The Effects of Residential
Locality on Parental and
Alloparental Investment among
the Aka Foragers of the Central
African Republic
Courtney L. Meehan
Washington State University
In this paper I examine the intracultural variability of parental and alloparental
caregiving among the Aka foragers of the Central African Republic. It has been
suggested that maternal kin offer higher frequencies of allocare than paternal kin
and that maternal investment in infants will decrease when alloparental assistance
is provided. Behavioral observations were conducted on 15 eight- to twelve-monthold infants. The practice of brideservice and the flexibility of Aka residence patterns offered a means to test the effect of maternal residence on parental and
alloparental investment. There was significant variation in the frequency of investment and who supplied care to infants depending on whether mothers resided with
their kin or their husbands' kin. However, in spite of the variation in allocare, when
all categories of caregivers were examined collectively, infants received similar
overall levels of care.
KEY WORDS:Aka foragers; Alloparenting; Hunter-Gatherers; Infant care; Parental
investment
ver the past several years there have been considerable and exciting additions to the theories of infant and child development. Although research
has traditionally focused on the mother as the central component of successful
infant development and secure attachments (Bowlby 1969), recent work particularly among forager groups (Blurton Jones 1993; Hewlett 1989; Ivey 1993,
2000; Tronick, Morelli, and Winn 1987) has led to a reexamination of this
O
Received March 2, 2004; accepted June 4, 2004; final version received August 2, 2004.
Address all correspondence to Courtney L. Meehan, Department of Anthropology, Washington State
University, Pullman, WA 99164-4910. E-mail: meehan@mail.wsu.edu
Human Nature, Spring 2005, Vol. 16, No. 1, pp. 5 8 - 8 0 .
1045-6767/98/$6.00
= .15
Effects of Residential Locality on Parental and AUoparental Investment
59
tenet and has given credence to the possibility that alloparenting is
underrepresented in our attempts to understand infant care (Hrdy 2005).
Alloparents are individuals other than the biological parents who invest in
children. They have been shown to increase maternal reproductive success
(Bereczkei and Dunbar 2002; Sear et al. 2003) and aid in infant survivorship
(Hawkes et al. 1997; Ivey 2000). Studies have shown that humans are cooperative childrearers and that successful rearing of offspring may be dependent
on alloparental assistance (Hrdy 2005; Ivey 2000).
In light of the extensive nature of food sharing, not to mention basic childcare
offered by alloparents to infants, humans are considered cooperative breeders.
As Hrdy (2005) notes, the unifying characteristic of cooperative breeding systems is that alloparental assistance is essential for the successful rearing of
offspring. Among cooperative breeding species, alloparents should alter the
tradeoff between quality and quantity through their assistance. Maternal reproductive success should be increased through the supplemental assistance
of alloparents, even when mothers reduce interbirth intervals or their overall
level of investment (Hrdy 1999, 2005). Among non-human species, alloparents
allow mothers to breed again sooner without risking the survival of their current offspring (Emlen 1992a, 1992b; Solomon and French 1997; Stacey and
Koenig 1990). Maternal cost/benefit tradeoffs between future and current reproduction and quality versus quantity of offspring are thereby offset and the
costs lowered by alloparental assistance. Both mothers and alloparents should
select particular investment strategies that increase their fitness. The costs and
benefits of particular behavioral strategies are considered against the background of the social and physical environment and alternative strategies (Williams 1966). Alloparents in many species behave in a way that results in these
maternal benefits, but Hrdy (2005) notes that lengthy human lifespans have
made it difficult for many researchers to examine the overall impact that
alloparents have on maternal reproductive success. However, several studies
among humans illustrate that alloparents can lower maternal costs and increase
maternal reproductive success (Flinn 1989; Kramer 2002; Sear et al. 2003;
Turke 1988).
Although the benefits of alloparental assistance on maternal fitness are clear,
Ivey (2000) notes that among the Efe the motivations for alloparents to cooperate in childrearing systems are often difficult to tease apart. Several hypotheses, stemming from a life history perspective, have been tested among
populations as a means of examining the socioecological conditions that may
foster alloparental caregiving. First, alloparents gain inclusive fitness benefits
from investing in infants. The most common form of alloparenting is from
genetically related individuals (Hrdy 1976, 1999; Ivey 1993, 2000; Weisner
and Gallimore 1977). The higher the degree of shared genetic relatedness, the
more investment one would predict. Nepotistic alloparental investment can
increase the caregivers' fitness through the survivorship and success of related
60
Human Nature / Spring 2005
infants. Second, reciprocity has been hypothesized as a means by which
alloparents may receive immediate or delayed benefits for their contributions.
Alloparents can receive reciprocal investment in their own children or a variety of other benefits that may enhance their fitness (Elmen 1994; Ivey 2000;
Strassman and Clarke 1998). For example, Elmen (1982a, 1982b) noted that
unrelated helpers benefit from aiding the reproductive success of another if
the environment is marginal and resources for reproduction are unpredictable.
