In this study we evaluated migration models to the Americas by using the information contained in native mitochondrial genomes (mitogenomes) from North America. Molecular and phylogeographic analyses of B2a mitogenomes, which are absent in Eskimo–Aleut and northern Na-Dene speakers, revealed that this haplogroup arose in North America ∼11–13 ka from one of the founder Paleo-Indian B2 mitogenomes. In contrast, haplogroup A2a, which is typical of Eskimo–Aleuts and Na-Dene, but also present in the easternmost Siberian groups, originated only 4–7 ka in Alaska, led to the first Paleo-Eskimo settlement of northern Canada and Greenland, and contributed to the formation of the Na-Dene gene pool. However, mitogenomes also show that Amerindians from northern North America, without any distinction between Na-Dene and non–Na-Dene, were heavily affected by an additional and distinctive Beringian genetic input. In conclusion, most mtDNA variation (along the double-continent) stems from the first wave from Beringia, which followed the Pacific coastal route. This was accompanied or followed by a second inland migratory event, marked by haplogroups X2a and C4c, which affected all Amerindian groups of Northern North America. Much later, the ancestral A2a carriers spread from Alaska, undertaking both a westward migration to Asia and an eastward expansion into the circumpolar regions of Canada. Thus, the first American founders left the greatest genetic mark but the original maternal makeup of North American Natives was subsequently reshaped by additional streams of gene flow and local population dynamics, making a three-wave view too simplistic.

The effects of European colonization on the genomes of Native Americans may have produced excesses of potentially deleterious features, mainly due to the severe reductions in population size and corresponding losses of genetic diversity. This assumption, however, neither considers actual genomic patterns that existed before colonization nor does it adequately capture the effects of admixture. In this study, we analyze the whole-exome sequences of modern and ancient individuals from a Northwest Coast First Nation, with a demographic history similar to other indigenous populations from the Americas. We show that in approximately ten generations from initial European contact, the modern individuals exhibit reduced levels of novel and low-frequency variants, a lower proportion of potentially deleterious alleles, and decreased heterozygosity when compared to their ancestors. This pattern can be explained by a dramatic population decline, resulting in the loss of potentially damaging low-frequency variants, and subsequent admixture. We also find evidence that the indigenous population was on a steady decline in effective population size for several thousand years before contact, which emphasizes regional demography over the common conception of a uniform expansion after entry into the Americas. This study examines the genomic consequences of colonialism on an indigenous group and describes the continuing role of gene flow among modern populations.

Objective Health research often focuses on moderate and vigorous intensity physical activity while neglecting low‐intensity habitual activities. Our aim was to understand habitual physical activity in women from a transitioning economy using a physical activity monitor. Methods This study investigated physical activity in 68 healthy premenopausal women (age 18–46) in rural Poland using FitBit One activity trackers for 1 week. Standard anthropometric techniques were used to measure height, weight, and body fat. Daily physical activity data were analyzed for step counts as well as duration and intensity. Results This sample of rural Polish women traveled a mean of 8428 (SD = 2650) steps per day. Time spent lightly active, fairly active, and very active were measured as 337.1 (SD = 87.8), 19.6 (SD = 30.5), and 6.7 (SD = 8.6) minutes per day, respectively. Total time active and time spent lightly active were associated with daily steps (P < 0.001 for both), and time lightly active increased with age (P = 0.02). No other significant relationships were observed between physical activity measures and BMI, age, or body fat. Conclusions In this sample, women spend a significant amount of time engaged in light‐intensity physical activity and travel a relatively high number of steps per day. Our data suggest that in this population, total daily activity does not depend on age in women between 18 and 46. We suggest that measurement methods which include low‐intensity activity may better characterize habitual physical activity in women who are expected to be performing large amounts of domestic labor.

Attachment theory holds that parental relationships have lifelong effects on offspring social lives. The tend-and-befriend hypothesis posits that female friendships among humans evolved as part of a primate-wide coping mechanism to mediate stress by relying on social support. Here we bridge developmental and evolutionary frameworks to examine adolescent girls' perception of their reliance on female friendship for social support, how perceptions of parental relationships affect peer relationships, and the extent to which parent and peer relationships buffer depressive symptoms. We predict perceived maternal relationship quality will be positively associated with close female friendships, and maternal relationships, paternal relationships, and female friendship will buffer depressive symptoms. Participants were adolescent girls from a summer science camp (N = 95). Participants filled out demographic information, social network surveys, the Parent-Adolescent Communication Scale, and the Center for Epidemiology Depression Scale. Data was analyzed with Pearson's correlations, t tests, and path analysis. Adolescent girls with few female friends, compared with girls who had more than two very close female friends, experienced more depressive symptoms (t = 3.382, p = .001, D = 0.784). Adolescent girls with few female friends experienced more depressive symptoms compared to girls with two or more very close female friends (t = 3.382, p = .001, D = 0.784). Stronger maternal and paternal relationships were associated with having more female friends (maternal: t = −3.213, p = .003, D = 0.837; paternal: t = −2.432; p = .017). In the path analysis model, only maternal relationship quality significantly predicted female friendship category (β = .33, CR = 2.770, p < .006). Furthermore, participants with two or more very close female friends and higher paternal relationship quality had significantly fewer depressive symptoms (friends; β = −.19, CR = −2.112, p = .035; paternal: β = −.33, CR = −3.220, p < .001), and older participants had more depressive symptoms (β = .17, CR = −1.931, p = .036). These results provide additional support for the tend-and-befriend hypothesis, suggesting that maternal tending sets the stage for close female friendships.

Objective: Age at menarche in Poland has varied with political and socioeconomic changes. An increase in age at menarche corresponded to a period of economic crisis and food rationing between 1976 and 1989. Experiencing food shortages in utero or during childhood development can affect menarcheal timing, but this national effect may be buffered in local agrarian regions growing their own food. Here we examine patterns of age at menarche over time in the rural, agrarian Beskid Wyspowy region of southern Poland.Methods: This study examined menarcheal timing using data collected from Polish women (n = 1326) recruited at the Mogielica Human Ecology Study Site between 2003 and 2018. Simple linear regressions were used to assess changing ages at menarche over time. Comparisons between ages at menarche for women born before and after the fall of communism in 1989 were assessed via one-way analysis of variance. Results: Age at menarche has declined over time in the Beskid Wyspowy region of southern Poland from 1920 to 2000 (R 2 = .08, P < .0001). There was not a statistically significant increase or decrease in age at menarche for women born and growing up during the period of food rationing. Conclusions:The declining age at menarche is likely reflective of a transitioning environment, suggesting that major socioeconomic changes affect life history traits like pubertal timing. Living in agricultural regions may have helped buffer the increasing ages at menarche seen in other areas of Poland during times of food rationing.