Access to Electric Light Is Associated with Shorter Sleep Duration in a Traditionally Hunter-Gatherer Community.

Access to electric light might have shifted the ancestral timing and duration of human sleep. To test this hypothesis, we studied two communities of the historically hunter-gatherer indigenous Toba/Qom in the Argentinean Chaco. These communities share the same ethnic and sociocultural background, but one has free access to electricity while the other relies exclusively on natural light. We fitted participants in each community with wrist activity data loggers to assess their sleep-wake cycles during one week in the summer and one week in the winter. During the summer, participants with access to electricity had a tendency to a shorter daily sleep bout (43 ± 21 min) than those living under natural light conditions. This difference was due to a later daily bedtime and sleep onset in the community with electricity, but a similar sleep offset and rise time in both communities. In the winter, participants without access to electricity slept longer (56 ± 17 min) than those with access to electricity, and this was also related to earlier bedtimes and sleep onsets than participants in the community with electricity. In both communities, daily sleep duration was longer during the winter than during the summer. Our field study supports the notion that access to inexpensive sources of artificial light and the ability to create artificially lit environments must have been key factors in reducing sleep in industrialized human societies.

Análisis longitudinal del comportamiento reproductivo de una población Toba en transición / /Análise longitudinal do comportamento reprodutivo de uma população Toba em transição / /Longitudinal analysis of reproductive behavior of a Toba transition population

Las variaciones demográficas de una población están frecuentemente asociadas a cambios ambientales. Por lo tanto, las particularidades sociales, económicas y culturales de poblaciones indígenas producirían una gran variedad de regímenes demográficos. Si bien en América Latina, en general, y Argentina, en particular, se registró un importante descenso de la fecundidad, las poblaciones indígenas exhiben cambios demográficos que difieren de esta tendencia. Este trabajo analiza parámetros de fecundidad y sus determinantes de la población Toba Cacique Sombrero Negro del norte argentino, la cual atraviesa cambios en su estilo de vida. Se entrevistaron 336 mujeres calculando las tasas de fecundidad, la probabilidad de agrandamiento de la familia y la tasa de esterilidad primaria para las mujeres nacidas entre 1920 y 1966. Se estimó la edad materna al primer hijo, el intervalo intergénesico, la edad materna al último hijo. Los resultados indican que, respecto a las mujeres nacidas entre 1920 y 1945, las mujeres nacidas entre 1946 y 1966, muestran un incremento de la fecundidad, una disminución de la edad materna al primer hijo, un mayor ritmo reproductivo y un incremento de la edad materna al último hijo. Estos resultados sugieren cambios sociales, sanitarios, biológicos y económicos favorables que habrían determinado el incremento de la fecundidad para la cohorte más joven...

As mudanças demográficas na população, muitas vezes, respondem às mudanças ambientais. Portanto, as características sociais, econômicas e culturais das populações indígenas produzem uma variedade de regimes demográficos. Enquanto na América Latina, em geral, e na Argentina, em particular, registrou-se um declínio significativo da fecundidade, as populações indígenas apresentam mudanças demográficas que diferem dessa tendência. Este artigo analisa os determinantes da fecundidade e da população Toba Cacique Black Hat, do norte da Argentina, por meio dos quais ocorreram mudanças em seu estilo de vida. Foram entrevistadas 336 mulheres, calculando-se as taxas de fecundidade, a probabilidade de uma família ampliada e a taxa de esterilidade primária para mulheres nascidas entre 1920 e 1966. Estimaram-se idade materna no primeiro parto, intervalo de nascimento e idade da mãe no último filho. Foram registrados aumento na fecundidade, diminuição na idade materna no primeiro filho, taxa de reprodução mais elevada e um aumento da idade materna no último filho na coorte de nascidas entre 1946 e 1966. Os resultados sugerem mudanças sociais, de saúde, biológicas e econômicas favoráveis, que têm proporcionado o aumento da fecundidade em coortes mais jovens...

Demographic variations in a given population are frequently associated to environmental changes. The social, economic, and cultural particularities of indigenous populations would then produce a great variety of demographic regimes. Although Latin America, in general, and in Argentina, in particular, have experienced an important decline in fertility, indigenous populations in this region show demographic changes that are at odds with this trend. This study evaluates fertility parameters and their determinants in the Toba population of Cacique Sombrero Negro, in northern Argentina, which is undergoing a significant lifestyle change. A total of 336 Toba women were interviewed, allowing the calculation of age-specific fertility rates, total fertility rates, parity progression ratios and primary infertility rates for women born between 1920 and 1966. For these women, we also estimated age of the mother at first birth, interbirth intervals and mother's age at last birth. Our results indicate that, compared to women born between 1920 and 1945, those born between 1946 y 1966 show an increase in fertility values, a decline in age at first birth, a faster reproductive pace and an increase in age at last birth. These results suggest favorable social, sanitary, biological and economic changes that would have determined an increase in fertility parameters in the younger cohort...

The reproductive transition in an indigenous population of northern Argentina.

Latin America has been registering a fast decrease in fertility rates since the mid-twentieth century. This change can be linked to the modernization process these populations have been undergoing. However, research with Latin American indigenous populations, which are undergoing relatively similar lifestyle changes, shows very different trends in fertility. The aim of this study was to analyze fertility patterns in the indigenous Toba community of Cacique Sombrero Negro, which is experiencing a rapid process of economic and social Westernization. Fertility patterns were analyzed between 1981 and 1999, the period for which the most accurate records were found. Results showed an overall increase in fertility rates and changes in the age of peak fertility across time periods. It is hypothesized that the lifestyle transition this population is experiencing leads to better access to resources that, in the absence of contraception, allow for a higher number of offspring. Nevertheless, this higher resource availability would be differential, affecting mostly the fertility of younger mothers.