Evolutionary medicine approaches to chronic disease: The case of irritable bowel syndrome.

Irritable bowel syndrome (IBS), a gastrointestinal disease, is a global phenomenon correlated with industrialization. We propose that an evolutionary medicine approach is useful to understand this disease from an ultimate perspective and conducted a scoping literature review to synthesize the IBS literature within this framework. Our review suggests five potential evolutionary hypotheses for the cause of IBS, including (a) a dietary mismatch accompanying a nutritional transition, (b) an early hygienic life environment leading to the immune system and microbiotic changes, (c) an outcome of decreased physical activity, (d) a response to changes in environmental light-dark cycles, and (e) an artifact of an evolved fight or flight response. We find key limitations in the available data needed to understand early life, nutritional, and socioeconomic experiences that would allow us to understand evolutionarily relevant risk factors and identify a need for further empirical research to distinguish potential causes and test evolutionary hypotheses.

Variation in the fusion sequence of primary and secondary ossification centers in the human skeleton.

OBJECTIVES: One of the biggest challenges for biological anthropologists is determining the minimum number of individuals in commingled skeletal samples in forensic or bioarcheological contexts. The fusion sequence of primary and secondary ossification centers is a promising, yet under-explored, process to improve identification of associated remains of subadults and young adults, but is limited by the lack of understanding of population variation in this aspect of human development. While prior studies show within-population variation in fusion sequence, possible geographic variation has not been systematically explored. MATERIALS AND METHODS: To explore potential variation in fusion sequence in different populations, we analyzed eight skeletal samples of East Asian, North American, African, and European ancestry. Forty-three epiphyses were cross tabulated to determine the order of beginning and completing fusion for each geographic group. Results were distilled into modal sequence (most common order) trajectories, including the variation around the modal sequence. RESULTS: Population variation occurs within and across all geographic groups, especially in later fusing sites. Some sites, such as the acromion and sacral elements, consistently exhibit greater variability. Among outliers from the modal sequence, it is more common for early-fusing sites to fuse late than for later-fusing sites to fuse early. The completing fusion trajectories vary less than the beginning fusion trajectories. DISCUSSION: Despite considerable variation within and among different geographic groups, there are shared commonalities across different samples that can facilitate differentiation of multiple individuals. With fewer outliers, the completing fusion trajectories are potentially of greater practical use in forensic and bioarcheological practice.