Schultz, A. H. Sex differences in the pelves of primates. Am. J. Phys. Anthropol. 7, 401–423 (1949).
Leutenegger, W. Beziehungen zwischen der Neugeborenengrösse und dem Sexualdimorphismus am Becken bei simischen Primaten. Folia Primatol. 12, 224–235 (1970).
Leutenegger, W. Functional aspects of pelvic morphology in simian primates. J. Hum. Evol. 3, 207–222 (1974).
Lindburg, D. G. Primate obstetrics: the biology of birth. Am. J. Primatol. 3, 193–199 (1982).
Gruss, L. T. & Schmitt, D. The evolution of the human pelvis: changing adaptations to bipedalism, obstetrics and thermoregulation. Philos. Trans. R. Soc. Lond. B Biol. Sci. 370, 20140063 (2015).
Trevathan, W. R. Human Birth: an Evolutionary Perspective (Routledge, 2017).
Trevathan, W. Primate pelvic anatomy and implications for birth. Philos. Trans. R. Soc. Lond. B Biol. Sci. 370, 20140065 (2015).
Washburn, S. L. Tools and human evolution. Sci. Am. 203, 63–75 (1960).
Rosenberg, K. R. The evolution of modern human childbirth. Yearb. Phys. Anthropol. 35, 89–124 (1992).
Haeusler, M. et al. The obstetrical dilemma hypothesis: there’s life in the old dog yet. Biol. Rev. Camb. Philos. Soc. 96, 2031–2057 (2021).
Laudicina, N. M., Piasecki, E., Stoller, M. & Cartmill, M. Obstetric constraints in six monkey genera. Am. J. Biol. Anthropol. 187, e70092 (2025).
Saiyed, S. T., Liubicich, R. C., Fidino, M. & Ross, S. R. Stillbirth rates across three ape species in accredited American zoos. Am. J. Primatol. 80, e22870 (2018).
Abee, C. R. The squirrel monkey in biomedical research. ILAR J. 31, 11–20 (1989).
Debyser, L. W. J. Platyrrhine juvenile mortality in captivity and in the wild. Int. J. Primatol. 16, 909–933 (1995).
Bowden, D., Winter, P. & Ploog, D. Pregnancy and delivery behavior in the squirrel monkey (Saimiri sciureus) and other primates. Folia Primatol. 5, 1–42 (1967).
Sesbuppha, W. et al. Stillbirths in Macaca fascicularis. J. Med. Primatol. 37, 169–172 (2008).
Roura-Torres, B., Amblard-Rambert, P., Lepou, P., Kappeler, P. M. & Charpentier, M. J. E. Stillbirth of a mandrill (Mandrillus sphinx) in the wild: perinatal behaviors and delivery sequences. Primates 65, 75–80 (2024).
Schlabritz-Loutsevitch, N. E. et al. The baboon model (Papio hamadryas) of fetal loss: maternal weight, age, reproductive history and pregnancy outcome. J. Med. Primatol. 37, 337–345 (2008).
Pillay, K. R. & Downs, C. T. Pregnancy complications in wild vervet monkeys in an urban mosaic landscape. Afr. J. Ecol. 62, e13251 (2024).
Stoller, M. K. The Obstetric Pelvis and Mechanism of Labor in Non-human Primates. PhD thesis, Univ. Chicago (1995).
Demuru, E., Ferrari, P. F. & Palagi, E. Is birth attendance a uniquely human feature? New evidence suggests that bonobo females protect and support the parturient. Evol. Hum. Behav. 39, 502–510 (2018).
Pan, W. et al. Birth intervention and non-maternal infant-handling during parturition in a nonhuman primate. Primates 55, 483–488 (2014).
Abitbol, M. M. Ontogeny and evolution of pelvic diameters in anthropoid primates and in Australopithecus afarensis (AL 288-1). Am. J. Phys. Anthropol. 85, 135–148 (1991).
Laudicina, N. M. & Cartmill, M. Bony birth-canal dimensions and obstetric constraints in hominoids. Am. J. Biol. Anthropol. 180, 442–452 (2022).
Webb, N. M. et al. Gradual exacerbation of obstetric constraints during hominoid evolution implied by re-evaluation of cephalopelvic fit in chimpanzees. Nat. Ecol. Evol. 8, 2228–2238 (2024).
Hammond, A. S. & Almecija, S. Lower ilium evolution in apes and hominins. Anat. Rec. 300, 828–844 (2017).
Senevirathne, G. et al. The evolution of hominin bipedalism in two steps. Nature 645, 952–963 (2025).
Gherman, R. B., Tramont, J., Muffley, P. & Goodwin, T. M. Analysis of McRoberts’ maneuver by x-ray pelvimetry. Obstet. Gynecol. 95, 43–47 (2000).
Grunstra, N. D. S. et al. Humans as inverted bats: a comparative approach to the obstetric conundrum. Am. J. Hum. Biol. 31, e23227 (2019).
Alba, D. M. Cognitive inferences in fossil apes (Primates, Hominoidea): does encephalization reflect intelligence? J. Anthropol. Sci. 88, 11–48 (2010).
