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In species in which males care for young, testosterone (T) is often high during mating periods but then declines to allow for caregiving of resulting offspring. This model may apply to human males, but past human studies of T and fatherhood have been cross-sectional, making it unclear whether fatherhood suppresses T or if men with lower T are more likely to become fathers. Here, we use a large representative study in the Philippines (n = 624) to show that among single nonfathers at baseline (2005) (21.5 ± 0.3 y), men with high waking T were more likely to become partnered fathers by the time of follow-up 4.5 y later (P < 0.05). Men who became partnered fathers then experienced large declines in waking (median: -26%) and evening (median: -34%) T, which were significantly greater than declines in single nonfathers (P < 0.001). Consistent with the hypothesis that child interaction suppresses T, fathers reporting 3 h or more of daily childcare had lower T at follow-up compared with fathers not involved in care (P < 0.05). Using longitudinal data, these findings show that T and reproductive strategy have bidirectional relationships in human males, with high T predicting subsequent mating success but then declining rapidly after men become fathers. Our findings suggest that T mediates tradeoffs between mating and parenting in humans, as seen in other species in which fathers care for young. They also highlight one likely explanation for previously observed health disparities between partnered fathers and single men.
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Longitudinal evidence that fatherhood decreases
testosterone in human males
Lee T. Gettler
, Thomas W. McDade
, Alan B. Feranil
, and Christopher W. Kuzawa
Department of Anthropology, and
Cells to Society, Center on Social Disparities and Health, Institute for Policy Research, Northwestern University, Evanston,
IL 60208; and
Ofce of Population Studies Foundation, University of San Carlos, Cebu City 6000, Philippines
Edited by A. E. Storey, Department of Psychology, Memorial University of Newfoundland, St. Johns, NF, Canada, and accepted by the Editorial Board July 28,
2011 (received for review May 10, 2011)
In species in which males care for young, testosterone (T) is often
high during mating periods but then declines to allow for
caregiving of resulting offspring. This model may apply to human
males, but past human studies of T and fatherhood have been
cross-sectional, making it unclear whether fatherhood suppresses
T or if men with lower T are more likely to become fathers. Here,
we use a large representative study in the Philippines (n= 624) to
show that among single nonfathers at baseline (2005) (21.5 ±0.3 y),
men with high waking T were more likely to become partnered
fathers by the time of follow-up 4.5 y later (P<0.05). Men who
became partnered fathers then experienced large declines in wak-
ing (median: 26%) and evening (median: 34%) T, which were
signicantly greater than declines in single nonfathers (P<0.001).
Consistent with the hypothesis that child interaction suppresses T,
fathers reporting 3 h or more of daily childcare had lower T at
follow-up compared with fathers not involved in care (P<0.05).
Using longitudinal data, these ndings show that T and reproduc-
tive strategy have bidirectional relationships in human males, with
high T predicting subsequent mating success but then declining
rapidly after men become fathers. Our ndings suggest that T
mediates tradeoffs between mating and parenting in humans, as
seen in other species in which fathers care for young. They also
highlight one likely explanation for previously observed health
disparities between partnered fathers and single men.
challenge hypothesis
human evolution
hormones and behavior
paternal care
reproductive ecology
In male mammals, testosterone (T) stimulates the development
and maintenance of traits and behaviors that contribute to
male mating effort, including musculature, libido, conspecic
aggressivity, and courtship (14). Although these T-driven traits
factor into mating success, male reproductive tness in some
avian and mammalian species also depends on contributions to
offspring care (5, 6). Because time and energy are nite (7),
males in these species often face tradeoffs between conicting
behaviors related to mating and parenting. Adjustment of T
production has been proposed as a physiological mechanism
underlying this tradeoff, with males who focus on mating effort
predicted to maintain elevated T, whereas males who cooperate
with a female partner and invest in parental care should reduce T
production (6, 8). This model is well supported by data from
a variety of avian species (6, 8), but evidence for its applicability
to mammalian species in which males provide direct care is
mixed (9). It is presently unclear whether T mediates the tradeoff
between mating and parenting effort in human males, who often
express paternal care facultatively.
Humans have been described as serial monogamists who fre-
quently engage in one or more long-lasting partnerships with
females during reproductive life spans that last several decades
(1012). Humans are one of the few mammalian species in which
paternal care is relatively common, with fathers often helping to
raise multiple overlapping offspring who are dependent well into
their second decade of life (5, 1315). If T contributes to human
male reproductive strategy, high initial T should enhance a mans
mating success, but men who have succeeded in securing a mate
and/or fathering a child should then down-regulate T, particu-
larly if they frequently care for their children (6, 8, 13).
Past human work provides indirect support for these expect-
ations largely using cross-sectional data. Multiple studies have
shown that partnered men have lower T compared with single
men (16, 17), and a large 10-y study of US servicemen found that
T decreased in men who married during the study period (18). In
comparisons of men varying in both relationship and parenting
status, partnered fathers have been shown to have the lowest T
overall, differing signicantly from single nonfathers in some
populations (1921), including the present study population (22,
23). There is also increasing evidence that caregiving predicts
which fathers have lowest T (20, 22, 24). Although these cross-
sectional correlations are generally consistent with the presumed
suppressive effect of partnering and fatherhood on T production
(a stateeffect), such ndings could alternatively result if men
with low T are more likely to become partnered or fathers (a
traiteffect) (25). However, to date, no human study has
monitored hormonal changes longitudinally as single nonfathers
transition into stable partnerships and become fathers.
To clarify the role of T in human male reproductive strategy,
we draw on data and biological samples collected in a large
sample of men participating in the Cebu Longitudinal Health
and Nutrition Survey (CLHNS), a representative 1-y birth cohort
study begun in the Philippines in 1983. In addition to longitu-
dinal questionnaire data, we collected saliva samples for T
measurement at waking (AM) and before bed (PM) in all par-
ticipants (n= 624) when they were 21.5 (±0.3) y of age (base-
line) and again when they were 26.0 (±0.3) y of age (follow-up).
