In contrast, thumb morphology and its precision grip never ceased undergoing changes, suggesting less acute selection pressures related to the evolution of the precision grip. We speculate that the results are possibly the evolutionary consequence of differential selection pressure on the big toe relative to the other toes related to the rise of bipedalism, which is proposed to have emerged very early in the hominin clade. The difference in PCo scores between the first and the other rays indicates that the integration between the thumb and the big toe is different from that between the lateral rays of the hand and foot. The results can be statistically evaluated. A novel landmark-based geometric morphometric approach focusing on covariation is based on a PCoA of the angles between PLS axes in morphospace. Generalized Procrustes analysis and two-block partial least squares (PLS) analyses were conducted. Landmarks were positioned on 3D surface models of the phalanges. Proximal phalanges of 76 individuals of unknown sex (Muséum national d'Histoire naturelle, Paris, and the Natural History Museum, London) were digitized using a surface scanner. The present study focuses on the covariation of the shape of proximal finger and toe phalanges of adult Homo sapiens to determine whether covariation is different in the first ray relative to the others, as its morphology is also different. 2011).Īs hands and feet are serially repeated corresponding structures in tetrapods, the morphology of fingers and toes is expected to covary due to a shared developmental origin. Within the basin the region of the Makapansgat site (white circle) is also associated with local active tectonics (Bailey et al. The Johannesburg Dome has been deeply dissected by erosion over the last 2–3Ma (Dirks et al. This boundary is therefore associated with downcutting and steep sided valleys associated with the upstream migration of nick points. This river and its tributaries have been extending their catchment by headward erosion of rivers resulting from uplift of the whole of southern Africa (Burke 1996). Part of the catchment boundary of the Limpopo River is shown. The Serengeti is unusual because it is both grassland and smooth, and consequently provides a misleading impression of local environments c) the Transvaal region, South Africa, showing vegetation (classified as in 2a) and topography. Yellow colours indicate ‘savannah’ vegetation (though most is not grassland). The black circles are hominin fossil sites. A) A continental map of African vegetation superimposed on a map of topography from SRTM30 data b) vegetation and topography in East Africa showing the prevalence of complex topography within and around the Rift Valley.
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