142 8 APRIL 2022 • VOL 376 ISSUE 6589 science.org SCIENCEPHOTO: FRANS DE WAALBy Barbara J. KingF
rans de Waal’s books, beginning
with Chimpanzee Politics (1982) up
through Mama’s Last Hug (2019),
illuminate for wide audiences the
social lives, cognitive abilities, and
emotions of animals, with an empha-
sis on monkeys and apes. Now, in his 13th
volume, Different, de Waal takes on a fresh
and controversial topic: the contribution
of biology to gender in humans.
This subject is an “ideological mine-
field,” de Waal notes, and he wonders
whether writing this book is one of his
“most foolish decisions.” But there is much
to learn from his perspective. A
smart interactionist framework,
in which biological and socioen-
vironmental influences on hu-
man behavior are entwined, sits
at the book’s heart.
De Waal embraces gender vari-
ability even as he describes evo-
lutionary influences on gender by
comparing humans to our closest
living relatives, chimpanzees and
bonobos. He misses opportunities,
however, to educate his readers ac-
curately when he underestimates
ways in which humans vary by
both gender identity and sex.
“I sincerely believe that the
best way to achieve greater equal-
ity will be to learn more about our
biology instead of trying to sweep
it under the rug,” he writes, urg-
ing the retirement of theories that see gen-
der as socially constructed, full stop. “The
most meaningful expressions of gender
have deeper roots, including the generally
greater physical combativeness of men or
the devotion of many women to children.”
Already, readers of this review may be
bristling. Aren’t these inaccurate, outdated
gender stereotypes? Yet de Waal offers
solid evidence to show that across pri-
mates—including our own species—physi-
cal violence is associated with males far
more often than with females, and attrac-
tion to infants with females far more often
than males, in alignment with evolution-ary pressures that differ by sex. Along the
way, he effectively deploys anecdotes from
primate research to emphasize how far bi-
ology is from determinist.
Male chimpanzees may become violent,
but they can also display cooperation. In
the Burgers’ Zoo chimp colony in the Neth-
erlands, for example, alpha male Nikkie
showed signs of being a potential threat
to the infant Roosje, who—along with her
adoptive mother—was being reintroduced
to the group after a period apart. Nikkie
was at first held back, and when he was
finally released, the colony’s two oldest
males did something unexpected: They po-
sitioned themselves strategically betweenRoosje and her mother and the path of Nik-
kie’s approach, with arms wrapped around
each other’s shoulders. “This was a sight to
behold, given that these two had been arch
enemies for years,” de Waal notes. Nikkie
carried out no violence that day and, in
fact, acted gently around Roosje.
Meanwhile, chimpanzee Donna at the
Yerkes Field Station in the United States
was a physically “robust” female with
broad shoulders “who acted more mascu-
line than other females.” Donna never ex-
hibited full sexual swelling at the time of
ovulation, as is typical, nor did she mate
or have offspring. De Waal concludes that
Donna was a “largely asexual gender-non-
conforming individual,” a remarkable infer-
ence that extends concepts usually reserved
for humans into the nonhuman world.De Waal speaks up repeatedly for the
rights of women as well as transgender
and gay people (overlapping categories, of
course). However, his language is at times
troublesome. His definition of gender, for
example, involves “culturally encouraged
sex roles in society.” This is fine, but he also
writes that “gender refers to the learned
overlays that turn a biological female into
a woman and a biological male
into a man,” a statement in line
with his view that sex is all about
biology and that we can assert an-
other person’s sex in “only a sec-
ond” just by looking.
To problematize the notion
that a person’s sex or gender is
detectable on sight as an exem-
plar of a fixed biological sex goes
beyond mere political correct-
ness. For one thing, intersex indi-
viduals, whom de Waal mentions
in passing, have genital tissue
and/or chromosomes that depart
from what is considered typical
presentation. They are biologi-
cally neither exclusively male nor
exclusively female. As biologist
Anne Fausto-Sterling pointed out
years ago, a person’s sex may be
socially constructed just as one’s gender is.
Moving into the realm of gender identity,
a person who is assigned female at birth may
be assumed by others to be a woman on the
basis of external cues, whereas in fact they
may identify not as a woman but as non-
binary and agender. Similarly, transgender
people may not inevitably feel that they
“belong to the opposite sex.” Such language
fails to recognize people who identify, for ex-
ample, as both man and woman, or neither.
Overall, however, Different offers a fasci-
nating and mostly forward-thinking look at
the biology and culture of human gender by
an esteemed primatologist. Occasionally, it
requires correction to reflect the full range
of human sex and gender diversity. j10.1126/science.abo1569BIOLOGYGender, biology, and behavior
There is much to learn from a primatologist’s framework for gender diversity
Diff erent: Gender
Through the Eyes of
a Primatologist
Frans de Waal
Norton, 2022. 408 pp.A bonobo mother looks on as her baby nurses.INSIGHTS | BOOKSThe reviewer is professor emerita of anthropology
at William & Mary, Williamsburg, VA 23185, USA.
Email: [email protected]0408Books_15351501.indd 142 4/1/22 4:32 PM