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They also supported the Phthiraptera as polyphyletic when the Liposcelididae and the Pachytroctidae are excluded (Fig.?1a). Both of these studies suggest that parasitism of vertebrates arose twice, once in the Amblycera and again in the common ancestor of the Ischnocera, Rhyncophthirina, and Anoplura. Under this new phylogeny, Smith et?al. [13] used molecular dating techniques, calibrated to louse and host fossils, to determine the approximate age when major louse clades diverged. They found that all four Phthiraptera families and the Liposcelididae had diverged during the Mesozoic, prior to the K-Pg boundary. Whereas Smith et?al. [13] found that the major families had Cretaceous origins, major radiations occurred late in the Cretaceous and early in the Cenozoic. Light et?al. [6] conducted an extensive phylogenetic analysis of the Anoplura, and dated their divergence with a molecular clock calibrated [http://www.selleckchem.com/products/Neratinib(HKI-272).html Neratinib] [http://en.wikipedia.org/wiki/RVX_208 RVX-208] to host divergence. They also found that the Anoplura diversified in the late Cretaceous, but that an additional major radiation occurred after the K-Pg boundary, following the radiation of mammals. Light et?al. [6] found considerable disagreement with accepted anopluran phylogenies, most importantly demonstrating that host switching had occurred multiple times in anopluran history. This suggests that rapid host switching, and subsequent extinctions in some groups, has played a major role in the post-K-Pg diversification of sucking lice. Whereas host specificity and co-speciation appear to be important in the evolution of the Anoplura, host associations may be less informative for louse phylogeny [6]. Humans are parasitized by two species of sucking lice, the pubic louse (Pthirus pubis Linnaeus), and head and body lice (Pediculus humanus Linnaeus). Recent studies have helped to establish the taxonomic rank of the human body louse and the phylogenetic relationships of Phtirus and Pediculus. Light et?al. [14] built a phylogenetic reconstruction of human head and body lice based on mitochondrial sequence data. They found that human [http://www.selleckchem.com/products/BMS-777607.html http://www.selleckchem.com/products/BMS-777607.html] body lice did not represent different species, but rather were eco-morphs of a single species. Reed et?al. [15] investigated the relationships of human, chimp (Pediculus schaeffi Farenholz) and gorilla (Pthirus gorillae Ewing) lice, using both mitochondrial and nuclear sequence data. Reed et?al. [15] found that human Pediculus species and P.?gorillae shared a common phylogenetic history with their primate hosts, but that P.?pubis did not. Light and Reed [16] later supported this topology by using multiple nuclear and mitochondrial markers. Both studies supported a divergence time of the human and gorilla species of Pthirus of about 3?million years ago (mya). Reed et?al. [15] suggested that the human public louse arose from a host switch from gorillas to humans c.?3?mya.