HYPOTHESES
This study examines parental and alloparental caregiving among the Aka
foragers in light of the cooperative breeding hypothesis. The following hypotheses address the socioecological conditions that affect maternal and
alloparental investment strategies. Variation in residence patterns is used to
examine intracultural variability in caregiving practices.
Hypothesis la. Significant differences exist in the type (high- and lowinvestment care) and frequency of allocare offered depending on whether
families reside matrilocally or patrilocally. Alloparents will offer higher frequencies of assistance when the potential fitness benefits are greatest. Owing
to paternal uncertainty, a father's kin may perceive fitness benefits as potentially lower than a mother's kin would and therefore reduce investment. Paternal certainty is considered a probable indicator of paternal investment in humans
(Gaulin and Schegel 1980). In recent years, researchers expanded this idea to
examine whether paternal certainty affects alloparental investment. A mother's
kin tend to have higher certainty of genetic relatedness. Studies by Gaulin et
al. (1997) and McBurney et al. (2002) have both shown a matrilateral bias in
investment. Therefore, it is hypothesized that Aka infants who reside with their
maternal kin will receive more alloparenting from all females than infants who
reside with their paternal kin. Infants residing with their maternal kin will also
benefit from greater allocaregiving owing to the long-standing reciprocal relationships that their mothers developed with other camp members.
Hypothesis lb. Grandmother's investment will be higher among maternal
grandmothers than among paternal grandmothers. Several recent studies suggest that paternal uncertainty plays a role in determining grandparental investment. Euler and Weitzel (1996) surveyed adults regarding grandparental
solicitude during their childhood. Their results indicated that maternal grandmothers offered the most care followed in order by maternal grandfathers,
paternal grandmothers, and finally paternal grandfathers. Most notably, the
results indicated that residential distance, grandparental age, or availability of
other grandparents did not influence grandparental care. Research in rural and
urban Greece and Germany (Pashos 2000) has shown a paternal grandparent
bias among rural Greeks and a maternal grandparent bias among urban Greeks.
Pashos suggests that the social environment largely determines grandparental
Effects of Residential Locality on Parental and Alloparental Investment
61
caregiving. Traditional rural Greek culture, with strong patrilineal ties, encourages a patrilineal bias in caregiving. He suggests that the maternal bias in
urban populations could be related to the emergence of Western cultural norms
in which females are more connected with their relatives than males. Although
Pashos notes that paternal certainty is likely higher in patrilineal traditions, he
states that paternal certainty does not in and of itself explain the paternal bias.
However, McBurney et al. (2002) notes that in Pashos' study the paternal bias in
caregiving is focused toward grandsons, which may simply be an extension of the
patriarchal norms, and that the patriarchal system is likely overriding the matrilateral bias. Evidence also shows that maternal grandmothers invest more in their
daughters' offspring than in their sons' offspring (Blurton Jones et al. 2005; Hawkes
et al. 1997). Hawkes et al. (2000) suggest that while grandmaternal assistance
directed toward a son's offspring could aid their own fitness, assistance directed
toward daughters' offspring yields clearer benefits owing to genetic certainty.
Hypothesis 2. Maternal caregiving will negatively correlate with alloparental
caregiving. Given the assumption that alloparents enhance maternal reproductive success, mothers should redirect investment from current to future offspring if alloparental care is high and of good quality (McKenna 1987).
THE AKAFORAGERS
The Aka are an interesting case study for several reasons. First, they exhibit
high levels of alloparental caregiving (Hewlett 1989, 1991b). In addition, residence patterns vary throughout a woman's reproductive career, affecting her
access to maternal kin. Therefore, residence patterns can be used as a means
of examining intracultural variability in alloparental caregiving.
The Aka are tropical forest foragers and are primarily net hunters. The individuals represented in this study are associated with the Bangandou village of
the Central African Republic. Aka live in camps of 25-35 individuals and
often move camp several times a year. They live in association with the Ngandu,
spending part of the year near the village to assist the Ngandu farmers. The
Aka stress gender and intergenerational equality and have a minimal political
hierarchy with few status positions (Bahuchet 1985; Hewlett 1991).
Infertility is an infrequent problem among the Aka. The total fertility rate for
postmenopausal women is approximately 5.5 (Hewlett 1991a). This rate is
between those of other hunter-gatherer groups, such as the !Kung at 4.69
(Howell 1979) and the Ache at 8.03 (Hill and Hurtando 1996). The interval
birth interval for Aka women averages 42 months, which again falls between
those of other hunter-gatherer groups, such as the !Kung at 49.4 months (Howell
1979), the Yanomamo at 34.4 (Melancon 1982), and the Ache at 37.6 months
(Hill and Hurtado 1996).
