Ethnic Percentage

[Sasso]

Does the ethic percentages ( i.e. West Asia 16%) that are found in your DNA determine the relationship to that ethnicity? For example, someones DNA says they are 70% Italian, 1% West Asian, 9% Iberian, and 20% Greek. Does the 70% mean that your closer ancestors (grandparents, great grandparents etc.) are Italian? And because you have 1% or less, this ethnicity was inherited farther in the past?

How do I know what ethnicity was inherited hundreds of years ago as opposed to more recent genetic markers?

[Miss Blue]

DNA companies analyze hundreds of thousands of SNPs (points on your DNA, like markers) that tend to be more variable (distinct) in different populations. They DNA test modern Italians, modern Greeks, modern West Asians, modern Iberians, etc., people who have a claim to having ancestral descent in the region, to comprise the "reference panels" for these population groups. Using these reference panels, DNA companies attempt to ascertain which SNP values occur in a given population. In other words, they're making an educated guess about where these hundreds of thousands of DNA markers come from in the world based on modern people in their reference panels.

"70% Italian" just means "about 70% of the markers we looked at are most often found in modern Italian populations." As you'd expect, though, the size of the reference panel, as well as the individuals chosen, can affect this number. Imagine if you were northern Italian and the panel was almost exclusively southern Italians. Or the reverse. What if there are only 20 people in the panel? It might not reflect the necessary diversity of the Italian population.

Additionally, Italy - like so many populations - is genetically admixed. That complex history is why large portions of your DNA most closely match external populations. Greek and West Asian likely aren't new introductions into your DNA. Italians carry those markers from historical admixing. It's difficult for DNA companies to tell whether it's a modern Greek or a modern Italian with Greek or West Asian ancestors. They just know the frequency at which those marker values occur in Italy versus Greece versus Spain/Portugal versus Great Britain, and so on.

[Anizio]

Remember ethnic % is an estimate of YOUR individual personal ethnicity, not a suggestion about the % of your ancestors who were of that ethnicity. You do not have DNA from all ancestors, and those you do you do not have in equal parts.