HENRY

Roughly 50% of the primate genome consists of mobile, repetitive DNA sequences such as Alu and LINE1 elements. The causes and evolutionary consequences of mobile element insertion, which have received considerable attention during the past decade, are reviewed in this article. Because of their unique mutational mechanisms, these elements are highly useful for answering phylogenetic questions.

 We demonstrate how they have been used to help resolve a number of questions in primate phylogeny, including the human-chimpanzee-gorilla trichotomy and New World primate phylogeny. Alu and LINE1 element insertion polymorphisms have also been analyzed in human populations to test hypotheses about human evolution and population affinities and to address forensic issues. Finally, these elements have had impacts on the genome itself. We review how they have influenced fundamental ongoing processes like nonhomologous recombination, genomic deletion, and X chromosome inactivation.

From: Mobile DNA elements in primate and human evolution (abstract).

A new Homo erectus find has shown that Tuberculosis is much older than originally thought. Previously, the earliest definite proof of TB’s existence dates to around 18,000 years in fossilised Buffalo, but this new skull shows small lesions that are characteristic of Tb and dates to around 500,000 years ago.  This suggests that TB has a long history of infecting not just humans, but other hominins too.

The paper, First Homo erectus from Turkey and implications for migrations into temperate Eurasia, is available in the American Journal of Physical Anthropology, and the abstract says -

Remains of fossil hominins from temperate regions of the Old World are rare across both time and space, but such specimens are necessary for understanding basic issues in human evolution including linkages between their adaptations and early migration patterns. We report here the remarkable circumstances surrounding the discovery of the first fossil hominin calvaria from Turkey. The specimen was found in the Denizli province of western Turkey and recovered from within a solid block of travertine stone as it was being sawed into tile-sized slabs for the commercial natural stone building market. The new specimen fills an important geographical and temporal gap and displays several anatomical features that are shared with other Middle Pleistocene hominins from both Africa and Asia attributed to Homo erectus.

It also preserves an unusual pathology on the endocranial surface of the frontal bone that is consistent with a diagnosis of Leptomeningitis tuberculosa (TB), and this evidence represents the most ancient example of this disease known for a fossil human. TB is exacerbated in dark-skinned peoples living in northern latitudes by a vitamin D deficiency because of reduced levels of ultraviolet radiation (UVR). Evidence for TB in the new specimen supports the thesis that reduced UVR was one of the many climatic variables presenting an adaptive challenge to ancient hominins during their migration into the temperate regions of Europe and Asia.

My new “favorite” blog -  The “Blog” of “Unnecessary” Quotation Marks

I recall something that I believe I heard Carl Sagan say either in an episode of Cosmos or in one of his earlier books, that one could store enough information to hold an entire encyclopedia by putting a notch in a stick, if only one could measure where the notch lies to some absurd astronomically precise figure.

The folks over at Whateveresque have been busy translating John Scalzi’s trip to the Creation museum (which we talked about last month) into LOLCat. Pages and pages of hilarious fun. My favorite is by Johnny Highground:

More wonderful pictures here…

Here, Eddie Izzard proposes his “Scrabble theory of English Spelling”, with a digression on the need for bilingualism:

Long-term evolution of transposable elements:

Transposable elements are often considered parasitic DNA sequences, able to invade the genome of their host thanks to their self-replicating ability. This colonization process has been extensively studied, both theoretically and experimentally, but their long-term coevolution with the genomes is still poorly understood. In this work, we aim to challenge previous population genetics models by considering features of transposable elements as quantitative, rather than discrete, variables. We also describe more realistic transposable element dynamics by accounting for the variability of the insertion effect, from deleterious to adaptive, as well as mutations leading to a loss of transposition activity and to nonautonomous copies. Individual-based simulations of the behavior of a transposable-element family over several thousand generations show different ways in which active or inactive copies can be maintained for a very long time. Results reveal an unexpected impact of genetic drift on the “junk DNA” content of the genome and strongly question the likelihood of the sustainable long-term stable transposition-selection equilibrium on which numerous previous works were based.