The Experts below are selected from a list of 4422 Experts worldwide ranked by ideXlab platform
Mark G. Thomas - One of the best experts on this subject based on the ideXlab platform.
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The evolution of lactase persistence in Europe. A synthesis of archaeological and genetic evidence
International Dairy Journal, 2012Co-Authors: Michela Leonardi, Mark G. Thomas, Pascale Gerbault, Joachim BurgerAbstract:Lactase persistence, the ability to digest the milk sugar lactose in adulthood, is highly associated with a T allele situated 13,910 bp upstream from the actual lactase gene in Europeans. The frequency of this allele rose rapidly in Europe after transition from hunter–gatherer to agriculturalist lifestyles and the introduction of milkable domestic species from Anatolia some 8000 years ago. Here we first introduce the archaeological and historic background of early farming life in Europe, then summarize what is known of the physiological and genetic mechanisms of lactase persistence. Finally, we compile the evidence for a co-evolutionary process between Dairying culture and lactase persistence. We describe the different hypotheses on how this allele spread over Europe and the main evolutionary forces shaping this process. We also summarize three different computer simulation approaches, which offer a means of developing a coherent and integrated understanding of the process of spread of lactase persistence and Dairying.
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Evolution of lactase persistence: an example of human niche construction
Philosophical transactions of the Royal Society of London. Series B Biological sciences, 2011Co-Authors: Pascale Gerbault, Yuval Itan, Dallas M. Swallow, Anke Liebert, Adam Powell, Mathias Currat, Joachim Burger, Mark G. ThomasAbstract:Niche construction is the process by which organisms construct important components of their local environment in ways that introduce novel selection pressures. Lactase persistence is one of the clearest examples of niche construction in humans. Lactase is the enzyme responsible for the digestion of the milk sugar lactose and its production decreases after the weaning phase in most mammals, including most humans. Some humans, however, continue to produce lactase throughout adulthood, a trait known as lactase persistence. In European populations, a single mutation (−13910*T) explains the distribution of the phenotype, whereas several mutations are associated with it in Africa and the Middle East. Current estimates for the age of lactase persistence-associated alleles bracket those for the origins of animal domestication and the culturally transmitted practice of Dairying. We report new data on the distribution of −13910*T and summarize genetic studies on the diversity of lactase persistence worldwide. We review relevant archaeological data and describe three simulation studies that have shed light on the evolution of this trait in Europe. These studies illustrate how genetic and archaeological information can be integrated to bring new insights to the origins and spread of lactase persistence. Finally, we discuss possible improvements to these models.
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Absence of the lactase-persistence-associated allele in early Neolithic Europeans
Proceedings of the National Academy of Sciences of the United States of America, 2007Co-Authors: Joachim Burger, M. Kirchner, Barbara Bramanti, Wolfgang Haak, Mark G. ThomasAbstract:Lactase persistence (LP), the dominant Mendelian trait conferring the ability to digest the milk sugar lactose in adults, has risen to high frequency in central and northern Europeans in the last 20,000 years. This trait is likely to have conferred a selective advantage in individuals who consume appreciable amounts of unfermented milk. Some have argued for the ''culture-historical hypothesis,'' whereby LP alleles were rare until the advent of Dairying early in the Neolithic but then rose rapidly in frequency under natural selection. Others favor the ''reverse cause hypothesis,'' whereby Dairying was adopted in populations with preadaptive high LP allele frequencies. Analysis based on the conservation of lactase gene haplotypes indicates a recent origin and high selection coefficients for LP, although it has not been possible to say whether early Neolithic European populations were lactase per- sistent at appreciable frequencies. We developed a stepwise strat- egy for obtaining reliable nuclear ancient DNA from ancient skel- etons, based on (i) the selection of skeletons from archaeological sites that showed excellent biomolecular preservation, (ii) obtain- ing highly reproducible human mitochondrial DNA sequences, and (iii) reliable short tandem repeat (STR) genotypes from the same specimens. By applying this experimental strategy, we have ob- tained high-confidence LP-associated genotypes from eight Neo- lithic and one Mesolithic human remains, using a range of strict criteria for ancient DNA work. We did not observe the allele most commonly associated with LP in Europeans, thus providing evi- dence for the culture-historical hypothesis, and indicating that LP was rare in early European farmers. ancient DNA Dairying selection
Laure Ségurel - One of the best experts on this subject based on the ideXlab platform.