Aka infants are raised in an intimate environment. Camps are built in a
circle with all entrances to the huts facing the center of the camp. The huts
62
Human Nature / Spring 2005
have no doors and their small size limits the types of activities that can occur
inside. Huts are only big enough to hold a four-foot-long bed and a fire and
are usually placed within 1-2 feet of each other (Hewlett 2000a). Camp members perform most activities outside in view of other residents. Infants are
therefore raised in a social unit that includes all members of a camp.
Infants are held throughout most of the day and sleep in the same bed with
their parents at night. Owing to the intensive daytime holding pattern and the
size of the hut and bed, parents and caregivers provide almost constant skinto-skin contact for infants (Hewlett 1991a, 2000b). During the day, infants are
generally held in a caregiver's lap or in a sling that rests on the mother's or
alloparent's side. Infants are therefore able to see their caregivers and receive
more continuous care than they would with other methods of holding. This
high degree of physical contact also allows infants to breastfeed on demand.
Nursing occurs several times an hour in short bouts. The level of physical
contact also results in attention quickly being offered to fussing or crying infants (Hewlett 2000b). Mothers and allomothers quickly react with soothing,
feeding, or nursing.
The intimacy Aka infants have with juvenile and adult caretakers is unmatched in Western society and contributes to the high levels of alloparenting
found in Aka society (Hewlett 1991a). The stable social units in which Aka
children are raised allow the same individuals to interact with the children
throughout their young lives. This environment creates an atmosphere in which
alloparents have daily interactions with infants and observation of their cues.
The Aka practice of brideservice allows for young women and often firsttime mothers to remain in their natal community during the period in which a
mother and infant might require the most assistance. The period of brideservice
usually lasts for a few years, approximately until the first child can walk (Hewlett
1991a; Shannon 1996). However, this period is quite flexible, and couples
often move back and forth between camps during and after the traditional
period of brideservice.
Several circumstances can occur to disrupt the traditional period of
brideservice. Men often need to leave their wife's camp and return to their
natal community during the first several years of marriage for a variety of
reasons, including desire to visit family members or a request from the husband's
family for him to return. When this occurs, the wife's family often requests that
their son-in-law return at a later date to finish his service. I asked many Aka
men why they were conducting brideservice past the traditional time period,
and while responses varied, many men laughed and sarcastically said,
"Brideservice is never over."
Women often will return to their natal community because they want to be
closer to their family. One woman I spoke with said that she woke up one
morning and told her husband that she wanted to live with her family for a
while and left. She told me she knew her husband liked her and would follow,
Effects of Residential Locality on Parental and Alloparental Investment
63
because he did not want to be away from her. He arrived in her parents' camp
a few days later. Of the fifteen families represented in this study, three families
resided matrilocally and two families resided patrilocally during the traditional
period of brideservice. Of the families in which the men had finished
brideservice or were continuing it past the traditional period, four resided
matrilocally and six resided patrilocally.
METHODS
The foIlowing study is based on ten months of research, which was conducted over three field seasons from 2000 to 2002. Behavioral observations
were conducted on 15 eight- to twelve-month-old infants (Table 1). Quantitative data were collected using a focal child sampling technique (Altmann 1974).
This involved observing the focal child and recording specific behaviors and
interactions. Observations were cued using a tape recorder and earphone, and
recorded on handheld data sheets. Infants' behaviors and the behaviors that
caregivers directed toward them were observed every 20 seconds. Each 20second interval concluded with a 10-second interval to record the observed
behaviors. These behaviors were recorded on-the-mark as instructed by the
tape recorder. Observations were conducted over a 12-hour daylight period (6:00
AM - 6:00 PM). Every 45 minutes of observation was followed by a 15-minute
break. Observation periods were divided into four 3-hour sessions, and infants
were observed over several days to enable the observation of multiple activities.
The combined observation period for all of the focal infants totaled 135 hours.
All of the infants were observed for 9 hours, which yields 1,080 intervals per
infant or 16,200 total intervals for all 15 infants. The behavioral observations
recorded infant visual orientation, infant state, caregivers' response to infants'
distress, infant behaviors, and caregiver behavior directed toward infant.
The Aka do not have birth records, nor do they keep of track of age. The
age of the infants was determined by season of birth, dentition, and relative
aging of other infants in camp or from nearby camps. Since the target infants
were all less than a year old, the season of birth quickly determined if they
were below the minimum of eight months or above the maximum of one year.
Dentition varied far more than originally expected; however, infants' ages were
verified through relative dating using the infants' birth orders.
The data presented in this paper represent all infant and caregiver activities
observed during daylight hours. Therefore, the data set offers a full picture of
infant and caregiver behavior in various settings. Infants were observed with
their caregivers in their camp, in the forest, on net hunts, and in the village.
