The new African genome: complex migration and tough selection

The new African genome: complex migration and tough selection
Make it bigger / A building in the village of Nadebele, South Africa. Needable language speakers, currently one million strong, have arrived in South Africa with the rise of Bantu.

Humanity originated in Africa, and has lived here for thousands of years. To understand our common genetic history, we must look to Africa. Nowhere on the planet, by contrast, did the African population exist throughout our history – they were not subject to the same kind of founding influences as the population spread to uncontrolled areas. Instead, the population erupted as the group moved to new areas within the continent.

Sorting it all out will be a challenge, but one that is made difficult by the fact that most of the genome data comes from people in the industrialized world, except for a poor sample of Africa’s vast population. This is beginning to change, and a new paper reports on the efforts of a group that has analyzed more than 400 African genomes, many from populations that have not previously participated in genome studies.

New diversification

New genetic variants are emerging all the time. As a result, there must be a lot of new varieties in the oldest population in Africa. While there are many, these populations can be difficult to identify; The study found that there are more than 2,000 ethnic-linguistic groups in sub-Saharan Africa, and only a small number of them have been sampled. The new study is a major step forward with more than 400 genome sequences of a geographically diverse population. But even there, it is limited, representing only 50 new ethnic-linguistic groups and people from the same country combining two large regions of the continent (Zambia for Central Africa and Botswana for South Africa).

The study has so far picked up about 3.4 million genetic variants that were not previously described, he said. These are the only sites in the genome with a single base (A, T, C, or G) that were not seen in other populations.

To put it in perspective, many of us have genetic variations. In a particular individual in the new study, these newly identified variants account for only about 2-5 percent of the total variations in their genomes – all the rest were previously observed. In addition, a large majority (88 percent) of them were seen only in a single person and this can only indicate a change that came about through a change in previous generations. So, there may be some new forms that will help us ignore the history of Africa’s population, most of which we have achieved is something you would expect to see random human beings elsewhere.

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If we were to get closer to a better grasp of the genetic variation that exists in Africa, we would expect to see a number of new variants adding new genome sequences to the analysis, as each new one would make fewer and fewer unknown ones. Therefore, researchers once did an analysis of the genome and found no evidence of its existence – we are still nowhere near listing human diversity completely. They have found that looking beyond the population of West Africa will give us the greatest increase in the change described earlier.

Population churning

To try to identify what the genome tells us about the history of the population, researchers turned Main component analysisWhich identifies the major sources of differences in a large set of data. The biggest difference is the different speakers of the other Niger-Congo languages. The second largest difference is the geographical distance between the Niger-Congo speakers in West Africa and South Africa. This is probably a product Assist migration, Which spreads a mixture of technology, language and DNA from a source in West-Central Africa, bringing them to the rest of the continent.

The researchers use the data to argue that the Bantu migration went from Zambia to South and East Africa, but their figures include a large number of Zambians, so it is not clear whether their results may have been biased. Will or will not.

The work also identified a number of ethnic-linguistic groups that may be worth looking at in more detail. One looked genetically similar to the people of East Africa but was located in West Africa. The other two populations were clearly associated with known language groups but were not part of the narrow genetic group that most speakers of that language came into.

Almost every population on Earth is a mixture of many resources. Ative Native Americans are mostly a mixture of East Asian and ancient Siberian populations, for example. Africans are no different, but the fact that they have lived on the same continent for so long adds to the complexity of these interventions. When the molecular properties of different parts of the new DNA are analyzed, the new data actually takes that home.

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The people of West Africa have a very large part of their DNA from which you can call the source of West Africa. But as you move east to Central Africa, there is a growing amount of what you have to call West-Central African DNA, which is later incorporated by Central Africa and later disintegrated and then south and east. A stupidity of Africa’s resources. There is a sudden shift from the resources of East Africa to the majority when you move from Central Africa to the East, with a growing contribution from South Africa if you change the South a little bit.

While geography bridges many differences, all populations contribute from remote parts of the continent. Therefore, although Bantu migration may be the largest event in recent African history, it stands at the peak of a long history of population interaction.

What is changing

Most changes in the human genome are completely silent, as they do not affect genes or other functions and therefore float randomly in populations. Some, however, offer evolutionary benefits, and it may be possible to detect signs of choice against or against certain forms.

Searching for these clues, the authors found exactly what you would expect based on previous studies of the human population. The most pressing strain of human development is disease, and the genes that are under the most pressure are involved in immune processes. Disease is followed by diet, and again, Africans are fairly common, with strong indications for the selection of genes rich in carbohydrate and lipid metabolism. There were some odd results, however, in the selection of genes involved in DNA repair, kidney disease, and uterine fibroids. Obviously, these need to be examined in more detail before we understand any of them or see if they are just enthusiastic.

Immune function is not the only way to control disease, as the effects of sickle cell traits on malaria are clear. And, because it is an African population, some of them have evidence of choice. But hemoglobin is not the only way to fight malaria, and some populations show evidence of selecting a different gene (G6PD). In some cases, the population with the highest frequency of sickle cell traits is completely depleted, while others with higher levels of G6PD selection are more likely to migrate.

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Aside from the cases where clear indications of selection are found, there are many cases where gene mutations have been disabled but are still present in many individuals in this data set. This is something that has been seen many times before and has been met with a bit of confusion. In many cases, we do not know what the gene does and therefore cannot tell whether we should be surprised at its loss. In others, the gene appears to be essential, based on studies of damage to rats. Over time, we may come close to understanding what is happening, but to do so, each of these genes will have to be studied separately.

The beginning of a story

Although it represents a major effort to understand the common genetic history of humanity, it is a publication rather than a complete story. We have come close to achieving full diversification of the African population but obviously not yet. And we’ve been able to gather more information about some of the migrations within Africa that we know about but not at the point where we can find out anything about migration. Don’t Know about.

This latter point is critical. At this stage, we can examine a piece of DNA and determine if it may have occurred in a West African population. But we can’t say much about how it ended in West Africa. Evidence that the Eurasian population took archaeological DNA from Neanderthals, The African population From the first branches of the human family tree. However, without a biological or DNA-based description of the branches, they remain “ghost lineages” that are invisible to us. It is possible that at present a small percentage of the sequences assigned to an African region belong to one of these branches, and we do not yet have the means to identify them.

Nature, 2020. DOI: 10.1038 / s41586-020-2859-7 (About DOIs).

Raven Weber

About the author: Raven Weber

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