DNA Use by Ancestry-type Registries

DNA Use by Ancestry-type Registries Jerry Davis So let me start by stating the obvious: the universe is infinite and our minds are not. Therefore we can never “know” everything and what we “know” changes as our knowledge becomes more complete. Also, everything is not about DNA. I don’t know hardly anyone who claims to be of Irish or Scottish extraction who has ever attempted to seriously reconnect with their “first culture”. The language, history, music, etc. are simply beyond time constraints and often not relevant to an individual’s personal situation. Even among actively existing, albeit struggling, cultures, like America’s NDN’s, very few can speak their native tongue and fewer still can live traditionally in their pre-Western traditions. So, fore with: I compare DNA testing to the lottery. Most of the time, you don’t get any numbers. Occasionally you will get 2 or even 3, but rarely 4, and never 5 or 6. Probability is about which numbers will win. This you don’t know until after the fact. You can make a wild guess based on which numbers win most often and what not, but the numbers are picked randomly, so there is no guarantee you pick the right ones. However, when you pick the correct numbers, you know you won. Genetic testing for ethnicity is similar. It’s all about relative relatedness because, at the simplest level, all living creatures have a nucleic acid blueprint (and even some we may not qualify as living). So at the simplest (and earliest) point in time in terms of relatedness, such things as blue-green algae, bacteria, and us fall into the same category, e.g. things with a nucleic acid body plan. We are talking 4 billion or more years ago before we people existed as we do presently. Some of these early life forms may or may not still exist. Although the blueprint spelled out by DNA consists of only 4 nucleic acids, they are arranged in many different patterns, such as genes, to code for structures and life processes essential to the particular species or cell (some species are one cell; others multicellular with distinct organ systems). So these groups of nucleic acids, arranged in a lineal chain within the larger genome (the so-called “double spiral”), may be classified as genes (that code for proteins, for instance) or may simply act as spacers or some other purpose. Most of DNA testing is concerned with the genes within the human genome. Although the same basic genes are found across the entire human race, they come in a variety of slightly different nucleic acid sequences called alleles. So, the structure the gene codes for, like skin color, may vary slightly from place to place accounting for different shades of skin, and different alleles can even produce a similar skin color. If we skip ahead from our beginnings to about 300 million years ago, we know by fossil records (not DNA) that reptiles and mammals (of which we are one) diverged about this time and became distinct entities. We could at that time lump ourselves together with reptiles, although at present we only share a little more than half of the same genome. If we jump ahead to perhaps 200,000 years ago, man, Homo sapiens, has arrived. At this point, we are sharing 98-99% of our genome with our closest relatives, such as chimps, bonobos, and extinct humans like Neanderthals and Denisovans. This doesn’t mean that our genome is the same as these other species. In fact, no 2 genomes are the same from individual to individual of the same species since parents don’t contribute the same parts of their genome equally when they share their DNA to produce the fertilized egg. It only means the percentage of identical genome that can be found in populations of the various related species. The remaining 1% or so is unique to the species only. But this 1% is not exactly the same from individual to individual. Variation exists primarily because as people wandered away from each other and became relatively isolated for long stretches of time, say in Europe or Australia, small, non-lethal mutations in the DNA within a population occurred, possibly to provide adaptive advantages in a particular environment for instance, or simply by accident. The most obvious evidence for this is skin color. Up until present times, people on or closest to the equator were invariably darker and those farther away were lighter. We presume from our own experiences with modern people living in areas they migrated to in the last few hundred years (light people moving towards the equator for instance) that UV exposure influenced the ability of some genes to be passed on because of mortality related to skin cancer for instance. Also, as today, there could have been skin-color-based class systems. Skin color itself however is determined by different variations of genes in different populations even though the effect is the same, e.g. darker or lighter skin. in any case, going back to probability and the lottery, our DNA and genes are determined at birth for the most part, although there is some evidence now that environmental factors can change the DNA from parents to offspring. By and large, then, our “lottery numbers” are fixed, so if we look at different genomes within the human population and contrast the various places where genes differ by ethnicity, we can compare the DNA and see how closely related an individual is to an ethnic group. If we look at a particular time frame where, until modern times, the ethnic group was common we can determine our ancestry within that particular time frame. One of the distinguishing features of hominids is their predisposition to migrate and adapt to novel places. Few, if any, species, for instance, can be found living and reproducing successfully in the Arctic, equatorial Africa, small islands in the middle of oceans, the tops of mountains, sterile deserts, etc. to mention a few of places people can be found around the world. The “modern times” distinction is important because modern technology, including advancements in travel and weaponry, have permitted distant people to colonize places they could never have invaded even a few thousand years ago, potentially throwing a wrench in their understanding of their own ancestry. Put another way, if you lived in North America 500 years ago, you knew who you were by your geographical location, language, and culture. No records were necessary or important except for oral histories, which became lost as the cultures were extirpated and diluted. DNA services, then, function by identifying regions of the genome that correspond to ethnicities of a known genetic make-up. This information can be formulated by studying the DNA of populations with a known historical record and geography or by reconstructing genomes from the DNA of deceased individuals of a known ethnicity. The “numbers” of the “lottery”, then, are the genes, and their corresponding alleles, of a particular individual that match ethnicity of a particular group. Naturally, one person shares relatedness with every other person on the planet since we all belong to the same