Dating the Origin of Language Using Phonemic Diversity

Language is a key adaptation of our species, yet we do not know when it evolved. Here, we use data on language phonemic diversity to estimate a minimum date for the origin of language. We take advantage of the fact that phonemic diversity evolves slowly and use it as a clock to calculate how long the oldest African languages would have to have been around in order to accumulate the number of phonemes they possess today. We use a natural experiment, the colonization of Southeast Asia and Andaman Islands, to estimate the rate at which phonemic diversity increases through time. Using this rate, we estimate that present-day languages date back to the Middle Stone Age in Africa. Our analysis is consistent with the archaeological evidence suggesting that complex human behavior evolved during the Middle Stone Age in Africa, and does not support the view that language is a recent adaptation that has sparked the dispersal of humans out of Africa. While some of our assumptions require testing and our results rely at present on a single case-study, our analysis constitutes the first estimate of when language evolved that is directly based on linguistic data

Patterns of Polymorphism and Demographic History in Natural Populations of Arabidopsis lyrata

Many of the processes affecting genetic diversity act on local populations. However, studies of plant nucleotide diversity have largely ignored local sampling, making it difficult to infer the demographic history of populations and to assess the importance of local adaptation. Arabidopsis lyrata, a self-incompatible, perennial species with a circumpolar distribution, is an excellent model system in which to study the roles of demographic history and local adaptation in patterning genetic variation.We studied nucleotide diversity in six natural populations of Arabidopsis lyrata, using 77 loci sampled from 140 chromosomes. The six populations were highly differentiated, with a median FST of 0.52, and structure analysis revealed no evidence of admixed individuals. Average within-population diversity varied among populations, with the highest diversity found in a German population; this population harbors 3-fold higher levels of silent diversity than worldwide samples of A. thaliana. All A. lyrata populations also yielded positive values of Tajima's D. We estimated a demographic model for these populations, finding evidence of population divergence over the past 19,000 to 47,000 years involving non-equilibrium demographic events that reduced the effective size of most populations. Finally, we used the inferred demographic model to perform an initial test for local adaptation and identified several genes, including the flowering time gene FCA and a disease resistance locus, as candidates for local adaptation events.Our results underscore the importance of population-specific, non-equilibrium demographic processes in patterning diversity within A. lyrata. Moreover, our extensive dataset provides an important resource for future molecular population genetic studies of local adaptation in A. lyrata

Fatores de risco para diárreia persistente em lactentes Risk factors to persistent diarrhea in infants

RACIONAL: A diarréia persistente é uma doença multicausal. A análise do risco para o prolongamento do quadro diarréico envolve variáveis ambientais, biológicas e do manejo clínico. OBJETIVO: Identificar fatores de risco para a diarréia persistente em crianças hospitalizadas na fase aguda do quadro diarréico. PACIENTES E MÉTODOS: O estudo foi do tipo caso-controle. A amostra consistiu de 216 crianças menores de 24 meses hospitalizadas por diarréia de início abrupto, no Instituto Materno-Infantil de Pernambuco, Recife, PE. O grupo de casos incluiu as crianças com diarréia persistente e o de controles aquelas com diarréia aguda. Foram analisadas variáveis socioeconômicas, biológicas, de morbidade anterior, clínicas e do manejo terapêutico prévio à admissão. Utilizou-se o odds ratio não ajustado e ajustado, com seus respectivos intervalos de confiança de 95%, observando-se o nível de significância de 5%. A análise multivariada foi feita através de regressão logística. RESULTADOS: O risco de persistência da diarréia foi maior nas crianças com: disenteria, febre no início do quadro, dieta suspensa e uso de antibiótico à admissão hospitalar. O risco de diarréia persistente foi cerca de três vezes maior para crianças sem geladeira no domicílio e que apresentavam hiperemia perianal ao exame físico na admissão hospitalar, sendo estas as variáveis que apresentaram significância estatística após o ajuste para fatores de confusão. CONCLUSÕES: A melhoria das condições ambientais e o manejo adequado e individualizado da criança hospitalizada por diarréia pode contribuir para a redução da morbidade da doença.<br>BACKGROUND: Persistent diarrhea is a multicausal disease. The analysis of risk factors for persistent diarrhea includes environmental and biological variables as well as therapeutical management. AIM: To identify risk factors for persistent diarrhea among children hospitalized with acute diarrhea. PATIENT AND METHODS: This is a case-control study. The sample consisted of 212 infants under 24 months, hospitalized with acute diarrhea, at the "Instituto Materno-Infantil de Pernambuco", Recife, PE, Brazil. Cases were infants with persistent diarrhea and controls those with acute diarrhea. Cases and controls were compared to a series of socio-economic, biological and clinical variables, previous morbidities and therapeutic management prior to hospital admission. Unadjusted and adjusted odds ratio were used with the respective 95% confidence intervals. It was adopted the level of significance of 5%. Logistic regression analysis was conducted to control for potential confounding factors. RESULTS: The risk of persistent diarrhea was higher for infants with: dysentery, fever at the onset of diarrhea, fasting and taking antibiotics prior to hospital admission. The variables that showed the highest adjusted odds ratios for persistent diarrhea were infants living in households without refrigerator and perianal hyperemia at hospital admission. CONCLUSIONS: The improvement of environmental conditions and an adequate clinical management of diarrhea for hospitalized infants may contribute to the reduction of diarrhea morbidity

