The ρ statistic is commonly used to infer chronological dates for molecular lineages, especially from mitochondrial DNA sequences obtained in anthropological contexts. Since this approach was described 12 years ago, it has been applied to estimate molecular dates in more than 200 studies, including some published in top-tier journals. However, this method has not been well evaluated, and the accuracy of dates obtained from the ρ statistic remains unknown, especially for genetic data collected from populations with complex demographic histories. Here, molecular dates inferred from ρ are compared against coalescent expectations from a range of demographic models. This exercise reveals considerable inaccuracy. Molecular dates based on ρ have a slight downward bias with large asymmetric variance and commonly exhibit substantial type I error rates, where the true age of a lineage falls outside the 95% confidence bounds derived from the variance of ρ. Furthermore, demography proves to be a strong confounding factor in estimating molecular dates accurately, especially for populations in which bottlenecks, founder events, and size changes have played important historical roles. Therefore considerable caution should be applied to inferences made from molecular dates based on the ρ statistic, many of which may be misleading and warrant considerable skepticism.

By the end of the 20th century most industrialized nations had undergone the so-called fertility transition, characterized by a reduction in fertility to below replacement level and a delay in age at initiation of child-bearing. An emerging concern is the severe economic and social consequences of this demographic decline. We present an overview of fertility changes in Italy in the second half of the 20th century and a mathematical model that may provide projections for the future of the demographic situation. Starting in 1950 the increment of the number of children born in Italy is initially positive; however, beginning in 1965 the trend suddenly becomes negative, and this negative trend further increased in 1975. A slight improvement is observed in 1980, followed by a stable situation beginning in 1987. Relevant socioeconomic and cultural events in Italy coincide with these variations in the fertility trend. Malnutrition, which had been endemic for centuries in some areas of central and southern Italy, disappeared rather abruptly in early 1960. The improvement in the economic situation was also associated with a decrease in illiteracy and with many sociocultural changes, with the emergence of new demands that decreased propensity for childbearing. The additional deceleration observed in 1975 corresponds to the diffusion of contraceptive procedures. The progression of sociocultural changes has led to a progressive liberation of women from the biological burden of childbearing. Two phenomena seem relevant in this context: women's emerging interest in entering the workforce and the possibility to disconnect sex from childbearing. The social function of feminism has overwhelmed the primary function of survival and diffusion of the species, giving rise to relevant and worrying demographic effects. However, the modern woman has an unconscious memory of her primary biological role, depending on both her genetic structure and cultural heritage, that should bring about a change in the present strong tendency to demographic decline. The basic notion of memory functions is widely recognized in sciences, for example, in the evolutionary theory of Darwin. Here, we introduce into the equations governing population growth a memory mechanism and a perturbation, and we estimate the reactions of the system to perturbations caused by environmental changes and subsequent delayed effects, such as those that appear in the birth rate beginning in 1965 and 1975. The mathematical modeling of the effects of perturbations of the fertility rate in the Italian population, with the introduction of a mathematical memory formalism, suggests that the effect is strongly reduced, with a relaxation time of about 10 years when the fertility rate approaches a stable value.

As part of an interdisciplinary research program on Alpine populations, we studied the biodemographic evolution of two populations of the Dauphiné in the period 1690–1799. We analyzed several indexes derived from surname analysis to infer the genetic structure of the populations. Although situated in the same area of the Dauphiné, the two communities of Vallouise and Chiomonte had different biodemographic characteristics. Vallouise was heavily populated but genetically homogeneous, whereas Chiomonte was less populated but more heterogeneous. The two districts also differed in geographic position: Vallouise was a glacier-enclosed valley that did not attract new inhabitants; Chiomonte was situated in an open valley served by important roads and thus was able to attract many new inhabitants. The demographic differences between the two populations explain the differences in genetic structure. The index of isonymous relationship (R_i) being different from 0 is due to the rare marriages between members of the two populations. Because R_i is based on surnames, which are mostly polyphyletic, it can overestimate the genetic relationships between the populations, as in the case of consanguinity assessed by matrimonial isonymy.

Stature, sitting height, stature by weight, and head circumference change with varying economic conditions during early childhood. Our hypothesis is that adult head shape, as well as head size, is influenced by changes in childhood nutrition. When economic conditions are bad, nutrition and health suffer, and the result is dolichocephaly. To test this hypothesis, we measured the head length, width, and circumference of 398 adult males in Jordan. Fifty-six percent are ethnic Jordanians, and 44% are ethnic Palestinians. We divided the modern history of Jordan and the West Bank into four periods developed from historical economic data. The results of the study show that the cephalic index (CI) among Jordanians increased significantly with economic improvement but decreased slightly during the best economic period, whereas CI remained stable across all periods among Palestinians. The pattern among Jordanians can be explained in terms of maternal environment and early childhood nutrition. The lack of pattern in Palestinians may be due to changing nursing practices, bottle feeding, or sleeping position. When economic conditions were bad, Jordanian mothers and infants suffered from malnutrition and deficits in health care services during pre- and postnatal periods. Infants were born with very low birth weight and longer heads. However, the highest mean value of head size, circumference, among Jordanians and Palestinians is obtained from individuals who were children during the bad economic period, an unexpected result. No significant linear or quadratic trend was found for either Palestinians' or Jordanians' head circumference over time.