Mothers and other caregivers continued their daily routines during the observation periods.
Qualitative data were also collected on the focal infants' mothers. I used
semi-structured interviews to elicit information on maternal preferences for
locality and their perceptions of alloparental assistance.
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Effects of Residential Locality on Parental and AIIoparental Investment
65
Coding Caregivers
Caregivers were coded by sex and age categories. The six categories were
juvenile, adult, and elderly males and females. Individuals who were under
the age of 18 were coded as juvenile males and females. Because the Aka do
not keep track of their age, the marital status of young men and women was
used to approximate age. Therefore, most individuals who were not married
and had no children were coded as juveniles. The adult category was used if a
male or female was married or had children. The few adults who were unmarried or did not have any children were coded based on obvious age cues.
Almost every adult female in both matrilocal and patrilocal camps had dependent children. Menopause and grandparental status determined the elderly category. Siblings were also coded by their age and sex but were analyzed
separately unless otherwise noted. Additionally, caregivers were given identification codes, and relationships between caregivers and the focal infants were
coded. Relationships were determined through detailed demographic information collected prior to the commencement of the behavioral observations or
through subsequent interviews if the caregiver was a visitor. This recording
system also enabled the coding of simultaneous interactions with an infant by
individuals in the same age and sex category to be recorded.
High- and Low-Investment Caregiving
Researchers have examined infant caregiving behaviors in terms of direct
and indirect care. Direct caregiving behaviors encompass activities such as
holding and feeding, while indirect caregiving behaviors are those that relate
to foraging for food or territory defense (Kleiman and Malcolm 1981; Marlowe
1999, 2005). The methodology of this study precluded recording of data on
indirect care; therefore, the focus will be on direct caregiving. Since the category of direct care includes all behaviors that require close proximity to infants, I divided it into two distinct categories to distinguish between
high-investment and low-investment caregiving. High-investment caregiving
behaviors require intimate contact or direct attention to the infant. The behaviors included in high-investment caregiving are holding; soothing; medical,
hygienic, and general caregiving; feeding; nursing; stimulating the infant; playing with the infant; and affectionate behaviors directed toward the infant. While
soothing does not always require intimate contact with the infant, this behavior is purposefully directed toward the infant and often interrupts the caregiver's
other activities. Low-investment behaviors are classified as those that result in
minimal energy expenditure. Behaviors included in the low-investment category are watching or checking on the infant, vocalizing to the infant, touching, and proximity to the infant. Low-investment behaviors are those in which
caregivers can continue other tasks with ease. Touching was coded as low-
66
Human Nature / Spring 2005
investment care in order to avoid overestimating the frequencies of highinvestment caregiving. Touching could at times be included as intimate contact and often was purposefully directed toward the infant. However, because
the Aka sit in close proximity to each other, it was difficult to establish intentionality for every instance of the behavior. Another example of low-investment care is
proximity. Proximity does not necessarily require any investment; it is defined
here as being a forearm's distance from the focal infant. Nevertheless, caretakers
within proximity would be more likely to offer allocare and high-investment
caregiving when needed. Each caregiving behavior is independent of other
behaviors. For example, a caregiver holding an infant (which includes touching) would only be coded as holding. On occasion, single behaviors, such as
holding, will be discussed for comparative purposes, but these individual variables to do not show a complete picture regarding the depth of care offered.
RESULTS
Variability in Demographic Features across Residence Patterns
Most Aka families eventually take up permanent residence in the husband's
camp. The likelihood of patrilocality increases with age and the number of
children the couple has together. Each of the four couples with four children in
this sample was residing patrilocally. Table 2 shows a comparison of demographic variables by residence pattern. Thirteen camps are represented in this
study. Camp size was consistent in most of the focal infant camps, and there
are no significant differences in camp sizes between matrilocal and patrilocal
settings. The mean number of individuals in a camp was 25.6 people. The
minimum number of individuals in a camp was 14 and the maximum was 35.
Camps along logging roads are much closer to one another than camps in
other settings, and camp sizes tend to be larger. However, for the families
represented here, no significant difference in camp size or the level of
alloparenting exists based on the setting of a camp in the forest, village, or
along a logging road.
No significant difference exists between the number of an infant's siblings
at the matrilocal and patrilocal camps (Table 2). The distribution of male and
female infants across the two camp settings is also equal (Fisher's exact test: r
= 0.1964, p = .405). Infants also have access to a similar number of potential
female caretakers in matrilocal (12.42) and patrilocal (10.25) camps. However, the average number of females in matrilocal camps who participated in
allocare (15.29) is significantly higher than in patrilocal camps (8.25).
Frequency of Behaviors
The remaining results in this paper are discussed in terms of the frequency
of behaviors rather than the amount of time caregivers spend assisting infants.
