Why do we like to cuddle?
2001-09-03 12:16 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
archershipsFrom a post to the
evolutionary psychology
mailing list:
The following is related to Dreamburn's question about concealed
ovulation and is from an upcoming paper (Geary, 2000, Evolution and
proximate expression of human paternal investment. Psychological
Bulletin, 92).
In addition, "non-reproductive sex" is, in fact,
reproductive, although it doesn't always lead to
conception: This sex for fun likely facilitates pair
bonding which, in turn, increases paternal investment and
decreases cuckoldry risks (i.e., increases paternity
certainty).
From the paper:
Because it is in women's best interest to secure paternal
investment, at a cost of lost mating opportunities for
men, any mechanism that reduced these opportunities was
likely to have originated in our female and not our male
ancestors. In fact, it is likely that the evolutionary
course toward paternal investment was initiated by
reproductive and social adaptations in our female
ancestors, given the strong bias of mammalian males toward
mating effort. Although it is not certain, these
mechanisms appear to include concealed ovulation, women's
aversion to casual sex, and female-female competition to
exclude competitors from the social group, as described
earlier (Geary, 1998).
The relation between concealed ovulation and paternal
investment is complex, however, and merits further
discussion. Dunbar's (1995) analysis of primate species
indicates that social monogamy and high levels of paternal
investment are almost always associated with concealed and
sometimes synchronized ovulation, but that concealed
ovulation is most common in primate species with high
risks of infanticide (Hrdy, 1979). In other words,
concealed ovulation is not always associated with high
levels of paternal investment but high levels of paternal
investment are typically associated with concealed
ovulation. One possibility is that reduced infanticide
risk -- that is, mating with many males and thus confusing
paternity -- was the initial selection pressure for
concealed ovulation in hominids (see Hrdy, 1979), although
men do not appear to be biologically biased toward
infanticide (Daly & Wilson, 1988). Concealed and later
synchronized ovulation (which prevents males from mating
with more than one fertile female at a time) appear to be
a further evolved strategy in some primate species, a
strategy to reduce the mating opportunities of males and
thereby reduce the opportunity cost of paternal investment
(Dunbar, 1995). Although conceal ovulation will increase
the amount of affiliation between males and females, it is
not sufficient to ensure paternal investment, especially
in multi-male, multi-female communities where alternative
mating opportunities are possible.
As noted earlier, once physical signs of pregnancy were
evident, males could abandon females and pursue other
mates, if an additional mechanism was not operating. It
appears that this mechanism is pair bonding (Lovejoy,
1981; MacDonald, 1992; Miller & Fishkin, 1997). In this
view, concealed ovulation increased the amount of
male-female affiliation time and resulted in prolonged
sexual activity, which, in turn, reduced the mating
opportunities of males and, at the same time, provided the
initial conditions for the evolution of pair bonding
(MacDonald, 1992). In addition to reducing the risk of
male abandonment during pregnancy, pair bonding would
facilitate the type of spousal relationship that appears
to facilitate paternal investment. Pair bonding would
also increase the sexual fidelity of females and thereby
increase paternity certainty, which, in turn, would result
in reproductive benefits for those males who invested in
offspring. Once male investment resulted in reproductive
benefits, such as reduced offspring mortality rates and
increased social competitiveness, the stage was set for
the further evolution of paternal investment.
On the other hand, if the benefits of hominid paternal
investment were similar to those found in extant
preindustrial and developing societies and in Western
nations prior to the demographic shift, than lower levels
of paternal than maternal investment would be expected
(and are found). If paternal investment yields
reproductive benefits but is not obligate -- and it does
not appear to be in humans -- then a focus on mating
effort, paternal effort, or some combination are viable
reproductive strategies for men. When both mating effort
and parental effort are viable options, considerable
variability in men's reproductive strategies would be
expected (and are found). Moreover, because paternal
investment does not appear to be obligate, it is in the
best interest of some women to attempt the cockoldry of
their social partners. Cockoldry risks, in turn, reduce
the level of paternity certainty and through this militate
against paternal investment. All of these factors lead to
the prediction of greater levels of maternal than paternal
investment and continued conflict between men and women
over this investment (Buss, 1994).
