Selective pressures in the human bony pelvis: Decoupling sexual dimorphism in the anterior and posterior spaces

2015 ◽  
Vol 157 (3) ◽  
pp. 428-440 ◽  
Author(s):  
Kirsten M. Brown
Keyword(s):  
Sexual Dimorphism ◽  
Selective Pressures ◽  
Bony Pelvis ◽  
Human Bony

scholarly journals Sexual dimorphism in skeletal shape in voles (Arvicolinae): disparate selection on male bodies and female heads

2020 ◽  
Vol 101 (4) ◽  
pp. 951-957
Author(s):  
Jeremy S Morris ◽  
Nala Rogers ◽  
Alan R Rogers ◽  
David R Carrier
Keyword(s):  
Sexual Dimorphism ◽  
Food Processing ◽  
Processing Efficiency ◽  
Selective Pressures ◽  
Skeletal Size ◽  
Quality Diet ◽  
Males And Females ◽  
Selection For ◽  
Functional Indices ◽  
Caloric Requirements

Abstract Sexual dimorphism evolves as a response to different selective pressures on males and females. In mammals, sexual selection on traits that improve a male’s ability to compete for access to mates is a common cause of sexual dimorphism. In addition to body mass, adaptations in specific components of the musculoskeletal system that increase strength, stability, and agility, may improve male fighting performance. Here we test the hypotheses that males, when compared to females, are more specialized for physical competition in their skeletal anatomy and that the degree of this sexual dimorphism increases with the intensity of male–male competition. In three species of voles (Cricetidae: Arvicolinae: Microtus), we found partial support for these hypotheses. Male-biased sexual dimorphism in a set of functional indices associated with improved fighting performance was identified in the postcranial anatomy. This dimorphism was greatest in the polygynous Microtus californicus, absent in the monogamous M. ochrogaster, and intermediate in the promiscuous or socially flexible M. oeconomus. However, in the skull, we found results opposite to our predictions. Females had larger skulls relative to overall skeletal size than did males. This may be associated with selection for increased food processing efficiency, which should be highly important because of the compounding effects of increased caloric requirements during gestation and lactation, and the generally low-quality diet of voles. In addition, larger heads in females may be associated with selection for greater digging ability or for defending offspring. These results suggest disparate selective pressures on the postcranial skeletons and skulls of male and female voles.

scholarly journals Seasonal dynamics of dental sexual dimorphism in the Atlantic stingray Dasyatis sabina

1996 ◽  
Vol 199 (10) ◽  
pp. 2297-2306 ◽  
Author(s):  
S Kajiura ◽  
T Tricas
Keyword(s):  
Sexual Dimorphism ◽  
Fossil Record ◽  
Reproductive Season ◽  
Sexually Dimorphic ◽  
Mating Season ◽  
Selective Pressures ◽  
Dasyatis Sabina ◽  
Atlantic Stingray ◽  
Cartilaginous Fishes

Cartilaginous fishes continuously replace their teeth throughout their life (polyphyodonty) and often show a sexually dimorphic dentition that was previously thought to be an invariant sex character. Radial vector analysis of tooth shape in the polyphyodontic stingray Dasyatis sabina across a consecutive 24 month period shows a stable molariform morphology for females but a periodic shift in male dentition from a female-like molariform to a recurved cuspidate form during the reproductive season. The grip tenacity of the male dentition is greater for the cuspidate form that occurs during the mating season than for the molariform dentition that occurs during the non-mating season. Dental sexual dimorphism and its sex-dependent temporal plasticity probably evolved via polyphyodontic preadaptation under selective pressures on both sexes for increased feeding efficiency and sexual selection in males to maximize mating success. These phenomena are important considerations for the identification and classification of cartilaginous fishes and possibly other polyphyodontic vertebrates in the fossil record.

scholarly journals Variation in obstetric dimensions of the human bony pelvis in relation to age-at-death and latitude

2018 ◽  
Vol 167 (3) ◽  
pp. 628-643 ◽  
Author(s):  
Benjamin M. Auerbach ◽  
Kathyrn A. King ◽  
Ryan M. Campbell ◽  
Meadow L. Campbell ◽  
Adam D. Sylvester
Keyword(s):  
Age At Death ◽  
Bony Pelvis ◽  
Human Bony

scholarly journals Developmental evidence for obstetric adaptation of the human female pelvis

2016 ◽  
Vol 113 (19) ◽  
pp. 5227-5232 ◽  
Author(s):  
Alik Huseynov ◽  
Christoph P. E. Zollikofer ◽  
Walter Coudyzer ◽  
Dominic Gascho ◽  
Christian Kellenberger ◽  
...  
Keyword(s):  
Sexual Dimorphism ◽  
Developmental Plasticity ◽  
Developmental Trajectories ◽  
Clinical Sample ◽  
Developmental Trajectory ◽  
Rapid Expansion ◽  
Nutritional Factors ◽  
Pelvic Morphology ◽  
Bony Pelvis ◽  
Narrow Pelvis

The bony pelvis of adult humans exhibits marked sexual dimorphism, which is traditionally interpreted in the framework of the “obstetrical dilemma” hypothesis: Giving birth to large-brained/large-bodied babies requires a wide pelvis, whereas efficient bipedal locomotion requires a narrow pelvis. This hypothesis has been challenged recently on biomechanical, metabolic, and biocultural grounds, so that it remains unclear which factors are responsible for sex-specific differences in adult pelvic morphology. Here we address this issue from a developmental perspective. We use methods of biomedical imaging and geometric morphometrics to analyze changes in pelvic morphology from late fetal stages to adulthood in a known-age/known-sex forensic/clinical sample. Results show that, until puberty, female and male pelves exhibit only moderate sexual dimorphism and follow largely similar developmental trajectories. With the onset of puberty, however, the female trajectory diverges substantially from the common course, resulting in rapid expansion of obstetrically relevant pelvic dimensions up to the age of 25–30 y. From 40 y onward females resume a mode of pelvic development similar to males, resulting in significant reduction of obstetric dimensions. This complex developmental trajectory is likely linked to the pubertal rise and premenopausal fall of estradiol levels and results in the obstetrically most adequate pelvic morphology during the time of maximum female fertility. The evidence that hormones mediate female pelvic development and morphology supports the view that solutions of the obstetrical dilemma depend not only on selection and adaptation but also on developmental plasticity as a response to ecological/nutritional factors during a female’s lifetime.

scholarly journals Obstetrical adaptation in the human bony pelvis: A morphometric approach

2009 ◽  
Vol 23 (S1) ◽  
Author(s):  
Kirsten Marie Brown ◽  
Valerie DeLeon ◽  
Christopher Ruff
Keyword(s):  
Bony Pelvis ◽  
Human Bony
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