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Early life 
At age 18, Sarah attended her mother's alma mater, Wellesley College in Massachusetts. Her intended philosophy major led her into research on Mayan folklore, leading to a transfer to Radcliffe College and major in anthropology. She graduated summa cum laude and Phi Beta Kappa in 1969 with that B.A.. (Her undergraduate thesis became the basis for The Black Man of Zincantan, published in 1972.)
Family life 
Blaffer met Daniel Hrdy at Harvard. They married in 1972 in Kathmandu. They have three children:
- daughter Katrinka, born to Hrdy at age 31
- daughter Sasha, born 1982, a week before Hrdy was scheduled to present a paper at Cornell University
- son Niko, born 1986, when she was 41
She lives with her husband in Northern California, where they operate the Citrona Farms walnut plantation. She is Professor Emeritus of Anthropology at the University of California at Davis, where she remains involved with the Animal Behavior Graduate Group.
Main research 
The Langurs of Abu 
Sarah Hrdy first became interested in langurs during an undergraduate primate behavior class taught by anthropologist Irven DeVore in 1968. Here, a remark by DeVore regarding the relationship between crowding and the killing of infants would forever change her life. After graduation, she returned to Harvard for graduate studies, with the goal of decoding this phenomenon of infanticide in langur colonies. Working under the supervision of DeVore and the evolutionary biologist Robert L. Trivers provided Hrdy with an introduction to a newly emerging outlook on the social world—that of sociobiology—which crystallized at Harvard during the early 1970s and shaped Hrdy's perspective on primatology in an enduring manner.
Hrdy's PhD thesis tested the hypothesis that overcrowding causes infanticide in langur colonies. She went to Mount Abu in India to study Hanuman Langurs, and concluded that infanticide was independent of overcrowding—it was possibly an evolutionary tactic: When an outside male takes over a group, he usually proceeds to kill all infants. This postulated tactic would be very advantageous to the male langurs who practiced infanticide. Turnover in a langur tribe occurs approximately every 27 months. The male who is taking over has a very small window of opportunity to pass on his genes, and if the females are already nursing infants, it's likely that they won't ovulate again for another year. Killing their dependent infants makes the females once again receptive to mating.
Female choice is subverted, as females are put under pressure to ovulate and are forced to breed with the infanticidal males. This is where the idea of sexual counter-strategies comes into play. Hrdy theorized that by mating with as many males as possible, particularly outside males who are not part of the colony, mothers are able to successfully protect their young, as males were unlikely to kill an infant if there was the slightest chance that it might be their own.
That gives an "illusion of paternity", as Trivers put it. The goal of the male langur is to maximize the proportion of his offspring, and according to Hrdy, a male who attacks his own offspring is rapidly selected against. While infanticide has been seemingly preserved across primate orders, Hrdy found no evidence to suggest that the human species has a 'genetic imperative' for infanticide.
In 1975 Hrdy was awarded her PhD for her research on langurs. In 1977 it was published in her second book, The Langurs of Abu: Female and Male Strategies of Reproduction. The controversy in the anthropology realm that her research sparked was not surprising—the classic belief that primates act for the good of the group was discarded, and the field of sociobiology gained increasing support. Many mistakenly assumed that she implied existence of an 'infanticidal gene' that could be conserved across primates. Today, her results and conclusions are widely received. Even Trivers, who once dismissed her apparently illogical convictions, admits that her theory regarding female sexual strategies has "worn well".
The Woman That Never Evolved 
Hrdy's third book came out in 1981: The Woman That Never Evolved. She begins chapter one with a sentence indicating that the results of her work suggest females should be given a lot more credibility than previously thought. "Biology, it is sometimes thought, has worked against women." Here, Hrdy expands upon female primate strategies. This book is one of the New York Times' Notable Books of 1981. In 1984 Hrdy co-edited Infanticide: Comparative and Evolutionary Perspectives. It was selected as one of the 1984–1985 "Outstanding Academic Books" by Choice, the Journal of the Association of College and Research Libraries.
Mother Nature 
In 1999, Hrdy published Mother Nature - Maternal Instincts and How They Shape the Human Species. She places a sociobiological twist on maternal instinct, and places "human mothers and infants in a broader comparative and evolutionary framework" offering a new perspective on mother-infant interdependence. She discusses how mothers are continually making trade-offs between quality and quantity" and weighing the best possible actions for both her and her infant. Hrdy's view is that there is no defined 'maternal instinct', as it depends on a number of variables, and is therefore not innate, as once thought. She also stands by her view that humans evolved as cooperative breeders, making them essentially unable to raise offspring without a helper. This is where the concept of allomothering comes in—relatives other than the mother, such as the father, grandparents, and older siblings, as well as genetically unrelated helpers, such as nannies, nurses, and child care groups, who spend time with an infant, leaving the mother with more free time to meet her own needs.
