Key concepts of the interview with Lluis Quintana-Murci
There is one general concept that should be clarified before you listen to the interview, as it is used many times, namely, adaptation and related concepts such as adaptive or advantageous mutation.
In biology, adaptation has three related meanings. First, it is the dynamic evolutionary process that fits organisms to their environment, enhancing their evolutionary fitness. Second, it is a state reached by the population during that process. Third, it is a phenotypic or adaptive trait, with a functional role in each individual organism, that is maintained and has evolved through natural selection. The change in DNA that is the basis for it is called adaptive mutation. Adaptation is an observable fact of life accepted by philosophers and natural historians since ancient times, regardless of their views on evolution. Evolution by natural selection provided the basis for understanding adaptation. The biochemical basis for the genetic basis of inheritance is found in the information from DNA, with different mutations being the basis for differences in adaptation.
1. Introgression (Part 2)
In genetics, introgression, also known as introgressive hybridization, is the movement of genes (gene flow) from one species into the gene pool of another by the repeated backcrossing of an interspecific hybrid with one of its parent species. It is interesting as the backcross happens when the differentiation is already very strong, more than usual amongst neighbouring populations (in which case, we would talk about hybridization). The most well-known case is the introgression of Neanderthals into the genome of non-African modern humans.
2. Lactose tolerance (Part 2)
Lactose tolerance, which results from lactase persistence, is the continued activity of the lactase enzyme in adulthood. Since lactase’s only function is the digestion of lactose in milk, in most mammal species, the activity of the enzyme is dramatically reduced after weaning. In some human populations, though, lactase persistence has recently evolved as an adaptation to the consumption of nonhuman milk and dairy products beyond infancy. The majority of people around the world remain lactase nonpersistent and, consequently, are affected by varying degrees of lactose intolerance as adults. However, not all genetically lactase-nonpersistent individuals are noticeably lactose intolerant, and not all lactose-intolerant individuals have the lactase-nonpersistence genotype.
3. Bantu languages and Bantu expansion (Part 2)
The Bantu languages constitute a traditional branch of the Niger–Congo languages. There are about 250 Bantu languages by the criterion of mutual intelligibility. Bantu languages are largely spoken east and south of present-day Cameroon, that is, in the regions commonly known as Central Africa, Southeast Africa and Southern Africa. Parts of the Bantu area include languages from other language families (see map).
Bantu languages descend from a common Proto-Bantu language, which is believed to have been spoken in what is now Cameroon in Central Africa. An estimated 2,500–3,000 years ago (1000 BC to 500 BC) or may be earlier, speakers of the Proto-Bantu language began a series of migrations eastward and southward, bringing agriculture with them. This Bantu expansion came to dominate sub-Saharan Africa east of Cameroon, an area where Bantu peoples now constitute nearly the entire population. Bantu peoples is used as a general label for the 300–600 ethnic groups in Africa who speak Bantu languages.
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