Y-chromosome and mitochondrial DNA testing is interesting and important for two main reasons:
1) These types of tests provide the most reliable and accurate way of predicting (even proving!) a genealogical relationship from a genetic match between individuals; and
2) These tests give you your haplogroup.
In this blog post, I will be talking about haplogroups.
Our African rootsWhat is a haplogroup? A haplogroup is essentially a branch on the human family tree, as traced by certain kinds of genetic markers (specifically, markers on the Y chromosome and in the cells' mitochondria). Haplogroups are often referred to as a kind of very large "clans".
Y-chromosomal (Y-DNA) haplogroups are inherited from father to son. Since the Y chromosome is the male sex chromosome, only men (and male-to-female transgender persons such as myself) can have a Y-DNA haplogroup. Mitochondrial (mtDNA) haplogroups are inherited from mother to child. Both women and men have mtDNA haplogroups; however, only women can pass their mitochondrial DNA on to her children.
In other words, Y-DNA haplogroups represent male-only family lines, while mtDNA haplogroups represent female-only family lines.
For more information (and visuals), visit National Geographic's website.
Also check out Roberta Estes' blog posts on mtDNA haplogroups and Y-DNA haplogroups.
Every living man today can trace their Y-DNA back to one common male ancestor, popularly known as Y-chromosomal Adam. Similarly, every living human being today can trace their mtDNA back to one common female ancestor, popularly known as Y-chromosomal Eve. This man and woman lived in... you guessed it: Africa. They lived long before homo sapiens sapiens ventured across the Bab-el-Mandeb strait into Asia and the rest of the world. The timeframe is mind-boggling. When "Adam" and "Eve" were around, the Neanderthals had Europe all to themselves.
Their names are a bit misleading; "Adam" and "Eve" were not (necessarily) a couple, and did not even (necessarily) live at the same time. In fact, they seem to have lived many millennia and many miles apart. "Adam" seems to have lived in West Central Africa about 338,000 years ago. "Eve" seems to have lived in Eastern Africa about 150,000 years ago. Since they lived long before the invention of agriculture, both "Adam" and "Eve" would have lived as hunters and gatherers, a lifestyle perhaps similar to that of the San people of Southern Africa in modern times, or the Biaka people of the Congo rainforest. "Adam" and "Eve" must have had some kind of language, but we do not know anything about it. In fact, having lived so far apart in time and space, they must surely have spoken very different and probably unrelated languages!
"Adam" lived extremely long ago, but except for the very oldest Y-DNA haplogroup (called A00), every male on Earth can trace his Y-DNA back to a man who lived much more recently. This man seems to have lived in Central or Northwestern Africa about 150,000 years ago, approximately at the same time as "Eve". One of his descendants, who lived about 70,000 years ago in the Rift Valley area of Eastern Africa, is the direct paternal ancestor of almost every male outside Africa today. For this reason, he is known as the "Eurasian Adam".
Haplogroup namesmtDNA haplogroups have alphanumerical names that look a bit like a secret code. However, there is a logic to it. My mitochondrial haplogroup, for instance, is called H5a1g1a. What this means is that I am a part of the main haplogroup H (which is the most common haplogroup in all of Europe); and within H, I belong to subclade H5, subclade H5a, subclade H5a1, and so on. H5a1g1a represents my terminal subclade, the end of my particular branch of haplogroup H.
Y-DNA haplogroups are also traditionally named using the same system, but as geneticists dug deeper into the various subclades and sub-subclades, these names eventually became extremely long and cumbersome and practically impossible to remember (such as O2a2b1a2a1a3b2b1a or R1b1a1a2a1a1c2b2a1b1a1a2b2a1). The names were also constantly changing as new subclades were being discovered and old ones rearranged. Because of this, the old naming system has been almost universally abandoned in the case of Y-DNA haplogroups, and today we usually just write the main haplogroup letter (such as R) and the name of the terminal genetic mutation (or the deepest mutation for which a positive test has been done). My haplogroup, for instance, is usually called R-L1335. However, since haplogroup R includes two very large subclades, R1a and R1b, I often prefer to write R1b-L1335 so that people immediately know that we're talking about a subclade of R1b.
Several people in my family have taken Y-DNA and mtDNA tests. I myself have taken both tests. My paternal grandfather and my paternal grandmother's brother have both taken the mtDNA test. My paternal grandmother's brother has also taken the Y-DNA test. The results are shown below in a family tree diagram, showing how the haplogroups have been inherited down my family lines. I am on the far left (R1b-L1335/H5a1g1a). Y-DNA haplogroups are written in blue, and mtDNA haplogroups are written in red.
My family's haplogroups
All the haplogroups in my close family are rather common European haplogroups. However, they have extremely diverse histories, and arrived in Europe at very different points in time.
Like all Eurasian Y-DNA haplogroups, R1b-L1335 ultimately originates with a man (a descendant of the "Eurasian Adam") who migrated from Eastern Africa to Western Asia starting around 70,000 years ago. My specific ancestral line followed the migrating herds of buffalo, antelope and mammoth into modern-day Iran and then further north into the vast steppes of Central Asia, steppes which at this point in time stretched all the way from France to Korea. Almost everyone with ancestry from the northern hemisphere (!) are descendants of one man who lived approximately 40,000 years ago in Iran or southern Central Asia. One branch of his descendants - my branch - survived the Ice Age in Siberia, and approximately 20,000-30,000 years ago, my direct paternal ancestors started moving west across the steppes. Haplogroup R1b seems to have originated in a man living in the Middle East or Southern Siberia approximately 12,000 years ago. A few thousand years later, R1b men started moving into Europe, either via the Pontic-Caspian steppe or via Anatolia, and probably bringing the Proto-Indo-European language with them. My sub-branch of R1b, called L21, descends from a man who lived just north of the Alps around 2000 BCE, and who probably spoke an early precursor of the Celtic (or even Italo-Celtic) languages. His descendants, my direct paternal ancestors, became part of the earliest migration of Celtic speakers into the British Isles, and today my particular branch, L1335, is concentrated in Scotland and Wales. My ancestors stayed in Scotland until one of them emigrated to Norway in the 1600s, bringing his Y-DNA with him. It continues to live on in me, and in his other direct paternal descendants.
R1b is the most common Y-DNA haplogroup in Western Europe, so my family's history is certainly not unique. However, that does not make it less interesting!
When it comes to mtDNA haplogroups, the stories are a bit less detailed, because mtDNA mutates much more rarely than Y-DNA, making it more difficult to trace through time and space.
Humankind truly is one large family.