Six new loci associated with body mass index highlight a neuronal influence on body weight regulation

Common variants at only two loci, FTO and MC4R, have been reproducibly associated with body mass index (BMI) in humans. To identify additional loci, we conducted meta-analysis of 15 genome-wide association studies for BMI (n > 32,000) and followed up top signals in 14 additional cohorts (n > 59,000). We strongly confirm FTO and MC4R and identify six additional loci (P < 5 x 10(-8)): TMEM18, KCTD15, GNPDA2, SH2B1, MTCH2 and NEGR1 (where a 45-kb deletion polymorphism is a candidate causal variant). Several of the likely causal genes are highly expressed or known to act in the central nervous system (CNS), emphasizing, as in rare monogenic forms of obesity, the role of the CNS in predisposition to obesity.

Pre-Columbian raised-field agriculture and land use in the Bolivian Amazon

We present an integrated palaeoecological and archaeobotanical study of pre-Columbian raised-field agriculture in the Llanos de Moxos, a vast seasonally inundated forest–savanna mosaic in the Bolivian Amazon. Phytoliths from excavated raised-field soil units, together with pollen and charcoal in sediment cores from two oxbow lakes, were analysed to provide a history of land use and agriculture at the El Cerro raised-field site. The construction of raised fields involved the removal of savanna trees, and gallery forest was cleared from the area by AD 310. Despite the low fertility of Llanos de Moxos soils, we determined that pre-Columbian raised-field agriculture sufficiently improved soil conditions for maize cultivation. Fire was used as a common management practice until AD 1300, at which point, the land-use strategy shifted towards less frequent burning of savannas and raised fields. Alongside a reduction in the use of fire, sweet potato cultivation and the exploitation of Inga fruits formed part of a mixed resource strategy from AD 1300 to 1450. The pre-Columbian impact on the landscape began to lessen around AD 1450, as shown by an increase in savanna trees and gallery forest. Although agriculture at the site began to decline prior to European arrival, the abandonment of raised fields was protracted, with evidence of sweet potato cultivation occurring as late as AD 1800.