All participants live in or around Cebu City, the Philippines,
where it is common for fathers to be involved in day-to-day care
of their children (22). Focusing on the subsample of men who
were single nonfathers at baseline (n= 465), we tested the hy-
potheses that (i) men with higher baseline T would have greater
mating success as indicated by being in a stable partnership
(married/cohabitating) and/or becoming a father by the time of
follow-up and (ii) these newly partnered new fathers would
subsequently show a greater decrease in T than men who
remained single nonfathers. We also tested the hypothesis that
(iii) fathers who reported spending more time in childcare would
have lower T at follow-up than fathers who reported spending
Author contributions: L.T.G., A.B.F., and C.W.K. designed research; L.T.G., T.W.M., A.B.F.,
and C.W.K. performed research; L.T.G. and C.W.K. analyzed data; and L.T.G., T.W.M.,
A.B.F., and C.W.K. wrote the paper.
The authors declare no conict of interest.
This article is a PNAS Direct Submission. A.E.S. is a guest editor invited by the Editorial
See Commentary on page 16141.
L.T.G. and C.W.K. contributed equally to this work.
To whom correspondence may be addressed. E-mail: or
This article contains supporting information online at
September 27, 2011
vol. 108
no. 39
less time in childcare, as would be consistent with a direct sup-
pressive role of caregiving on T among fathers.
In observational research, correlated nonmeasured factors can
inuence both predictor and outcome variables, and thus lead to
confounded associations. Here, we use an econometric change
model that minimizes the likelihood of such confounding, be-
cause any permanent or stable factors that differ among men but
that have not changed in the follow-up period are included
within the error term of both regression models, and thus are
eliminated as potential inuences on any change in T experi-
enced during the period of follow-up (26).
Table 1 summarizes sociodemographic and biological charac-
teristics for the full sample and also stratied on a median split of
AM T measured at follow-up (2009). When the full sample was
considered, all men showed a modest but signicant decrease in
both AM and PM T between baseline and follow-up, consistent
with age-related declines documented previously (27). Men with
high T tended to have completed more years of education,
whereas men with low and high T did not differ in anthropo-
metric measures. Consistent with the results presented below,
a greater proportion of partnered men and fathers had T below
the median.
We rst used logistic regression to test whether T at baseline
predicted reproductive status at follow-up (n= 465; Table S1).
Consistent with our hypothesis, single nonfathers with greater
AM T at baseline were more likely to become newly partnered
[odds ratio (OR) = 1.20, P= 0.044] and newly partnered new
fathers (OR = 1.21, P= 0.048) by the time of follow-up in 2009.
We next tested whether men who became newly partnered
new fathers during the period of follow-up experienced a greater
decline in T relative to men who remained single nonfathers
between baseline and follow-up. Consistent with this hypothesis,
men who were both newly partnered and new fathers showed the
largest declines in AM and PM T between 2005 and 2009 (Fig. 1
Aand B), and their declines in both AM (median: 26%) and
PM (median: 34%) T were signicantly greater than the
modest age-related declines in AM (median: 12%) and PM
(median: 14%) T observed among single nonfathers (P<0.001,
n= 465; Fig. 1Band Tables S2 and S3). Newly partnered men
who remained nonfathers at follow-up showed declines in AM
(median: 10%) and PM (median: 32%) T (Fig. 1A) that were
not signicantly different from those of single nonfathers [ab-
solute change in AM T (ΔAM T), P= 0.499; ΔPM T, P= 0.167;
Fig. 1Band Tables S2 and S3]. Effects of change in partnering
and fatherhood status on ΔAM and ΔPM T were not sub-
stantially affected after adjusting for self-reported psychosocial
stress and sleep quality, neither of which signicantly predicted
ΔT (all P>0.3; Tables S2 and S3). In addition, men who were
partnered fathers in 2005 and who already had low T at baseline
showed only slight within-group declines in both ΔAM T (me-
dian: 7%, P= 0.048; n= 83) and ΔPM T (median: 3%, P=
0.374) by follow-up in 2009 (Fig. 1Aand Table S4).
We next tested whether the large decrease in T among new
fathers was contingent on the age of a mans youngest child.
Although all new fathers, regardless of their youngest childs age,
experienced a signicant reduction in AM and/or PM T com-
pared with nonfathers (Fig. 2 and Tables S5 and S6), fathers with
newborns (1 mo old or less) at the time of follow-up hormone
assessment showed signicantly greater declines in AM (P=
0.023) and PM (P= 0.003) T compared with fathers whose
youngest child was older than 1 y of age, which was not ac-
counted for by reports of psychosocial stress, sleep quality, or
involvement in caregiving (Tables S7 and S8). Men with new-
borns also differed signicantly for ΔAM T compared with men
with infants between 1 mo and 1 y of age (P= 0.007).
Finally, we evaluated whether men who were fathers at follow-
up (n= 312) varied in T based on their self-reported in-
volvement in childcare in 2009, controlling for sleep quality,
psychosocial stress, and number of children. Men reporting 13h
of daily childcare had signicantly lower AM T compared with
fathers reporting not being involved with care (Fig. 3), whereas
fathers reporting the highest involvement in childcare (3 h or
more per day) showed signicantly lower values of both AM and
PM T compared with men reporting no care (Fig. 3). Consistent
with the hypothesis that childcare suppresses T, among men who
began as nonpartnered nonfathers at baseline (n= 162), time
Fig. 1. (A) Within-group changes in AM and PM T values between 2005 and 2009. Mean values of T, adjusted for time of saliva collection and usual wake
time (AM), were compared using paired ttests. Group 1 (n= 83) comprised men who were partnered and fathers in 2005 and 2009. Group 2 (n= 257)
comprised men who were not partnered in 2005 and 2009 and were never fathers. Group 3 (n= 46) comprised men who became partnered between 2005 and
2009 and were never fathers. Group 4 (n= 162) comprised men who became partnered and were rst-time fathers between 2005 and 2009. *P<0.05; **P<
P<0.0001. Error bars indicate SEM. P, partnered. (B) Between-group changes in AM and PM T values between 2005 and 2009 based on partnering and
parenting status. Group descriptions are as in A. Values were adjusted for time of saliva collection and usual wake time (AM) and are derived from regressing
the change in T on changes in partnering and parenting status, with group 2 as the comparison group, controlling for sleep quality and psychosocial stress
(Tables S2 and S3). Partnered fathers are included for visual comparison but were not part of the regression analyses. ***P<0.001. Error bars indicate SEM.
