Search Results

Three factors contribute to the rapid evolutionary rate and rate heterogeneity in animal mitochondrial DNA (mtDNA). First, different mtDNA lineages feature different DNA replication mechanisms with different mutation spectra. Slow-evolving mtDNAs in Cnidaria and Porifera exhibit strand asymmetric patterns consistent with those of single-origin DNA replication in eubacteria, whereas fast-evolving mtDNAs in other metazoan lineages exhibit distinct strand asymmetric patterns consistent with the error-prone strand displacement replication. The strand asymmetry in mutation spectrum, coupled with strand switching of genes, contributes significantly to the rapid evolution of animal mtDNA. Second, different metazoan mtDNAs have evolved at least seven genetic codes resulting in diverging selection on codon usage. Third, metazoan mitochondrial tRNA pools are relatively autonomous, with tRNAs encoded by mtDNA, in contrast to plant mitochondrial tRNA pools. A gain or loss of a tRNA gene in metazoan mtDNA often leads to readily detectable substitutions leading to new codon adaptation.

Popular philosophical associations of tropical forests, and forests in general, with an inherent ancestral state, away from the stresses, pollution, and technosphere of modern life, are nicely summarized by Murakami’s quote above (2002). Given the probable origins of the hominin clade in tropical forests, this quote is also apt from an evolutionary standpoint. Yet, somewhat surprisingly, tropical forests have frequently been considered impenetrable barriers to the global migration of Homo sapiens (Gamble, 1993; Finlayson, 2014). As was the case with the focus on ‘savannastan’ in facilitating the Early Pleistocene expansion of Homo erectus discussed in Chapter 3 (Dennell and Roebroeks, 2005), the movement of H. sapiens into tropical regions such as South Asia, Southeast Asia, and Australia has tended to be linked to Late Pleistocene periods when forests contracted and grasslands expanded (Bird et al., 2005; Boivin et al., 2013). Alternative narratives have focused on the importance of coastal adaptations as providing a rich source of protein and driving cultural and technological complexity, as well as mobility, in human populations during the Middle and Late Pleistocene (Mellars, 2006; Marean, 2016). The evidence of early art and symbolism at coastal cave sites such as Blombos in South Africa (Henshilwood et al., 2002, 2011; Vanhaeren et al., 2013) and Taforalt in North Africa (Bouzouggar et al., 2007) is often used to emphasize the role of marine habitats in the earliest cultural emergence of our species. Indeed, for the last decade, the pursuit of rich marine resources (Mellars, 2005, 2006) has been a popular explanation for the supposed rapidity of the ‘southern dispersal route’, whereby humans left Africa 60 ka, based on genetic information (e.g., Macaulay et al., 2005), to reach the Pleistocene landmass that connected Australia and New Guinea (Sahul) by c. 65 ka (Clarkson et al., 2017). In both of these cases, the coast or expanses of grassland have been seen as homogeneous corridors, facilitating rapid expansion without novel adaptation.

Mitochondrial DNA (mtDNA) studies of modern human populations have made unique contributions to the understanding of human evolution due to two important features of this gene: their lack of recombination and their rate of mutation. This chapter first examines how rapid evolution and maternal transmission affect phylogenic reconstruction. A human female passes on her mitochondrial genes whereas a human male does not. Since females are almost always sure of maternity, mtDNA is preferred for tracing genealogies in many populations with different cultural norms for mate choice and long-term pair bonds. Mitochondrial DNA is a very sensitive indicator of population history. This chapter presents two reasons that reduce mitochondrial variability compared to other species: genetic bottle-necks and lineage sorting. The human mtDNA tree is also presented. The study has encountered several criticisms in the past. However, these criticisms are answered in this chapter.

This chapter presents the age-at-death and sex distributions at all three sites, and the strontium isotope and ancient mtDNA data from Conchopata. Those demographic data are used to reconstruct the forms of community organization at each site and how they differ. At Conchopata, there are significantly more females than males, and the author suggests that this may be because men died while away on military campaigns, never to return to their home community to receive proper burial. The Beringa demographic profile appears to represent the once-living community and indicates that it was a village community with extended family groups. The La Real demographic profile is not representative of a once-living community; there are few infants and children, and significantly more men than women, which likely reflects a burial program whereby adult men were preferentially selected for burial there.

