Age of cichlids: new dates for ancient lake fish radiations

Timing divergence events allow us to infer the conditions under which biodiversity has evolved and gain important insights into the mechanisms driving evolution. Cichlid fishes are a model system for studying speciation and adaptive radiation, yet, we have lacked reliable timescales for their evolution. Phylogenetic reconstructions are consistent with cichlid origins prior to Gondwanan landmass fragmentation 121-165 MYA, considerably earlier than the first known fossil cichlids (Eocene). We examined the timing of cichlid evolution using a relaxed molecular clock calibrated with geological estimates for the ages of 1) Gondwanan fragmentation and 2) cichlid fossils. Timescales of cichlid evolution derived from fossil-dated phylogenies of other bony fishes most closely matched those suggested by Gondwanan breakup calibrations, suggesting the Eocene origins and marine dispersal implied by the cichlid fossil record may be due to its incompleteness. Using Gondwanan calibrations, we found accumulation of genetic diversity within the radiating lineages of the African Lakes Malawi, Victoria and Barombi Mbo, and Palaeolake Makgadikgadi began around or after the time of lake basin formation. These calibrations also suggest Lake Tanganyika was colonized independently by the major radiating cichlid tribes that then began to accumulate genetic diversity thereafter. These results contrast with the widely accepted theory that diversification into major lineages took place within the Tanganyika basin. Together, this evidence suggests that ancient lake habitats have played a key role in generating and maintaining diversity within radiating lineages and also that lakes may have captured preexisting cichlid diversity from multiple sources from which adaptive radiations have evolved.

Writing center handbooks and travel guidebooks : redesigning instructional texts for multicultural, multilingual, and multinational contexts

In an increasingly interconnected world characterized by the accelerating interplay of cultural, linguistic, and national difference, the ability to negotiate that difference in an equitable and ethical manner is a crucial skill for both individuals and larger social groups. This dissertation, Writing Center Handbooks and Travel Guidebooks: Redesigning Instructional Texts for Multicultural, Multilingual, and Multinational Contexts, considers how instructional texts that ostensibly support the negotiation of difference (i.e., accepting and learning from difference) actually promote the management of difference (i.e., rejecting, assimilating, and erasing difference). As a corrective to this focus on managing difference, chapter two constructs a theoretical framework that facilitates the redesign of handbooks, guidebooks, and similar instructional texts. This framework centers on reflexive design practices and is informed by literacy theory (Gee; New London Group; Street), social learning theory (Wenger), globalization theory (Nederveen Pieterse), and composition theory (Canagarajah; Horner and Trimbur; Lu; Matsuda; Pratt). By implementing reflexive design practices in the redesign of instructional texts, this dissertation argues that instructional texts can promote the negotiation of difference and a multicultural/multilingual sensibility that accounts for twenty-first century linguistic and cultural realities. Informed by the theoretical framework of chapter two, chapters three and four conduct a rhetorical analysis of two forms of instructional text that are representative of the larger genre: writing center coach handbooks and travel guidebooks to Hong Kong. This rhetorical analysis reveals how both forms of text employ rhetorical strategies that uphold dominant monolingual and monocultural assumptions. Alternative rhetorical strategies are then proposed that can be used to redesign these two forms of instructional texts in a manner that aligns with multicultural and multilingual assumptions. These chapters draw on the work of scholars in Writing Center Studies (Boquet and Lerner; Carino; DiPardo; Grimm; North; Severino) and Technical Communication (Barton and Barton; Dilger; Johnson; Kimball; Slack), respectively. Chapter five explores how the redesign of coach handbooks and travel guidebooks proposed in this dissertation can be conceptualized as a political act. Ultimately, this dissertation argues that instructional texts are powerful heuristic tools that can enact social change if they are redesigned to foster the negotiation of difference and to promote multicultural/multilingual world views.

Common and unexpected findings in mummies from ancient Egypt and South America as revealed by CT

Computed tomography (CT) has proved to be a valuable investigative tool for mummy research and is the method of choice for examining mummies. It allows for noninvasive insight, especially with virtual endoscopy, which reveals detailed information about the mummy's sex, age, constitution, injuries, health, and mummification techniques used. CT also supplies three-dimensional information about the scanned object. Mummification processes can be summarized as "artificial," when the procedure was performed on a body with the aim of preservation, or as "natural," when the body's natural environment resulted in preservation. The purpose of artificial mummification was to preserve that person's morphologic features by delaying or arresting the decay of the body. The ancient Egyptians are most famous for this. Their use of evisceration followed by desiccation with natron (a compound of sodium salts) to halt putrefaction and prevent rehydration was so effective that their embalmed bodies have survived for nearly 4500 years. First, the body was cleaned with a natron solution; then internal organs were removed through the cribriform plate and abdomen. The most important, and probably the most lengthy, phase was desiccation. After the body was dehydrated, the body cavities were rinsed and packed to restore the body's former shape. Finally, the body was wrapped. Animals were also mummified to provide food for the deceased, to accompany the deceased as pets, because they were seen as corporal manifestations of deities, and as votive offerings. Artificial mummification was performed on every continent, especially in South and Central America.