Gettler et al. PNAS
September 27, 2011
vol. 108
no. 39
spent in childcare as fathers (at follow-up) was not predicted by
either AM T [ordered logistic OR = 1.12, 95% condence in-
terval (CI): 0.841.48; P= 0.441] or PM T (OR = 0.89, 95% CI:
0.671.18; P= 0.417) measured at baseline.
Among the men in our sample who were single nonfathers as
young adults, those with higher waking T were more likely to
have become a partnered father by the time of follow-up. Once
these men entered stable partnerships and became new fathers,
they subsequently experienced a large decline in T, which was
greater than the comparably modest declines seen in single
nonfathers during the same period. Finally, fathers who were
most involved in childcare had lower T compared with fathers
who did not participate in care. Using longitudinal data, these
results demonstrate that high T not only predicts mating success
(i.e., partnering with a female and fathering a child) in human
males but that T is then greatly reduced after men enter stable
relationships and become fathers. The nding that high in-
volvement in childcare was associated with low T measured at
follow-up but was not related to baseline T supports the hy-
pothesis that direct care of dependent offspring suppressed T
among the fathers in our sample (20, 22). Our ndings suggest
that human males have an evolved neuroendocrine architecture
that is responsive to committed parenting, supporting a role of
men as direct caregivers during hominin evolution (13, 14, 21).
Our results provide longitudinal evidence that high T predicts
subsequent mating success in human males. Although we did not
measure the behavioral or physical pathways linking T with
mating success in this analysis, T has previously been shown to
bolster traits related to mating effort and attractiveness, such as
musculature (1, 28, 29), motivation to win during competition
(30), and pursuit of social dominance (2, 31). Men with higher T
have also been shown to have physical attributes deemed at-
tractive by females and to have more recent and lifetime sexual
partners (3234). Although families traditionally played a pri-
mary role in arranging courtship and marriage in the Philippines,
courting in recent decades has gradually moved toward males
and females meeting independent of familial control (35). Mens
romantic prospects may thus be increasingly contingent on male-
male competition, particularly in social and economic domains
(36). This trend has likely increased the potential for high T to
factor into male mating success.
Although helpful in securing mates, many T-stimulated
behaviors may conict with partnership stability and parenting
(4, 33). Indeed, men with higher T have been shown to be more
likely to have marital problems and to be divorced (4, 18),
whereas men with lower T have been found to spend more time
with their wives (21). In an experimental setting, men with
greater T also reported feeling less sympathy or need to respond
to infant cries compared with men with lower T (37). Although
prior cross-sectional studies have led to speculation that father-
hood decreases T in human males (19, 22, 24), our longitudinal
results demonstrate that fatherhood causes T to decline and
remain low. These ndings were not substantively changed when
covariates (psychosocial stress and sleep quality) that might be
expected to mediate the relationship between fatherhood/
marriage and T were included in models and are consistent with a
previous longitudinal report that men who were married experi-
enced decreased T (18).
We also found that T at follow-up was lowest among fathers
reporting more hours spent in childcare. Although this nding
could result if men with low T at baseline were more likely to get
involved in childcare, instead, we found that childcare in-
volvement was unrelated to T at baseline. Familial composition
was not a confounding inuence on the relationships that we
documented, which is consistent with previous research from
Cebu reporting that fathers did not alter their childcare partici-
pation based on their number of children (38). Together, these
ndings provide longitudinal support for the hypothesis that
interacting with a dependent child suppresses T (20, 22, 24). In
prior research conducted in two neighboring cultural groups in
Tanzania, fathers in the population in which paternal care is the
cultural norm had lower T, whereas this was not found among
fathers in the group in which paternal care is absent (20). In
a study of a polygynous Senegalese society, it was found that
fathers who were highly invested in their children, as reported by
the childrens mothers, had lower T compared with fathers who
were less invested (24). Lower T has also been associated with
nurturing behaviors among fathers (37, 39).
Fig. 2. Between-group changes in AM and PM T values between 2005 and
2009 with fathers stratied by child age. Values are adjusted for time of
saliva collection and usual wake time (AM) and are derived from regressing
the change in T on fatherhood, stratied by child age, with men who were
not fathers in 2005 and 2009 as the comparison group, and controlling for
sleep quality and psychosocial stress (Tables S5 and S6). Fathers of newborns
were men whose youngest child was in the perinatal period [1 mo (m) old or
less]. Fathers of infants were men whose youngest child was older than 1 mo
(m) but 1 y (yr) old or less. ^P<0.10; **P<0.01; ***P<0.001. Error bars
indicate SEM.
Fig. 3. 2009 AM and PM T values among fathers varying in daily physical
childcare. Values were derived from regressing T on daily paternal caregiv-
ing, controlling for time of saliva collection, usual wake time (AM), sleep
quality, psychosocial stress, and number of children, with fathers who
reported no involvement in childcare as the comparison group. No care (n=
34), 01h(n= 37), 13h(n= 139), 3+ h (n= 102). Regression models were
calculated with robust SEs.
P= 0.020;
P= 0.044;
P= 0.015. AM model: R
0.047; PM model: R
= 0.046. Error bars indicate SEM.
| Gettler et al.
