Stable population structure in Europe since the Iron Age, despite high mobility.

Ancient DNA research in the past decade has revealed that European population structure changed dramatically in the prehistoric period (14,000-3000 years before present, YBP), reflecting the widespread introduction of Neolithic farmer and Bronze Age Steppe ancestries. However, little is known about how population structure changed from the historical period onward (3000 YBP - present). To address this, we collected whole genomes from 204 individuals from Europe and the Mediterranean, many of which are the first historical period genomes from their region (e.g. Armenia and France). We found that most regions show remarkable inter-individual heterogeneity. At least 7% of historical individuals carry ancestry uncommon in the region where they were sampled, some indicating cross-Mediterranean contacts. Despite this high level of mobility, overall population structure across western Eurasia is relatively stable through the historical period up to the present, mirroring geography. We show that, under standard population genetics models with local panmixia, the observed level of dispersal would lead to a collapse of population structure. Persistent population structure thus suggests a lower effective migration rate than indicated by the observed dispersal. We hypothesize that this phenomenon can be explained by extensive transient dispersal arising from drastically improved transportation networks and the Roman Empire's mobilization of people for trade, labor, and military. This work highlights the utility of ancient DNA in elucidating finer scale human population dynamics in recent history.

A genetic history of continuity and mobility in the Iron Age central Mediterranean.

The Iron Age was a dynamic period in central Mediterranean history, with the expansion of Greek and Phoenician colonies and the growth of Carthage into the dominant maritime power of the Mediterranean. These events were facilitated by the ease of long-distance travel following major advances in seafaring. We know from the archaeological record that trade goods and materials were moving across great distances in unprecedented quantities, but it is unclear how these patterns correlate with human mobility. Here, to investigate population mobility and interactions directly, we sequenced the genomes of 30 ancient individuals from coastal cities around the central Mediterranean, in Tunisia, Sardinia and central Italy. We observe a meaningful contribution of autochthonous populations, as well as highly heterogeneous ancestry including many individuals with non-local ancestries from other parts of the Mediterranean region. These results highlight both the role of local populations and the extreme interconnectedness of populations in the Iron Age Mediterranean. By studying these trans-Mediterranean neighbours together, we explore the complex interplay between local continuity and mobility that shaped the Iron Age societies of the central Mediterranean.

Ancestry runs deeper than blood: the evolutionary history of ABO points to cryptic variation of functional importance.

The ABO histo-blood group, first discovered over a century ago, is found not only in humans but also in many other primate species, with the same genetic variants maintained for at least 20 million years. Polymorphisms in ABO have been associated with susceptibility to a large number of human diseases, from gastric cancers to immune or artery diseases, but the adaptive phenotypes to which the polymorphism contributes remain unclear. We suggest that variation in ABO has been maintained by frequency-dependent or fluctuating selection pressures, potentially arising from co-evolution with gut pathogens. We further hypothesize that the histo-blood group labels A, B, AB, and O do not offer a full description of variants maintained by natural selection, implying that there are unrecognized, functionally important, antigens beyond the ABO group in humans and other primates.

The Arabidopsis gene hypersensitive to phosphate starvation 3 encodes ethylene overproduction 1.

When plants are subjected to a deficiency in inorganic phosphate (Pi), they exhibit an array of responses to cope with this nutritional stress. In this work, we have characterized two Arabidopsis mutants, hps3-1 and hps3-2 (hypersensitive to Pi starvation 3), that have altered expression of Pi starvation-induced (PSI) genes and enhanced production of acid phosphatase (APase) when grown under either Pi sufficiency or deficiency conditions. hps3-1 and hps3-2, however, accumulate less anthocyanin than the wild type when grown on a Pi-deficient medium. Molecular cloning indicated that the phenotypes of hps3 mutants were caused by mutations within the ETO1 (ETHYLENE OVERPRODUCTION 1) gene. In Arabidopsis, ETO1 encodes a negative regulator of ethylene biosynthesis, and mutation of ETO1 causes Arabidopsis seedlings to overproduce ethylene. The ethylene biosynthesis inhibitor aminoethoxyvinyl glycine or the ethylene perception inhibitor Ag(+) suppressed all the mutant phenotypes of hps3. Taken together, these results provide further genetic evidence that ethylene is an important regulator of multiple plant responses to Pi starvation. Furthermore, we found that a change in ethylene level has differential effects on the expression of PSI genes, maintenance of Pi homeostasis, production of APase and accumulation of anthocyanin. We also demonstrated that ethylene signaling mainly regulates the activity of root surface-associated APases rather than total APase activity.