Pelvic Sexual Dimorphism Research Articles

Degree of pelvic sexual dimorphism in human populations. A greene t-test application

The knowledge of sexual dimorphisms is important in many aspects of paleodemography and paleobiology. One major problem lies in a correct sexual diagnosis. However, due to the different methodologies employed to estimate the degree of sexual dimorphism, the comparison of the results remains difficult. The Greene t-test (1989) is accurate for a comparative analysis of raw data. On the basis of 18 measurements of theos coxae the test is made to evaluate the degree of sexual dimorphism. The data collected are employed to investigate the pelvic sexual dimorphism within a recent sample of known sex, and among the Afalou-bou Rhummel — Taforalt (Epipaleolithic of Northern Africa) and the Teviec — Hoedic samples (Mesolithic of France). A comparative analysis is applied to a few recent samples. The results indicate the stability of sexual dimorphism pattern in recent and past populations.

Pelvic sexual dimorphism and relative neonatal brain size really are related

Primate species in which the neonatal brain size is large relative to the birth canal tend to have more sexually dimorphic pelves: this is a classic comparative relation, discovered by Schultz and Leutenegger. The original work did not correct for phylogenetic nonindependence of the data points; it only partly corrected for body size; it used ratios in both variables, and the size of the female pubis featured in both x- and y-variables. A recent publication by Tague placed a question mark over the validity of the relation. I therefore retested it, correcting for all four statistical defects. A strongly significant statistical relation exists.

Sexual dimorphism and allometry in primate ossa coxae

Five measurements were taken on the ossa coxae of 454 adult primates representing Ceboidea, Cercopithecoidea and Hominoidea. Sex differences in these variables and their relationships to overall body size and sexual dimorphism were tested by means of Student's T-test and regression analysis. The study attempts to clarify the nature of primate pelvic sexual dimorphism, including allometric effects, and more specifically, test the assertion made by Mobb and Wood (1977) that sexual dimorphism in body size in not an important determinant in pelvic sex differences. Variables that contribute to the size of the birth canal tend to be larger in females than males in all taxa studied except two. In these, Hylobates and Alouatta, there were no significant differences between the sexes for any of the five variables. In general, sexual dimorphism in variables contributing to the size of the birth canal was correlated (r approximately or equal to 0.8) with sexual dimorphism in body size. Furthermore, the coefficients of allometry underlying pelvic sex differences were shown to be moderately correlated (r approximately or equal to 0.5) with sexual dimorphism in size. The influence of other adaptive factors on primate pelvic sexual dimorphism are also briefly discussed.

Bony pelvic sexual dimorphism in the rat

AbstractNormal pelvic dimorphism is the result of the male pelvis acquiring morphological features during postnatal development that differ from those of the female. The first dimorphic features appear at 32 days of age. At 76 days of age the male pelvis has eleven dimorphic features that constitute the dimorphism of the normal adult. The development of five of the 11 features is dependent on the presence of the testes, whereas, the other six develop independently of the testes. The testes‐dependent features develop in males castrated at birth and treated with testosterone. The postnatal development of the female‐type pelvis in the normal female is not dependent on the presence of the ovaries.

INHIBITION OF PELVIC CHANGES OCCURRING DURING PREGNANCY IN MICE BY TESTOSTERONE PROPIONATE1

DURING LATE PREGNANCY the pelvis of the guinea pig enlarges by a hyperI trophy of an interpubic ligament. These changes have been reproduced experimentally in female or male guinea pigs following adequate treatment with estrogens and relaxin (1). They involved a transformation of the interpubic synchondrosis to a pubic symphysis and then, associated with some bone destruction, a proliferation of the fibrous ligament to separate the pubes for variable distances (2,3). A sexual dimorphism of the pelvis also exists in the pocket gopher, first becom ing apparent at sexual maturity. The pubic bones were decalcified at the symphysis under the influence of the ovarian hormone (4). A pelvic sexual dimorphism also occurs in another rodent, the mouse (5). The pubic bones separated at the symphysis during the first pregnancy and these changes were augmented with succeeding pregnancies. The alterations of pelvic structure were reproduced and augmented by the injections of estrogens.