Although all new fathers had lower T than men remaining
single nonfathers, our results also suggest that fathers of new-
borns (1 mo old or less) experienced a large transient decline in
T that was signicantly greater than that of fathers whose
youngest child was older than 1 mo of age. This nding is con-
sistent with a previous cross-sectional study in which fathers of
newborns were found to have lower T compared with a group of
expectant fathers, whose T had been measured during their
partnerspregnancies (39). In another study in which expectant
fathers were sampled for T multiple times during their partners
pregnancies and after the women gave birth, those men with high
T during the pregnancy showed a signicant decline in the rst
week after birth (40). Viewed alongside these past ndings, the
steep transient T decrease that we document among fathers with
newborns could indicate an anticipatory psychological compo-
nent to mens T decline around the time of birth of their chil-
dren. Alternatively, our control variables may not fully capture
the scope of sleep disruption and psychosocial adjustments that
accompany a familys accommodation of a newborn baby, which
could contribute to this large short-term T decline in the post-
partum period. Taken together, our ndings suggest that antic-
ipatory or other effects unique to the immediate period of
parturition are likely additive to the more sustained effects of
caregiving in suppressing paternal T.
Our results are consistent with ndings from many bird spe-
cies, among which fathers often show declines in T during
periods in which they help raise young (6, 41). Relevant ndings
from other mammals are less consistent, with fathers having
lower T in some (4245) but not all (4648) mammalian species
in which fathers assist with offspring care. Analogies to bird and
other mammalian species are somewhat constrained because
humans are not seasonal breeders and have signicantly longer
interbirth intervals (34 y) and slowly developing dependent
offspring (49, 50). Moreover, human malespredisposition to-
ward paternal care is likely a derived trait that emerged during
hominin evolution (1315, 51, 52). Thus, compared with other
species with paternal care, mens T might decrease with father-
hood and then remain low over a longer and more sustained time
period corresponding to the slow life history of humans and the
prolonged dependency of offspring (50, 53, 54).
There is considerable interest in the health differentials be-
tween fathers and single men (55), and it is often reported that
married men and fathers have lower risk for certain diseases and
mortality (5658). Our ndings suggest that fathers are likely
exposed to lower levels of T throughout much of their prime
reproductive years, which could contribute to some of these
health differentials. For instance, high T may increase risk for
prostate cancer and adverse cholesterol proles, and high T has
also been linked to risk-taking behaviors that can affect mens
health, such as drug and alcohol use and promiscuity (33, 59, 60).
Our nding that men who end up as fathers tend to have higher
T to begin with also suggests that some of the benets of low T
among fathers could be offset by higher T exposure among these
men before becoming fathers, which could hinder efforts to
identify the health impacts of being a partnered father. Thus, our
ndings point to likely health effects of fatherhood and also
underscore some of the complexities of this exposure. The large
reductions in circulating T among the new fathers in our sample
provide a strong rationale to investigate linkages between fa-
therhood status and risk for diseases related to T exposure.
In sum, our results provide longitudinal conrmation that T
exhibits a bidirectional relationship with reproductive strategy in
human males. Single nonfathers with higher T at baseline were
more likely to be partnered fathers 4.5 y later. After becoming
partnered fathers, these men experienced dramatic reductions
in both waking and evening T, which were substantially greater
than the age-related declines observed in single nonfathers. Our
nding that caregiving fathers had lower T than fathers who did
not invest in care supports the hypothesis that father-child in-
teraction likely contributes to suppressed paternal T among fathers.
Table 1. Sample characteristics stratied on low and high follow-up (2009) AM T (n= 624)
All (n= 624) Low AM T* (n= 316) High AM T* (n= 308)
Mean ±SD Mean ±SD Mean ±SD Pvalue
Demographic characteristics
Age, y 26.0 ±0.3 26.0 ±0.3 26.0 ±0.3 0.57
Highest grade completed 11.5 ±4.8 11.2 ±4.8 11.9 ±4.8 0.07
T values
AM T 2005, pg/mL 192.8 ±74.1 175.5 ±65.7 210.5 ±77.9 0.0001
AM T 2009, pg/mL
162.0 ±61.8 115.9 ±30.8 209.2 ±48.4 0.0001
PM T 2005, pg/mL 117.7 ±51.9 112.3 ±50.0 123.3 ±53.2 0.0001
PM T 2009, pg/mL
92.6 ±39.2 79.3 ±32.4 106.2 ±40.9 0.0001
Anthropometric measures
Body fat percentage 20.1 ±5.2 19.9 ±5.3 20.2 ±5.1 0.40
Body mass index, kg/m
22.7 ±3.6 22.5 ±3.8 22.9 ±3.4 0.23
Relationship characteristics
Partnered 2005 19.7% 20.6% 18.8% 0.59
Partnered 2009 54.0% 59.8% 48.1% 0.003
Duration of relationship
,y 3.7±2.4 3.6 ±2.4 3.8 ±2.4 0.45
Fatherhood characteristics
Father 2005 16.0% 15.8% 16.2% 0.89
Father 2009 50.0% 56.0% 43.8% 0.002
No. children
1.6 ±0.8 1.6 ±0.8 1.7 ±0.8 0.18
Age of oldest child
,y 3.4±2.2 3.2 ±2.2 3.6 ±2.2 0.16
*Test for signicant differences by median split of 2009 AM T (low AM T <155.6 pg/mL <high AM T); unpaired,
two-tailed ttest or χ
Paired ttests comparing 2005 and 2009 AM and PM T (both P<0.0001).
Restricted to partnered men in 2009 (n= 337).
Restricted to fathers in 2009 (n= 312).
Gettler et al. PNAS
September 27, 2011
vol. 108
no. 39
These results point to an important role of the hypothalamic-
pituitary-gonadal axis as a mediator of the tradeoff between
investments in parenting and mating in human males, similar to
what is seen in other species in which paternal care is common.
They also add to evidence that human males have an evolved
neuroendocrine architecture shaped to facilitate their role as fa-
thers and caregivers as a key component of reproductive success.
Study Population. Data were collected in 2005 and 2009 as part of the CLHNS,
a representative population-based birth cohort study of mothers and their
infants born in 19831984 (61). Men (n= 624) were an average of 26.0 ±0.3
(SD) y old at the time of data and sample collection in 2009. Socioeconomic,
demographic, and behavioral data were collected during in-home interviews
administered by Cebuano-speaking interviewers (61). Men were classied as
partneredif they identied themselves as married or in a cohabitating
relationship (22). Fathers were dened as men who reported having one or
more biological children. Fathers of newborns were dened as men whose
youngest child was in the perinatal period (1 mo old or less). Fathers of
infants were dened as men whose youngest child was older than 1 mo of
age but less than 1 y old. Paternal caregiving was assessed via the question,
How much time do you usually spend providing physical care to your
children on a daily basis?with men grouped by no contact/0 min, less than
1h,13 h, and 3+ h.
