In the last part of this series, we started to talk about Homo erectus, one of our earlier hominid ancestors, and the first one to go global. H. erectus emerged in Africa about 2 million years ago, and from there spread out across the globe. Skeletons have been found in Africa as early as 300,000 years ago. Homo erectus skeletons are found in Asia from 1.8 mya ago to about 300 Kya. In Europe we find skeletons dating from about 800,000 – 300,000 years ago.
The reason these skeletons are so important is because H. erectus is ancestral to two populations that are very important to this series; ourselves, Homo sapiens, and a cousin population in Homo neanderthalensis. The Neanderthals,
There is a lot I am skipping over here, and plenty of details that have to be omitted for brevity reasons. Suffice to say, that somewhere around 350Kya, Homo sapiens emerged out of Africa and began their long trek across the globe. At the same time in Europe and into East Asia, arose the Neanderthals.
Which brings us down to about 50,000 years ago, in a world covered in ice (at least in the north), and with two kinds of hominids living side by side in Europe. It is here we get to the real marrow of this series, where I actually start talking about my own ancestors, as revealed through genetic testing. At this point it is important to make a distinction about what kind of genetics we are talking about, because there are three “kinds” that are often discussed in these conversations; Y-chromosomal DNA, Mitochondrial DNA, and autosomal DNA.
Y-Chromosomal DNA is pretty self explanatory, as it comes from the Y Chromosome found in males, and is used to trace a straight line through ones paternal ancestry, father – grandfather – great grandfather and so on.
Mitochondrial DNA is also pretty straight forward, it is extracted from the DNA of mitochondria, the “power plants” of our cells. This type of DNA is inherited through the maternal line only, mother – grandmother – great grandmother. You get the idea.
I have had testing done on both of the former two types, but I am not going to talk about these just yet. Because, I will be talking about Autosomal DNA, which comes from the autosomes, the first 22 bases pairs of chromosomes in our genetic material. It excludes chromosome 23, because this is is often to referred to as the “sex chromosome”. In males, it is a Y, in females an X. This chromosome is not included in autosomal testing.
The reason I will be talking about autosomal first is because in many ways it is the most comprehensive. While the Y testing can tell me about my paternal line, and the mitochondrial can tell me about my maternal line, autosomal DNA can tell me about my ancestors across ALL lines in my ancestral lineage. This is done by comparing my own DNA with other known samples, either from living people or from DNA extracted from ancient skeletons. I’ll let you guess which we will be talking about.
Which brings us to my first 2 matches, from 50 kya and 30 kya ago. And as you may have already guessed, these matches are from a Neanderthal and a Denisovan skeleton. The location is in the place now known as the Denisova Cave, in Altai Mountains, Siberia.
Really, in so many ways the Denisova Cave is a tale of three different hominins. (2) Modern humans on one hand, and also the Denisovans and Neanderthals. Seriously folks, I have included plenty of links at the bottom for those that are curious. Wikipedia is good for a general overview of course, but it’s real value lies in the bibliographies on these pages. Those can lead to other websites as well as academic literature on these subjects.
I digress a little bit. In this cave were found numerous fossils from all three hominins, and a few of these fossils still contained viable DNA, which was tested and eventually released publicly. Most of the DNA for the Denisovan came from a small bit of bone, a part of the pinkie. It had once belonged to a little girl. The Neanderthal DNA came from a toe bone, and it belonged to a female.
Once the data was made available to the public, it was possible to compare to that of living people. People like myself. That is how my own DNA, and my own ancestry came into the picture; behold!
50 kya Altai Neanderthal match; 2.47 % (1)
30 kya Altai Denisovan; 1.93%
And that is where I am going to leave this part of the series. Seriously folks, there is a ton of information out there if you are curious about these things. Of course, I am always open for questions and will answer them to the best of my ability.
Thanks for reading!
Using “total shared DNA” calibration in the Ancient Calculator tool.
A note on language use. You will see me vary between using the term “hominid” and “hominin”. Both are in fact accurate in this sense, but “hominid” refers to the family Homindae, which includes the great apes. It is a “wide use” term, whereas “hominin” is more restrictive, and refers mostly to the members of genus Homo, that is humans and our closest relations.
Sources and references;
Essentials of Physical Anthropology: Discovering our Origins. By Clark Spencer Larsen