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      Out of Africa: origins of the Taenia tapeworms in humans.

      Proceedings of the Royal Society B: Biological Sciences
      Africa, Animals, Biological Evolution, Hominidae, parasitology, Host-Parasite Interactions, Humans, Phylogeny, Species Specificity, Taenia, classification, genetics, pathogenicity

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          Abstract

          Phylogenetic and divergence date analyses indicate that the occurrence of Taenia tapeworms in humans pre-dates the development of agriculture, animal husbandry and domestication of cattle (Bos spp.) or swine (Sus scrofa). Taeniid tapeworms in Africa twice independently colonized hominids and the genus Homo prior to the origin of modern humans. Dietary and behavioural shifts, from herbivory to scavenging and carnivory, as early Homo entered the carnivore guild in the Pliocene/Pleistocene, were drivers for host switching by tapeworms to hominids from carnivores including hyaenids and felids. Parasitological data provide a unique means of elucidating the historical ecology, foraging behaviour and food habits of hominids during the diversification of Homo spp.

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          Most cited references25

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          Sequence and gene organization of mouse mitochondrial DNA.

          The complete sequence of the 16,295 bp mouse L cell mitochondrial DNA genome has been determined. Genes for the 12S and 16S ribosomal RNAs; 22 tRNAs; cytochrome c oxidase subunits I, II and III; ATPase subunit 6; cytochrome b; and eight unidentified proteins have been located. The genome displays exceptional economy of organization, with tRNA genes interspersed between rRNA and protein-coding genes with zero or few noncoding nucleotides between coding sequences. Only two significant portions of the genome, the 879 nucleotide displacement-loop region containing the origin of heavy-strand replication and the 32 nucleotide origin of light-strand replication, do not encode a functional RNA species. All of the remaining nucleotide sequence serves as a defined coding function, with the exception of 32 nucleotides, of which 18 occur at the 5' ends of open reading frames. Mouse mitochondrial DNA is unique in that the translational start codon is AUN, with any of the four nucleotides in the third position, whereas the only translational stop codon is the orthodox UAA. The mouse mitochondrial DNA genome is highly homologous in overall sequence and in gene organization to human mitochondrial DNA, with the descending order of conserved regions being tRNA genes; origin of light-strand replication; rRNA genes; known protein-coding genes; unidentified protein-coding genes; displacement-loop region.
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            Rates of mitochondrial DNA evolution in sharks are slow compared with mammals.

            The rate of mitochondrial DNA (mtDNA) evolution has been carefully calibrated only in primates. Similarity between the primate calibration and rates estimated for other vertebrates has led to widespread assumption of a constant molecular clock in vertebrates even though this has never been rigorously tested. We report here the examination of mtDNA sequence variation for 13 species of sharks from two orders that are well represented in the fossil record to test the constancy hypothesis. Nucleotide substitution rates in the cytochrome b and cytochrome oxidase I genes in sharks are seven- to eightfold slower than in primates or ungulates. This difference in substitution rate cannot be explained by nucleotide composition bias, codon-usage bias, selection, or choice of genes sequenced, and was confirmed by comparing species recently separated by the rise of the Isthmus of Panama. Such differences in mtDNA substitution rates among taxa indicate that it is inappropriate to use a calibration for one group to estimate divergence times or demographic parameters for another group. High-resolution studies of molecular evolutionary rates require taxon-specific calibrations.
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              Disparate rates of molecular evolution in cospeciating hosts and parasites.

              DNA sequences for the gene encoding mitochondrial cytochrome oxidase I in a group of rodents (pocket gophers) and their ectoparasites (chewing lice) provide evidence for cospeciation and reveal different rates of molecular evolution in the hosts and their parasites. The overall rate of nucleotide substitution (both silent and replacement changes) is approximately three times higher in lice, and the rate of synonymous substitution (based on analysis of fourfold degenerate sites) is approximately an order of magnitude greater in lice. The difference in synonymous substitution rate between lice and gophers correlates with a difference of similar magnitude in generation times.
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                Author and article information

                Journal
                11345321
                1088669
                10.1098/rspb.2000.1579

                Chemistry
                Africa,Animals,Biological Evolution,Hominidae,parasitology,Host-Parasite Interactions,Humans,Phylogeny,Species Specificity,Taenia,classification,genetics,pathogenicity

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