Compared to other primates, modern humans face high rates of maternal and neonatal morbidity and ... more Compared to other primates, modern humans face high rates of maternal and neonatal morbidity and mortality during childbirth. Since the early 20th century, this “difficulty” of human parturition has prompted numerous evolutionary explanations, typically assuming antagonistic selective forces acting on maternal and fetal traits, which has been termed the “obstetrical dilemma.” Recently, there has been a growing tendency among some anthropologists to question the difficulty of human childbirth and its evolutionary origin in an antagonistic selective regime. Partly, this stems from the motivation to combat increasing pathologization and overmedicalization of childbirth in industrialized countries. Some authors have argued that there is no obstetrical dilemma at all, and that the difficulty of childbirth mainly results from modern lifestyles and inappropriate and patriarchal obstetric practices. The failure of some studies to identify biomechanical and metabolic constraints on pelvic di...
Integrating Evolutionary Biology into Medical Education, 2019
Women’s reproductive health is often appropriately the focus of medical attention and interventio... more Women’s reproductive health is often appropriately the focus of medical attention and intervention in developed countries today. We argue, however, that clinical treatment can benefit from a greater understanding of the conditions under which female reproductive biology evolved. Reproductive factors such as timing of menarche and first reproduction, ovulatory cycles, levels of reproductive hormones, and fertility are shaped by local conditions, lived experiences of each woman, and evolutionary forces that have operated for many millennia on ancestral women. Aspects of our reproductive biology that we take for granted and think of as “natural” are actually products of our recent and current lifestyles—this includes monthly menstrual periods for much of women’s reproductive years for a total of as many as 450 cycles in their lifetimes. More typical of the human experience relevant to evolution is less frequent menstrual periods interrupted by pregnancy and several years of lactation f...
The anatomical details of a birth scene depicted on Classic Mimbres (A.D. 1000-1150) bowls from s... more The anatomical details of a birth scene depicted on Classic Mimbres (A.D. 1000-1150) bowls from southwestern New Mexico can provide clues to gender relations in Classic Mimbres society. The scenes show an infant emerging facing forward (unusual in human birth) with its arms up (virtually unknown in human birth). These details suggest that the scene was painted by someone unfamiliar with the birthing process. Ethnographically, men rarely see human births. Thus, it is likely that the birth scene, and perhaps other Mimbres pottery designs, were painted by men.
... I am appreciative of helpful feedback and responses to inquiries from Virginia Vitzthum, Cale... more ... I am appreciative of helpful feedback and responses to inquiries from Virginia Vitzthum, Caleb ''Tuck'' Finch, Kathryn Dettwyler, Chris Kuzawa, Sara Stinson, Mel Konner, and my ''consultants'' Jennie Lentz, Marcia Trevathan, and the students in my Anthropology of Reproduction ...
Anatomical record (Hoboken, N.J. : 2007), May 1, 2017
Birth mechanics in early hominins are often reconstructed based on cephalopelvic proportions, wit... more Birth mechanics in early hominins are often reconstructed based on cephalopelvic proportions, with little attention paid to neonatal shoulders. Here, we find that neonatal biacromial breadth can be estimated from adult clavicular length (R(2) = 0.80) in primates. Using this relationship and clavicular length from adult Australopithecus afarensis, we estimate biacromial breadth in neonatal australopiths. Combined with neonatal head dimensions, we reconstruct birth in A. afarensis (A.L. 288-1 or Lucy) and find that the most likely mechanism of birth in this early hominin was a semi-rotational oblique birth in which the head engaged and passed through the inlet transversely, but then rotated so that the head and shoulders remained perpendicular and progressed through the midplane and outlet oblique to the main axis of the female pelvis. Any other mechanism of birth, including asynclitic birth, would have resulted in either the head or the shoulders orthogonal to the short anteroposteri...
In this issue Clinton Burleson of New Mexico State University at Alamo gordo and Wenda Trevathan ... more In this issue Clinton Burleson of New Mexico State University at Alamo gordo and Wenda Trevathan of New Mexico State University at Las Cruces describe an example of an "expert system" called SkelMAP, to be used in helping students and professionals conduct skeletal analysis in both forensic and archaeological research situations. In both cases, it should be of great practical help to people working with skeletal materials.
