The origins and spread of domestic horses from the Western Eurasian steppes

Domestication of horses fundamentally transformed long-range mobility and warfare¹. 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 BC³. Other longstanding candidate regions for horse domestication, such as Iberia⁵ and Anatolia⁶, 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 association⁷ between horseback riding and the massive expansion of Yamnaya steppe pastoralists into Europe around 3000 BC^8,9 driving the spread of Indo-European languages¹⁰. 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.

Cerebrospinal fluid and human immunodeficiency virus. Findings in healthy, asymptomatic, seropositive men

Involvement of the central nervous system by human immunodeficiency virus is an important cause of morbidity and mortality. We have undertaken a longitudinal study of asymptomatic individuals found to be human immunodeficiency virus seropositive to identify and characterize cerebrospinal fluid abnormalities early in the disease process. Our findings in 25 individuals have been notable for a frequent incidence of cerebrospinal fluid abnormalities. Pleocytosis or elevated cerebrospinal fluid protein was found in 12 (48%) of 15 patients studied. Oligoclonal banding was present in 6 (26%) of 23 patients. Human immunodeficiency virus was isolated by culture in 4 asymptomatic patients. The cerebrospinal fluid abnormalities we observed indicate an active process occurring in the central nervous system, even in early human immunodeficiency virus infection in asymptomatic patients. Serial observation of these patients for development of neuropsychiatric findings may provide answers to the significance of cerebrospinal fluid abnormalities identified in these patients.