CERTAIN PHASES IN THE EVOLUTION OF MAN

Mosaic patterns of homoplasy accompany the parallel evolution of suspensory adaptations in the forelimb of tree sloths (Folivora: Xenarthra)

We examine how derived functional signal and phylogenetic inheritance interact in the forelimb of tree sloths, to understand the relative contribution of each in the evolution of a novel morphobehavioural suite. Molecular and craniodental data demonstrate that extant tree sloths evolved suspensory behaviours and associated morphologies from a non-suspensory ancestor independently of one another, making them a useful model system. We find that convergence in univariate traits is expressed mosaically, although the signal is largely functional. Three-dimensional analyses suggest there is greater conservatism of gross morphology in more proximal bones than in more distal elements. Convergence in some univariate scapular traits is independent of the gross morphology of the scapula itself, demonstrating that functionally relevant morphologies were mapped on to a more conserved scapular shape. Our results suggest that morphological homoplasy is expressed in a mosaic manner. The relationship between homoplasy and trait integration may be more nuanced than previously thought, even within a single adaptive system.

Evolution of the female pelvis and relationships to pelvic organ prolapse

The female pelvis provides support for the lower limbs as well as for the gastrointestinal tract, the bladder, and the reproductive organs. It must also serve as a passageway for defecation, urination, and, possibly, delivery of an infant. The bones, ligaments, and muscles of the human female pelvis have evolved from our early ancestors. Pelvic organ prolapse may occur because of the limitations involved with adapting the pelvic bones, muscles, and ligaments previously used for other purposes into a supportive role. Here we review these changing roles and functions of nonhuman primate and human female anatomy.