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The human genetic diversity of the Americas has been shaped by several events of gene flow that have continued since the Colonial Era and the Atlantic slave trade. Moreover, multiple waves of migration followed by local admixture occurred in the last two centuries, the impact of which has been largely unexplored.Here we compiled a genome-wide dataset of ~12,000 individuals from twelve American countries and ~6,000 individuals from worldwide populations and applied haplotype-based methods to investigate how historical movements from outside the New World affected i) the genetic structure, ii) the admixture profile, iii) the demographic history and iv) sex-biased geneflow dynamics, of the Americas.We revealed a high degree of complexity underlying the genetic contribution of European and African populations in North and South America, from both geographic and temporal perspectives, identifying previously unreported sources related to Italy, the Middle East and to specific regions of Africa.

In human populations natural selection is shifting to the side of prenatal development and appears as negative outcomes of pregnancies such as spontaneous abortions, ectopic pregnancies and stillbirths. Therefore, it is important to study dynamics of changes in reproductive characteristics and selection indexes of the populations in order to predict possible problems and numbers of genetic burden in the populations. Ukraine is poorly studied in this area. The aim of the study was to investigate indicators which characterize the population structure of Lutsk city, the intensity of natural selection, migration and their dynamics in two generations. 583 post-reproductive age females were anonymously questioned. Age, places of birth of the couple, the number of pregnancies and their outcomes were considered. Results show that natural selection indexes (Crow’s indexes) are decreasing from the first generation (0,26) to the second (0,20). Migration coefficients in the population of Lutsk decreased from 0.89 to 0.82 per generation and show intensive urbanization of the city for the studied time. The efficiency of the migration is low, since the biggest number of migrants come from the villages of the Volyn region (45% for first generations and 64% for the second one), or adjacent regions of Ukraine (35% and 27%, respectively). The population of Lutsk has a narrowed type of reproduction, where average number of offspring per female equal 1,86 for the first generation and 1,73 for the second generation.