Form space principal component analysis.

<p>The first three PCs in Procrustes form space account for approximately 94% of the total form variance for block 1 and 98% of that for block 2. Chimpanzees (blue trajectory) and humans (black trajectory) have distinct curvilinear ontogenetic trajectories. Blue dots: chimpanzee fetuses (a, b) to neonates (c). Black dots: humans from birth (d) to ~1 y.o. (e), red dots: from ~1 to ~2.5 y.o., green dots: from 2.5 to 5.5 y.o (f). Pink dots: regression estimates at age a, b, c, d, e and f visualized in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0081287#pone-0081287-g002" target="_blank">Figure 2</a>. The 3D reconstructions of blocks 1 and 2 show the landmark and semilandmark configurations (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0081287#pone.0081287.s001" target="_blank">Figure S1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0081287#pone.0081287.s003" target="_blank">Table S1</a> for complete description). Note the parallel orientations of trajectories between a) and b) in chimps and between d) and e) in humans demonstrates similar developmental pathways within a different anatomical context.