Rosenberg, K. R. & Trevathan, W. R. Birth, obstetrics and human evolution. BJOG 109, 1199–1206 (2002).
Garber, P. A. & Leigh, S. R. Ontogenetic variation in small-bodied New World primates: implications for patterns of reproduction and infant care. Folia Primatol. 68, 1–22 (1997).
Smith, R. J. & Jungers, W. L. Body mass in comparative primatology. J. Hum. Evol. 32, 523–559 (1997).
Smith, R. J. & Leigh, S. R. Sexual dimorphism in primate neonatal body mass. J. Hum. Evol. 34, 173–201 (1998).
Prestes, N. C. et al. Cesarean sections in marmosets: white-tufted marmoset (Callithrix jacchus). Vet. Zootec. 21, 92–97 (2014).
Mosdol, G. Caesarean section in the Java monkey (Macaca irus): a case report. J. Small Anim. Pract. 17, 519–525 (1976).
Schlabritz-Loutsevitch, N. et al. Parturition in baboons (Papio spp.). Sci. Rep. 8, 1174 (2018).
Lovejoy, C. O. Evolution of human walking. Sci. Am. 259, 118–125 (1988).
Borell, U. & Fernström, I. The movements at the sacro-iliac joints and their importance to changes in the pelvic dimensions during parturition. Acta Obstet. Gynecol. Scand. 36, 42–57 (1957).
Pink, K. E. et al. No birth-associated maternal mortality in Japanese macaques (Macaca fuscata) despite giving birth to large-headed neonates. Proc. Natl Acad. Sci. USA 121, e2316189121 (2024).
Arulkumaran, S., Ledger, W., Denny, L. & Doumouchtsis, S. Oxford Textbook of Obstetrics and Gynaecology (Oxford Univ. Press, 2019).
Nguyen, N. et al. Comparative primate obstetrics: observations of 15 diurnal births in wild gelada monkeys (Theropithecus gelada) and their implications for understanding human and nonhuman primate birth evolution. Am. J. Phys. Anthropol. 163, 14–29 (2017).
Kawada, M., Nakatsukasa, M., Nishimura, T., Kaneko, A. & Morimoto, N. Covariation of fetal skull and maternal pelvis during the perinatal period in rhesus macaques and evolution of childbirth in primates. Proc. Natl Acad. Sci. USA 117, 21251–21257 (2020).
Duboscq, J., Neumann, C., Perwitasari-Farajallah, D. & Engelhardt, A. Daytime birth of a baby crested black macaque (Macaca nigra) in the wild. Behav. Processes 79, 81–84 (2008).
Smelzer, J. S. Prevention and management of shoulder dystocia. Clin. Obstet. Gynecol. 29, 299–308 (1986).
Torres-Tamayo, N., Buck, L. T., Hirasaki, E., Rae, T. C. & Betti, L. Variation in pubic symphysis fusion across primates: implications for obstetric adaptation. Am. J. Biol. Anthropol. 186, e25064 (2025).
Morimoto, N., Kawada, M., Tomizawa, Y., Kaneko, A. & Nishimura, T. Pelvic shape change in adult Japanese macaques and implications for childbirth at old age. Proc. Natl Acad. Sci. USA 120, e2300714120 (2023).
Torres-Tamayo, N., Rae, T. C., Hirasaki, E. & Betti, L. Testing the reliability of the rearticulation of osteological primate pelves in comparative morphological studies. Anat. Rec. 307, 2816–2833 (2024).
Smith, T. D., DeLeon, V. B., Vinyard, C. & Young, J. W. Skeletal Anatomy of the Newborn Primate (Cambridge Univ. Press, 2020).
Hamada, Y., Udono, T., Teramoto, M. & Hayasaka, I. Body, head, and facial growth: comparison between macaques (Macaca fuscata) and chimpanzee (Pan troglodytes) based on somatometry. Ann. Anat. 186, 451–461 (2004).
Schlager, S. In Statistical Shape and Deformation Analysis (ed. Zheng, G.) 217–256 (Elsevier, 2017).
Kappeler, P. M. & Pereira, M. E. Primate Life Histories and Socioecology (Univ. Chicago Press, 2003).
Leutenegger, W. Maternal–fetal weight relationships in primates. Folia Primatol 20, 280–293 (1973).
Warton, D. I. & Weber, N. C. Common slope tests for bivariate errors-in-variables models. Biometrical J. 44, 161–174 (2002).
Felsenstein, J. Phylogenies and the comparative method. Am. Nat. 125, 1–15 (1985).
R Core Team. R: A Language and Environment for Statistical Computing (R Foundation for Statistical Computing, 2024).
Rosenberg, K. R. & Trevathan, W. R. Bipedalism and human birth: the obstetrical dilemma revisited. Evol. Anthropol. 4, 161–168 (1995).
Tague, R. G. Pelvic sexual dimorphism among species monomorphic in body size: relationship to relative newborn body mass. J. Mammal. 97, 503–517 (2016).