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Why and when was lactase persistence selected for? Insights from Central Asian herders and ancient DNA
PLoS Biology, 2020Co-Authors: Laure Ségurel, Céline Bon, Perle Guarino-vignon, Nina Marchi, Sophie Lafosse, Romain Laurent, Alexandre Fabre, Tatyana Hegay, Evelyne HeyerAbstract:The genetic adaptation of humans to the consumption of milk from Dairying animals is one of the most emblematic cases of recent human evolution. While the phenotypic change under selection, lactase persistence (LP), is known, the evolutionary advantage conferred to persistent individuals remains obscure. One informative but underappreciated observation is that not all populations whose ancestors had access to milk genetically adapted to become lactase persistent. Indeed, Central Asian herders are mostly lactase nonpersistent, despite their significant dietary reliance on dairy products. Investigating the temporal dynamic of the −13.910:C>T Eurasian mutation associated with LP, we found that, after its emergence in Ukraine 5,960 before present (BP), the T allele spread between 4,000 BP and 3,500 BP throughout Eurasia, from Spain to Kazakhstan. The timing and geographical progression of the mutation coincides well with the migration of steppe populations across and outside of Europe. After 3,000 BP, the mutation strongly increased in frequency in Europe, but not in Asia. We propose that Central Asian herders have adapted to milk consumption culturally, by fermentation, and/or by colonic adaptation, rather than genetically. Given the possibility of a nongenetic adaptation to avoid intestinal symptoms when consuming dairy products, the puzzle then becomes this: why has LP been selected for at all?
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On the Evolution of Lactase Persistence in Humans.
Annual review of genomics and human genetics, 2017Co-Authors: Laure Ségurel, Céline BonAbstract:Lactase persistence—the ability of adults to digest the lactose in milk—varies widely in frequency across human populations. This trait represents an adaptation to the domestication of Dairying animals and the subsequent consumption of their milk. Five variants are currently known to underlie this phenotype, which is monogenic in Eurasia but mostly polygenic in Africa. Despite being a textbook example of regulatory convergent evolution and gene-culture coevolution, the story of lactase persistence is far from clear: Why are lactase persistence frequencies low in Central Asian herders but high in some African hunter-gatherers? Why was lactase persistence strongly selected for even though milk processing can reduce the amount of lactose? Are there other factors, outside of an advantage of caloric intake, that contributed to the selective pressure for lactase persistence? It is time to revisit what we know and still do not know about lactase persistence in humans.
Céline Bon - One of the best experts on this subject based on the ideXlab platform.
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Why and when was lactase persistence selected for? Insights from Central Asian herders and ancient DNA
PLoS Biology, 2020Co-Authors: Laure Ségurel, Céline Bon, Perle Guarino-vignon, Nina Marchi, Sophie Lafosse, Romain Laurent, Alexandre Fabre, Tatyana Hegay, Evelyne HeyerAbstract:The genetic adaptation of humans to the consumption of milk from Dairying animals is one of the most emblematic cases of recent human evolution. While the phenotypic change under selection, lactase persistence (LP), is known, the evolutionary advantage conferred to persistent individuals remains obscure. One informative but underappreciated observation is that not all populations whose ancestors had access to milk genetically adapted to become lactase persistent. Indeed, Central Asian herders are mostly lactase nonpersistent, despite their significant dietary reliance on dairy products. Investigating the temporal dynamic of the −13.910:C>T Eurasian mutation associated with LP, we found that, after its emergence in Ukraine 5,960 before present (BP), the T allele spread between 4,000 BP and 3,500 BP throughout Eurasia, from Spain to Kazakhstan. The timing and geographical progression of the mutation coincides well with the migration of steppe populations across and outside of Europe. After 3,000 BP, the mutation strongly increased in frequency in Europe, but not in Asia. We propose that Central Asian herders have adapted to milk consumption culturally, by fermentation, and/or by colonic adaptation, rather than genetically. Given the possibility of a nongenetic adaptation to avoid intestinal symptoms when consuming dairy products, the puzzle then becomes this: why has LP been selected for at all?
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On the Evolution of Lactase Persistence in Humans.
Annual review of genomics and human genetics, 2017Co-Authors: Laure Ségurel, Céline BonAbstract:Lactase persistence—the ability of adults to digest the lactose in milk—varies widely in frequency across human populations. This trait represents an adaptation to the domestication of Dairying animals and the subsequent consumption of their milk. Five variants are currently known to underlie this phenotype, which is monogenic in Eurasia but mostly polygenic in Africa. Despite being a textbook example of regulatory convergent evolution and gene-culture coevolution, the story of lactase persistence is far from clear: Why are lactase persistence frequencies low in Central Asian herders but high in some African hunter-gatherers? Why was lactase persistence strongly selected for even though milk processing can reduce the amount of lactose? Are there other factors, outside of an advantage of caloric intake, that contributed to the selective pressure for lactase persistence? It is time to revisit what we know and still do not know about lactase persistence in humans.
Joachim Burger - One of the best experts on this subject based on the ideXlab platform.