She is a strong advocate for making affordable child care a priority.
Significant works 
- 1972 - The Black-man of Zinacantan: A Central American Legend. The Texas Pan American Series. Austin: University of Texas Press. ISBN 0-292-70701-0.
- 1977 - The Langurs of Abu: Female and Male Strategies of Reproduction. Cambridge: Harvard University Press. ISBN 0-674-51058-5.
- 1981 - The Woman that Never Evolved. Cambridge: Harvard University Press. (Chosen by the New York Times Book Review as one of Notable Books of the Year in Science and Social Science.) 1982, Japanese edition, Tokyo: Shisaku-sha Publishing; 1984, 5th printing of paperback edition, Cambridge; 1984, 1st French edition, Des guenons et des femmes. Paris: Editions Tierce, in press, 2nd French edition, Paris: Payot et Rivage; 1985, Italian edition, La Donna Che Non si E'evoluta, Franco Angeli Editore. ISBN 0-674-95539-0.
- 1984 - Hausfater, G. and S. Hrdy, eds. Infanticide: Comparative and Evolutionary Perspectives. New York: Aldine Publishing Co. (Selected as one of the 1984-85 "Outstanding Academic Books" by Choice, the Journal of the Association of College and Research Libraries.) ISBN 0-202-36221-3.
- 1999 - Mother Nature: A History of Mothers, Infants and Natural Selection. New York: Pantheon. A BOMC Alternative Selection; Selected by both Publisher's Weekly and by Library Journal as one of Best Books of 1999 and a finalist for PEN USA West 2000 Literary Award for Research Nonfiction. Won the Howells Prize for Outstanding Contribution to Biological Anthropology. (Published in UK as Mother Nature: Natural selection and the female of the species. London: Chatto and Windus); also translated into Dutch, German, Italian and Portuguese. ISBN 0-679-44265-0.
- 2001 - "The Past, Present, and Future of the Human Family." The Tanner Lectures on Human Values, Delivered at University of Utah February 27 and 28, 2001.
- 2005 - The 92nd Dahlem Workshop Report, "Attachment and Bonding: A New Synthesis." Edited by C. S. Carter, L. Ahnert, K. E. Grossmann, S. B. Hrdy, M. E. Lamb, S. W. Porges, and N. Sachser. ©MIT Press. ISBN 0-262-03348-8.
- 2009 - Mothers and Others: The Evolutionary Origins of Mutual Understanding. Cambridge: Harvard University Press. ISBN 0-674-03299-3.
- 1977 - Hrdy, S., D. B. Hrdy and John Melville Bishop. Stolen copulations; Play and Kidnapped, 16 mm, color.
- 1980 - Hrdy, S., Vishnu Mathur and William Whitehead. "Hanuman langur: Monkey of India," 30 minutes, color. Canadian Broadcasting Corporation. Available on video cassette: CBC Enterprises, P. O. Box 500, Terminal A, Toronto, Ontario, Canada M5W 1E6.
- 1983 - "Treatment for film on reproductive strategies of female primates," for BBC Natural History Unit, Bristol, UK.
- 1988 - "Monkeys of Abu." National Geographic Explorer. May 1988.
- 1990 - Nature Advisory Board, Channel Thirteen New York for series on the natural history of sex.
- 1990 - Consultant for "Human Nature" for the British Broadcasting Corporation, Bristol, UK.
- 2001 - Advisor for PBS series "Evolution".
- Guggenheim Fellow
- Member, National Academy of Sciences
- Member, American Academy of Arts and Sciences
- Member, California Academy of Sciences
- 2003 recipient, University of California Panunzio award (honoring outstanding scholarly work and service achievements since retirement)
- NYT Notable Books of 1981, The Woman That Never Evolved
- Publisher's Weekly, "Best Books of 1999", Mother Nature
- Library Journal, "Best Books of 1999", Mother Nature
- Howells Prize for Outstanding Contributions to Biological Anthropology, Mother Nature
- "Scientists' Nightstand: Interview with Sarah Hrdy", American Scientist, Nov. 25, 2003.
- Susan Caba, "She loves me, she loves me not", Salon.com, Dec. 9, 1999 (reviewing and discussing Mother Nature, and interviewing Hrdy)
- Claudia Glenn Dowling, "The Hardy Sarah Blaffer Hrdy", Discover Magazine, March 1, 2003 (interview, discussion of Mother Nature and other work)