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68
Human Nature / Spring 2005
The frequencies of behaviors offer a picture of the depth of care offered to
infants. For example, if only the amount of time is examined, an infant who is
sitting on its mother's lap for a half an hour while the mother cooks dinner
would be shown as receiving equal caregiving as an infant who was being
held by one juvenile female, fed by another, and washed by a third during the
same period. Since an infant commonly interacts with multiple caregivers in
one interval, the frequencies reported in the following results represent multiple individuals and multiple independent caregiving behaviors within each
interval. Therefore, the frequencies are presented as the number of caregiving
behaviors directed to the infant and include multiple interactions within single
intervals.
Do Infants Receive More Allocare from Matrilineal Kin ?
The average frequency of caregiving behaviors by juvenile and adult female allocaregivers is higher in all caregiving categories in matrilocal as compared to patrilocal camps. Juvenile and adult females show significant or very
strong trends toward higher levels of matrilocal alloparenting for most individual caregiving behaviors as well. In matrilocal camps, juvenile and adult
females are more than twice as likely to be in close proximity to the infant
(Mann-Whitney U = 11.00, p = 0.054). The frequency of non-sibling, juvenile
and adult female holding is close to five times as great in matrilocal camps
(Mann-Whitney U = 8.5, p = 0.021). Infants living matrilocally receive 2.5
times more physical contact (holding and touching) from juvenile and adult
female allocaregivers (Mann-Whitney U = 10.00, p = 0.40). Most infants living patrilocally did not receive caregiving from adult females. Women living
in the infant's father's camp were not likely to touch (Fisher's exact test: r =
.7888, p < .01), or hold (Fisher's exact test: r = .6001, p < .05), focal infants.
When behavioral categories were examined collectively (high- and lowinvestment caregiving), the two localities demonstrate a significant difference
in the frequency of allocare. Infants living in matrilocal camps receive 3.4
times more high-investment caregiving from juvenile females (matrilocal mean
= 62.71, patrilocal m e a n = 18.62) and 6.4 times m o r e h i g h - i n v e s t m e n t
caregiving from adult females (matrilocal mean = 28.86, patrilocal mean =
4.50). In Table 3, the average frequencies of caregiving behaviors of juvenile
and adult females are presented in terms of high- and low-investment care and
are then combined to show an overall trend of total care given to infants.
When juvenile and adult female alloparents are analyzed together, high- and
low-investment and total caregiving are significantly different between the
two samples (Table 3).
Given the practice of brideservice and the assumption that first-time mothers reside with their kin, one might assume that infants whose families are
residing matrilocally receive more care because of heightened risk factors as-
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70
Human Nature I Spring 2005
sociated with first-time mothers (Hrdy 1976). However, this sample does not
show a bias toward matrilocality for primiparous mothers (Fisher's exact test:
r = .189, p = .4266). In both residential patterns adult females showed higher
frequencies of high-investment caregiving, but it was not significant at the .05
level.
Comparison of All Non-Sibling Female Alloparents
Table 3 also examines the differences in investment by non-sibling female
(juvenile, adult, and elderly) alloparents based on residence pattern. The overall frequency of high-investment, low-investment, and total care offered to
Aka infants is higher in matrilocal camps. However, female high-investment
care is not significantly different by camp setting--but this includes the investment by an unusually high investing paternal grandmother (which will be discussed in more detail below). Her caregiving was the highest of all non-maternal
caregivers and was quite unusual. If she is removed from this sample,
matrilocally residing infants receive significantly more care from non-sibling
matrilocal females (Mann-Whitney U = 7.00; p = .026). Even with this grandmother included, infants received significantly more low-investment caregiving
and significantly more total (high- and low-investment) caregiving when the
family is residing matrilocally.
Sibling Investment
The frequency of Aka sibling care is not significantly different based on
whether the family is residing matrilocally or patrilocally (Table 3). As shown
above, patrilocal families have on average more offspring, although the difference is not statistically significant. In both residence patterns, Aka siblings
participate in allocare, but they participate less than other female caregivers
combined. The lack of significance is expected. Sibling caregivers regardless
of camp locality have strong relationships with their mothers and siblings. In
addition, forager siblings tend to invest less overall than do siblings in farming
societies (Hewlett 1991b).
Paternal Investment
Aka fathers are known throughout the hunter-gatherer and parental investment literature for their high levels of investment (Hewlett 1991a). However,
when paternal investment is examined by residential pattern (Table 3), they
show a trend of engaging in high-investment caregiving more in their own
camps than when residing with their wife's family (Table 3). Aka fathers in
their natal groups also show a trend, albeit not significant, toward holding their
infants more than fathers living in their wife's camp. When residing in their
natal camps, fathers hold their infants 6.1% of its total holding time, compared
Effects of Residential Locality on Parental and Alloparental Investment
71
with 1.0% of the total holding time when the fathers are living in their wife's
camp. The overall averages of paternal holding are lower than Hewlett's data
of 8.7% because three fathers, two in the patrilocal category and one in the
matrilocal category, left on trips during the observation period. This probably
explains the lowered overall level of paternal investment recorded. However,
there is variation between camp settings. Aka fathers seem to be offering less
paternal investment when they reside in their wife's camp. The frequency of
high-investment, low-investment, and total care offered by fathers is significantly lower in matrilocal settings.
