Aeta was one of the earliest inhabitants in the Philippines Author: Seanaleta.
Source: Wikipedia. CC BY-SA 4.0
To identify the origin of Indo-Europeans, linguistics, archaeology and history have unfortunately failed. We will therefore call on a more recent discipline: population genetics.
This branch of genetics is the study of the reproduction of populations. Previously, evolution was studied from the point of view of individuals only. Nowadays, it is also done from the point of view of populations.
Individuals are a distribution of genotypes and it is the population that generates these genotypes. These contain the information carried by the genome of an organism, contained in the DNA of each cell. Our human genome contains between 28,000 and 34,000 genes spread over 46 chromosomes grouped into 23 pairs. One of these pairs consists of the chromosomes that determine a person’s sex. A man carries a Y chromosome and an X chromosome. And a woman carries two X chromosomes.
Population genetics uses the Y chromosome as a ‘marker’. Finally, a ‘satellite’ genome called mitochondrial DNA (mtDNA) is distinct from our DNA. And only the mother passes it on. This genome refers to mitochondria present in so-called eukaryotic cells. All this to say that population genetics also uses it as a ‘marker’.
In population genetics, the different Y chromosomes are grouped into ‘haplogroups’. A haplogroup is a group of similar haplotypes (group of alleles) that share a common ancestor with a single-nucleotide polymorphism mutation.
The Y Chromosome Consortium (YCC, 1991–2012) defined the first nomenclature in 2002. According to this nomenclature, our human genus has 20 haplogroups (noted from A to T). A haplogroup descends directly from another or from a mutation. Here is our (simplified) ‘genetic tree’ in diagram form. The haplogroups are highlighted in yellow (or grey for black and white publication) and the mutations are highlighted in white.
What is most striking is the ‘convoluted’ transition between haplogroup F and the following ones. Now, let’s try to translate this tree on the population level, knowing that the numerous human migrations do not make the exercise easy. To do this, we will look for the population (or even the region) where we find the best representation for each of them. Here is the same genetic tree (simplified) from the population point of view.
Indigenous Americans and Indo-Europeans are descended from the haplogroup of the Aeta people. And the latter currently resides in the Philippines. Native Americans and Indo-Europeans evolved on two and unrelated continents before the official discovery of America in 1492. From the point of view of human palaeontology, the only place where they could have crossed paths is in the Far East, 15 to 20,000 years ago. This was before the future Indians migrated to America through the Bering Strait (which connects Siberia and Alaska) and before the future Indo-Europeans migrated to Central Asia and Europe.
Mitochondrial Eve is the name given to a hypothetical woman who is believed to be the newest common maternal ancestor of humanity. And cases of paternal transmission of mitochondrial DNA are very rare.
Considering the rate of mutation (the molecular clock concept) in this DNA, calculations suggest that the mitochondrial Eve lived about 150,000 years ago. Phylogeny also suggests that she lived in East Africa. Phylogeny is the study of the relationships between individuals, populations or species.
Mitochondrial DNA has 33 haplogroups (A to Z, plus 7 variations of L). Here is our second (simplified) ‘gene tree’ in diagram form. The haplogroups are on a yellow background (or grey for a black and white publication) and the mutations are on a white background. And the L is the mitochondrial Eve.
Unlike the Y chromosome, the translation of this tree into populations is impossible. But since haplogroups are concentrated in certain regions, we will nevertheless draw attention to some unusual elements.
For example, we go directly from the L3 of East Africa to the M and N pair in the Far East and Oceania, without passing through the East and Central Asia. Our ancestor ’L3’ seemed to have good navigational skills.
The Far Eastern M has produced half of the world’s population. And the Oceanian N has produced the other half. Haplogroup R, mainly present in Oceania, is the ancestor of the majority of Caucasus populations, the Middle East and Western Europe. To put it mildly, human migration has made two complete changes of direction: first, ‘all the way to the east’ and second, ‘all the way to the west’.
If Indo-European originated in South-east Asia, it probably left the ‘family nest’ early. He then colonised regions in Asia, concentrating on temperate zones between the 30th and 50th (geographical) parallels. This choice could be explained by an early aptitude for agriculture and a taste for a fairly rural lifestyle.
It remains to be explained why the ancestors of the Amerindians headed east (America) and why their Indo-European ‘cousins’ went the other way. We know today that the Amerindians liked the great outdoors for hunting. As the seasons changed, they did not hesitate to move around either. However, this characteristic can be found in the Indo-European populations of the Central Asian steppes.
One thing is certain: Indo-Europeans and Amerindians were never afraid of wide open spaces and long journeys. ‘What is the origin of the Gauls of Roman Celtic?’ For the moment, the only certain answer can be summarised: ‘far away’.