Numerous studies of human populations in Europe and Asia have revealed a concordance between their extant genetic structure and the prevailing regional pattern of geography and language. For native South Americans, however, such evidence has been lacking so far. Therefore, we examined the relationship between Y-chromosomal genotype on the one hand, and male geographic origin and linguistic affiliation on the other, in the largest study of South American natives to date in terms of sampled individuals and populations. A total of 1,011 individuals, representing 50 tribal populations from 81 settlements, were genotyped for up to 17 short tandem repeat (STR) markers and 16 single nucleotide polymorphisms (Y-SNPs), the latter resolving phylogenetic lineages Q and C. Virtually no structure became apparent for the extant Y-chromosomal genetic variation of South American males that could sensibly be related to their inter-tribal geographic and linguistic relationships. This continent-wide decoupling is consistent with a rapid peopling of the continent followed by long periods of isolation in small groups. Furthermore, for the first time, we identified a distinct geographical cluster of Y-SNP lineages C-M217 (C3*) in South America. Such haplotypes are virtually absent from North and Central America, but occur at high frequency in Asia. Together with the locally confined Y-STR autocorrelation observed in our study as a whole, the available data therefore suggest a late introduction of C3* into South America no more than 6,000 years ago, perhaps via coastal or trans-Pacific routes. Extensive simulations revealed that the observed lack of haplogroup C3* among extant North and Central American natives is only compatible with low levels of migration between the ancestor populations of C3* carriers and non-carriers. In summary, our data highlight the fact that a pronounced correlation between genetic and geographic/cultural structure can only be expected under very specific conditions, most of which are likely not to have been met by the ancestors of native South Americans.

BackgroundOne of the most important dietary shifts underwent by human populations began to occur in the Neolithic, during which new modes of subsistence emerged and new nutrients were introduced in diets. This change might have worked as a selective pressure over the metabolic pathways involved in the breakdown of substances extracted from food. Here we applied a candidate gene approach to investigate whether in populations with different modes of subsistence, diet-related genetic adaptations could be identified in the genes AGXT, PLRP2, MTRR, NAT2 and CYP3A5.ResultsAt CYP3A5, strong signatures of positive selection were detected, though not connected to any dietary variable, but instead to an environmental factor associated with the Tropic of Cancer. Suggestive signals of adaptions that could indeed be connected with differences in dietary habits of populations were only found for PLRP2 and NAT2. Contrarily, the demographic history of human populations seemed enough to explain patterns of diversity at AGXT and MTRR, once both conformed the evolutionary expectations under selective neutrality.ConclusionsAccumulated evidence indicates that CYP3A5 has been under adaptive evolution during the history of human populations. PLRP2 and NAT2 also appear to have been modelled by some selective constrains, although clear support for that did not resist to a genome wide perspective. It is still necessary to clarify which were the biological mechanisms and the environmental factors involved as well as their interactions, to understand the nature and strength of the selective pressures that contributed to shape current patterns of genetic diversity at those loci.Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-015-0212-1) contains supplementary material, which is available to authorized users.

One of the most challenging points for ancient DNA studies on human remains is that analysing procedures involve partial or total destruction of the samples, which usually are unique and irreplaceable. This is what prevents museums, anthropologists or archaeologists from giving samples for genetic investigation. So that it is interesting to find an analysing method without destroying them. In this study, it was carried out the evaluation of a non-destructive extraction DNA protocol on 4 Neolithic individuals, from Can Gambús (Sabadell, Spain) and 4 pre Bell Beaker period individuals, from Los Cercados (Valladolid, Spain). Along this work, it was discussed the efficiency of the non-destructive protocol, valuing the obtained result, and the evidences state of preservation after the whole procedure.

Column title: G277S does not affect iron absorption in iron deficient women ABSTRACT Background. Iron deficiency anaemia is one of the most important nutritional

The extent of racemization of aspartic acid (Asp) -expressed as D/L ratio-has been used as a marker of biomolecular degradation in ancient remains. However, Asp racemization rate is highly variable, and depends on biochemical and geochemical factors. In this paper we aim to determine to which extent the fraction analyzed and the Results show significant differences between the D/L Asp ratios obtained in dentine and whole tooth fractions from the same tooth and individual, as well as among dentine samples from the same archaeological site and among samples of the same age from different, though nearby, archaeological sites. Ancient DNA (aDNA) could be characterized in the majority of the samples, independently from their racemization values, which suggests that other factors, apart from the sample preservation stage, are more significantly affecting the racemization rate. A generalized use of the Asp racemization ratio as a threshold value for ancient DNA preservation needs to be questioned until further methodological standardization is considered.