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Introduction
Published in Eve K. Boyle, Vondel S. E. Mahon, Rui Diogo, Handbook of Muscle Variations and Anomalies in Humans, 2022
Eve K. Boyle, Vondel S. E. Mahon, Rui Diogo
Some authors suggest that cases in which complex structures are formed early in “normal” ontogeny but later become lost/indistinct during development (so-called “hidden variation”), may allow organisms to have greater ontogenetic potential early in development. If faced with external perturbations (e.g., climate change, habitat occupied by new species), evolution can use that potential (adaptive plasticity: e.g., West-Eberhard 2003). However, authors such as Gould (1977, 2002) and Alberch (1989) suggested that these cases support instead a “constrained” (internalist) rather than an “adaptationist” (externalist) view of evolution. This is because it is not likely that the persistence of some muscles in later developmental stages of karyotypically abnormal humans is due to natural selection and adaptive evolution. This corresponds with the idea defended by Galis and Metz (2007: 415–416): “without denying the evolutionary importance of phenotypic plasticity and genetic assimilation, we think that for the generation of macro-evolutionary novelties the evidence for the impact of hidden variation is limited” (see also Levinton 2001).
William Bateson (1861–1926)
Published in Krishna Dronamraju, A Century of Geneticists, 2018
Haldane (1957) knew Bateson well from 1919 until his death. He wrote: “Bateson…could be described as an angry and obstinate old man. But his anger was largely reserved for inaccuracy and loose thinking, and for certain types of injustice. His obstinacy made it difficult to convince him of the truth of theories which had previously been asserted without adequate evidence and were now being substantiated. Correns (1902) in a brilliant guess embodied in a diagram without adequate explanation, had put forward the theory linear arrangement of genes on chromosomes. Bateson, quite rightly, had not accepted the hypothesis. When Bridges and Sturtevant proved it, he was hard to convince, though he was finally convinced of the fact that genes were associated with chromosomes. On the other hand, he instantly accepted new generalisations provided they were statements of fact not involving theoretical superstructures. Thus, he was, I think, the first person to believe my own generalisation about sex-ratio and unisexual sterility in hybrid animals, though not, of course, the rather incoherent explanation of it which I gave. He then displayed a characteristic combination of anger at my ignorance with great generosity in helping me with his immense knowledge of the by-ways of entomological literature. To me, at least, he showed no signs whatever of a senile failure of original thought. On the contrary his last posthumously published paper on the genetics of bolting in root crops initiated a line of research which was later developed by Waddington in his studies on genetic assimilation.”
Genetic substructure and admixture of Mongolians and Kazakhs inferred from genome-wide array genotyping
Published in Annals of Human Biology, 2020
Jing Zhao, Jin Sun, Ziyang Xia, Guanglin He, Xiaomin Yang, Jianxin Guo, Hui-Zhen Cheng, Yingxiang Li, Song Lin, Tie-Lin Yang, Xi Hu, Hua Du, Peng Cheng, Rong Hu, Gang Chen, Haibing Yuan, Xiu-Fang Zhang, Lan-Hai Wei, Hu-Qin Zhang, Chuan-Chao Wang
We showed that there are genetic substructures within Mongolians corresponding to Ölöd, Chahar, and Inner Mongolian clusters, which is consistent with their tribe classifications. The substructure is shaped by the relatedness of Mongolians to West Eurasians. Mongolians and Kazakhs are on a genetic cline in terms of different proportions of West Eurasian related admixture from 6% to 40%. The genetic source for the West Eurasian ancestry was most likely Bronze Age Steppe population-related. We note that the small number of sampled individuals from different tribes is a limitation of the study. However, our findings are consistent with archaeological and ancient genomic evidence that the Bronze Age Steppe populations shaped the culture and genetic makeup of northern Eurasia through rapid expansion (Allentoft et al. 2015; Narasimhan et al. 2018). Moreover, the dominant paternal lineages detected in different tribes were consistent with the previous studies and geographical distribution. Therefore, the observed genetic substructure in Mongolians in our study was plausibly a real signal, suggesting the formation of different Mongolian tribes probably involved genetic assimilation of surrounding populations. A priority for future work is to obtain a larger number of samples from diverse tribes to comprehensively reveal the genetic diversity and population history of Mongolians.
