Adaptations to water stress and pastoralism in the Turkana of northwest Kenya.

The Turkana people inhabit arid regions of east Africa-where temperatures are high and water is scarce-and they practice subsistence pastoralism, such that their diet is primarily composed of animal products. Working with Turkana communities, we sequenced 367 genomes and identified 8 regions putatively involved in adaptation to water stress and pastoralism. One of these regions includes a putative enhancer for STC1-a kidney-expressed gene involved in the response to dehydration and the metabolism of purine-rich foods such as red meat. We show that STC1 is induced by antidiuretic hormone in humans, is associated with urea levels in the Turkana themselves, and is under strong selection in this population (s∼0.041). This work highlights that partnerships with subsistence-level groups can lead to new models of human physiology with biomedical relevance.

Heritability of anti-predatory traits: vigilance and locomotor performance in marmots.

Animals must allocate some proportion of their time to detecting predators. In birds and mammals, such anti-predator vigilance has been well studied, and we know that it may be influenced by a variety of intrinsic and extrinsic factors. Despite hundreds of studies focusing on vigilance and suggestions that there are individual differences in vigilance, there have been no prior studies examining its heritability in the field. Here, we present one of the first reports of (additive) genetic variation in vigilance. Using a restricted maximum likelihood procedure, we found that, in yellow-bellied marmots (Marmota flaviventris), the heritability of locomotor ability (h(2)=0.21), and especially vigilance (h(2) = 0.08), is low. These modest heritability estimates suggest great environmental variation or a history of directional selection eliminating genetic variation in these traits. We also found a significant phenotypic (r(P) = -0.09 +/- 0.04, P = 0.024) and a substantial, but not significant, genetic correlation (r(A) = -0.57 +/- 0.28, P = 0.082) between the two traits (slower animals are less vigilant while foraging). We found no evidence of differential survival or longevity associated with particular phenotypes of either trait. The genetic correlation may persist because of environmental heterogeneity and genotype-by-environment interactions maintaining the correlation, or because there are two ways to solve the problem of foraging in exposed areas: be very vigilant and rely on early detection coupled with speed to escape, or reduce vigilance to minimize time spent in an exposed location. Both strategies seem to be equally successful, and this 'locomotor ability-wariness' syndrome may therefore allow slow animals to compensate behaviourally for their impaired locomotor ability.

Cancer mortality and saccharin consumption in diabetics.

The mortality experience of 5971 members of the British Diabetic Association (BDA) was followed-up for between five and eight years to mid-1973. Overall, 1207 deaths occurred compared with 778 expected from the mortality of the population of England and Wales in 1972. This excess of deaths was due almost entirely to diabetes mellitus and ischaemic heart disease. Deaths from cancer (128) were significantly fewer than expected (168), mainly because of a deficit in the number of deaths from cancers related to smoking (cancers of the buccal cavity and pharynx, oesophagus, respiratory system, and bladder). There was also a lower than expected mortality from chronic bronchitis and emphysema. Data on saccharin consumption by BDA members showed that more than half of them used saccharin tablets daily, with an overall daily intake of three to six tablets, depending on age and sex. Information on a small sample of survivors from the mortality study suggested that about 23% of them would have taken saccharin daily for 10 years or more and 10% for 25 years or more by the end of the follow-up. It was concluded that these relatively high levels of saccharin intake had not increased the risk of cancer in general among BDA members.