Estimating the numbers of residences, and thus the residential densities and populations, of ancient settlements remains a significant problem. This is true even for ‘greenfield’ sites due to the differential visibility of structures made of different materials in aerial and geophysical surveys. In this paper, we take advantage of statistical relationships among elements of the built environments of Roman cities in Britannia and more broadly across the Empire, to estimate the total number of buildings, total population and population density of Silchester. The results indicate that the current site plan dramatically under-represents these values. We also consider the implications of our results for broader discussions of urbanism in Britannia.

We recently reported on the radio-frequency attenuation length of cold polar ice at Summit Station, Greenland, based on bi-static radar measurements of radio-frequency bedrock echo strengths taken during the summer of 2021. Those data also allow studies of (a) the relative contributions of coherent (such as discrete internal conducting layers with sub-centimeter transverse scale) vs incoherent (e.g. bulk volumetric) scattering, (b) the magnitude of internal layer reflection coefficients, (c) limits on signal propagation velocity asymmetries (‘birefringence’) and (d) limits on signal dispersion in-ice over a bandwidth of ~100 MHz. We find that (1) attenuation lengths approach 1 km in our band, (2) after averaging 10 000 echo triggers, reflected signals observable over the thermal floor (to depths of ~1500 m) are consistent with being entirely coherent, (3) internal layer reflectivities are ≈–60$\to$–70 dB, (4) birefringent effects for vertically propagating signals are smaller by an order of magnitude relative to South Pole and (5) within our experimental limits, glacial ice is non-dispersive over the frequency band relevant for neutrino detection experiments.

The 2020 volume of History in Africa is the eleventh produced by the current editorial team. It will also be the last, as we are handing over to a brand-new team, consisting of esteemed colleagues Lorelle Semley, Sandra Barnes, Bayo Holsey, and Egodi Uchendu.

We used a combination of accelerator mass spectrometry (AMS) radiocarbon dating, optically stimulated luminescence (OSL) age estimates, and stratigraphic data from cores collected along the southern margin of the Green Bay Lobe (GBL) of the Laurentide Ice Sheet to provide new information on the timing and dynamics of the end of advance of the GBL and the dynamics of the ice sheet while very near its maximum position. Coring at multiple sites along the margin of the GBL indicate that ice had reached a stable position near its maximum extent by 24.7 ka; that ice advanced several kilometers to the Marine Isotope Stage 2 maximum position sometime shortly after 21.2 ka; and that ice remained at or beyond that position through the time interval represented by an OSL age estimate of 19.2 ± 3.2 ka. The timeline developed from these chronological data is internally consistent with, and further refines, AMS radiocarbon ages and OSL age estimates previously published for the southern margin of the GBL. It also provides new chronological control on the expansion of the GBL from its late Marine Isotope Stage (MIS) 3 extent to its MIS 2 maximum.

Twenty-six percent of children experience a traumatic event by the age of 4. Negative events during childhood have deleterious correlates later in life, including antisocial behavior. However, the mechanisms that play into this relation are unclear. We explored deficits in neurocognitive functioning, specifically problems in passive avoidance, a construct with elements of inhibitory control and learning as a potential acquired mediator for the pathway between cumulative early childhood adversity from birth to age 7 and later antisocial behavior through age 18, using prospective longitudinal data from 585 participants. Path analyses showed that cumulative early childhood adversity predicted impaired passive avoidance during adolescence and increased antisocial behavior during late adolescence. Furthermore, poor neurocognition, namely, passive avoidance, predicted later antisocial behavior and significantly mediated the relation between cumulative early childhood adversity and later antisocial behavior. This research has implications for understanding the development of later antisocial behavior and points to a potential target for neurocognitive intervention within the pathway from cumulative early childhood adversity to later antisocial behavior.

Although there has been considerable scholarly interest in the nature of ancient cities, it has been difficult to identify and explore quantitative patterns in their design and amenities. Here, the authors offer a model for the relationship between the population size and infrastructural area of settlements, before testing it against measures of urban form in the Roman Empire. They advocate a more consistent approach to the investigation of settlements that is capable of not only incorporating sites with divergent physical forms and historical trajectories into the same model, but also able to expose their similarities and differences.

Winter wheat cultivars that are competitive with weeds help control weeds in crop rotations. Ten winter wheat cultivars were evaluated for interference with summer annual grasses in the wheat and the subsequent grain sorghum crop in a winter wheat-ecofallow sorghum-fallow rotation in which there are two 10–mo fallow periods and two crops in 3 yr during 1983 to 1987. The medium–tall (100 to 109 cm tall) and medium–statured (90 to 99 cm tall) winter wheat cultivars (‘Buckskin’, ‘Siouxland’, ‘Lancota’, ‘Centurk 78’, and ‘Brule’) were more competitive than medium-short (80 to 89 cm tall) and short (68 to 79 cm tall) cultivars (‘Eagle’, ‘Homestead’, ‘Colt’, ‘Vona’, and ‘TAM 101’). Atrazine plus paraquat was applied to all cultivars 30 d after wheat harvest. When grain sorghum was planted in areas previously seeded with medium–tall and medium-statured winter wheat, summer annual grass weed biomass in sorghum was 61% less than in grain sorghum seeded into areas previously planted with medium-short and short wheat cultivars. Use of pendimethalin plus 2,4–D in winter wheat and glyphosate plus alachlor in grain sorghum eliminated differences in summer annual grass weed density and weed biomass among wheat cultivars. Sorghum grain yields were improved 7% when herbicides were used in the winter wheat and sorghum but value of the increase was less than cost of herbicides. Substituting less costly herbicides for herbicides used in this study still would not have been enough to pay for cost of herbicides for five cultivars. Grain sorghum grown on weed–free stubble of medium–tall and medium–statured winter wheat produced more grain than grain sorghum grown after medium–short and short-statured winter wheat by 5%. Volunteer wheat density during the fallow period following grain sorghum was lower in areas originally seeded to Centurk 78 and Siouxland wheat while volunteer wheat density was higher in areas planted to Homestead and Vona.

Repeated outburst flooding from glacial Lake Missoula, Montana, affected large areas of Washington during Marine Oxygen Isotope Stage 2 (29–14 ka). We present the first high-resolution rock magnetic results from two sites that are critical to interpreting these outburst floods and that provide evidence of sediment provenance: glacial Lake Missoula, the source of the floods; and glacial Lake Columbia, where floodwaters interrupted sedimentation. Magnetic carriers in glacial Lake Missoula varves are dominated by hematite, whereas those in outburst flood sediments and glacial Lake Columbia sediments are mainly magnetite and titano-magnetite. Stratigraphic variation of magnetic parameters is consistent with changes in lithology. Importantly, magnetic properties highlight depositional processes in the flood sediments that are not evident in the field. In glacial Lake Columbia, hematite is present in fine silt and clay deposited near the end of each flood as fine sediment settled out of the water column. This signal is only present at the end of the floods because the hematite is concentrated in the finer-grained sediment transported from the floor of glacial Lake Missoula, the only possible source of hematite, ~ 240 km away.