No abstract

In European and many African, Middle Eastern and Southern Asian populations lactase persistence (LP) is the most strongly selected monogenic trait to have evolved over the last 10,000 years 1 . While LP selection and prehistoric milk consumption must be linked, considerable uncertainty remains concerning their spatiotemporal configuration and specific interactions 2,3 . We provide detailed distributions of milk exploitation across Europe over the last 9k years using c. 7,000 pottery fat residues from >550 archaeological sites. European milk use was widespread from the Neolithic period onwards but varied spatially and temporally in intensity. Surprisingly, comparison of model likelihoods indicates that LP selection varying with levels of prehistoric milk exploitation provides no better explanation of LP allele frequency trajectories than uniform selection since the Neolithic. In the UK Biobank 4,5 cohort of ~500K contemporary Europeans, LP genotype was only weakly associated with milk consumption and did not show consistent associations with improved fitness or health indicators. This suggests other hypotheses on the beneficial effects of LP should be considered for its rapid frequency increase. We propose that lactase non-persistent individuals consumed milk when it became available, but that under particular conditions and microbiological milieux this was disadvantageous, driving LP selection in prehistoric Europe. Comparison of model likelihoods indicates that population fluctuations, settlement density and wild animal exploitationproxies for these driversprovide better explanations of LP selection than the extent of milk exploitation. These findings offer new perspectives on prehistoric milk exploitation and LP evolution.

The Sun sporadically produces eruptive events leading to intense fluxes of solar energetic particles (SEPs) that dramatically disrupt the near-Earth radiation environment. Such events have been directly studied for the last decades but little is known about the occurrence and magnitude of rare, extreme SEP events. Presently, a few events that produced measurable signals in cosmogenic radionuclides such as 14C, 10Be and 36Cl have been found. Analyzing annual 14C concentrations in tree-rings from Switzerland, Germany, Ireland, Russia, and the USA we discovered two spikes in atmospheric 14C occurring in 7176 and 5259 BCE. The ~2% increases of atmospheric 14C recorded for both events exceed all previously known 14C peaks but after correction for the geomagnetic field, they are comparable to the largest event of this type discovered so far at 775 CE. These strong events serve as accurate time markers for the synchronization with floating tree-ring and ice core records and provide critical information on the previous occurrence of extreme solar events which may threaten modern infrastructure.

LVR-Landes Museum Bonn for accessing the material from Königshoven 14 and R. Brunning from the South West Heritage Trust for sharing excavations pictures of the Sweet Track. Author Contributions RPE conceived the project. ECa, RPE and ABay wrote the paper. ECa, TDJK and RPE developed the method for dating lipids. ECa, JD and TG performed the preparation of pottery vessels for radiocarbon analysis. ECa and TDJK generated the radiocarbon measurements and performed data analysis. ABay undertook the statistical modelling of the radiocarbon dates.

Preparative capillary gas chromatography (pcGC) is widely used for the isolation of single compounds for radiocarbon determinations. While being effective at isolating compounds, there are still genuine concerns relating to contamination associated with the isolation procedure, such as incomplete removal of solvent used to recover isolated compounds from the traps and cross-contamination, which can lead to erroneous C determinations. Herein we describe new approaches to identifying and removing these two sources of contamination. First, we replaced the common "U" trap design, which requires recovery of compounds using organic solvent, with a novel solventless trapping system (STS), consisting of a simple glass tube containing a glass wool plug, allowing condensation of a target compound in the wool and its solventless recovery by pushing the glass wool directly into a foil capsule for graphitization. With the STS trap, an average of 95.7% of the target compound was recovered, and contamination from column bleed was reduced. In addition, comparison ofC determinations of fatty acid methyl ester (FAME) standards determined offline to those isolated by pcGC in STS traps showed excellent reproducibility and accuracy compared to those isolated using the commercial "U" traps. Second, "coldspots" were identified in the instrument, i.e., the termini of capillaries in the preparative unit, which can be cleaned of compounds condensed from earlier runs using a heat gun. Our new procedure, incorporating these two modifications, was tested on archeological fat hoards, producing C dates on isolated C and C fatty acids statistically consistent with the bulk dates of the archeological material.

