Some science stories I found interesting below the fold.
First, from the “evolution is irrelevant to medicine” department, and from Science Daily 16th-Century Korean Mummy Provides Clue to Hepatitis B Virus Genetic Code. Scientists extracted genetic material of the Hepatitis B virus from the liver of a Korean mummy dating to the 16th century.
Using modern-day molecular genetic techniques, the researchers compared the ancient DNA sequences with contemporary viral genomes disclosing distinct differences. The changes in the genetic code are believed to result from spontaneous mutations and possibly environmental pressures during the virus evolutionary process. Based on the observed mutations rates over time, the analysis suggests that the reconstructed mummy’s hepatitis B virus DNA had its origin between 3,000 to 100,000 years ago.
Next, an article in Science looks at Kinship Categories Across Languages Reflect General Communicative Principles. I don’t have access, but here is the abstract:
Languages vary in their systems of kinship categories, but the scope of possible variation appears to be constrained. Previous accounts of kin classification have often emphasized constraints that are specific to the domain of kinship and are not derived from general principles. Here, we propose an account that is founded on two domain-general principles: Good systems of categories are simple, and they enable informative communication. We show computationally that kin classification systems in the world’s languages achieve a near-optimal trade-off between these two competing principles. We also show that our account explains several specific constraints on kin classification proposed previously. Because the principles of simplicity and informativeness are also relevant to other semantic domains, the trade-off between them may provide a domain-general foundation for variation in category systems across languages.
A paper in PNAS looks at Community differentiation and kinship among Europe’s first farmers. Researches used strontium isotope analysis to look at community structure in the Central European Neolithic. I don’t have access but here is the abstract:
Community differentiation is a fundamental topic of the social sciences, and its prehistoric origins in Europe are typically assumed to lie among the complex, densely populated societies that developed millennia after their Neolithic predecessors. Here we present the earliest, statistically significant evidence for such differentiation among the first farmers of Neolithic Europe. By using strontium isotopic data from more than 300 early Neolithic human skeletons, we find significantly less variance in geographic signatures among males than we find among females, and less variance among burials with ground stone adzes than burials without such adzes. From this, in context with other available evidence, we infer differential land use in early Neolithic central Europe within a patrilocal kinship system.
An interesting paper in Nature, Birds have paedomorphic dinosaur skulls, uses geometric morphometrics to understand the evolution of avian skulls. Here is the abstract:
The interplay of evolution and development has been at the heart of evolutionary theory for more than a century. Heterochrony—change in the timing or rate of developmental events—has been implicated in the evolution of major vertebrate lineages such as mammals, including humans1. Birds are the most speciose land vertebrates, with more than 10,000 living species representing a bewildering array of ecologies. Their anatomy is radically different from that of other vertebrates. The unique bird skull houses two highly specialized systems: the sophisticated visual and neuromuscular coordination system, allows flight coordination and exploitation of diverse visual landscapes, and the astonishing variations of the beak enable a wide range of avian lifestyles. Here we use a geometric morphometric approach integrating developmental, neontological and palaeontological data to show that the heterochronic process of paedomorphosis, by which descendants resemble the juveniles of their ancestors, is responsible for several major evolutionary transitions in the origin of birds. We analysed the variability of a series of landmarks on all known theropod dinosaur skull ontogenies as well as outgroups and birds. The first dimension of variability captured ontogeny, indicating a conserved ontogenetic trajectory. The second dimension accounted for phylogenetic change towards more bird-like dinosaurs. Basally branching eumaniraptorans and avialans clustered with embryos of other archosaurs, indicating paedomorphosis. Our results reveal at least four paedomorphic episodes in the history of birds combined with localized peramorphosis (development beyond the adult state of ancestors) in the beak. Paedomorphic enlargement of the eyes and associated brain regions parallels the enlargement of the nasal cavity and olfactory brain in mammals. This study can be a model for investigations of heterochrony in evolutionary transitions, illuminating the origin of adaptive features and inspiring studies of developmental mechanisms.