Prevalence of Barrett's esophagus in individuals without typical symptoms of gastroesophageal reflux disease Prevalência do esôfago de Barrett em indivíduos sem sintomas típicos da doença por refluxo gastroesofágico

BACKGROUND: Barrett’s esophagus, the major risk factor for esophageal adenocarcinoma, is detected in approximately 10%-14% of individuals submitted to upper endoscopy for the assessment of gastroesophageal reflux disease related symptoms. Prevalence studies of Barrett’s esophagus in individuals without typical symptoms of gastroesophageal reflux disease have reported rates ranging from 0.6% to 25%. AIM: To determine the prevalence of Barrett’s in a Brazilian population older than 50 years without typical symptoms of gastroesophageal reflux disease. METHODS: A total of 104 patients (51 men), mean age of 65 years, with an indication for upper endoscopy but without symptoms of heartburn and/or acid regurgitation (determined with a validated questionnaire) were recruited. Subjects submitted to upper endoscopic examination in the last 10 years or using antisecretory medication (proton pump inhibitors) during the last 6 months were not included. Methylene blue chromoscopy was performed during the endoscopic exam to facilitate identification of the metaplastic epithelium. RESULTS: Barrett’s esophagus was diagnosed endoscopically and confirmed by histology in four patients, all of them males. The metaplastic segment was short (less than 3 cm) and free of dysplasia in all patients. The prevalence of Barrett’s esophagus was 7.75% in the male population and 3.8% in the general population studied. CONCLUSION: Due to the low prevalence of Barrett’s esophagus found in the present study, associated with the finding of short-segment Barrett’s esophagus in all cases diagnosed and the absence of dysplasia in the material analyzed, endoscopic screening for Barrett’s esophagus in patients above the age of 50 without the classical symptoms of gastroesophageal reflux disease is not indicated for the Brazilian population.<br>RACIONAL: O esôfago de Barrett, principal fator de risco para o adenocarcinoma do esôfago, é uma complicação da doença por refluxo gastroesofágico de longa duração, sendo detectado em, aproximadamente, 10%-14% dos indivíduos submetidos a endoscopia digestiva alta para avaliação de sintomas relacionados à doença por refluxo gastroesofágico. Estudos de prevalência do esôfago de Barrett em indivíduos sem sintomas típicos de doença por refluxo gastroesofágico mostram taxas oscilando entre 0,6% e 25%. OBJETIVO: Determinar a prevalência do esôfago de Barrett em indivíduos maiores de 50 anos sem os sintomas clássicos da doença por refluxo gastroesofágico. MÉTODOS: Foram recrutados 104 pacientes (51 homens e 53 mulheres), idade média 65 anos, com indicação de se submeterem a endoscopia digestiva alta, porém sem sintomas de pirose e/ou regurgitação ácida (certificados através de questionário validado). Foram excluídos indivíduos com exame endoscópico prévio nos últimos 10 anos ou que fizeram uso de medicação anti-secretora nos últimos 6 meses. Durante o exame endoscópico foi realizada cromoscopia com azul de metileno, para facilitar a identificação do epitélio metaplásico. RESULTADOS: O esôfago de Barrett foi diagnosticado por endoscopia e confirmado pela histologia em quatro pacientes, todos do sexo masculino. Os segmentos metaplásicos eram curtos (inferior a 3 cm) e livre de displasia em todos os pacientes. A prevalência encontrada foi de 7,75% na população masculina e 3,8% na população geral avaliada. CONCLUSÃO: Diante da baixa prevalência do esôfago de Barrett encontrada no presente estudo, associada ao achado de segmento curto de Barrett em todos os casos diagnosticados e ausência de displasia no material analisado, rastreamento endoscópico para o esôfago de Barrett em pacientes acima de 50 anos sem os sintomas clássicos da doença por refluxo gastroesofágico não se justificaria na população brasileira