The International Encyclopedia of Human Sexuality, 2015
Life history theory provides a way of viewing life course traits such as length of gestation, dur... more Life history theory provides a way of viewing life course traits such as length of gestation, duration of lactation, onset of puberty, and developmental state at birth through the lens of evolution. Given that energy for growing and reproducing is available in limited supply, life history theory argues that natural selection has shaped life history traits in ways that increase reproductive success. It helps predict what will be traded for what, under certain environmental conditions, including social and cultural circumstances, and enhances understanding of the human tradeoff of quality of offspring over quantity. Keywords: evolutionary tradeoffs; life history traits; reproduction
Compared to other primates, modern humans face high rates of maternal and neonatal morbidity and ... more Compared to other primates, modern humans face high rates of maternal and neonatal morbidity and mortality during childbirth. Since the early 20th century, this “difficulty” of human parturition has prompted numerous evolutionary explanations, typically assuming antagonistic selective forces acting on maternal and fetal traits, which has been termed the “obstetrical dilemma.” Recently, there has been a growing tendency among some anthropologists to question the difficulty of human childbirth and its evolutionary origin in an antagonistic selective regime. Partly, this stems from the motivation to combat increasing pathologization and overmedicalization of childbirth in industrialized countries. Some authors have argued that there is no obstetrical dilemma at all, and that the difficulty of childbirth mainly results from modern lifestyles and inappropriate and patriarchal obstetric practices. The failure of some studies to identify biomechanical and metabolic constraints on pelvic di...
Integrating Evolutionary Biology into Medical Education, 2019
Women’s reproductive health is often appropriately the focus of medical attention and interventio... more Women’s reproductive health is often appropriately the focus of medical attention and intervention in developed countries today. We argue, however, that clinical treatment can benefit from a greater understanding of the conditions under which female reproductive biology evolved. Reproductive factors such as timing of menarche and first reproduction, ovulatory cycles, levels of reproductive hormones, and fertility are shaped by local conditions, lived experiences of each woman, and evolutionary forces that have operated for many millennia on ancestral women. Aspects of our reproductive biology that we take for granted and think of as “natural” are actually products of our recent and current lifestyles—this includes monthly menstrual periods for much of women’s reproductive years for a total of as many as 450 cycles in their lifetimes. More typical of the human experience relevant to evolution is less frequent menstrual periods interrupted by pregnancy and several years of lactation f...
The anatomical details of a birth scene depicted on Classic Mimbres (A.D. 1000-1150) bowls from s... more The anatomical details of a birth scene depicted on Classic Mimbres (A.D. 1000-1150) bowls from southwestern New Mexico can provide clues to gender relations in Classic Mimbres society. The scenes show an infant emerging facing forward (unusual in human birth) with its arms up (virtually unknown in human birth). These details suggest that the scene was painted by someone unfamiliar with the birthing process. Ethnographically, men rarely see human births. Thus, it is likely that the birth scene, and perhaps other Mimbres pottery designs, were painted by men.
... I am appreciative of helpful feedback and responses to inquiries from Virginia Vitzthum, Cale... more ... I am appreciative of helpful feedback and responses to inquiries from Virginia Vitzthum, Caleb ''Tuck'' Finch, Kathryn Dettwyler, Chris Kuzawa, Sara Stinson, Mel Konner, and my ''consultants'' Jennie Lentz, Marcia Trevathan, and the students in my Anthropology of Reproduction ...
Anatomical record (Hoboken, N.J. : 2007), May 1, 2017
Birth mechanics in early hominins are often reconstructed based on cephalopelvic proportions, wit... more Birth mechanics in early hominins are often reconstructed based on cephalopelvic proportions, with little attention paid to neonatal shoulders. Here, we find that neonatal biacromial breadth can be estimated from adult clavicular length (R(2) = 0.80) in primates. Using this relationship and clavicular length from adult Australopithecus afarensis, we estimate biacromial breadth in neonatal australopiths. Combined with neonatal head dimensions, we reconstruct birth in A. afarensis (A.L. 288-1 or Lucy) and find that the most likely mechanism of birth in this early hominin was a semi-rotational oblique birth in which the head engaged and passed through the inlet transversely, but then rotated so that the head and shoulders remained perpendicular and progressed through the midplane and outlet oblique to the main axis of the female pelvis. Any other mechanism of birth, including asynclitic birth, would have resulted in either the head or the shoulders orthogonal to the short anteroposteri...
In this issue Clinton Burleson of New Mexico State University at Alamo gordo and Wenda Trevathan ... more In this issue Clinton Burleson of New Mexico State University at Alamo gordo and Wenda Trevathan of New Mexico State University at Las Cruces describe an example of an "expert system" called SkelMAP, to be used in helping students and professionals conduct skeletal analysis in both forensic and archaeological research situations. In both cases, it should be of great practical help to people working with skeletal materials.
The International Encyclopedia of Human Sexuality, 2015
Life history theory provides a way of viewing life course traits such as length of gestation, dur... more Life history theory provides a way of viewing life course traits such as length of gestation, duration of lactation, onset of puberty, and developmental state at birth through the lens of evolution. Given that energy for growing and reproducing is available in limited supply, life history theory argues that natural selection has shaped life history traits in ways that increase reproductive success. It helps predict what will be traded for what, under certain environmental conditions, including social and cultural circumstances, and enhances understanding of the human tradeoff of quality of offspring over quantity. Keywords: evolutionary tradeoffs; life history traits; reproduction
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