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Abrupt climate fluctuations during the Holocene and Late Pleistocene times have been associated with change in ocean circulation, although their causes remains uncertain. A major cooling event in the Holocene occurred between 8,400 and 8,000 years ago in central Greenland and around the north eastern North Atlantic Ocean. It is argued that the event was due to a massive outflow of fresh water from the Hudson Strait based on estimates of the marine reservoir for Hudson Bay. This lends support to the hypothesis that the sudden rise in freshwater flux from the waning Laurentide ice sheet lessened sea surface salinity and altered ocean circulation.

Horses revolutionized human history with fast mobility 1 . However, the timeline between their domestication and their widespread integration as a means of transport remains contentious 2-4 . Here we assemble a collection of 475 ancient horse genomes to assess the period when these animals were first reshaped by human agency in Eurasia. We find that reproductive control of the modern domestic lineage emerged around 2200 BCE, through close-kin mating and shortened generation times. Reproductive control emerged following a severe domestication bottleneck starting no earlier than approximately 2700 BCE, and coincided with a sudden expansion across Eurasia that ultimately resulted in the replacement of nearly every local horse lineage. This expansion marked the rise of widespread horse-based mobility in human history, which refutes the commonly held narrative of large horse herds accompanying the massive migration of steppe peoples across Europe around 3000 BCE and earlier 3,5 . Finally, we detect significantly shortened generation times at Botai around 3500 BCE, a settlement from central Asia associated with corrals and a subsistence economy centred on horses 6,7 . This supports local horse husbandry before the rise of modern domestic bloodlines., (© 2024. The Author(s).)

Domestication of horses fundamentally transformed long-range mobility and warfare 1 . However, modern domesticated breeds do not descend from the earliest domestic horse lineage associated with archaeological evidence of bridling, milking and corralling 2-4 at Botai, Central Asia around 3500 BC 3 . Other longstanding candidate regions for horse domestication, such as Iberia 5 and Anatolia 6 , have also recently been challenged. Thus, the genetic, geographic and temporal origins of modern domestic horses have remained unknown. Here we pinpoint the Western Eurasian steppes, especially the lower Volga-Don region, as the homeland of modern domestic horses. Furthermore, we map the population changes accompanying domestication from 273 ancient horse genomes. This reveals that modern domestic horses ultimately replaced almost all other local populations as they expanded rapidly across Eurasia from about 2000 BC, synchronously with equestrian material culture, including Sintashta spoke-wheeled chariots. We find that equestrianism involved strong selection for critical locomotor and behavioural adaptations at the GSDMC and ZFPM1 genes. Our results reject the commonly held association 7 between horseback riding and the massive expansion of Yamnaya steppe pastoralists into Europe around 3000 BC 8,9 driving the spread of Indo-European languages 10 . This contrasts with the scenario in Asia where Indo-Iranian languages, chariots and horses spread together, following the early second millennium BC Sintashta culture 11,12 ., (© 2021. The Author(s).)

For the purpose of detecting the effects of human activities on climate change, it is important to document natural change in past climate. In this context, it has proved particularly difficult to study the variability in the occurrence of extreme climate events, such as storms with exceptional rainfall. Previous investigations have established storm chronologies using sediment cores from single lakes, but such studies can be susceptible to local environmental bias. Here we date terrigenous inwash layers in cores from 13 lakes, which show that the frequency of storm-related floods in the northeastern United States has varied in regular cycles during the past 13,000 years (13 kyr), with a characteristic period of about 3 kyr. Our data show four peaks in storminess during the past 14 kyr, approximately 2.6, 5.8, 9.1 and 11.9 kyr ago. This pattern is consistent with long-term changes in the average sign of the Arctic Oscillation, suggesting that modulation of this dominant atmospheric mode may account for a significant fraction of Holocene climate variability in North America and Europe.