Weight (kg), height (cm), and triceps skinfold thickness (mm) were
measured using standard anthropometric techniques (62). Body fat per-
centage was calculated from triceps skinfold thickness using body density
estimates and a body composition predictive equation (63). The body mass
index was calculated as the ratio of weight (kg)/height (m
). Self-reported
psychosocial stress in the month preceding sampling was quantied via
a modied version of the 10-item Perceived Stress Scale (PSS) (64). Sleep
quality was assessed via self-reports of how many days per week subjects
woke up feeling rested. This research was conducted under conditions of
informed consent with human subject clearance from the Institutional Re-
view Boards of the University of North Carolina at Chapel Hill and North-
western University.
Salivary T Collection and Measurement. The same saliva collection procedures
were used in 2005 and 2009. Each participant was provided with instructions
and two polypropylene tubes for saliva collection. The rst sample was
collected immediately before bed (PM) at mean sampling times of 10:14 PM ±
1:38 (SD) in 2005 and 10:04 PM ±1:33 (SD) in 2009. The participants were
instructed to collect the second sample immediately on waking the follow-
ing morning (AM) and to report the time of saliva collection. Mean AM
sampling times were 6:30 AM ±1:13 (SD) in 2005 and 6:48 AM ±1:28 (SD) in
2009. Saliva tubes were collected on the second day by an interviewer and
stored at 35 °C until shipment on dry ice to Northwestern University, where
they were stored at 80 °C.
Salivary T Assessment. T concentrations were determined at the Laboratory
for Human Biology Research at Northwestern University using an enzyme
immunoassay protocol developed for use with saliva samples (kit no. 1-2402;
Salimetrics). Interassay coefcients of variation were 13.7% and 11.5% for
high and low control samples, respectively, in 2005 samples and 7.8% and
17.9% for high and low control samples, respectively, in 2009 samples.
Sample Selection. During a 1-y period in 19831984, the CLHNS surveyed
w28,000 households in randomly selected neighborhoods in metro Cebu
City, inviting all pregnant women to participate (acceptance rate of 96%, n=
3,080 singleton liveborns). Thus, the original sample was representative of
births during that year. Subsequent attrition has largely been attributable to
out-migration, and the refusal rate for the subjects in adult surveys has
typically been w5% (61). During the 2005 survey, 1,008 (62%) of the original
cohort of 1,633 liveborn males were located and were willing to be inter-
viewed, and 908 (56% of original cohort) men were located and enrolled in
2009. Subjects lost to attrition have generally been from higher socioeco-
nomic status households (61), which is also true of the present sample (see
below). Participants were compensated 100 pesos (w$2 US) for their time.
Anal sample of 624 individuals had all required data and met all criteria
for inclusion. Seventy-three men were excluded from this analysis because
they were nightshift workers or had sleep patterns consistent with night-
shift work, which is associated with disrupted circadian rhythms for T (65,
66). Four subjects were excluded as outliers because their T values were very
high (all were 6+ SD above the sample mean), suggesting contamination of
the saliva sample by blood, and one subject was excluded because of a T
value below the assay detection limit. Because this sample is drawn from
a cultural setting in which it is rare for men to become new fathers outside
of stable romantic partnerships or to le for divorce, there were few single
new fathers (n=12)ordivorcedmen(n= 9), who therefore were excluded
from longitudinal analyses. We assessed whether subjects in the analysis
differed from excluded men. Excluded individuals were born to mothers
(P<0.10) and fathers (P<0.01) who were more educated. However, there
were no signicant differences between the subsample used here and
the original baseline cohort in birth weight, birth length, birth order,
household income, parental height, or mother or fathers age at baseline
(all P>0.10).
Statistical Analysis. All analyses were conducted using version 10 of Stata
(Stata Corporation). AM T (pg/mL), PM T (pg/mL), sleep quality, and PSS were
all analyzed as continuous variables. AM and PM T were each adjusted for
time of sampling (AM and PM) and usual wake time (AM) before calculating
absolute change in T (ΔT) between baseline (2005) and follow-up (2009). All
other models were also adjusted for time of sampling (AM and PM) and
usual wake time (AM). Average self-reported stress and sleep quality were
calculated as the mean of 2005 and 2009 values (26).
Paired ttests were used to compare adjusted values of baseline T and
follow-up T. Multiple logistic regression was used to predict 2009 partner-
ship and fatherhood status from baseline T (z-scored) among men who were
single or were not fathers in 2005. Multiple linear regression was used to
predict ΔT based on partnership and fatherhood status changes between
2005 and 2009, controlling for sleep quality and self-reported stress, among
men who were single nonfathers at baseline. Multiple linear regression was
used to predict ΔT among men who were single nonfathers at baseline,
based on the age of fathersyoungest child at follow-up, with child age
stratied according to whether the youngest child was a perinatal infant (1
mo old or less), nonperinatal infant (older than 1 mo but less than 1 y), or
noninfant (older than 1 y). Multiple linear regression was also used to assess
differences in fathersT values (2009) based on self-reported hours spent in
direct physical childcare. Ordered logistic regression was used to predict
mens self-reported hours spent in direct physical childcare (2009) from
baseline T (z-scored) among men who were single nonfathers in 2005, with
all models meeting the parallel regression assumption based on the Brant
test. Statistical signicance was evaluated at P<0.05, with relationships with
0.05 <P<0.10 interpreted as a borderline statistical trend. All regression
models were tested for heteroscedasticity using the BreuschPagan/Cook
Weisberg test and were calculated with robust SEs where appropriate.
