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Past values for the geomagnetic intensity may be obtained by laboratory analysis of the thermoremanent magnetization carried by clay baked in ancient times. From global averages1–3 of such determinations it is commonly accepted that the intensity in any given region went through a broad maximum about 2,000 years ago, reaching a level ∼50% higher than at present. Here we present results obtained from a wide range of Chinese pottery, spanning the interval from 4000 BC to the present, indicating that the field behaviour was more complex. The intensity was high between 1500 and 1000 BC and again in the first half of the first millennium AD. Comparison with results reported4,5 for Western Asia, Egypt and Crete suggests that these high values are due to non-dipole disturbances in the geomagnetic field, consistent with long-term records6–8 of the cosmogenic radioisotopes 14C and 10Be.

21 pages, 3 figures, supplementary information https://doi.org/10.1038/s41586-022-04932-6.-- Data availability: Fossil diversity digitized data and those data downloaded from the Sepkoski’s Online Genus Database (http://strata.geology.wisc.edu/jack/) are provided as source data with this paper. Diversity data downloaded from the Ocean Biodiversity Information System (OBIS) database (www.obis.org) are also provided as source data with this paper. Source data are provided with this paper.-- Code availability: The coupled palaeogeographical–diversification model presented here uses input data of seafloor age distributions and palaeoenvironmental conditions from the siwill22/agegrid-0.1 v1-alpha palaeogeographical model and the cGENIE Earth system model, respectively. The code used to reconstruct seafloor age distributions from GPlates full-plate tectonic reconstructions is available at Zenodo (https://doi.org/10.5281/zenodo.3271360). The code for the version of the ‘muffin’ release of the cGENIE Earth system model used in this paper is tagged as v0.9.30, and is available at Zenodo (https://doi.org/10.5281/zenodo.6676435). Configuration files for the specific experiments presented in the paper can be found in the directory: genie-userconfigs/PUBS/published/Cermeno_et_al.2022. Details of the experiments, plus the command line needed to run each one, are given in the readme.txt file in that directory. The code for the muffingen boundary file generator, is available at Zenodo (https://doi.org/10.5281/zenodo.6676451). The code for the coupled palaeogeographical–diversification model is available at Zenodo (https://doi.org/10.5281/zenodo.6535496). The code is also available at GitHub (https://github.com/CarmenGarciaComas/INDITEK); this is the recommended mode of access as it will contain any updates and clarifications The fossil record of marine invertebrates has long fuelled the debate as to whether or not there are limits to global diversity in the sea1,2,3,4,5. Ecological theory states that, as diversity grows and ecological niches are filled, the strengthening of biological interactions imposes limits on diversity6,7. However, the extent to which biological interactions have constrained the growth of diversity over evolutionary time remains an open question1,2,3,4,5,8,9,10,11. Here we present a regional diversification model that reproduces the main Phanerozoic eon trends in the global diversity of marine invertebrates after imposing mass extinctions. We find that the dynamics of global diversity are best described by a diversification model that operates widely within the exponential growth regime of a logistic function. A spatially resolved analysis of the ratio of diversity to carrying capacity reveals that less than 2% of the global flooded continental area throughout the Phanerozoic exhibits diversity levels approaching ecological saturation. We attribute the overall increase in global diversity during the Late Mesozoic and Cenozoic eras to the development of diversity hotspots under prolonged conditions of Earth system stability and maximum continental fragmentation. We call this the ‘diversity hotspots hypothesis’, which we propose as a non-mutually exclusive alternative to the hypothesis that the Mesozoic marine revolution led this macroevolutionary trend12,13 This work was funded by research grant CGL2017-91489-EXP from the Spanish government. A.P. acknowledges funding from the European Union’s Horizon research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 838373. S.W. was supported by NSFC grant no. 41972237 and ARC grant nos DP180102280 and DP200100966. M.J.B. acknowledges support through ERC Advanced Grant ‘Innovation’ (ERC 788203). P.C. and S.M.V. acknowledge support through grant no. CTM2017-87227-P. A.R. acknowledges NSF grant EAR-2121165, as well as support from the Heising–Simons Foundation. The Institut de Ciències del Mar (CSIC) received funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S) Peer reviewed

Northeastern Siberia has been inhabited by humans for more than 40,000 years but its deep population history remains poorly understood. Here we investigate the late Pleistocene population history of northeastern Siberia through analyses of 34 newly recovered ancient genomes that date to between 31,000 and 600 years ago. We document complex population dynamics during this period, including at least three major migration events: an initial peopling by a previously unknown Palaeolithic population of ‘Ancient North Siberians’ who are distantly related to early West Eurasian hunter-gatherers; the arrival of East Asian-related peoples, which gave rise to ‘Ancient Palaeo-Siberians’ who are closely related to contemporary communities from far-northeastern Siberia (such as the Koryaks), as well as Native Americans; and a Holocene migration of other East Asian-related peoples, who we name ‘Neo-Siberians’, and from whom many contemporary Siberians are descended. Each of these population expansions largely replaced the earlier inhabitants, and ultimately generated the mosaic genetic make-up of contemporary peoples who inhabit a vast area across northern Eurasia and the Americas. Analyses of 34 ancient genomes from northeastern Siberia, dating to between 31,000 and 600 years ago, reveal at least three major migration events in the late Pleistocene population history of the region.

Climate change has led to concerns about increasing river floods resulting from the greater water-holding capacity of a warmer atmosphere1. These concerns are reinforced by evidence of increasing economic losses associated with flooding in many parts of the world, including Europe2. Any changes in river floods would have lasting implications for the design of flood protection measures and flood risk zoning. However, existing studies have been unable to identify a consistent continental-scale climatic-change signal in flood discharge observations in Europe3, because of the limited spatial coverage and number of hydrometric stations. Here we demonstrate clear regional patterns of both increases and decreases in observed river flood discharges in the past five decades in Europe, which are manifestations of a changing climate. Our results—arising from the most complete database of European flooding so far—suggest that: increasing autumn and winter rainfall has resulted in increasing floods in northwestern Europe; decreasing precipitation and increasing evaporation have led to decreasing floods in medium and large catchments in southern Europe; and decreasing snow cover and snowmelt, resulting from warmer temperatures, have led to decreasing floods in eastern Europe. Regional flood discharge trends in Europe range from an increase of about 11 per cent per decade to a decrease of 23 per cent. Notwithstanding the spatial and temporal heterogeneity of the observational record, the flood changes identified here are broadly consistent with climate model projections for the next century4,5, suggesting that climate-driven changes are already happening and supporting calls for the consideration of climate change in flood risk management. Analysis of a comprehensive European flood dataset reveals regional changes in river flood discharges in the past five decades that are consistent with models suggesting that climate-driven changes are already happening.

Science and Civilisation in China. Volume 6, Part II Agriculture. By Francesca Bray. Cambridge University Press: 1984. Pp. 724, £50, $99.50.