Female Preference for Locality
Each of the focal infants' mothers was asked to discuss the level of assistance that she received at her current location. Assistance was categorized as
sharing (food, water, or other items) and childcare assistance. Women were
also asked to discuss who their friends were and what qualities of a friend were
important. It was originally hypothesized that women living matrilocally would
report greater assistance both from kin and non-kin in their communities. The
high certainty of genetic relatedness to the infant combined with long-term
relationships between the mother and potential caregivers would lead to a reduction in the cost of allocate on the part of the caregiver.
All but two of the fifteen mothers said they would rather live in their parents' camp when they had a child because they stated they receive higher
levels of assistance. The assistance was always attributed to the mother's parents and siblings. Women (n -- 5) whose mothers were deceased stated that
they would rather live at home because of paternal and sibling assistance.
One of the women who said it did not matter where she resided had been
living in her husband's camp for a long time. She had three other children
besides the focal infant, plus children from a previous marriage. Thus she
was an experienced mother and caregiver. The other woman who stated
that residence did not concern her was interviewed in front of individuals
from her husband's family. This was their first child, and while her comments to other questions were forthright, she became quite distant and
quiet during this part of the interview. It is possible she felt uncomfortable
stating that the assistance she received from other women was not equal to
what she might get at home. However, many other women answered this question openly in front of their husband's kin, and no one seemed to take offense
at the answer. Other women sitting close by would often add their opinions as
well.
Subjective reports from the interviews supported the findings from the behavioral observations. Women defined friends as individuals who gave things
or shared food and other items with them. Women in both camp settings stated
that jealousy was a constant strain on friendships. Friendships were accompa-
72
Human Nature I Spring 2005
nied by considerable gossiping, which caused problems with the other women
in camp. Not surprisingly, women in their husband's camps, where female kin
did not surround them, felt that they did not have as many friends as they did
when they resided in their own parents' camp. In both settings, women claimed
difficulty in establishing non-kin friendships. Even women living matrilocally
usually listed their sisters, cousins, or other female relatives as those individuals with whom they had a friendship. However, when questioned regarding
non-sibling friends, women living in their natal communities could mention at
least one woman.
The number of friends listed depended on age. Of the five youngest mothers--those who had only one child--three lived in their own family's camp
and two lived in their husbands'. All three of the matrilocally residing mothers
named between two and five friends. One of the mothers living in her husband's
camp named four friends and the other named none. The former woman did
not live close to her parents' camp; she had known all of the women she listed
as friends from her youth, and they lived in surrounding camps. Women explained that as they got older it was more difficult to keep friendships. In cases
regarding older women and/or those living with their husbands' families, the
friends they mentioned were individuals from their past who lived in their
natal community. Those women who did have female friends (n = 8) stated
that friends were good to have because you could leave your infant with them
(if the father was not present) when you went to collect water or firewood. Aka
mothers rarely leave an infant with either kin or non-kin for an extended period of time, but neither of those tasks requires a lengthy investment by the
alloparent.
Do Maternal Grandmothers Invest More Than Paternal Grandmothers?
The importance of grandmaternal investment has been used to explain long
postmenopausal lifespans, as well as impacts on maternal fertility and infant
survivorship (Hawkes 1997). In particular, maternal grandmothers offer the
most support, although patrilocal residence patterns would minimize the assistance that maternal grandmothers could offer. Hawkes et al. (2000) suggest
that variation in residence patterns is substantial, and among non-equestrian,
non-fishing-dependent hunters, matrilocal residence patterns are not uncommon. Marlowe (2005) notes that among the Hadza, 68% of couples with living
mothers reside in the camp with the wife's mother. This variation could help
explain periods of matrilocality, such as among the Aka, whereby women can
receive the support of their mothers when they most need it. Evidence shows
that grandmothers direct assistance to the daughters that require the most aid
(Blurton Jones et al. 2005, Hawkes et al. 1997).
The sample size in this study limited the analysis on elderly female participation in infant care. Nevertheless, the following analysis seeks to examine
Effects of Residential Locality on Parental and Alloparental Investment
73
grandmaternal caregiving. Some of the infants lacked grandmothers (n = 8) or
other elderly females in camp. Eleven of the fifteen Aka infants had an elderly
female present in camp. Of the eleven elderly females, seven were actual grandmothers. Three of the seven were maternal grandmothers and four were paternal grandmothers. The following analysis will focus only on grandmothers
because elderly female participation in caregiving was rare if they were not the
actual grandmother.