Paternal Y chromosomal genotyping reveals multiple large-scale admixtures in the formation of Lolo-Burmese–speaking populations in southwest China
Published in Annals of Human Biology, 2019
Jianxin Guo, Bingying Xu, Lanjiang Li, Guanglin He, Han Zhang, Hui-Zhen Cheng, Jinxing Ba, Xiaomin Yang, Lanhai Wei, Rong Hu, Chuan-Chao Wang
In our study, we genotyped and analysed 43 Y chromosome SNPs of Yunnan Yi and Bai males to investigate the paternal genetic structure and population relationships. The Lolo-Burmese–speaking groups Bai and Yi in Yunnan experienced multiple large-scale admixtures, these include the expansion of northern Neolithic farming populations, as shown with a high frequency of haplogroup O2a2b1a1-Page23 from the Upper-Middle Yellow River Basin; the genetic assimilation of surrounding Tai-Kadai populations, as shown with the high frequency of haplogroup O1a-M119; the demographic expansion driven by Neolithic agricultural revolution from southern China, as shown with the high frequency of haplogroup O1b-P31; and the population migration from northern and eastern China related to military immigration of the great Mongolian expansion or guard towns in early and middle Ming dynasty, as shown with the high frequencies of haplogroups C-M216 and O2a1b-002611. Our study suggests that the agriculture-induced, military and political expansions might have reshaped the paternal population structure in Lolo-Burmese–speaking populations.
Multiple genetic analyses for Chinese Hunan Han population via 46 A-STRs
Published in Annals of Human Biology, 2022
Yunying Zhang, Yating Fang, Man Chen, Ming Zhao, Hui Xu, Congying Zhao, Jiangwei Lan, Bofeng Zhu
In general, population genetic analyses mainly focus on differences and similarities between populations, which fundamentally result from differences and similarities in the distributions of genes or genotypes, and can be comprehensively studied and interpreted from different perspectives by various methods. In the present study, population genetic analyses were performed at two levels, namely the interpopulation level focussing on the genetic distances (DA values) and locus-by-locus comparisons, and the overall level including the principal component analysis and phylogenetic analysis. For the sake of promoting understanding between the Hunan Han population and other groups from China in the matter of genetic relationships, 13 representative populations amounting to 6378 individuals were obtained for comprehensive population comparisons with the above analytical methods. Through the relative magnitude of values, genetic distances (DA) revealed genetic differences among ethnic minorities as well as between ethnic minorities and Chinese Han populations, and also revealed the genetic similarities among Han populations from various geographical regions. Furthermore, the scattering tendency of most ethnic minorities (Sichuan Tibetan, Hainan Ha Hlai, Yi from West China) in the PCA plot, and the prominent clade in phylogenetic trees consisting of Sichuan Tibetans, Yi from West China and Gansu Hui together reflected the genetic differentiations between the Han populations and minority ethnic groups selected in this study. A previous study using 37,994 Y-STR haplotypes (Nothnagel et al. 2017) also proved that Han populations showed the pronounced genetic discrepancies with ethnic minority groups, especially Kazaks and Tibetans. Besides, results from both PCA and phylogenetic analyses showed subtle differences between southern Han Chinese and northern Han Chinese, as evidenced by the finding that southern Han Chinese including Hunan Han, Guangdong Han, Zhejiang Han populations made one cluster, while Shaanxi Han, Beijing Han, Shandong Han and Liaoning Han from Northern China formed another cluster. The results observed in this study were consistent with previous findings (Chu et al. 1998; Xue et al. 2008) based on population data from ethnic minorities and Han populations in China. The studied Hunan Han population, as presented in DA distances and locus-by-locus comparisons, kept relatively remote relationships with Sichuan Tibetans, Hainan Ha Hlai and Yi from West China, which was basically identified with the results of PCA and phylogenetic analyses. Population genetic analyses also reflected that the Hunan Han had closer genetic affinities with other Han populations, especially southern Han Chinese, and a geographically close ethnic minority group, namely the Hubei Tujia group. Due to the increasing population movement as well as frequent gene exchange, stronger genetic assimilation could be observed not only in populations with ethnic affinities but also in geographically close populations. The present results obtained from this study basically conformed to the previous findings by means of different genetic markers, such as autosomal STRs (Guo et al. 2015), Y Chromosome markers (Xie et al. 2004), and single nucleotide polymorphisms (He et al. 2021).