species (generally described as similar individuals that can produce viable offspring, “viable” meaning capable of living to reproductive age and producing more viable offspring indefinitely given a large enough population). At some point, however, the number of matching alleles, similar to lottery numbers compared to the winning numbers, decreases to a vanishingly small group. At this point, ethnicity can be recognized. Eventually, as the genome of one person further resembles that of others, actual relatedness can be inferred. Of course, many confounding factors can skew the results of even the best efforts of geneticists unless the entire human genome of an individual has actually been mapped which is prohibitively expensive given the 3 billion base pairs and 20 - 25,000 genes, all somewhat different, in each person. Potential for error can occur when a particular allele occurs in diverse, relatively unrelated, populations. At this point, one has to make a best guess effort based on other alleles and known history of the individual. Cultures in past times have also been invaded and instilled with DNA from outside populations that eventually lose their influence. But their DNA imprint still exists. Here is where the time frame one is looking at becomes important, and sometimes terms like “Irish” or “Scottish” become rather meaningless because the area was invaded multiple times over millennia, again depending on the time frame. DNA “services” that claim to identify a nationality are often doing a disservice because the ancestral nationality they are promoting didn’t even exist at the time. For modern study of individual ancestry, often historical records are better than DNA when they exist. And some do exist for hundreds of years into the past if one knows where or how to look. Finally, different ways exist to look at the same information. For instance, the human genome actually contains 2 different sets of DNA, the larger genome present in the nucleus of each cell, and the much smaller genome found in the numerous mitochondria found within each cell. The mitochondria are the “power plants” of the cell and are thought to have resulted from a commensal (symbiotic) relationship that happened millions of years ago. In other words, the larger (eukaryotic - possessing a nucleus) cell provided a safe haven for the smaller (prokaryotic - no nucleus) mitochondria which in turn produced energy to help drive the larger cell. In any case, the mitochondria are inherited almost exclusively from the maternal parent (mother) through the egg. Although male sperm also have mitochondria, they aren’t known to have been incorporated into the mature fertilized ovum (egg) meaning the mitochondrial DNA forms an unbroken line of relatedness back through the entire history of the human race. However, the mitochondrial DNA does accumulate mutations over time. Obviously if these mutations prevented the mitochondria from doing their job, the cell would die, so only non-lethal mutations are transmitted from offspring to offspring. These mutations can be correlated to specific ethnicities. Similarly the y-chromosome obviously only occurs in the paternal parent (father). This DNA, similar to mitochondrial DNA, forms an unbroken line down through the history of the human race and the mutation can be similarly mapped among the various human populations through study of present day groups and DNA recovered from prehistoric remains. The transmission of genetic information from human parents to their offspring is accomplished by sexual reproduction. In nearly all people (not including the tiny minority with genetic diseases and abnormalities, like Down Syndrome), the nuclear genome consists of 23 pairs of chromosomes (termed “diploid) which helps to account for the remarkable stability of heritable characteristics, since 1 strand of the chromosome can act as a failsafe for the other strand and the cell can actively repair the DNA if it detects a flaw. In sexual reproduction, 1 strand of nuclear DNA is contributed from each parent (All of the mitochondrial DNA is contributed by the mother). Only half of the genome being transmitted, in other words, only 1 strand, is termed, “haploid”. So the mother’s egg and father’s sperm are “haploid”. After fertilization, the egg will have a complete set of chromosomes again (e.g. diploid). Of course, on either side for various reasons, such as the 2 named in the previous paragraph, some of the DNA is identifiable as coming exclusively from one parent or the other, described as a “haplotype” (derived from one of the 2 haploid strands of DNA). Because of the mutations over time among various, then relatively isolated, populations (such as Native America prior to the Western invasion), these haplotypes can often be ascribed to particular ethnicities or populations of individuals. They are referred to by a particular numeric/alphabetic label but some can be broadly interpreted as, for instance, “Native American” and can be identified as deriving from the mother or the father. So everyone’s mother has a particular maternal haplotype since everyone shares the same maternal mitochondria, but a paternal haplotype can’t be assigned to a woman, since she has no Y-chromosome. Lastly, “relatedness” washes out very quickly. The surname of any individual has been preserved down through time, in the US by the paternal lineage, but the surname does not necessarily indicate the degree of relatedness. Seven generations (about 200 years) of a person’s ancestry will contain as many as 128 different individuals and many surnames. In other words, you are much more closely related to your mother (different last name) than the Davis 7 generations back in the family tree. In Native America, people often had several names during their lifetime, but were eventually assigned names by the government or church, etc. to provide accountability. These were even mis-translated (Kangi Shunka Manitou = “Crow Coyote” = Crow Dog). In addition, many cultures, such as Scandinavia, simply modified the first name for use as the surname, making genealogy easy but essentially useless without additional information (Father, Hans Hendricksen; Son, Jorgen Hansen; Grandson, Jens Jorgensen). African-Americans typically adopted or were assigned Western names and their original African names dropped. In many cases, as in Native America, names were translated from one language to another or were re-spelled to make pronunciation and usage easier (Lockhart = Lockard; Gaugnier = Gonyer, etc.). Some cultures use only first names. Here in America, we use a specific name in order to provide accountability and correct identification which may be supplemented by signatures or fingerprints, etc. In any case, this completes my brief review of the use of DNA for ancestry purposes which, of course, is best used in conjunction with historical sources as well. This is not an exhaustive discussion of DNA registries or methods and is mostly done off the top of my head. I don’t claim to be the final authority. It is for basic informational purposes only.