Aka infants received similar care from grandmothers in both residential patterns. No significant difference existed between elderly female high- and lowinvestment or total care. Interestingly, the highest investing grandmother was
a paternal grandmother. Her high-investment caregiving frequencies were more
than double those of the next highest investing grandmother, who was a maternal grandmother. However, there were several unique factors surrounding this grandmother and infant. First, the infant fussed and cried frequently.
Much of the grandmother's caregiving behavior was directed toward soothing the infant or actively trying to keep the infant from starting to cry. The
infant's fussing and crying frequency (140.0) was more than double the
sample average (52.73). Second, this was her daughter-in-law's first child
and she was living with her husband's family, which is unusual. In addition, the mother was most likely the youngest mother in the sample. She
had less experience with caregiving than other women, who often have
one or two children before they permanently reside in their husband's family
camp. Primiparous mothers have been associated with increased risk factors for child mortality (Hrdy 1976). I noted several occurrences of this
grandmother offering to help her daughter-in-law after she had been unsuccessful at soothing the infant. The infant's distress was not related to any
visible illness. She was a healthy, plump infant, but very aggressive. She would
often push or thrash at her caregiver. This paternal grandmother was undoubtedly a high-investing grandmother, often taking some of the responsibility
away from her new daughter-in-law, who obviously needed help with a very
fussy infant.
All three of the infants who resided in the same camp as their maternal
grandmother received high-investment care from them; however, only two of
the four infants residing with their paternal grandmother received any highinvestment care from their grandmothers. The three maternal grandmothers
directed 63, 133, and 151 high-investment behaviors toward their grandchild
over the observation period. Of the four paternal grandmothers, two offered
no high-investment care, one directed 28 high-investment behaviors toward
their grandchild, and the final paternal grandmother offered 360 high-investment behaviors. Given the obvious problems with such a small sample of
grandmothers, and the tremendous difference between the paternal grandmother
discussed above and the other paternal grandmothers, further research will be
needed to address this question.
74
Human Nature / Spring 2005
Do Mothers Reduce Investment in Infants When Allomothers Are Available
or When the Frequency of Alloparenting Is High?
While significant differences in allocare are prevalent among female
alloparents and fathers, no significant difference exists in maternal caregiving.
Mothers on average offer lower frequencies of caregiving in matriiocal camps,
but statistically it is not different from average investment in patrilocal camps.
Maternal high-investment care, low-investment care, and the total frequency
of maternal caregiving did not differ significantly based on residence pattern.
According to the second hypothesis, which suggested that maternal investment would be negatively correlated with alloparental investment, alloparenting
should reduce the overall time that mothers must spend caregiving. Among nonhuman primates, maternal kin most frequently provide alloparenting (Hrdy 1981),
and mothers that receive allocare for their infants are able to spend more time
away from their infants (Fairbanks 1990). The methodology in this paper (focal
infant follows) precludes any analysis regarding maternal behavior while they
are not visible or engaged in childcare, but the assumption is that high levels
of positive allocate will enable the mother to pursue other economic activities.
In order to examine this hypothesis, sibling care, the number of participating
females, alloparental investment, and total care by all individuals were examined
for correlations with maternal behavior. No significant correlations exist between
any of these variables and maternal investment in either camp setting. However,
mothers residing in their natal camps show trends of reducing low-investment
behaviors (Pearson r = -0.706, p = .077) and overall investment (Pearson r =
-0.730, p = .062) when high levels of direct female alloparental care are given
to the infant. This trend is not apparent in patrilocal settings.
Do Infants Residing Matrilocally Receive Higher Frequencies of High- and
Low-Investment Caregiving ?
The total frequencies of caregiving that infants receive from mothers, fathers, and all other caregivers in matrilocal and patrilocal camps are remarkably similar considering the variability found in the age/sex categories. Table
4 illustrates the total frequency of Aka caregiving, including maternal caregiving
the infants received, dependent on residence pattern. Although male alloparents
were not analyzed separately, because of their overall low level of investment,
Table 4 includes them in order to examine the total amount of care infants
received. High-investment caregiving and total allocare offered are not significantly different in matrilocal and patrilocal camps. Low-investment
caregiving shows a trend, albeit not significant, for higher frequencies in matrilocal settings (Mann-Whitney U = 10.29, p = .072). However, it should be noted
again that low-investment caregiving is less costly to the alloparent, and most
of the difference is due to proximity.
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76
Human Nature / Spring 2005
DISCUSSION
The analyses show significant differences in alloparental care among the
Aka, indicating a matrilateral bias. Hypothesis l a suggested that infants would
receive greater frequency of high-investment allocare if they resided in their
mother's camp. Infants residing matrilocally have significantly more alloparents
and receive higher frequencies of caregiving behaviors from maternal kin.
