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Journal abstracts 2005
LaDeana W. Hillier, et al. 2005. Nature 434: 724-731
Human chromosome 2 is unique to the human lineage in being the product of a head-to-head fusion of two intermediate-sized ancestral chromosomes. Chromosome 4 has received attention primarily related to the search for the Huntington’s disease gene, but also for genes associated with Wolf-Hirschhorn syndrome, polycystic kidney disease and a form of muscular dystrophy. Here we present approximately 237 million base pairs of sequence for chromosome 2, and 186 million base pairs for chromosome 4, representing more than 99.6% of their euchromatic sequences. Our initial analyses have identified 1,346 protein-coding genes and 1,239 pseudogenes on chromosome 2, and 796 protein-coding genes and 778 pseudogenes on chromosome 4. Extensive analyses confirm the underlying construction of the sequence, and expand our understanding of the structure and evolution of mammalian chromosomes, including gene deserts, segmental duplications and highly variant regions.
Early Homo at Swartkrans, South Africa: a review of the evidence and an evaluation of recently proposed morphs
Grine, F. E. Jan/Feb 2005. South African Journal of Science 101 (1/2): 43-52
The site of Swartkrans provided the first evidence for the contemporaneity of two early hominin genera, Paranthropus and Homo. In large measure, the fossils that are attributable to Homo consist of incomplete fragments and isolated teeth, which has led to an understandable degree of controversy regarding their taxonomic affinities. While all authorities seem to be in agreement that the Swartkrans australopith fossils constitute a single species, P. robustus, the number, identity and affinities of the species of Homo represented in these deposits remain unresolved issues. It has been proposed most recently that several distinct 'morphs' of this genus are represented at this site. However, a number of the specimens comprising these proposed morphological groups have been misidentified either taxonomically or anatomically. As such, the validity of these proposed associations and the morphological distinctions that might have characterized them are compromised. The proposition that more than one 'morph', or species, of Homo is represented at Swartkrans is neither novel nor unreasonable, but the evidence that has been cited most recently does not lend support to such a conclusion.
First occurrence of early Homo in the Nachukui Formation (West Turkana, Kenya) at 2.3-2.4 Myr
Sandrine Prat, et al. 2005. Journal of Human Evolution 49(2): 230-240
Cognitive abilities and techno-economic behaviours of hominids in the time period between 2.6-2.3 Myr have become increasingly well- documented. This time period corresponds to the oldest evidence for stone tools at Gona (Kada Gona, West Gona, EG 10-12, OGS 6-7), Hadar (AL 666), lower Omo valley (Ftji1, 2 & 5, Omo 57, Omo 123) in Ethiopia, and West Turkana (Lokalalei sites -LA1 & LA2C-) in Kenya. In 2002 a new palaeoanthropological site (LA1¦Á), 100 meters south of the LA1 archaeological site, produced a first right lower molar of a juvenile hominid (KNM-WT 42718). The relative small size of the crown, its marked MD elongation and BL reduction, the relative position of the cusps, the lack of a C6 and the mild expression of a protostylid, reinforced by metrical analyses, demonstrate the distinctiveness of this tooth compared with Australopithecus afarensis, A. anamensis, A. africanus and Paranthropus boisei, and its similarity to early Homo. The LA1¦Á site lies 2.2 m above the Ekalalei Tuff which is slightly younger than Tuff F dated to 2.34 ¡À 0.04 Myr. This juvenile specimen represents the oldest occurrence of the genus Homo in West Turkana.
Genomic evolution of MHC class I region in primates
Kaoru Fukami-Kobayashi, et al. 2005. PNAS 102(26): 9230-9234
To elucidate the origins of the MHC-B-MHC-C pair and the MHC class I chain-related molecule (MIC)A-MICB pair, we sequenced an MHC class I genomic region of humans, chimpanzees, and rhesus monkeys and analyzed the regions from an evolutionary standpoint, focusing first on LINE sequences that are paralogous within each of the first two species and orthologous between them. Because all the long interspersed nuclear element (LINE) sequences were fragmented and nonfunctional, they were suitable for conducting phylogenetic study and, in particular, for estimating evolutionary time. Our study has revealed that MHC-B and MHC-C duplicated 22.3 million years (Myr) ago, and the ape MICA and MICB duplicated 14.1 Myr ago. We then estimated the divergence time of the rhesus monkey by using other orthologous LINE sequences in the class I regions of the three primate species. The result indicates that rhesus monkeys, and possibly the Old World monkeys in general, diverged from humans 27-30 Myr ago. Interestingly, rhesus monkeys were found to have not the pair of MHC-B and MHC-C but many repeated genes similar to MHC-B. These results support our inference that MHC-B and MHC-C duplicated after the divergence between apes and Old World monkeys.
Generation and annotation of the DNA sequences of human chromosomes 2 and 4
LaDeana W. Hillier, et al. Nature 434, 724-731
Human chromosome 2 is unique to the human lineage in being the product of a head-to-head fusion of two intermediate-sized ancestral chromosomes. Chromosome 4 has received attention primarily related to the search for the Huntington's disease gene, but also for genes associated with Wolf-Hirschhorn syndrome, polycystic kidney disease and a form of muscular dystrophy. Here we present approximately 237 million base pairs of sequence for chromosome 2, and 186 million base pairs for chromosome 4, representing more than 99.6% of their euchromatic sequences. Our initial analyses have identified 1,346 protein-coding genes and 1,239 pseudogenes on chromosome 2, and 796 protein-coding genes and 778 pseudogenes on chromosome 4. Extensive analyses confirm the underlying construction of the sequence, and expand our understanding of the structure and evolution of mammalian chromosomes, including gene deserts, segmental duplications and highly variant regions.
The press release for the above article is at http://news-info.wustl.edu/news/page/normal/5045.html?emailID=4976.
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Patterns of size sexual dimorphism in Australopithecus afarensis: Another look
S.-H. Lee. Homo - Journal of Comparative Human Biology 56(3): 219-232, 8 December 2005
Size sexual dimorphism is one of the major components of morphological variation and has been associated with socioecology and behavioral variables such as mating patterns. Although several studies have addressed the magnitude and pattern of sexual dimorphism in Australopithecus afarensis, one of the earliest hominids, consensus has yet to be reached. This paper uses assigned resampling method, a data resampling method to estimate the magnitude of sexual dimorphism without relying on individual sex assessments, to examine the fossil hominid sample from Hadar. Two questions are asked: first, whether sexual dimorphism in a selected sample of skeletal elements of A. afarensis is the same as that in living humans, chimpanzees, or gorillas; and second, whether different skeletal elements reflect variation in sexual dimorphism in the same way. All possible metric variables were used as data in applying the method, including seven variables from three elements (mandibular canine, humerus, femur). Analyses show that A. afarensis is similar in size sexual dimorphism to gorillas in femoral variables, to humans in humeral variables, and to chimpanzees in canine variables. The results of this study are compatible with the hypothesis that the pattern of sexual dimorphism in A. afarensis is different from any that are observed in living humans or apes.
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