Fertility Differences Between Migrants and Stayers in a Polygamous Context: Evidence from Senegal

This study takes a ‘country-of-origin’ or dissimilation perspective to compare the timing of births and completed fertility of international migrants and of those who stay at origin. In order to disentangle selection effects determining differential fertility behaviour of migrants, other mechanisms explaining migrant fertility (disruption, interrelation of events) are also examined. Furthermore, we take into consideration the prevalence of polygamy in Senegal to enhance our knowledge of migrant fertility in this specific context. For the empirical analysis, we use longitudinal data collected in the framework of the MAFE-Senegal project (Migrations between Africa and Europe), which includes retrospective life histories of non-migrants in Senegal and migrants in France, Italy and Spain. We estimate discrete time hazard models and Poisson regressions for male and female respondents separately to analyse the timing of first and higher-order births as well as completed fertility. The results show a strong disruptive effect of migration on childbearing probabilities for men and women, clearly related to the geographic separation of partners due to the out-migration of the man. Increased birth risks in the first year upon arrival could be observed for migrant women following their husbands to Europe, suggesting an interrelation of migration and fertility events. Regarding completed fertility, migrants have significantly fewer children by the age of 40 compared to their non-migrant counterparts, which among men is largely driven by a strong negative effect of polygamous migrants.

Dynamics of indexes of reproduction and selection in three generations of the urbanized population

Aim. Due to the fact that women's reproductive behavior has been changing with the development of civilization, from natural uncontrolled fertility in the early stages of human development to reproductive technologies in our time, the aim of this work was to study the direction and intensity of natural selection index and changes of the quantitative characteristics of reproduction in women residents of Kharkiv in three successive generations. Methods. Material was collected in 1990 and 2017. The obstetric and gynecological history of the inhabitants of Kharkiv was studied. The first generation included 589 women who were born in 1900–1925, 244 women born in the period 1928–1955, made up the second generation, 288 women who were born in 1956–1979, were assigned to third generation. Results. The total selection index is reduced from 0.56 in the first generation to 0.29 and 0.28 in the second and third generations, respectively. Over the eighty-year period, the differential fertility rate has decreased. The percentage of women with pathological pregnancies increased from 4.9 in the first generation, to 22.5 in the second and 18.4 in the third generation. Conclusions. The total selection index in the Kharkiv population into three successive generations has decreased by half: from 0.56 to 0.28, the index of differential mortality has decreased by almost four times. Keywords: reproductive characteristics, Kharkov population, Crow's index, selection, generations.

Genetic load and biological changes to extant humans

Extant humans are currently increasing their genetic load, which is informing present and future human microevolution. This has been a gradual process that has been rising over the last centuries as a consequence of improved sanitation, nutritional improvements, advancements in microbiology and medical interventions, which have relaxed natural selection. Moreover, a reduction in infant and child mortality and changing societal attitudes towards fertility have led to a decrease in total fertility rates (TFRs) since the 19th century. Generally speaking, decreases in differential fertility and mortality have meant that there is less opportunity for natural selection to eliminate deleterious mutations from the human gene pool. It has been argued that the average human may carry ~250–300 mutations that are mostly deleterious, as well as several hundred less-deleterious variants. These deleterious alleles in extant humans mean that our fitness is being constrained. While such alleles are viewed as reducing human fitness, they may also have had an adaptive function in the past, such as assisting in genetic complexity, sexual recombination and diploidy. Saying this, our current knowledge on these fitness compromising alleles is still lacking.

Whole genomes reveal severe bottleneck among Asian hunter-gatherers following the invention of agriculture

The invention of agriculture (IOA) by anatomically modern humans (AMH) around 10,000 years before present (ybp) is known to have led to an increase in AMH’s carrying capacity and hence its population size. Reconstruction of historical demography using high coverage (~30X) whole genome sequences (WGS) from >700 individuals from different South Asian (SAS) and Southeast Asian (SEA) populations reveals that although several present day populous groups did indeed experience a positive Neolithic Demographic Transition (NDT), most hunter-gatherers (HGs) experienced a demographic decrease. Differential fertility between HGs and non-HGs, exposure of HGs to novel pathogens from non-HGs could have resulted in such contrasting patterns. However, we think the most parsimonious explanation of the drastic decrease in population size of HGs is their displacement/enslavement by non-HGs.Significance StatementThe invention of agriculture, around 10000 years ago, facilitated more food production which could feed larger populations. This had far-reaching socio-political and demographic impacts, including a ~10,000 fold increase in global population-size in the last 10,000 years. However, this increase in population size is not a universal truth and present day hunter-gatherer populations, in contrast, have dwindled in size, often drastically. The signatures of this rise in population size are discernible from the genomes of present-day individuals. Using genomic data, we show that for the majority of Asian hunter-gatherers, population-sizes drastically decreased following the invention of agriculture. We argue that a combination of displacement, enslavement and disease resulted in the decimation of hunter-gatherer societies.

