Genomic insights into the formation of human populations in East Asia.

The deep population history of East Asia remains poorly understood owing to a lack of ancient DNA data and sparse sampling of present-day people1,2. Here we report genome-wide data from 166 East Asian individuals dating to between 6000 BC and AD 1000 and 46 present-day groups. Hunter-gatherers from Japan, the Amur River Basin, and people of Neolithic and Iron Age Taiwan and the Tibetan Plateau are linked by a deeply splitting lineage that probably reflects a coastal migration during the Late Pleistocene epoch. We also follow expansions during the subsequent Holocene epoch from four regions. First, hunter-gatherers from Mongolia and the Amur River Basin have ancestry shared by individuals who speak Mongolic and Tungusic languages, but do not carry ancestry characteristic of farmers from the West Liao River region (around 3000 BC), which contradicts theories that the expansion of these farmers spread the Mongolic and Tungusic proto-languages. Second, farmers from the Yellow River Basin (around 3000 BC) probably spread Sino-Tibetan languages, as their ancestry dispersed both to Tibet-where it forms approximately 84% of the gene pool in some groups-and to the Central Plain, where it has contributed around 59-84% to modern Han Chinese groups. Third, people from Taiwan from around 1300 BC to AD 800 derived approximately 75% of their ancestry from a lineage that is widespread in modern individuals who speak Austronesian, Tai-Kadai and Austroasiatic languages, and that we hypothesize derives from farmers of the Yangtze River Valley. Ancient people from Taiwan also derived about 25% of their ancestry from a northern lineage that is related to, but different from, farmers of the Yellow River Basin, which suggests an additional north-to-south expansion. Fourth, ancestry from Yamnaya Steppe pastoralists arrived in western Mongolia after around 3000 BC but was displaced by previously established lineages even while it persisted in western China, as would be expected if this ancestry was associated with the spread of proto-Tocharian Indo-European languages. Two later gene flows affected western Mongolia: migrants after around 2000 BC with Yamnaya and European farmer ancestry, and episodic influences of later groups with ancestry from Turan.

Distracted Driving Laws and Motor Vehicle Crash Fatalities.

BACKGROUND: Motor vehicle crashes (MVCs) continue to be the leading cause of death in youth 16 to 24 years old in the United States. Distracted driving has been shown to increase the risk of MVCs in all drivers, particularly teenagers. We aimed to determine the association between fatal MVC rates involving 16- to 19-year-old drivers and state distracted driving laws. METHODS: We conducted a retrospective time series analysis of fatal MVCs in the United States involving drivers and passengers 16 to 19 years old from 2007 to 2017 using the Fatality Analysis Reporting System. Multivariable negative binomial regression analysis was performed to compare MVC rates across states on the basis of different types and strengths of distracted driving laws. RESULTS: There were 38 215 drivers 16 to 19 years old involved in fatal MVCs from 2007 to 2017. Incidence of fatal MVCs was highest for 19-year-old drivers (27.2 out of 100 000 19-year-old persons) and lowest for 16-year-olds (10.7 out of 100 000). States with primarily enforced texting bans had lower MVC fatality rates overall involving 16- to 19-year-old drivers (adjusted incidence rate ratio: 0.71; 95% confidence interval: 0.67-0.76). Texting bans and handheld bans for all drivers were associated with decreased MVC fatalities in all age groups. CONCLUSIONS: In the United States, primarily enforced distracted driving laws are associated with a lower incidence of fatal MVCs involving 16- to 19-year-old drivers. Bans on all handheld device use and texting bans for all drivers are associated with the greatest decrease in fatal MVCs. Adoption of universal handheld cellphone bans in all states may reduce the incidence of distracted driving and decrease MVC fatalities.

The formation of human populations in South and Central Asia.

By sequencing 523 ancient humans, we show that the primary source of ancestry in modern South Asians is a prehistoric genetic gradient between people related to early hunter-gatherers of Iran and Southeast Asia. After the Indus Valley Civilization's decline, its people mixed with individuals in the southeast to form one of the two main ancestral populations of South Asia, whose direct descendants live in southern India. Simultaneously, they mixed with descendants of Steppe pastoralists who, starting around 4000 years ago, spread via Central Asia to form the other main ancestral population. The Steppe ancestry in South Asia has the same profile as that in Bronze Age Eastern Europe, tracking a movement of people that affected both regions and that likely spread the distinctive features shared between Indo-Iranian and Balto-Slavic languages.

Palaeo-Eskimo genetic ancestry and the peopling of Chukotka and North America.

Much of the American Arctic was first settled 5,000 years ago, by groups of people known as Palaeo-Eskimos. They were subsequently joined and largely displaced around 1,000 years ago by ancestors of the present-day Inuit and Yup'ik1-3. The genetic relationship between Palaeo-Eskimos and Native American, Inuit, Yup'ik and Aleut populations remains uncertain4-6. Here we present genomic data for 48 ancient individuals from Chukotka, East Siberia, the Aleutian Islands, Alaska, and the Canadian Arctic. We co-analyse these data with data from present-day Alaskan Iñupiat and West Siberian populations and published genomes. Using methods based on rare-allele and haplotype sharing, as well as established techniques4,7-9, we show that Palaeo-Eskimo-related ancestry is ubiquitous among people who speak Na-Dene and Eskimo-Aleut languages. We develop a comprehensive model for the Holocene peopling events of Chukotka and North America, and show that Na-Dene-speaking peoples, people of the Aleutian Islands, and Yup'ik and Inuit across the Arctic region all share ancestry from a single Palaeo-Eskimo-related Siberian source.