Where Are We From?
Our DNA has locked within it our genetic history including a personal mixture of DNA markers that show the geographic origins of our own ancestors. We can explore our personal ancestry using commercially available DNA testing that reveals where our ancestors lived; how our unique blend of DNA is inherited from the different ethnic peoples who flourished before the modern period at a time when populations were stable and movement between and within continents was quite limited.
The Human species, Homo sapiens (Latin for wise man) evolved in Africa. The earliest human fossils were found in Ethiopia and date from around 200,000 years ago. Around 70,000 – 100,000 years ago a group of our ancestors moved out of Africa (probably just one group containing only a few hundred individuals) and initiated a branch of humankind that would eventually colonise the Middle East, Asia, Australia, Europe and the Americas. The process of colonising every corner of the globe took many tens of thousands of years. Over that time populations in different locations became established and some seeded further migration creating branches and sub-branches of the earliest settled groups.
Diagram showing ancient human migrations in red (1) from east Africa to other parts of the world. Approximate migration times in years are also shown. Some regions were already inhabited by Neanderthals (2) and other human-like species (3) now extinct.
Individual populations, once established, were small by modern standards and were isolated from each other by natural barriers and physical distances. Over time each evolved their own physical characteristics like skin, hair and eye color in response to environmental and climatic conditions. DNA changes (mutations) not only allowed physical characteristics to evolve but also randomly introduced a series of other DNA sequence differences some of which became established as the distinctive DNA markers for each ancient population that gave rise to the modern populations we now recognize. Recent advances in DNA technology are revealing the different groups of DNA types (haplogroups) that are associated with different populations and this has proved an important tool to help understand the migrations of humans across the continents over time.
A fascinating discovery is the compelling DNA evidence that early humans occasionally interbred with at least two other human-like (hominin) species, namely Neanderthals and Denisovans. These hominin species went extinct between 30,000 and 40,000 years ago but before then they had coexisted with humans for many thousands of years. Neanderthals were prevalent throughout the Middle East, Europe and West Asia and Denisovans inhabited North and Southeast Asia. Up to 4% of the DNA of European and Asian peoples is inherited from Neanderthals. Also, modern East Asian, Australian Aboriginal and Melanesian peoples have been shown to have up to 6% of their DNA in common with Denisovans.
Ancestry DNA Tests
Each of the different categories of DNA can be used to tell you something about your early ancestry. For instance there are lots of data that connects mtDNA (mitochondrial DNA) haplogroups with ancient populations. MtDNA testing can give you an idea of the ancient origins of the DNA that has been passed to you through your mothers unbroken female line; a thin thread that stretches right back to near the beginnings of humanity. Mathematical logic tells us it is inevitable that only a single mitochondrial lineage will have survived if you go back far enough and it is certain that everyone alive today has inherited his or her mtDNA from one African woman who lived around a hundred and fifty thousand years ago. She is known as “mitochondrial Eve” and all the different haplogroups observed in people today represent mutations that occurred in later generations within her dynasty.
Similarly Y-chromosome DNA tests such as Y-STR tests can trace your origins along your direct male line, a lineage that started for all of us with “Y-chromosome Adam” who lived a hundred thousand or so years ago. (The reference here to Adam and Eve is purely figurative, it is not intended to suggest they were a mating couple or even that they lived at exactly the same time). Autosomal DNA SNP tests, unlike mtDNA and Y-DNA, give an overall picture of your ancestry from all of your ancestors male and female. (See the inheritance of different kinds of DNA).
In general the best DNA methods to explore your ancestry and the ones that give you most information analyze SNPs that are found all through your DNA including within mtDNA and the Y-chromosome. Several hundred thousand SNPs can be tested all at once in a single test. Non-SNP mtDNA tests and Y-STR tests are also available – Family Tree DNA (FTDNA) is the leading company for non-SNP testing. Unless you have a sizeable budget, separate mtDNA and Y-STR tests can get expensive depending how detailed you want to go and can only give you information about unbroken female and male lines.
Cost and Choices
If you are only interested in ancestry DNA testing and are not testing because you want to research your family tree or find relatives, a good choice is to join the National Genographic project called Geno 2.0 (incorporating the National Geographic DNA test). At $199 the test is a bit more expensive than some of the others but it targets an array of SNPs that are present across your autosomal DNA as well as many SNPs present in your mtDNA and, (for males) Y chromosome. Your results include a separate analysis of each of these categories of DNA.
If, however, it is not only ancestral information that interests you and you also want to research your family tree and connect with relatives then Geno 2.0 is not for you. The SNP tests from 23andMe, FTDNA and Ancestry.com are a bit cheaper each at $99 and, although they give little or no separate information about your maternal and paternal lines, they represent excellent value because you get family tree services as well as ancestral analysis at no extra cost. The 23andMe SNP test uses most DNA markers and gives the most accurate breakdown of your continental and regional origins and, in addition to family genealogy services, it gives you a range of personal medical information to boot. Go to this link at the International Society of Genetic Genealogy (ISOGG) for a detailed comparison of the main tests available Autosomal DNA Testing Comparison Chart .
What Do The Results Tell You?
Whichever test you choose you will be given an estimate of the composition of your DNA based on statistically inferred percentages that you have inherited from different continental and regional populations. It is striking that almost everyone shows at least some diversity in the mix. There are numerous reference populations that portions of your DNA might be assigned to; for example, West African, Mediterranean, South East Asian, Northern European, Native American to name but a few.
Depending on the company and the diversity of your own ancestors, specific countries that most correspond to your mix of markers might also be quoted. You may also be associated with particular medieval lineages such as Ashkenazi Jews who are thought to have settled in Europe around the seventh century or Niall of the nine Hostages the Irish King whose dynasty dominated Ireland for several centuries from the sixth century onwards. In general terms, the more specific the association to a particular population or lineage or historic figure, the greater the margin of error. Even with the advanced technology available today, only broad estimates are meaningful; any report that resembles fine precision is almost certainly misleading. Things are improving all the time, however, as we find out more about DNA markers and how they segregate between populations. The power of the tests themselves is also developing and we can look forward to the regular emergence of more, wonderful detail about our human story.
Finally, the percentage of your DNA, if any, that is from Neanderthals and/or Denisovans is reported to you if you test with the National Genographic project (Neanderthal, Denisovan) or 23andMe (Neanderthal only).