ACKNOWLEDGMENTS. Linda Adair played a central role in designing and
implementing the CLHNS survey from which these data and samples were
obtained. Greg Duncan provided statistical advice. Jeffrey Huang helped
with laboratory work. We thank the Ofce of Population Studies, University
of San Carlos, Cebu, Philippines, for its role in study design and data
collection and the Filipino participants who provided their time for this
study. This work was supported by the Wenner Gren Foundation (Grants
7356 and 8186), National Science Foundation (Grants BCS-0542182 and BCS-
0962212), Interdisciplinary Obesity Center (Grant RR20649), and Center for
Environmental Health and Susceptibility (Grant ES10126; Project 7-2004-E).
L.T.G. was supported by a National Science Foundation Graduate Research
Fellowship during write-up.
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... At the end of the 20th century, sex hormones and genetics played a similar role in gender differentiation. However, some researchers have identified the one-sidedness of these theories, synthesized the two mainstream theories, and proposed new ideas: both "sex hormone regulation" and "genomic inheritance" may contribute to differences in human gender behavior (Auyeung et al., 2009;Gettler et al., 2011). ...
... Children's biological characteristics may indirectly influence parental gender socialization through their gender behavior. For example, sex hormones or genes that lead to differences in children's sex behavior will cause parents to treat them differently, which also strengthens the gender behavior differences in children's biological factors (Gettler et al., 2011). The family ecosystem is a "petri dish" for individual gender role development. ...
... C. Wingfield, 1984). A similar pattern has been described in human males, where one longitudinal study showed that single men with higher testosterone were more likely to become partnered fathers over the ensuing four years, but then experienced a decrease in testosterone upon becoming a father that was in proportion to the amount of time spent with their infant (Gettler, McDade, Feranil, & Kuzawa, 2011). ...
... It is possible that different hormonal states of fathers with younger and older children could contribute to this finding. For example, fathers with younger children may have lower testosterone levels (Gettler et al., 2011) compared with fathers with older children. ...
A common life history theory trade-off is that which males face between mating effort and parental effort. This trade-off is observed across species, among individuals within a species, and within individuals across their lifespan. Recent studies suggest the possibility of more rapid trade-offs or motivational shifts in response to transient aspects of the social environment. We were interested in whether exposure to matingrelated stimuli would negatively impact men's evaluation of parental-related stimuli and vice-versa, and whether this response would differ between fathers and non-fathers. In two separate experiments, a total of 160 heterosexual or bisexual men rated how appealing they found 40 images of attractive infants and 40 images of attractive adult females. Half of all participants viewed infant images before viewing female images, and the other half viewed female images before infant images. In both experiments, fathers rated infant stimuli as more appealing than did non-fathers when infants were presented before females, but not when infants were presented after females. That is, priming fathers with female stimuli negatively impacted their ratings of infants. On the other hand, priming men with pictures of cute infants before viewing females did not impact ratings of female pictures, in either fathers or non-fathers. Nor did priming fathers with pictures of another highly rewarding stimulus - highly appealing foods - decrease their ratings of infants. The negative effect of female pictures on fathers' subsequent ratings of infant stimuli is consistent with the possibility that the female pictures activated motivational systems related to mating effort, which in turn inhibited motivational systems related to parental effort, rendering the infant stimuli less appealing. Our findings suggest that human fathers may be susceptible to transient shifts in life history strategy as a function of their immediate social environment.
... Hormones that underpin maternal care, such as oxytocin and prolactin, which operate through evolutionaryconserved mechanisms, are similarly activated in fathers but in ways that are less obligatory and causal and in response to ongoing exposure to mother and infant (Bales & Saltzman, 2016;Feldman, 2019). Cortisol activates in new fathers in response to infant cries and signals for care (Storey et al., 2000) and testosterone, which is associated with aggression, status, and mate selection, decreases at the transition to fatherhood in coordination with the degree of father involvement (Gettler et al., 2014;Gettler, McDade, Feranil, et al., 2011;Nunes et al., 2001). It has been further shown that extended exposure to pups activates hormonal and neural paternal response (Bales & Saltzman, 2016;Horrell et al., 2017), highlighting the link between the degree of father involvement and alterations in the father's neurobiological response. ...
... Studies on the paternal brain have mainly been conducted in more affluent cultures, including the United States (Kim et al., 2014;Kuo et al., 2012;Marshall et al., 2022;Rilling & Mascaro, 2017), the Netherlands (van't Veer et al., 2019), Germany (Wittfoth-Schardt et al., 2012), Israel (Abraham et al., 2014;Atzil et al., 2012), and Japan (Diaz-Rojas et al., 2023), and show similarities in activation patterns, but studies in developing countries have not been conducted. With regards to hormonal changes, research in both the Philippines (Gettler, McDade, Feranil, et al., 2011), and Western countries (Corpuz et al., 2021;Gordon et al., 2017) show decline in testosterone at the transition to fatherhood that correlates with the degree of father involvement, suggesting the possibility for a universal phenomenon. ...
Full-text available
Fathers have been an important source of child endurance and prosperity since the dawn of civilization, promoting adaptation to social rules, defining cultural meaning systems, teaching daily living skills, and providing the material background against which children developed; still, the recent reformulation in the role of the father requires theory-building. Paternal caregiving is rare in mammals, occurring in 3-5% of species, expresses in multiple formats, and involves flexible neurobiological accommodations to ecological conditions and active caregiving. Here, we discuss father contribution to resilience across development. Our model proposes three tenets of resilience - plasticity, sociality, and meaning - and discussion focuses on father-specific contributions to each tenet at different developmental stages; newborn, infant, preschooler, child, and adolescent. Father's style of high arousal, energetic physicality, guided participation in daily skills, joint adventure, and conflict resolution promotes children's flexible approach and social competence within intimate bonds and social groups. By expanding children's interests, sharpening cognitions, tuning affect regulation, encouraging exploration, and accompanying the search for identity, fathers support the sense of meaning, enhancing the human-specific dimension of resilience. We end by highlighting pitfalls to paternal contribution, including absence, abuse, rigidity, expectations, and gender typing, and the need to formulate novel theories to accommodate the "involved dad."