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The evolution of lactase persistence in Europe. A synthesis of archaeological and genetic evidence
International Dairy Journal, 2012Co-Authors: Michela Leonardi, Mark G. Thomas, Pascale Gerbault, Joachim BurgerAbstract:Lactase persistence, the ability to digest the milk sugar lactose in adulthood, is highly associated with a T allele situated 13,910 bp upstream from the actual lactase gene in Europeans. The frequency of this allele rose rapidly in Europe after transition from hunter–gatherer to agriculturalist lifestyles and the introduction of milkable domestic species from Anatolia some 8000 years ago. Here we first introduce the archaeological and historic background of early farming life in Europe, then summarize what is known of the physiological and genetic mechanisms of lactase persistence. Finally, we compile the evidence for a co-evolutionary process between Dairying culture and lactase persistence. We describe the different hypotheses on how this allele spread over Europe and the main evolutionary forces shaping this process. We also summarize three different computer simulation approaches, which offer a means of developing a coherent and integrated understanding of the process of spread of lactase persistence and Dairying.
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Evolution of lactase persistence: an example of human niche construction
Philosophical transactions of the Royal Society of London. Series B Biological sciences, 2011Co-Authors: Pascale Gerbault, Yuval Itan, Dallas M. Swallow, Anke Liebert, Adam Powell, Mathias Currat, Joachim Burger, Mark G. ThomasAbstract:Niche construction is the process by which organisms construct important components of their local environment in ways that introduce novel selection pressures. Lactase persistence is one of the clearest examples of niche construction in humans. Lactase is the enzyme responsible for the digestion of the milk sugar lactose and its production decreases after the weaning phase in most mammals, including most humans. Some humans, however, continue to produce lactase throughout adulthood, a trait known as lactase persistence. In European populations, a single mutation (−13910*T) explains the distribution of the phenotype, whereas several mutations are associated with it in Africa and the Middle East. Current estimates for the age of lactase persistence-associated alleles bracket those for the origins of animal domestication and the culturally transmitted practice of Dairying. We report new data on the distribution of −13910*T and summarize genetic studies on the diversity of lactase persistence worldwide. We review relevant archaeological data and describe three simulation studies that have shed light on the evolution of this trait in Europe. These studies illustrate how genetic and archaeological information can be integrated to bring new insights to the origins and spread of lactase persistence. Finally, we discuss possible improvements to these models.
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Absence of the lactase-persistence-associated allele in early Neolithic Europeans
Proceedings of the National Academy of Sciences of the United States of America, 2007Co-Authors: Joachim Burger, M. Kirchner, Barbara Bramanti, Wolfgang Haak, Mark G. ThomasAbstract:Lactase persistence (LP), the dominant Mendelian trait conferring the ability to digest the milk sugar lactose in adults, has risen to high frequency in central and northern Europeans in the last 20,000 years. This trait is likely to have conferred a selective advantage in individuals who consume appreciable amounts of unfermented milk. Some have argued for the ''culture-historical hypothesis,'' whereby LP alleles were rare until the advent of Dairying early in the Neolithic but then rose rapidly in frequency under natural selection. Others favor the ''reverse cause hypothesis,'' whereby Dairying was adopted in populations with preadaptive high LP allele frequencies. Analysis based on the conservation of lactase gene haplotypes indicates a recent origin and high selection coefficients for LP, although it has not been possible to say whether early Neolithic European populations were lactase per- sistent at appreciable frequencies. We developed a stepwise strat- egy for obtaining reliable nuclear ancient DNA from ancient skel- etons, based on (i) the selection of skeletons from archaeological sites that showed excellent biomolecular preservation, (ii) obtain- ing highly reproducible human mitochondrial DNA sequences, and (iii) reliable short tandem repeat (STR) genotypes from the same specimens. By applying this experimental strategy, we have ob- tained high-confidence LP-associated genotypes from eight Neo- lithic and one Mesolithic human remains, using a range of strict criteria for ancient DNA work. We did not observe the allele most commonly associated with LP in Europeans, thus providing evi- dence for the culture-historical hypothesis, and indicating that LP was rare in early European farmers. ancient DNA Dairying selection
M J Auldist - One of the best experts on this subject based on the ideXlab platform.
