Tomenable
Elite member
- Messages
- 5,419
- Reaction score
- 1,337
- Points
- 113
- Location
- Poland
- Ethnic group
- Polish
- Y-DNA haplogroup
- R1b-L617
- mtDNA haplogroup
- W6a
I noticed already some time ago, that:
And I found similar opinions by others:
But I wasn't sure why was this the case.
Until I found this post on Anthrogenica:
http://www.anthrogenica.com/showthr...lculators-more&p=145261&viewfull=1#post145261
23andMe experts are very careful (which is why they have all of these "Broadly something" things). Nothing is noise there. I would say that they are actually too careful with detecting admixtures.
By too careful I mean reluctant to tell you about minor or "uncertain" admixtures.
And I found similar opinions by others:
In my observation 23andme underestimates Eastern Euro admixture when someone still plots in a very West Euro countries. It might look unsure so it ends up mostly in "Broadly..." or "Unassigned", even in Speculative mode.
Which is probably why Poles usually get the same % of "North Slavic" in DNA.Land as their % of "East Euro" in 23andMe, but Westerners usually tend to get more "North Slavic" than "East Euro".
As it seems, 23andMe tend to label such admixtures as "Broadly something".
23andme shows your ethnic heritage from the last 500 years in form of bounded geographical areas you are native to . on gedmatch your genome gets broken down further in more detailed components in a larger than 500 year past timeframe.
But I wasn't sure why was this the case.
Until I found this post on Anthrogenica:
http://www.anthrogenica.com/showthr...lculators-more&p=145261&viewfull=1#post145261
23andMe's speculative mode greatly overestimates major components, and underestimates minor components. This is due to their methodology of snipping the genome into 100 SNP segments to compare against the limited references they have. So for example, if 60% of the the segment indicates Middle Eastern, and 40% indicates S Asian, that segment is assigned 100% Middle Eastern. In effect 40% of the segment, which is S Asian is ignored, and the whole segment is assigned Middle-Eastern.
Also, their methodology includes segment smoothing, which means if there are chunks of minor components in a segment, they are ignored.
That is how Iranians and W Asians turn out 98-100% