A new primate from the Middle Eocene of Myanmar and the Asian early origin of anthropoids. (25/2344)

A new genus and species of anthropoid primate, Bahinia pondaungensis gen. et sp. nov., is described from the Yashe Kyitchaung locality in the Late Middle Eocene Pondaung Formation (Myanmar). It is related to Eosimias, but it is represented by more complete remains, including upper dentition with associated lower jaw fragment. It is interpreted as a new representative of the family Eosimiidae, which corresponds to the sister group of the Amphipithecidae and of all other anthropoids. Eosimiidae are now recorded from three distinct Middle Eocene localities in Asia, giving support to the hypothesis of an Asian origin of anthropoids.  (+info)

Nuclear DNA sequences from late Pleistocene megafauna. (26/2344)

We report the retrieval and characterization of multi- and single-copy nuclear DNA sequences from Alaskan and Siberian mammoths (Mammuthus primigenius). In addition, a nuclear copy of a mitochondrial gene was recovered. Furthermore, a 13,000-year-old ground sloth and a 33,000-year-old cave bear yielded multicopy nuclear DNA sequences. Thus, multicopy and single-copy genes can be analyzed from Pleistocene faunal remains. The results also show that under some circumstances, nucleotide sequence differences between alleles found within one individual can be distinguished from DNA sequence variation caused by postmortem DNA damage. The nuclear sequences retrieved from the mammoths suggest that mammoths were more similar to Asian elephants than to African elephants.  (+info)

Late quaternary extinction of a tree species in eastern North America. (27/2344)

Widespread species- and genus-level extinctions of mammals in North America and Europe occurred during the last deglaciation [16,000-9,000 yr B.P. (by (14)C)], a period of rapid and often abrupt climatic and vegetational change. These extinctions are variously ascribed to environmental change and overkill by human hunters. By contrast, plant extinctions since the Middle Pleistocene are undocumented, suggesting that plant species have been able to respond to environmental changes of the past several glacial/interglacial cycles by migration. We provide evidence from morphological studies of fossil cones and anatomical studies of fossil needles that a now-extinct species of spruce (Picea critchfieldii sp. nov.) was widespread in eastern North America during the Last Glacial Maximum. P. critchfieldii was dominant in vegetation of the Lower Mississippi Valley, and extended at least as far east as western Georgia. P. critchfieldii disappeared during the last deglaciation, and its extinction is not directly attributable to human activities. Similarly widespread plant species may be at risk of extinction in the face of future climate change.  (+info)

Allosaurus, crocodiles, and birds: evolutionary clues from spiral computed tomography of an endocast. (28/2344)

Because the brain does not usually leave direct evidence of its existence in the fossil record, our view of this structure in extinct species has relied upon inferences drawn from comparisons between parts of the skeleton that do fossilize or with modern-day relatives that survived extinction. However, soft-tissue structure preservation may indeed occasionally occur, particularly in the endocranial space. By applying modern imaging and analysis methods to such natural cranial "endocasts," we can now learn more than ever thought possible about the brains of extinct species. I will discuss one such example in which spiral computed tomography (CT) scanning analysis has been successfully applied to reveal preserved internal structures of a naturally occurring endocranial cast of Allosaurus fragilis, the dominant carnivorous dinosaur of the late Jurassic period. The ability to directly examine the neuroanatomy of an extinct dinosaur, whose modern-day relatives are birds and crocodiles, has exciting implications about Allosaurus' behavior, its adaptive responses to its environment, and its eventual extinction.  (+info)

A simple explanation for taxon abundance patterns. (29/2344)

For taxonomic levels higher than species, the abundance distributions of the number of subtaxa per taxon tend to approximate power laws but often show strong deviations from such laws. Previously, these deviations were attributed to finite-time effects in a continuous-time branching process at the generic level. Instead, we describe herein a simple discrete branching process that generates the observed distributions and find that the distribution's deviation from power law form is not caused by disequilibration, but rather that it is time independent and determined by the evolutionary properties of the taxa of interest. Our model predicts-with no free parameters-the rank-frequency distribution of the number of families in fossil marine animal orders obtained from the fossil record. We find that near power law distributions are statistically almost inevitable for taxa higher than species. The branching model also sheds light on species-abundance patterns, as well as on links between evolutionary processes, self-organized criticality, and fractals.  (+info)

Microscopic investigation in fossil hominoidea: a clue to taxonomy, functional anatomy, and the history of diseases. (30/2344)

Ten selected samples of fossilized bones (including Australopithecus, Homo erectus, Homo neandertalensis, and Homo sapiens sapiens) were examined by light microscopy using plane and polarized light. The histomorphological findings show that microscopic research adds much to what can be ascertained by marcoscopic examination or by X-ray techniques. In particular, emphasis was placed on taxonomy, functional anatomy of bones, and causes of some of the diseases of early hominids. Anat Rec (New Anat): 257:225-232, 1999.  (+info)

Morphological variation in great ape and modern human mandibles. (31/2344)

Adult mandibles of 317 modern humans and 91 great apes were selected that showed no pathology. Adult mandibles of Pan troglodytes troglodytes, Pongo pygmaeus pygmaeus and Gorilla gorilla gorilla and from 2 modern human populations (Zulu and Europeans from Spitalfields) were reliably sexed. Thirteen measurements were defined and included mandibular height, length and breadth in representative positions. Univariate statistical techniques and multivariate (principal component analysis and discriminant analysis) statistical techniques were used to investigate interspecific variability and sexual dimorphism in human and great ape mandibles, and intraspecific variability among the modern human mandibles. Analysis of interspecific differences revealed some pairs of variables with a tight linear relationship and others where Homo and the great apes pulled apart from one another due to shape differences. Homo and Pan are least sexually dimorphic in the mandible, Pan less so than Homo sapiens, but both the magnitude of sexual dimorphism and the distribution of sexually dimorphic measurements varied both among and between modern humans and great apes. Intraspecific variation among the 10 populations of modern humans was less than that generally reported in studies of crania (74.3% of mandibles were correctly classified into 1 of 10 populations using discriminant functions based on 13 variables as compared with 93% of crania from 17 populations based on 70 variables in one extensive study of crania). A subrecent European population (Poundbury) emerged as more different from a recent European population (Spitalfields) than other more diverse modern populations were from each other, suggesting considerable morphological plasticity in the mandible through time. This study forms a sound basis on which to explore mandibular variation in Neanderthals, early Homo sapiens and other more ancient fossil hominids.  (+info)

Relationships of the extinct moa-nalos, flightless Hawaiian waterfowl, based on ancient DNA. (32/2344)

The extinct moa-nalos were very large, flightless waterfowl from the Hawaiian islands. We extracted, amplified and sequenced mitochondrial DNA from fossil moa-nalo bones to determine their systematic relationships and lend insight into their biogeographical history. The closest living relatives of these massive, goose-like birds are the familiar dabbling ducks (tribe Anatini). Moa-nalos, however, are not closely related to any one extant species, but represent an ancient lineage that colonized the Hawaiian islands and evolved flightlessness long before the emergence of the youngest island, Hawaii, from which they are absent. Ancient DNA yields a novel hypothesis for the relationships of these bizarre birds, whereas the evidence of phylogeny in morphological characters was obscured by the evolutionary transformation of a small, volant duck into a giant, terrestrial herbivore.  (+info)