anything only if the possessor was its mother, and even then delivery would be grudging.

  61. Melis et al. 2006a; de Waal 1996, 1997.

  62. Pollick and de Waal 2007.

  63. See Wiessner 2005 for ways in which talking can substitute for, as well as fan, aggression.

  64. Bird-David 1990; Hewlett, Lamb, et al. 2000. The developmental implications of growing up in what these researchers call a “giving” environment are discussed below in Chapter 4.

  65. Shostak 1976:256.

  66. Blurton Jones 1984; Moore 1984.

  67. Parish 1998; Parish and de Waal 2000; Kano 1992:74, 166–170.

  68. Höhmann and Fruth 1996:53. Most other cases of “tolerated taking” in primates are likely to involve infants getting a brief pick-me-up from the breast milk of an allomother—for example, O’Brien 1998 for capuchin monkeys; Smith et al. 2001 for tamarins; Pereira and Izard 1989 for lemurs.

  69. Burkart et al. 2007. See also de Kort, Emery, and Clayton 2006 for jackdaws.

  70. Cosmides 1989; Ridley 1996.

  71. Rilling et al. 2002, 2004b.

  72. Ambrose 1998. This point continues to be debated, but archaeologists Marwick (2003) and McBrearty and Brooks (2000) make a convincing case.

  73. For discussion of how humans get psychologically prepared to commit genocide through propaganda and other means, see Roscoe 2007. For case study see Browning 1998. On role of competition for resources see Diamond 2005, esp. pp. 323ff. For more on situation-based compunctions against murder see Hauser 2006.

  74. See Zinn 2003:1–3; Earle 1997:37.

  75. Discussed in van der Dennen 1995.

  76. For an authoritative overview, see Johnson and Earle 2000 and references therein. For spread of conquerors’ genes in the case of Genghis Khan, see Zerjal et al. 2003.

  77. Dawkins 1976:75ff for elaboration of underlying logic.

  78. I am indebted to the novelist Edmund White (2001:14) for his articulation of what being “compassionate” means.

  79. Harpending et al. 1996; Wade 2006 and references therein.

  80. I have in mind figures on the order of one person per square mile, as is typical of some twentieth-century Kalahari desert foragers (Thomas 2006). Several people per square mile, as reported for Andaman Islanders, would probably be on the high end (Kelly 2005).

  81. Smith 2007 and references therein, quotations from pp. 141–142. See also Bowles 2006, following Darwin 1874, for similar conclusions.

  82. Hare and Tomasello 2004.

  83. Polly Wiessner, personal communication, 2005.

  84. Lancaster and Lancaster 1987; Kaplan 1994.

  2. WHY US AND NOT THEM?

  1. Examples selected from the chapter titles of Darwin’s The Expression of the Emotions in Man and Animals, first published in 1872.

  2. Hobson 2004:270.

  3. Melis et al. 2006a, 2006b.

  4. Long considered uniquely human, socially contagious yawning also occurs in chimpanzees (Anderson and Matsuzawa 2006). For helping see Warneken and Tomasello 2006 and Boesch and Boesch-Achermann 2000:246–248. For adoptions of orphaned kin see Goodall 1986.

  5. For a published version of this story, see de Waal 1997:156. For more on his views of our “common ground” with other primates see de Waal 2006.

  6. Warneken et al. 2006; Warneken and Hare 2007.

  7. These experiments were designed by an imaginative young postdoc on Tomasello’s team named Brian Hare, now at Duke University. For more on the greater skill displayed by chimps in competitive compared with cooperative tasks, see Hare and Tomasello 2004.

  8. Herrmann et al. 2007.

  9. Melis et al. 2006a.

  10. Jensen et al. 2006. These results are not consistent with claims widely made in the media about how nonhuman primates have an innate sense of fairness that leads them to reject a reward if another monkey gets a better reward for the same effort. These claims derived from an interesting series of experiments in Brosnan and de Waal 2003. See Brosnan, Schiff, and de Waal 2005 for extensions of this work with chimpanzees. See Jensen et al. 2007 for discussion of the differences.

  11. Contrast interpretations of de Waal 2006 or de Waal as cited in Zimmer 2006 with those of Silk et al. 2005; also Vonk et al. 2008. In particular, Preston and de Waal (2002) stress the importance of interpreting experiments such as
those by Silk et al. within the context of other long-standing experiments in this area. They cite Stanley Milgram’s famous experiments years ago in which human subjects were willing to inflict painful electric shocks on others when authority figures instructed them to. They are struck by the contrast between Milgram’s Yale undergraduates and those of rhesus macaque monkeys, who opted to starve for days rather than pull a chain that delivered food but in doing so imposed an electric shock on another monkey. Monkeys who had experienced such shocks themselves, as well as monkeys with previous familiarity with their victims, were the least willing to impose a shock and starved longest before pulling the chain. To de Waal, such findings (e.g., Masserman et al. 1964) imply that monkeys are more caring than people are, rather than the other way around. Monkeys, on the other hand, do not respond to authority figures and experimental stress tests the same way human subjects do. This is an ongoing debate.

  12. For example, in a lecture at a conference on attachment held at UCLA in 2002, the psychiatrist Daniel Stern specifically referred to the role of intersubjectivity in enhancing shared vigilance and thus helping otherwise defenseless early hominins survive on the African savanna.

  13. Jane Goodall in an interview with Virginia Morell (2007:52).

  14. Hauser 1996.

  15. Hobson 2004:2; cf. Premack 2004:320; Tomasello et al. 2005. For insightful discussion of social challenges and primate preadaptations contributing to the cognitive capacities needed for syntax, see Cheney and Seyfarth 2007, ch. 10.

  16. Langford et al. 2006 and references therein.

  17. Greene et al. 2002.

  18. For more on the evolution of maternal emotions, see Leckman et al. 2005.

  19. See Keverne et al. 1996; Panksepp 2000; Zahn-Waxler 2000; MacLean 1985.

  20. Allman 2000:98–102.