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In the 20th century Spain maintained some of the highest rates of consanguineous marriage in Europe. In many regions these rates were still high in the 1950s and 1960s but then decreased rapidly, and by the 1970s a generalized transformation in mating patterns was under way. In the following decades the marriage of persons closely related by birth became rare. Consanguinity and inbreeding have been much studied in Spain but almost exclusively in the central and northern regions of the country. This is the first study of a whole large diocese in the southern region of Andalusia. This article is based on the analysis of 15,440 records of consanguineous unions registered between 1900 and 1979 in the Archbishopric of Granada in Andalusia. In this period, the rate of consanguinity up to second cousins was 5.51%, and the mean coefficient of inbreeding, α, was 2.04 × 10–3. There is a high range of variability within the research area: the rate of consanguinity was more than three times higher in rural areas (6.74%; α = 2.44 × 10–3) than in the capital city (2.03%; α = 0.93 × 10–3). There was a high frequency of unions between first cousins and first cousins once removed. These amounted to 35.3% and 13% of all consanguineous marriages, respectively, and contributed to 70% of α-values. Consanguinity here has been strongly related to local endogamy. Thus, 76% of all consanguineous couples were born in the same locality, and 89% resided in the same locality at marriage. By the end of the 1960s premarital migration increased and local endogamy started to decrease. On the other hand, inbreeding is inversely related to spatial endogamy. The more inbred couples, such as uncles-nieces (C12) or first cousins (C22), show significantly higher exogamy rates than second cousins (C33) and third cousins (C44), and higher rates of premarital migration. Neither males nor females in intrafamily unions seem to be significantly younger than those in nonconsanguineous unions. Considering their temporal evolution, consanguinity rates increased in the first third of the century, reaching a maximum in the late 1920s, when over 7.4% of all marriages were consanguineous (8.3% for the rural areas), and the resulting α-value was the highest of the century (α = 2.71 × 10–3 for the whole diocese; α = 3.00 × 10–3 for the rural areas). Rates of inbreeding remained high until the 1950s and decreased thereafter in a period of accelerated emigration to cities, urbanization, industrialization, and social modernization. Overall, levels of inbreeding are similar and sometimes larger than those found in dioceses in the northwest of Spain, although marriages between uncle and niece were less common. Some of the counties in the diocese had very high consanguinity levels, not only the isolated area of La Alpujarra, previously studied, but also other ecological and historical microregions (comarcas). These results indicate that the widely accepted north-south divisions of the Iberian Peninsula in terms of consanguinity and inbreeding patterns require considerable reevaluation.
With the ongoing growth of gene-based research in recent decades, examining changes that have taken place in structures over the course of evolution has become increasingly accessible. One intriguing subject at the forefront of evolutionary research is how environmental pressures affect species evolution through epigenetic adaptation. This article presents the available molecular components of adaptation to cold environments in two extinct mammals: the woolly mammoth and the Neanderthal. These two species coexisted in similar geographic and environmental European settings during the Middle and Upper Pleistocene, and both were direct descendants of African ancestors, although both fully evolved and adapted in Europe during the Middle Pleistocene. The authors assessed the degree of resemblance between mammoth and Neanderthal genetic components by reviewing three case studies of relevant gene variants and alleles associated with cold-climate adaptation found in both genomes. Their observations present the likelihood of a molecular resemblance between the suites of cold adaptation traits in the two species.
A number of recent articles have appeared on the hominin Denisova fossil remains. Many of them focus on attempts to produce DNA sequences from the extracted samples. Often these project mitochondrial DNA (mtDNA) sequences from the fossils of a number of Neandertals and the Denisovans in an attempt to understand the evolution of Middle Pleistocene human ancestors. These articles introduce a number of problems in the interpretation of speciation in hominins. One concerns the degradation of the ancient DNA and its interpretation as authentic genetic information. Another problem concerns the ideas of “species” versus “population” and the use of these ideas in building evolutionary diagrams to indicate ancestry and extinction. A third issue concerns the theory of haplotypes in the mtDNA. Given the severe constraints on mutations in the mtDNA genome to maintain functionality and the purifying processes to reduce such mutations in the ovaries, putative geographic and historical variations seem contradictory. Local diversity and variations in supposed “macrohaplotypes” are explained as back migrations or back mutations, which dilutes the robust nature of the theory. A central issue involves what human variation means, how much population variation there has been in the past, and whether this variation distinguishes hominid speciation or is simply a process of anagenesis. This brings up the question of how much can be interpreted from the analysis of DNA. Some businesses today claim to be able to use DNA analysis to discover past ethnic identities, and a new niche in restaurants is producing “DNA” menus. Perhaps some caution is in order.