... The challenge hypothesis has many predictions: (1) during mating season, T will rise as a response to sexual stimuli of receptive females; (2) the increase in T motivates males to compete for access to receptive females and provides metabolic energy for courtship and fighting; (3) at the end of the breeding season, T decreases [10,13,14] and males become unresponsive to females sexual solicitations, e.g., when these are experimentally induced with estrogen treatment [24]; (4) T remains at low levels while males are involved in paternal care (e.g., in monogamous birds and in humans) and in conjunction with a rise in prolactin and oxytocin [25]. ...
Full-text available
The “challenge hypothesis” predicts higher male–male aggressive behavior along with increases in testosterone levels during times of reproductive challenges and social instability. In addition, in some primate species, higher glucocorticoid levels can be observed as well, but this is usually modulated by dominance rank. We studied rank-related aggressive behavior, mating activity, and fecal testosterone and glucocorticoid metabolites (fTm and fGCm) in male stumptail macaques (Macaca arctoides) in order to test some predictions of the “challenge hypothesis”. Over a 20-month period, we collected data on aggressive behavior and copulation, as well as fecal samples (n = 700) to quantify fTm and fGCm in seven adult stumptail males living in captivity. During periods of mating activity, male-to-male aggression increased in higher- and middle-ranking males. Neither fTm nor fGCm levels predicted male-to-male aggression. fGCm levels (but not fTm) were positively associated with male-to-female aggression; however, this association was pronounced during periods of mating activity. fGCm levels differed according to social rank, with middle-ranking males having the highest levels. Both hormones were higher during periods of mating activity, but only in higher- and middle-ranking males. Taken together, our findings partially support the challenge hypothesis in a non-seasonal primate and shed some light on the unique social and mating system of the stumptail macaque.
... Another issue is that studies identifying a link between lower levels of testosterone and higher paternal involvement are correlational, and as such the direction of causality is unclear. It is possible that becoming a more involved father lowers circulating testosterone levels; indeed, Gettler et al. (2011) found that higher levels of paternal involvement directly leads to lower levels of testosterone in men. ...
Full-text available
Purpose Facial femininity in men is purportedly used as a cue by women as a signal of paternal involvement. However, evidence for this claim is questionable. Previous findings have shown that paternal involvement is linked to testosterone, but have not investigated facial masculinity directly, while other studies have found that facial masculinity is negatively associated with perceptions of paternal involvement but do not assess the accuracy of this judgement. Here, we assess whether facial masculinity in men is used as a cue to paternal involvement, and whether this cue is accurate. Methods We collected facial photographs of 259 men (156 of which were fathers) who also completed self-report measures of paternal involvement. Facial images were then rated by a separate group of raters on facial masculinity, attractiveness, and perceived paternal involvement. Shape sexual dimorphism was also calculated from the images using geometric morphometrics. Results We found that facial masculinity was not associated with perceptions of paternal involvement, nor was it related with self-reported paternal involvement. Interestingly, facial attractiveness was negatively associated with perceptions of paternal involvement, and we found partial evidence that facial attractiveness was also negatively associated with self-reported paternal involvement. Conclusion These findings challenge the hypothesis that sexual dimorphism is used as a cue to paternal involvement, and perhaps indicate that facial attractiveness is more important for this judgement instead.
... For instance, men are more likely to adopt a short-term mating strategy if they are young (Buss, 2012); high in attractiveness, social status, or wealth (Buss, 1989;Clark, 2006;Gangestad & Simpson, 2000;Landolt et al., 1995); high in extraversion but low in agreeableness and conscientiousness (Schmitt & Shackelford, 2008); have a dark triad personality (high in narcissism, Machiavellianism, and psychopathy; Schmitt et al., 2017); have masculine faces (Rhodes et al., 2005) or V-shaped torsos (Hughes & Gallup, 2003); or have high testosterone levels (Marzoli et al., 2018). With regard to the latter, testosterone levels reduce when men marry and father children (Gettler et al., 2011;Gray & Campbell, 2009), but reduce less in men who adopt a dual mating strategy by continuing to seek extra-pair mating opportunities (Jones et al., 2013;Welling et al., 2008). ...
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Humans have a complex and dynamic mating system, and there is evidence that our modern sexual preferences stem from evolutionary pressures. In the current paper we explore male use of a dual mating strategy: simultaneously pursuing both a long-term relationship (pair-bonding) as well as short-term, extra-pair copulations (variety-seeking). The primary constraint on such sexual pursuits is partner preferences, which can limit male behavior and hence cloud inferences about male preferences. The aim of this study was to investigate heterosexual male mating preferences when largely unconstrained by female partner preferences. In service of this goal, female full-service sex workers (N = 6) were surveyed on the traits and behaviors of their male clients (N = 516) and iterative cluster analysis was used to identify male mating typologies. Two clusters emerged: clients seeking a pair-bonding experience and clients seeking a variety experience. Results also suggested that romantically committed men were more likely to seek a variety experience than a relationship experience. We conclude that men desire both pair-bonding and sexual variety, and that their preference for one might be predicted by fulfilment of the other. These findings have implications for relationships, providing insight into motivations for male infidelity.
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Background: Cognitive impairment is projected to rise substantially by 2050, particularly in low- and middle-income countries with aging populations. Reproductive life history may be associated with later-life cognitive function. We aim to estimate the association between number of children and mid- to later-life cognitive performance. Method: Data were from 5059 older adults (46% men) aged ≥40 years in the population-representative rural cohort of the "Health and Aging in Africa: A Longitudinal Study of an INDEPTH Community in South Africa" (HAALSI). We fit linear regression and modified Poisson models to estimate the associations between number of children and cognitive function. Analyses were stratified by sex/gender, controlling for age, education, literacy, self-reported childhood health, country of birth, and father's occupation. Results: After adjustment, men with any number of children and women with 5+ children had higher cognitive function compared to those without children (estimate;[95% CI]: Men: 1-2: 0.29[0.13 - 0.45], 3-4: 0.50[0.34 - 0.65], 5+: 0.48[0.33 - 0.63]; Women: 5+: 0.17[0.01 - 0.34]). Results from the adjusted modified Poisson regression models found that for men and women, groups with any number of children showed a lower prevalence of cognitive impairment than the group with 0 children (PR[95% CI] Men: 1-2: 0.48[0.31 - 0.75], 3-4: 0.21[0.12 - 0.37], 5+: 0.28[0.19 - 0.41], Women: 1-2: 0.52[0.31 - 0.88], 3-4: 0.55[0.33 - 0.91], 5+: 0.41[0.25 - 0.69]). Conclusion: Among older rural South African adults, having children was associated with greater cognitive performance and lower prevalence of cognitive impairment. Men tended to have larger protective associations than women, which may be due to sex/gender differences in biological and social roles of childbearing and rearing. Understanding the complex relationship between having children and later-life cognitive function may help identify interventions to reduce the impact of cognitive decline.
