Humanity originated in Africa, and lived there for thousands of years. To understand our shared genetic history, we must look to Africa. Unlike elsewhere on the planet, however, the populations of Africa were present throughout our history pop they were not subject to the same kind of founding influences, as the population is seen to expand into innumerable popped areas. Instead, as groups moved to new locations on the continent, those people suffered.
Sorting out all of this would be a challenge, but it is hardened by the fact that most of the genome data comes from people in the industrial world, giving weak samples to the vast population of Africa. That is starting to change, and there is a new paper report on the efforts of a group that has analyzed more than 400 African genomes, many coming from populations that have not previously participated in genome studies.
New variety
All the time new genetic variants are emerging. As a result, the oldest population. The people of Africa should have the most innovation variations. This population can be difficult to identify when there are so many; The study noted that there are more than 2,000,000 ethnic language groups in sub-Saharan Africa, and only a small number of them have been sampled. The new study is a big step, with more than 400 complete genome sequences of a geographically dispersed population. But even there, it is limited, adding only 50 new ethnic groups to the continent and two vast territories of continents, represented by people from only one country (Zambia for Central Africa and Botswana for South Africa).
That said, the study still selects more than 4.4 million genetic variants that have not been previously described. This genome has the same sites with bases (A, T, C or G) that were not found in other populations there.
To put it in perspective, most of us have many genetic variations. In a typical individual in a new study, these newly identified types account for only 2–5 percent of the total variation in their genome, all the rest were previously observed. In addition, most of them (88 percent) were found in only one person and therefore can only represent the diversity caused by changes in the last few generations. So, there may be some new types that will help us adapt to the history of the population of Africa, most of the things we have discovered are the kind that you would expect to see random humans elsewhere.
If we have a good grip on the genetic diversity present in Africa, we would expect the tail of new variants to close as new genome sequences are added to the analysis, as each new one adds less and less and more strangers. Therefore, researchers analyzed one genome at a time and found no evidence that this happened – we are still nowhere near a complete list of human diversity. However, they find that looking beyond the West African population will be the biggest increase in the diversity described earlier.
Population churning
To try to identify what the genome tells us about the history of the population, the researchers turned to key component analysis, which identifies the main sources of differences in the vast set of data. Different speakers of Niger-Congo languages from all the rest. The second largest difference reflects the geographical distance between the Niger-Congo speakers of West Africa and South Africa. Presumably this is a product of the Bantu migration, spreading a mixture of technology, language and DNA from West-Central African sources, bringing them to the rest of the continent.
Researchers use this information to argue that Bantu migration passed through Zambia toward South and East Africa, but their data includes many Zambians, so it is not clear whether its results could be biased.
The work also identifies a number of ethnic groups that are worth looking at in more detail. One was genetically similar to East Africa but was located in West Africa. The other two populations were clearly associated with well-known language groups but were not part of the tight genetic cluster within most other speakers of that language.
Almost every population on Earth is a combination of many sources – Native Americans are mostly a mix of East Asian and ancient Siberian populations, for example. African peoples are certainly not different, but the fact that they have lived on the same continents for a very long time increases the complexity of these interactions. The new data actually drives that house when analyzed for the origin of different segments of DNA.
What you can call a West African resource is that people in West Africa have a large part of their DNA. But when you go east to Central Africa, there is an increasing amount of codification as West-Central African DNA, which was later joined by Central Africans and then displaced and then a fantastic source of South and East African resources. If you turn a little to the south, with the increased contribution of South Africa, there is a sudden shift in the majority from the East African resources flowing out of the East African source.
While geography seems to carry most of the differences, all populations contribute to remote areas of the continent. So, while the Bantu migration may be the largest event in recent African history, it is at the peak of a long history of population interaction.
What is changing
Most variations in the human genome are completely silent, as they do not affect genes or other functions and therefore float randomly through the population. Few, however, provide developmental benefits, and it is possible to find a signal of choice for or against a specific variation.
In search of these clues, the authors found exactly what you expected based on previous studies of the human population. The strongest pressure on human evolution is disease, and the genes that are under the most pressure are involved in immune function. The disease is followed by diet and again, the people of Africa are quite typical with strong indications of selection on some genes associated with carbohydrate and lipid metabolism. Some dubbed ball results were found, however, for DNA repair, kidney disease, and selection for different types of genes involved in uterine fibroids. Naturally, we have to examine this in more detail before we can make any sense out of it or whether it is just enthusiastic.
Immune function is not the only way to handle diseases, as the effects of sickle cell characteristics on malaria are obvious. And, this is the 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 selection of different genes (G6pd). In some cases, as a result of population migration with a higher frequency of sickle cell characteristic, possibly. As a result of the migration, G6PD has ended up next to others with higher levels of choice.
Aside from cases where there are clear indications of selection, there are many cases that have been inactivated by gene mutations but are still present in multiple individuals in this data set. It’s going to be something I’ve seen many times before and got a little confused. In many cases, none of us know what the gene does and therefore cannot say whether we should be surprised by its loss. In others, the gene appears to be essential based on studies of its damage actually occurring in mice. Over time, we may come close to understanding what is happening, but to do this we must study each of these genes individually.
The beginning of the story
While this represents a major effort to understand the shared genetic history of humanity, it is more of an introduction than a whole story. We have come close to capturing the full diversity of the African population but clearly not yet done. And we’ve been able to gather more information about some of the migration destinations in Africa that we know about but not where we can think of anything about migration. No To know about no.
The next point is rather important. At this stage, we can examine part of the DNA and determine if it originated in the West African population. But we can’t say much about how it ended up in the first place in West Africa. There is evidence that since Eurasian populations extracted ancient DNA from Neanderthals, Africans extracted DNA from the previous branches of the human family tree. But, without the remains of those branches or DNA-based descriptions, it remains a “ghost lineage” that is invisible to us. It is possible that a small percentage of the order we currently assign to an African region belongs to one of these branches, and we do not yet have the tools to identify it.
Nature, 2020. DOI: 10.1038 / s41586-020-2859-7 (about DOI).