PLoS One has a paper that looks at Functional Morphometric Analysis of the Furcula in Mesozoic Birds The article is open access. I haven’t read it yet so here is the abstract:
The furcula displays enormous morphological and structural diversity. Acting as an important origin for flight muscles involved in the downstroke, the form of this element has been shown to vary with flight mode. This study seeks to clarify the strength of this form-function relationship through the use of eigenshape morphometric analysis coupled with recently developed phylogenetic comparative methods (PCMs), including phylogenetic Flexible Discriminant Analysis (pFDA). Additionally, the morphospace derived from the furculae of extant birds is used to shed light on possible flight adaptations of Mesozoic fossil taxa. While broad conclusions of earlier work are supported (U-shaped furculae are associated with soaring, strong anteroposterior curvature with wing-propelled diving), correlations between form and function do not appear to be so clear-cut, likely due to the significantly larger dataset and wider spectrum of flight modes sampled here. Interclavicular angle is an even more powerful discriminator of flight mode than curvature, and is positively correlated with body size. With the exception of the close relatives of modern birds, the ornithuromorphs, Mesozoic taxa tend to occupy unique regions of morphospace, and thus may have either evolved unfamiliar flight styles or have arrived at similar styles through divergent musculoskeletal configurations.
PhysOrg has an interesting bit on what dental calculus ( a subject I have blogged aboutbefore) can tell us about the diet of Neanderthals (among others). Whereas in the post of mine, linked to above, the researched concerned the DNA of the bacteria that form plaque, and eventually carries, this paper deals with solidified plaque – called calculus – and the organic materials that can become trapped in it.
Calculus contains pollen grains and microscopic fossilized plant pieces called phytoliths, in addition to starch grains and even bacteria. Fragments of bacterial DNA found in calculus can help identify specific pathogens that were once present in the mouths of ancient people.
The plant evidence can be definitive enough to suggest the species that was consumed, or it may suggest what part of a plant was eaten, such as a fruit or leaf. This can help track the use, spread and evolution of food plants, including agricultural varieties, through time and space.
Finally, Nature Geoscience has an interesting paper, Landslide erosion coupled to tectonics and river incision that looks at the effects of the interaction of plate tectonics, stream cutting, and landslides on the landscape. I don’t have access, but here is the abstract:
The steep topography of mountain landscapes arises from interactions among tectonic rock uplift, valley incision and landslide erosion on hillslopes. Hillslopes in rapidly uplifting landscapes are thought to respond to river incision into bedrock by steepening to a maximum stable or ‘threshold’ angle1, 2, 3. Landslide erosion rates are predicted to increase nonlinearly as hillslope angles approach the threshold angle1, 2, 3, 4, 5, 6, 7. However, the key tenet of this emerging threshold hillslope model of landscape evolution—the coupled response of landslide erosion to tectonic and fluvial forcing—remains untested. Here we quantify landslide erosion rates in the eastern Himalaya, based on mapping more than 15,000 landslides on satellite images. We show that landslide erosion rates are significantly correlated with exhumation rates and stream power and that small increases in mean hillslope angles beyond 30° translate into large and significant increases in landslide erosion. Extensive landsliding in response to a large outburst flood indicates that lateral river erosion is a key driver of landslide erosion on threshold hillslopes. Our results confirm the existence of threshold hillslopes and demonstrate that an increase in landslide erosion rates, rather than steepened hillslope angles, is the primary mechanism by which steep uplands respond to and balance rapid rates of rock uplift and bedrock river incision in tectonically active mountain belts.
Incidentally, I would recommend reading the above paper in conjunction with Landscapes of human evolution: models and methods of tectonic geomorphology and the reconstruction of hominin landscapes and Landscapes and their relation to hominin habitats: Case studies from Australopithecus sites in eastern and southern Africa.
Filed under: Interesting Science News |