Preparative capillary gas chromatography (PCGC) is the central technique used for the purification of volatile or semivolatile organic compounds for radiocarbon analysis using accelerator mass spectrometry (AMS). While thicker film columns offer efficient separations, cyclic poly(dimethylsiloxanes) (PDMS) derived from the column's stationary phase have been highlighted as a potential source of contaminant carbon in "trapped" compounds. The PDMS CH groups are of "infinite" radiocarbon age due to the fossil carbon origin of the feedstock used in production. Hence, column bleed, if present at sufficiently high concentrations, would shift the radiocarbon ages of trapped compounds to older ages. Quantification of the column bleed in trapped samples, however, is extremely challenging and up to now has only been achieved through indirect C determinations of chromatographic blanks, which are used for postC determination "corrections". As part of wider investigations aimed at better understanding the chemical nature of contamination in compound-specific C determinations, herein, we report a rigorous approach to column bleed identification and quantification. Using reference fatty acid methyl esters (FAMEs),H nuclear magnetic resonance spectroscopy (NMR), employing a 700 MHz instrument equipped with a 1.7 mm microcryoprobe optimized for H observation, was able to detect low submicrogram amounts of low molecular weight compounds (<500 Da). Direct quantification of PCGC "trapped" FAMEs was achieved based on the recorded H NMR spectra. Gravimetrically prepared calibration mixtures of cyclic PMDSs and FAMEs showed column bleed abundance to be below 0.03% w/w of the "trapped" FAMEs, which would lead to a maximum shift in radiocarbon age of<3 years toward older values. We therefore conclude that column bleed contamination has a negligible effect on the C determination of FAMEs prepared using the chromatographic method described. TheH NMR analysis also revealed the absence of other protonated carbon-containing components that would affect radiocarbon determinations at the precisions achievable by AMS.

Organic residue analyses of archaeological ceramics can provide important insights into ancient foodways. To date, however, there has been little critical reflection on how lipid residues might (or might not) reflect dietary practices or subsistence strategies more generally. A combination of ethnoarchaeological research and chemical and isotopic analyses of lipid residues from pottery made and used by modern Samburu pastoralists in northern Kenya was undertaken to supplement the interpretive framework used in archaeological investigations. A total of 63 potsherds were collected from various contexts, including settlement sites and rockshelters, and analysed using gas chromatography (GC), gas chromatography-mass spectrometry (GC-MS) and gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). The results showed that the free fatty acids, palmitic (C 16:0 ) and stearic (C 18:0 ), dominated the lipid profiles, with extremely broad ranges of δ 13 C values. The majority of the Δ 13 C values from Samburu pots suggest that vessels were intensively used to process ruminant carcass products, yet the Samburu economy is not, in fact, meat-based at all. Despite an overall reliance on dairy products, milk is rarely processed in ceramic vessels, largely due to cultural prohibitions. Surprisingly, a number of vessels from one site, Naiborkeju Hill, were used to process dairy products. Compound-specific radiocarbon dating of lipids from these sherds suggests that this pottery originated from an earlier period, demonstrating a possible shift in ceramic use by pastoralist communities in this region over time. The overall conclusion is that lipid residues may not necessarily reflect, in a simple way, the day-to-day consumption or the perceived relative importance of different foodstuffs. In the Samburu case, lipid residues reflect the functional and ideological suitability of ceramics for processing only certain types of food (meat/fat/bones), despite an overall reliance on milk. These conclusions are important when considering the origins and development of African pastoralism, for example, as interpreted from the archaeological record.

The development of pastoralism transformed human diets and societies in grasslands worldwide. The long-term success of cattle herding in Africa has been sustained by dynamic food systems, consumption of a broad range of primary and secondary livestock products, and the evolution of lactase persistence (LP), which allows digestion of lactose into adulthood and enables the milk-based, high-protein, low-calorie diets characteristic of contemporary pastoralists. Despite the presence of multiple alleles associated with LP in ancient and present-day eastern African populations, the contexts for selection for LP and the long-term development of pastoralist foodways in this region remain unclear. Pastoral Neolithic (c. 5000 to 1200 BP) faunas indicate that herders relied on cattle, sheep, and goats and some hunting, but direct information on milk consumption, plant use, and broader culinary patterns is rare. Combined chemical and isotopic analysis of ceramic sherds (n = 125) from Pastoral Neolithic archaeological contexts in Kenya and Tanzania, using compound-specific δ13C and Δ13C values of the major fatty acids, provides chemical evidence for milk, meat, and plant processing by ancient herding societies in eastern Africa. These data provide the earliest direct evidence for milk product consumption and reveal a history of reliance on animal products and other nutrients, likely extracted through soups or stews, and plant foods. They document a 5,000-y temporal framework for eastern Africa pastoralist cuisines and cultural contexts for selection for alleles distinctive of LP in eastern Africa.