The interview data also supported this hypothesis that when long-standing
reciprocal relationships between a mother and camp members are present,
female allocare will be higher in frequency. Since first-born infants do not
receive significantly more care from female alloparents in either matrilocal or
patrilocal camps, the hypothesis of parity influencing alloparental investment
is not supported. Therefore, the question needs to be examined not in terms of
maternal inexperience (i.e., infant need) but through the mother/alloparent relationship and the infant/alloparent relationship.
For Aka infants residing matrilocally, paternal investment is minimal but
female alloparental investment is remarkably high. For Aka infants residing
patrilocally, paternal investment is high but female alloparental investment is
quite low. Three avenues of explanation are possible. First, fathers are relieved
from childcare responsibilities in matrilocal camps because of the willingness
of female alloparents to offer assistance. Second, female alloparents offer higher
frequencies of care to infants residing matrilocally owing to high certainty of
genetic relatedness. Third, female alloparents offer higher frequencies of
ailoparental care in matrilocal camps because they detect a deficiency in paternal investment. Fathers living in their spouse's camp are often doing brideservice.
Young husbands are hard to find during the day, as they leave early and come
home late in order to avoid being asked to work by the wife's family (Hewlett,
personal communication 2003). This may be one factor that contributes to
their lower level of investment. Mothers living in their own camps also have
multiple female kin with whom they conduct subsistence activities. An absent
husband would not likely decrease their overall foraging success, especially in
regards to female kin's foraged food items. Hewlett (1991b) suggests that the
lower levels of paternal involvement may be due to the availability of other
adult females to assist with childcare. It is possible that the same pattern of
willing female caretakers in matrilocal camps is allowing lower levels of paternal investment than are found among fathers in patrilocal camps. However,
this last possible avenue of explanation does not explain the lack or low level
of investment by female alloparents residing in patrilocal camps. It seems more
reasonable to consider paternal certainty as an influencing factor for nongrandparental female allocare.
Hypothesis lb suggests that maternal grandmothers invest more than paternal grandmothers. This hypothesis was not supported. Grandmothers' investment seemed to be equal across residential patterns. However, as mentioned
Effects of Residential Locality on Parental and Alloparental Investment
77
above, the high-investing paternal grandmother was quite unusual and her
circumstances were not common owing to the Aka practice of brideservice.
Further research with a larger sample of grandmothers will be needed to examine this issue.
Hypothesis 2, suggesting that maternal caregiving should be lower when
high levels of alloparenting are given to infants, was also not supported. Maternal behavior across residence patterns was consistent with overall averages
of maternal investment, and the variation that exists is predictable. This study
did not statistically demonstrate a direct correlation between high frequencies
of alloparental behavior and a reduction in maternal frequencies of caregiving.
However, maternal behavior in matrilocal camps shows a trend of reducing
low-investment and total care levels when the infant received more highinvestment female alloparenting. If alloparents are aiding maternal reproductive success through other means by allowing them to shift strategies, these
avenues need to be explored. The methodology of the study (focal infant follows) did not allow reliable data on maternal workload and foraging success.
Future research should examine whether alloparents increase maternal reproductive success and decrease interbirth intervals.
While the data show that alloparental assistance is higher from maternal kin,
it also shows that infants have numerous avenues for receiving care. The similar overall averages of caregiving by mothers, fathers, siblings, and all
alloparents in matrilocal and patrilocal camps suggest that alloparents' investment strategies take into account multiple socioecological factors, including
the relationship to the mother and paternal certainty. Parental, sibling, and
alloparental care equalized caregiving frequencies and, in the end, showed
levels that were standard and culturally acceptable.
In both camp settings mothers repeatedly stated that they would prefer to
live with their kin when they have a young child. This preference might illustrate that while the overall levels of caregiving are equal, having multiple
caregivers may be beneficial to the mother and infant. In matrilocal camps,
mothers have multiple options for additional caregivers; thus they are more
likely to have an available alloparent at any given moment. Ivey (2000:864)
notes that the number of alloparents available to an infant is positively correlated with infant survivorship. While individual caregivers certainly have high
levels of investment, the availability of multiple caregivers can insure that an
infant always has access to investment. Close association with maternal kin is
likely to be helpful to the mother and infant, but future research may determine the exact effect on Aka maternal reproductive success and infant survivorship.
I am indebted to the Aka families who allowed me to live and work with them. I would also
like to thank the government of the Central African Republic for authorizing my research.
I offer my thanks to Barry S. Hewlett for his advice and assistance and to Hillary Fouts, who
helped me in the early stages of this research project.
78
Human Nature [ Spring 2005
Courtney L. Meehan is a Ph.D. student in cultural anthropology at Washington State University. Her research interests include parenting, alloparenting, female social networks, and
female-female cooperation and competition.
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