David C. Geary, Ph.D. Department of Psychology 210
McAlester Hall University of Missouri Columbia, MO
65211-2500
evolutionary psychology
mailing list:
The following is related to Dreamburn's question about concealed
ovulation and is from an upcoming paper (Geary, 2000, Evolution and
proximate expression of human paternal investment. Psychological
Bulletin, 92).
In addition, "non-reproductive sex" is, in fact,
reproductive, although it doesn't always lead to
conception: This sex for fun likely facilitates pair
bonding which, in turn, increases paternal investment and
decreases cuckoldry risks (i.e., increases paternity
certainty).
From the paper:
Because it is in women's best interest to secure paternal
investment, at a cost of lost mating opportunities for
men, any mechanism that reduced these opportunities was
likely to have originated in our female and not our male
ancestors. In fact, it is likely that the evolutionary
course toward paternal investment was initiated by
reproductive and social adaptations in our female
ancestors, given the strong bias of mammalian males toward
mating effort. Although it is not certain, these
mechanisms appear to include concealed ovulation, women's
aversion to casual sex, and female-female competition to
exclude competitors from the social group, as described
earlier (Geary, 1998).
The relation between concealed ovulation and paternal
investment is complex, however, and merits further
discussion. Dunbar's (1995) analysis of primate species
indicates that social monogamy and high levels of paternal
investment are almost always associated with concealed and
sometimes synchronized ovulation, but that concealed
ovulation is most common in primate species with high
risks of infanticide (Hrdy, 1979). In other words,
concealed ovulation is not always associated with high
levels of paternal investment but high levels of paternal
investment are typically associated with concealed
ovulation. One possibility is that reduced infanticide
risk -- that is, mating with many males and thus confusing
paternity -- was the initial selection pressure for
concealed ovulation in hominids (see Hrdy, 1979), although
men do not appear to be biologically biased toward
infanticide (Daly & Wilson, 1988). Concealed and later
synchronized ovulation (which prevents males from mating
with more than one fertile female at a time) appear to be
a further evolved strategy in some primate species, a
strategy to reduce the mating opportunities of males and
thereby reduce the opportunity cost of paternal investment
(Dunbar, 1995). Although conceal ovulation will increase
the amount of affiliation between males and females, it is
not sufficient to ensure paternal investment, especially
in multi-male, multi-female communities where alternative
mating opportunities are possible.
As noted earlier, once physical signs of pregnancy were
evident, males could abandon females and pursue other
mates, if an additional mechanism was not operating. It
appears that this mechanism is pair bonding (Lovejoy,
1981; MacDonald, 1992; Miller & Fishkin, 1997). In this
view, concealed ovulation increased the amount of
male-female affiliation time and resulted in prolonged
sexual activity, which, in turn, reduced the mating
opportunities of males and, at the same time, provided the
initial conditions for the evolution of pair bonding
(MacDonald, 1992). In addition to reducing the risk of
male abandonment during pregnancy, pair bonding would
facilitate the type of spousal relationship that appears
to facilitate paternal investment. Pair bonding would
also increase the sexual fidelity of females and thereby
increase paternity certainty, which, in turn, would result
in reproductive benefits for those males who invested in
offspring. Once male investment resulted in reproductive
benefits, such as reduced offspring mortality rates and
increased social competitiveness, the stage was set for
the further evolution of paternal investment.
On the other hand, if the benefits of hominid paternal
investment were similar to those found in extant
preindustrial and developing societies and in Western
nations prior to the demographic shift, than lower levels
of paternal than maternal investment would be expected
(and are found). If paternal investment yields
reproductive benefits but is not obligate -- and it does
not appear to be in humans -- then a focus on mating
effort, paternal effort, or some combination are viable
reproductive strategies for men. When both mating effort
and parental effort are viable options, considerable
variability in men's reproductive strategies would be
expected (and are found). Moreover, because paternal
investment does not appear to be obligate, it is in the
best interest of some women to attempt the cockoldry of
their social partners. Cockoldry risks, in turn, reduce
the level of paternity certainty and through this militate
against paternal investment. All of these factors lead to
the prediction of greater levels of maternal than paternal
investment and continued conflict between men and women
over this investment (Buss, 1994).
David C. Geary, Ph.D. Department of Psychology 210
McAlester Hall University of Missouri Columbia, MO
65211-2500