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composition coagulation properties and cheesemaking potential of milk from cows undergoing extended lactations in a pasture based Dairying system
Journal of Dairy Science, 2010Co-Authors: M J Auldist, C Grainger, A V Houlihan, Jeffery J Mayes, Roderick P W WilliamsAbstract:Extending the lactation length of dairy cows beyond the traditional 10 mo toward lactations of up to 22 mo has attracted interest in the pasture-based seasonal Dairying systems of Australia and New Zealand as a way of alleviating the need for cows to conceive during peak lactation, such as is required to maintain seasonally concentrated calving systems. Lactation lengths longer than 10 mo instead provide cows with more time to cycle and conceive after parturition and may therefore be more suitable systems for high-producing Holstein-Friesian cows. Before recommending such systems there is a need to evaluate the effects of long lactations on the suitability of milk for manufacture of high-quality dairy products. In the current experiment, the composition of milk from cows entering the second half of a 22-mo lactation was examined in detail and compared with that from cows undergoing a traditional 10-mo lactation. On 2 occasions, coagulation properties were measured using low amplitude strain oscillation rheometry, and Cheddar cheese was made in 250-L pilot-scale vats. Results showed that milk from extended lactations had higher concentrations of fat and protein than cows undergoing 10-mo lactations under similar management conditions and at the same time of year. The ratio of casein to true protein was not affected by lactation length and neither were the proportions of individual caseins. The increase in milk solids during extended lactations translated into a more rapid rate of coagulation and ultimately a firmer curd on one of the two occasions. Milk from extended lactations yielded more cheese per 100 kg of milk, and there were few differences in the composition or organoleptic properties of the cheese. These data are the first to show that pasture-based dairy industries could embrace the use of extended lactations without compromising the core business of producing high-quality dairy products.
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comparative reproductive performance and early lactation productivity of jersey holstein cows in predominantly holstein herds in a pasture based Dairying system
Journal of Dairy Science, 2007Co-Authors: M J Auldist, C Grainger, M F Pyman, K L MacmillanAbstract:Abstract The aim of this study was to compare the reproductive performance, milk production, live weight, and body condition loss during early lactation of purebred Holstein (H) cows to Jersey×H (J×H) crossbred cows in 4 Victorian herds. Cows of H and J×H breeding were managed together within each herd, and all herds had a seasonally concentrated calving pattern that commenced in early spring (July). All crossbred cows included in the study were 25, 50, or 75% H and were considered collectively as J×H regardless of the sire and dam breeds used to reach those percentages. Each herd owner provided records of reproductive performance and milk production. Compared with H cows, J×H cows had higher first-service conception rates (52 vs. 42%), higher percentages confirmed pregnant by 6 (68 vs. 54%) and 14 wk (86 vs. 78%) after the first day of inseminating, and lower final not-in-calf rates (11 vs. 16%); however, these differences were not observed in all herds. A random selection of H and J×H cows had body condition assessed on 3 occasions between the start of calving and the first day of the artificial insemination program. The selected cows were also weighed on the final occasion. Overall, body condition scores were slightly higher for J×H cows than for H cows, but changes in body condition score between calving and the start of inseminating were similar between breed groups. The H cows were 40kg heavier than J×H cows and had daily milk yields in early lactation that were 2.2kg higher. Daily yields of milk fat and protein did not differ between H and J×H cows during the study period. The improved reproductive performance of J×H cows compared with H cows may render them more suitable for use in dairy herds with seasonally concentrated calving patterns. Their improved reproductive performance was not associated with differences in condition loss in early lactation.
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effects of varying lactation length on milk production capacity of cows in pasture based Dairying systems
Journal of Dairy Science, 2007Co-Authors: M J Auldist, G Obrien, D Cole, K L Macmillan, C GraingerAbstract:The aim of this experiment was to quantify the milk production capacity of cows undergoing extended lactations while fed a pasture-based diet typical of those used in the seasonal-calving Dairying systems of Victoria, Australia. One hundred twenty-five Holstein cows were randomly assigned to 1 of 5 groups. Breeding was progressively delayed after calving to enable management of the groups for lactation lengths of 10, 13, 16, 19, and 22 mo (equivalent to calving intervals of 12 to 24 mo). Cows were provided with a daily energy intake of at least 180 MJ of metabolizable energy/cow. This was supplied primarily by grazed pasture with supplementary cereal grain, pasture silage, and hay. Cows were dried off when milk volume fell below 30 kg/wk or when they reached 56 d before their expected calving date. Most cows (>96%) could lactate above this threshold for 16 mo, >80% for 19 mo, and >40% for 22 mo. There were negative relationships between lactation length and annual production of milk and milk solids (milk fat + protein), but losses were small until 16 mo. Annualized yields of milk solids were 497, 498, 495, 474, and 463 kg/cow for the 10, 13, 16, 19, and 22 mo groups, respectively. This reduction in annual production of milk solids with increasing lactation length was relatively less than for milk volume because during extended lactation, cows produced milk with higher concentrations of protein. Cows undergoing extended lactations also finished their lactations having gained more body weight and body condition than cows lactating for only 10 mo. The data showed that many cows on pasture-based diets were capable of lactating longer than the 10 mo that is standard for Victorian herds with seasonally concentrated calving patterns. Further, such extended lactations could be achieved with little penalty in terms of annual milk solids production.