Differential fertility makes society more conservative on family values

Data from the General Social Survey indicate that higher-fertility individuals and their children are more conservative on “family values” issues, especially regarding abortion and same-sex marriage. This pattern implies that differential fertility has increased and will continue to increase public support for conservative policies on these issues. The association of family size with conservatism is specific to traditional-family issues and can be attributed in large part to the greater religiosity and lower educational attainment of individuals from larger families. Over the 2004 to 2018 period, opposition to same-sex marriage and abortion was 3 to 4 percentage points more prevalent than it would have been were traditional-family conservatism independent of family size in the current generation. For same-sex marriage, evolutionary forces have grown in relative importance as society as a whole has liberalized. As of 2018, differential fertility raised the number of US adults opposed to same-sex marriage by 17%, from 46.9 million to 54.8 million.

Measuring Selection Intensities Among Kolam Population: Manifested through Differential Fertility and Differential Mortality

The objective of the study is to understand the selection intensities among Kolam, a particularly vulnerable tribal group (PVTG) of Adilabad district of Telangana State, India. Two prominent methods were employed to understand the intensities by using Crow’s index and modified formula as given by Johnston and Kensinger’s method. The intensities are computed on the basis of the reproductive history of mother with completed fertility and the results were compared with the available works on populations belonging to Andhra Pradesh, Telangana and India. The Crow’s total index (II) value was found to be 0.3863. The mortality (Im) component was found to be 0.2151 while fertility (If) component was found to be 0.1712. The contribution of mortality component is greater than that of fertility component among the present studied population using Crow’s index. According to Johnston and Kensinger, the total index (II) was found to be 0.6017. Fertility component was found to be 0.2368, prenatal mortality component (Ime) and postnatal mortality component (Ime/Pb) where observed to be 0.0675 and 0.0933 respectively. Therefore, it is clear from the results that postnatal mortality contributes more than prenatal mortality for selection, i.e., Johnston and Kensinger’s Index (0.6017) contributes more towards selection intensity than Crow’s index (0.3863). Natural selection takes place when there is variability of fitness observed through the differences in fertility and mortality in any population.

Fertility of Pedicellate Spikelets in Sorghum Is Controlled by a Jasmonic Acid Regulatory Module

As in other cereal crops, the panicles of sorghum (Sorghum bicolor (L.) Moench) comprise two types of floral spikelets (grass flowers). Only sessile spikelets (SSs) are capable of producing viable grains, whereas pedicellate spikelets (PSs) cease development after initiation and eventually abort. Consequently, grain number per panicle (GNP) is lower than the total number of flowers produced per panicle. The mechanism underlying this differential fertility is not well understood. To investigate this issue, we isolated a series of ethyl methane sulfonate (EMS)-induced multiseeded (msd) mutants that result in full spikelet fertility, effectively doubling GNP. Previously, we showed that MSD1 is a TCP (Teosinte branched/Cycloidea/PCF) transcription factor that regulates jasmonic acid (JA) biosynthesis, and ultimately floral sex organ development. Here, we show that MSD2 encodes a lipoxygenase (LOX) that catalyzes the first committed step of JA biosynthesis. Further, we demonstrate that MSD1 binds to the promoters of MSD2 and other JA pathway genes. Together, these results show that a JA-induced module regulates sorghum panicle development and spikelet fertility. The findings advance our understanding of inflorescence development and could lead to new strategies for increasing GNP and grain yield in sorghum and other cereal crops.

Is Selection Necessary for Evolution? A Dynamics of Coastal Population of India

Nature provides a good opportunity to understand the dynamics of evolution. The country has a huge coastline, which experiences socio-cultural and natural vulnerability. The aim of the paper has been to describe the pattern of selection intensity among the east and west coastal populations of India. Differential fertility and mortality were collected from 2,099 females (mothers) of the western coasts of India, and secondary data were collected from the eastern coast of India for comparison purposes. Selection potential was computed using Crow’s index and Johnston & Kensinger’s index. The data involved a total of 7,512 pregnancies during their reproductive lifespan and the successful outcomes (live births) were 7,073. The total index (It) for eastern coast varied from 0.221 to 1.078. For the west coast, it varied from 0.262 to 0.617. Among the eastern coastal population groups, the mortality component of selection is comparatively higher than its fertility component, while it is just the reverse among the western coastal population groups.

MTNR-1A Gene Polymorphism in Two Tropical Sheep breeds of South India

The present study was carried out to evaluate the genetic polymorphism in Ovine MTNR1A of two tropical breeds ie., highly prolific NARI Suwarna sheep and Mandya sheep from southern peninsular region of India with respect to differential fertility. Fifty animals from each breed were randomly selected and subjected to RsaI-RFLP analysis of exon-2 of Ovine MTNR1A. The study revealed monomorphic patterns in all the animals for both the breeds. PCR amplicon of 824 bp fragments with four cut sites at 53 bp, 320 bp, 343 bp and 754 bp, resulted in 411 bp, 267 bp, 70 bp, 53 bp and 23 bp. Only presence of CC genotypes at rs406779174 SNP of Ovine MTNR1A in both the breeds supports non-seasonality in breeding of these animals and no association of SNP with increased fecundity of NARI Suwarna sheep over Mandya sheep.