Every person once in life asks himself the eternal question: “Where did I come from?” These three words have haunted us individually, at the family level and even as a society and have aroused our curiosity to the point of entering our dreams. Did my ancestors fight in World War I? Does the blood of a revolutionary who was present at the storming of the Bastille run through my veins? Did my ancestors belong to the Eastern or Western Roman Empire? In which branch of the Homo sapiens that inhabited the Earth is my lineage? We have always wanted to know where in history our origins have been located and what we share with those civilizations that built the current cultures that are now spread throughout the 5 continents.
At present, the answers to these questions could be found in a part of the studies of evolution and population genetics that is known as genetic ancestry. The genetic ancestry applied to humans, or better known as dna test of origin, studies the genetic relationships of one or several individuals with an ethnic group, a town or a geographical situation. Generally, in these relationships, the human genetic diversity is studied, which would reflect the demographic/migratory movements of our species since its expansion about 100,000 years ago and compare it with that of current or previous individuals or social groups. While it is true that our species has always tried to move throughout our planet, migratory movements have not been as fast compared to those that occurred as a result of globalization. In this way, ethnic groups and populations were genetically more isolated and homogeneous, a very important fact when preparing the references that will increase the precision of these studies.
At first, the DNA tests of population origin were made by studying the differences in the blood groups of the ancestral populations, for example, the 0+ group is more frequent in Latin America and in Native Americans, while the B+ group is more frequent. common in East Asia. These studies have evolved very quickly due to two factors such as the birth of new DNA sequencing technologies and the lower costs of these technologies. The collection of DNA sequences in databases of different ethnic groups and peoples, as well as the lowering of costs in genotyping and sequencing, led many companies to make available to their clients the possibility of performing DNA tests of ancestral origin.
Currently, thesecommercial DNA tests of origin make it possible to estimate the percentage of mixture of populations that left their mark on an individual based on mutation patterns. These mutations are compared to a reference data set generated from mutation frequencies calculated for both ethnicities and different majority populations. There are several ways to calculate this genetic ancestry depending on the part of the genome that is studied:
- Studying the pattern of mutations found on the Y chromosome can reveal which branch of humanity’s genetic tree your paternal line is on. This is because the human Y chromosome is inherited directly from parents to male offspring, maintaining itself in a similar way to maintaining a family name. In this way, a history can be traced from the Adam of the Y chromosome, who is the oldest man with whom we all have some mutations in common, to the last known branch of this tree and link this history to your paternal surname, even following the routes of migration and differentiation that your ancestors did.
- If you study the pattern of mutations found in the genes that your mitochondria possess, cellular organelles that serve to supply us with energy from oxygen and nutrients, we will be able to elucidate where your female ancestors come from, this is because the mitochondrial chromosome is inherited directly from mother to sons and daughters. Thus, the maternal lineage can be explored from the Eve of the mitochondrial chromosome, to the mutations that differentiate current populations.
- Finally, si se estudia if the pattern of common mutations found in the rest of the chromosomes as a whole is studied, the percentage of ancestry that cannot be collected in the previous cases can be estimated. Thus, a higher number of mutations is used taking into account the genetic relationships between your paternal and maternal ancestors. Due to the exchange processes of genetic material of these chromosomes, we can define different blocks of DNA, which have different ancestral origins. In this way, these different blocks that make up an individual’s DNA are like the pages of the book that tells the story of their origins and that they may belong to various peoples or ethnic groups.
What can be expected from the DNA tests of origin at the individual level?
These tests are carried out with the same tools with which evolutionary relationships between humans are studied in evolutionary genetics research centers.
Since 2007, when the first genetic tests began to be offered to consumers, up to the present, the usefulness of genetic ancestry tests has grown in many aspects and they still have a lot of potential to discover. The most relevant information that this type of test can provide you is the knowledge of your roots beyond genealogy., the ethnicity percentage estimate can help trace the historical heritage of your surnames. Along the same lines, these tests are of even greater interest in adopted people and people who do not have a known origin, such as the famous stolen children, Holocaust survivors, or people who have slave ancestry.
In addition to these uses, numerous unexpected utilities have been found, such as discovery of infidelities, forensic uses, uses in aspects of health due to diseases that are more characteristic of some populations than others, discovery of distant relatives, etc…
What should I not expect from a genetic ancestry test?
- Matches between different companies: Each of the companies uses its own reference data, as well as its own algorithm to calculate an estimate of membership in one population or another. There is also variation between the genome positions of the platform that each company uses in their analyses. This sum of variations causes the proportions for each ancestry to also vary.
- Bureaucracy: Although it is true that in some countries a genetic test, usually a paternity test, can be used to grant nationality, in the vast majority of countries a genetic test of ancestors is not useful, nor is it usual to use the results of the tests of ancestry as a way to enter a tribal group or apply to obtain benefits for belonging to minority ethnic groups.
- Paternity: Although it can serve as support or even reveal a secret such as infidelities, the DNA test of origin or ancestors is not a highly reliable paternity test. If you need to perform a paternity test or other kinship test, you can find more information here.
What is the future of genetic ancestry?
In 2018, the large genetic ancestry test companies or DNA test of origin have sold around 30 million tests. The growth due to concern and curiosity to learn more about our past, as well as technical improvements in terms of sequencing and genotyping mean that the tools and protocols are increasingly refined, reaching increasingly accurate estimates. The most demanding ambition of this field is to bring this knowledge of ancestry to the field of health and for this reason numerous studies are associating ancestry with a predisposition to develop or avoid certain diseases.. With patience, scientific method, and data, genetic ancestry will enter the world of genetic counseling as a new category.