The Indian Himalayas, being semi-isolated geographically, provide ideal conditions for population genetics investigations. The main aim of this study is to genetically characterize and analyze the genetic structure of the people of Uttarakhand, a newly created North Indian hill state in the Central Himalayas, using original phenotype and allele-frequency data on a battery of seven red cell enzyme polymorphisms. For this analysis, blood samples were collected from 3,222 unrelated subjects belonging to various endogamous caste populations (Brahmin, Rajput, and Shilpkar) and tribal Bhotia inhabiting seven different districts in the Garhwal (northern) and Kumaon (southern) regions of Uttarakhand. Hemolysates were typed for isozymes of ESD, PGM1, ADA, AK1, GLO1, ACP1, and GPI using standard electrophoretic techniques. The genetic structure of these regional caste and tribal population groups was investigated with the help of different statistical measures. The present biochemical marker results show that the overall genetic constitution of the different populations of Uttarakhand is rather heterogeneous but similar to that of various caste and tribal populations of the neighboring hill state of Himachal Pradesh, situated on Uttarakhand's western border. The extent of genic differentiation observed in different contemporary populations of Garhwal was twice as high as that of Kumaon. Interestingly, in genetic distance dendrograms of both the regions and of all of Uttarakhand, all the Shilpkar groups are differentiated from the remaining groups of Brahmin, Rajput, and Bhotia. The genetic constitution of the Shilpkar (a scheduled caste population of Uttarakhand) and to a lesser extent that of the Bhotia (a scheduled tribe population of Uttarakhand) are rather different from both the Brahmin and Rajput high-caste populations, which tend to show genetic similarities between them. These observations are corroborated by the known ethnohistory of different populations of Uttarakhand.

Currently, language and cultural practices are the only criteria to distinguish between Berber autochthonous Tunisian populations. To evaluate these populations' possible genetic structure and differentiation, we have analyzed 15 autosomal short tandem repeat loci (CSF1PO, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, D21S11, FGA, TH01, TPOX, VWA, D2S1338, and D19S433) in three southern Tunisian Berber groups: Sened, Matmata, and Chenini-Douiret. The exact test of population differentiation based on allele frequencies at the 15 loci shows significant P values at 7 loci between Chenini-Douiret and both Sened and Matmata, whereas just 5 loci show significant P values between Sened and Matmata. Comparative analyses between the three Berber groups based on genetic distances show that P values for F_ST distances are significant between the three Berber groups. Population analysis performed using Structure shows a clear differentiation between these Berber groups, with strong genetic isolation of Chenini-Douiret. These results confirm at the autosomal level the high degree of heterogeneity of Tunisian Berber populations that had been previously reported for uniparental markers.

To determine the influence of the MDR1 C3435T polymorphism on the development of childhood acute lymphoblastic leukemia (ALL), we studied 107 children with ALL and 111 healthy subjects. All subjects were genotyped for the C3435T polymorphism using the polymerase chain reaction–restriction fragment length polymorphism method. The genotype frequencies in the patients were 17% homozygous CC, 61% heterozygous CT, and 22% homozygous TT; in healthy individuals the genotype frequencies were 14% CC, 53% CT, and 33% TT. In patients with ALL the allele frequencies were 0.47 for the C allele and 0.53 for the T allele; in the healthy group these allele frequencies were 0.40 and 0.60 for the C and T alleles, respectively. No significant differences in allele frequency (p > 0.176) and genotype frequency (p > 0.255) were detected between the two groups. These findings suggest that the CT or TT genotype does not increase the risk for childhood ALL in Mexican patients. On the other hand, significant differences in allele frequencies were detected in the comparison of Mexican healthy subjects with other populations. Whether these differences are fortuitous or related to diverse genetic backgrounds remains to be elucidated.

Cytochrome 1A1 (CYP1A1), glutathione transferase M1 (GSTM1), and glutathione transferase T1 (GSTT1) catalyze the bioactivation and detoxification of a wide variety of xenobiotic compounds that are mutagenic and/or carcinogenic (e.g., polycyclic aromatic hydrocarbons). Genetic polymorphisms of these metabolizing enzymes have been shown to affect individual susceptibility to environmental carcinogenic compounds. Although several studies have been published on the relationship between CYP1A1*2C, GSTM1*0, or GSTT1*0 polymorphism and cancer, not all findings can be extrapolated to other populations because of interethnic variability. Here, we investigate the frequency of CYP1A1*2C, GSTM1*0, or GSTT1*0 in a sample of Mexican Mestizos. We find that the frequency of GSTM1*0 is 0.335, that of GSTT1*0 is 0.121, and that of GSTM1*0 GSTT1*0 is 0.023. The frequency of CYP1A1*2C is 0.54. Similitude analysis sets the Latin American populations in a common cluster near the Asian population, suggesting that the CYP1A1*2C polymorphism may have originated from this population and suffered a founder effect in the American population. Analysis of CYP1A1*2C, GSTM1*0, and GSTT1*0 haplotypes reveals that 35% of the population has some combination of risk genotypes. Taken together, these results point to a high susceptibility of the Mexican Mestizo population to the effects of environmental carcinogens.