Adapting to varied natural environments was key for the ancestors of modern humans to successfully settle the rest of world after they migrated out of Africa. Different population need to face the different environment and develop the different custom. The environment diversity product various nature selection force to human genome. For more comprehensive understanding the adaption mode to different environment factors, we employ methods of molecular evolution to investigate following three special adaptation examples: human adapt to living environment; human ancestral allele adapt to the modern environment; human gene degeneration. Maintaining a balance between ATP synthesis and heat generation is crucial for adapting to changes in climate. Variation in the mitochondrial DNA (mtDNA), which encodes 13 subunits of the respiratory chain complexes, may contribute to climate adaptation by regulating thermogenesis and the use of bioenergy. However, studies looking for a relationship between mtDNA haplogroups and climate have obtained mixed results, leaving unresolved the role of mtDNA in climate adaptation. Since mtDNA content can regulate human bioenergy processes and is known to influence many physiological traits and diseases, it is possible that mtDNA content contributes to climate adaptation in human populations. Here, we analyze the distribution of mtDNA content among 27 Chinese ethnic populations residing across China and find a significant association between mtDNA content and climate, with northern populations having significantly higher mtDNA content than southern populations. Functional studies have shown that high mtDNA content correlates with an increase in the expression of energy metabolism enzymes, which may accelerate thermogenesis. This suggests that the significantly higher mtDNA content observed in northern populations may confer a selective advantage in adapting to colder northern climates. Ancestral alleles are more likely to reflect ancient adaptations to the past lifestyle, some new mutations that disrupt the function of genes operating involved in crucial pathways. This is well known about the association between derived alleles and common complex diseases. However, the role of ancestral susceptibility in common diseases has long been underestimated. Several ancestral-susceptibility genes have been identified mainly involved in metabolism or salt homeostasis, both of which suggest that ancestral alleles adapted to past environment may be poorly adapted to the new one due to human lifestyle shift. We use the genomes wild association study (GWAS) data to detect ancestral-susceptibility on a genome-wide scale. A rigorous screening was then performed to search for disease-susceptible SNPs reported independently in at least two different populations, of which, 60 alleles proved to be evolutionarily conserved among 14 mammals. Our enrichment analyses provide a reliable result confirming the ancestral susceptibility to metabolic disorders as well as to immune dysregulations, both of whose risk factors are associated with shifting environment. There are some genes which played an important role for the adaptation to environment and no longer important to the modern lifestyle. These genes were degeneration by accumulating a significant high level deleterious mutation or large-scale insertion or deletion. In this evolution mode, some disease associated variation might be kept and increased in human population. We tried to find relax negative selection genes in human genomes by using 7 primates sequence data and human 1000 genome data. Several genetics index have been chosen to determine the relax signal. At last, we detect 518 candidate relax genes in human populations. The GO analysis show a significant enrichment in olfactory receptor pathway which has been proven in previous reports. Meanwhile, we found that the distribution of relax genes have some specificity between different human populations.
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