This chapter reviews and synthesizes research on hormonal correlates of sexual maturation and adult reproductive function in owl monkeys and how those hormones respond to changes in the social and physical environment. We first briefly summarize the methods that have been utilized to assess hormone metabolite concentrations and the methodological challenges researchers currently face, both in the field and in the laboratory. We consider initially what we know from studies of captive individuals, which have examined different species and are the source of most data. We follow with a presentation of the insights into the reproductive ecology and behavioral endocrinology of owl monkeys in a wild population of Azara’s owl monkey (Aotus azarae) in Formosa, Argentina, and discuss how these data may inform our understanding of pair formation, pair-bonding, and parental care in pair-living and sexually monogamous taxa. While knowledge of the reproductive and behavioral endocrinology of wild owl monkeys is still emerging, ovarian cycles in adult females and associations between cortisol and biparental care in both sexes have been well described. Monitoring of wild subadult females has indicated that the onset of ovarian cycling commences prior to dispersing, which suggests that, in contrast to some callitrichids, subadult female owl monkeys do not experience endocrine suppression. Our understanding of the endocrine correlates of male reproductive behavior and seasonal variation in reproductive hormones is still being developed.
The parenting brain may undergo remodeling that supports the adjustment to new parenthood. Prior work on human mothers has found gray matter volume decreases from preconception to early postpartum in multiple structures, including the left hippocampus, which was the only structure to show gray matter volume recovery at 2 years postpartum. This is consistent with evidence from animal models that the hippocampus is unusually plastic across reproductive transitions. However, no studies have focused specifically on hippocampal volume changes in human fathers. Among 38 men who were scanned by magnetic resonance imaging (MRI) before and after having their first child, individual differences in left hippocampal volume changes were associated with men's prenatal oxytocin, postpartum testosterone, and postpartum adaptation to parenthood. Across the whole sample, hippocampal volumes did not change significantly from prenatal to postpartum. However, men who showed larger increases in left hippocampal volume from prenatal to postpartum reported stronger parent-child bonding and affectionate attachment and lower parenting stress. Fathers with higher levels of prenatal oxytocin showed larger left hippocampal volume increases across the transition to parenthood. In turn, greater increases in left hippocampal volume predicted lower postpartum testosterone after adjusting for prenatal testosterone. These findings did not extend to the right hippocampus. In conclusion, remodeling of the left hippocampus across the transition to new fatherhood may reflect adaptation to parenthood in human males.
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A combination of field and laboratory investigations has revealed that the temporal patterns of testosterone (T) levels in blood can vary markedly among populations and individuals, and even within individuals from one year to the next. Although T is known to regulate reproductive behavior (both sexual and aggressive) and thus could be expected to correlate with mating systems, it is clear that the absolute levels of T in blood are not always indicative of reproductive state. Rather, the pattern and amplitude of change in T levels are far more useful in making predictions about the hormonal basis of mating systems and breeding strategies. In these contexts we present a model that compares the amplitude of change in T level with the degree of parental care shown by individual males. On the basis of data collected from male birds breeding in natural or captive conditions, polygynous males appear less responsive to social environmental cues than are monogamous males. This model indicates that there may be widely different hormonal responses to male-male and male-female interactions and presumably equally plastic neural mechanisms for the transduction of these signals into endocrine secretions. Furthermore, evidence from other vertebrate taxa suggests strongly that the model is applicable to other classes
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Two hypotheses have been offered to explain the relation between testosterone and antisocial behavior in delinquent and criminal populations. One is that testosterone leads directly to antisocial behavior. The other is that a constellation of dominance, competitiveness, and sensation seeking associated with testosterone leads to either antisocial or prosocial behavior, depending upon an individual's resources and background. Analysis of archival data from 4,462 U.S. military veterans supported the first hypothesis: Testosterone was correlated with a variety of antisocial behaviors among all individuals. However, socioeconomic status (SES) proved to be a moderating variable, with weaker testosterone-behavior relationships among high SES subjects.
While it is obvious that a birth will increase a woman's time devoted to child care, it is less obvious where the additional time comes from. Using data from the Philippines, the author estimates the average time spent in child care, market work, housework, and leisure by mothers, fathers, and older children both before and after the birth of a child. Comparison of the effects of the birth on time allocation across households indicates that the time adjustments made after the birth of a first child are significantly greater than those made after the births of subsequent children. The results also indicate that mothers bear over 90 percent of the time costs of children in families with no older children. When older children are present, however, mothers' percentage contribution falls considerably.
National survey data are used to compute mortality rates for persons in different living arrangements. Mortality is lower for married persons than for nonmarried persons; lower for married persons with children than for those without children; and lower for nonmarried persons who are household heads than for those who are not heads. Two approaches are considered: (1) social processes select healthy persons to the statuses of spouse, parent, and household head; (2) those statuses protect their occupants against risk of death. The protection hypothesis succeeds better than the selection hypothesis in accounting plausibly for the sex and age pattern of status differences in mortality.
We examine the relationship of testosterone to tendencies to marry and divorce, and to the quality of marriage, of a large representative sample of men. The analysis shows that men producing more testosterone are less likely to marry and more likely to divorce. Once married they are more likely to leave home because of troubled marital relations, extramarital sex, hitting or throwing things at their spouses, and experiencing a lower quality of marital interaction. Sociological models that might be informed by this finding are examined, and its implications for subsequent research are discussed.