Voyagers from the Marquesas Islands were among the first to settle Hawai`i, as evidenced by similarities in the languages of the two archipelagos and the early presence in Hawai`i of Polynesian rats (Rattus exulans) shown by mtDNA analysis to be associated with the Marquesas. This chapter reviews two Marquesan tribal groups. One, the society after which Hawaiian state emergence conjectural stage 3 is modeled, is the single-community tribe of Taiohae valley on the south coast of Nuku Hiva. The single symbolic chief (haka`iki) resembles a Tikopia chief. Unlike Tikopia, this tribe is constantly interacting with other tribes. The other example is `Ua Pou, the only Marquesan case of an entire multicommunity island united, like a small Hawaiian district, under of a single leader, and the basis for conjectural stage 4. The term “community center” refers to a remarkably large and massively constructed Marquesan architectural complex.

Danforth and colleagues report on demography, diet, mitochondrial DNA, and biological stress in remains from Moran, Mississippi, part of New Biloxi, a French colonial settlement. This study is unique, since at the time of this writing, skeletal remains were identified at only six French sites in the U.S. These authors test whether the historically documented policies implemented under “Code Noir” were actually practiced and enforced at the settlement, segregating the European settlers, enslaved Africans and their descendants, and Native Americans. The authors were surprised by the high number of young males of European ancestry they encountered. Stable isotope data indicated that their diets were dominated by C3 based plants and only one had C4 based diet. Although the human remains were small and few possessed high levels of enamel defects, Danforth and colleagues found low levels of physiological stress. They conclude that either the burials from Moran were not part of New Biloxi and did not suffer to the degree the settlers of New Biloxi suffered or there was strict enforcement of segregation, with the remains of other groups interred elsewhere, and the conditions were not as poor for the Moran group as historical documents about New Biloxi say.

This chapter deals with Cavalli-Sforza’s early work in the development of statistical and computer techniques to create human population trees on the basis of the genetics of blood groups. The history within was now conceived to reside in the gene. At the same time, also Cavalli-Sforza synthesized knowledge from other fields such as archaeology, linguistics, and history with the genetic data to arrive at encompassing pictures of modern human population migrations. This also generated controversy, especially with exponents of cultural anthropology. Cavalli-Sforza’s team at Stanford University was a center of human population genetic research and pioneered the development of DNA analysis for the establishment of genetic kinship trees. mtDNA and Y-chromosomal markers became the most important objects for the reconstruction of modern human evolution. On the basis of that knowledge and the out-of-Africa hypothesis, diverse branches of the human origins sciences became integrated and the new view of human evolution was popularized.

This chapter deals with the similarities and differences between Homo neanderthalensis and Homo sapiens, by considering genetic, brain, and cognitive evidence. The genetic differentiation emerges from fossil genetic evidence obtained first from mtDNA and later from nuclear DNA. With high throughput whole genome sequencing, sequences have been obtained from the Denisova Cave (Siberia) fossils. Nuclear DNA of a third species (“Denisovans”) has been obtained from the same cave and used to define the phylogenetic relationships among the three species during the Upper Palaeolithic. Archaeological comparisons make it possible to advance a four-mode model of the evolution of symbolism. Neanderthals and modern humans would share a “modern mind” as defined up to Symbolic Mode 3. Whether the Neanderthals reached symbolic Mode 4 remains unsettled.

This chapter covers the different types of direct to consumer DNA tests for genealogy. They are technically similar but a bit different from those used for medical and health conditions, as genealogy tests focus on identifying “matches,” or relatives who’ve also tested based on shared SNPs or other similarities. Consumers can choose from autosomal DNA, Y-chromosome, and mtDNA tests, depending on their interests and research goals. Unlike the other tests, genealogy DNA tests compare your results with those of others and predict a relationship based on the amount of DNA you share. This adds an extra layer of complexity but is no less rewarding, and the findings can be no less surprising. Understanding how these tests work and what they show enables consumers to choose the specific ones that will be most helpful in compiling their genetic genealogy.

Conservation genetics is a relatively young interdisciplinary field. Essentially, it concerns the application of genetic methods to threatened species. It aims to obtain detailed insights about their evolution, ecology, taxonomy, and population genetics and to inform conservation strategies. This chapter discusses the application of the most commonly used molecular techniques to the conservation of primates, with a focus on non-invasive samples. Recent technological advances in sequencing techniques are allowing the transition from classical population genetic studies, based on few markers, to studies based on whole-genome information. The main techniques and concepts are broadly explored and practical examples are given together with pointers to recent studies and reviews. The aim is to give the reader a general understanding of what the field of conservation genetics is, how it can be applied to primate research and conservation, and how it will likely change in the future.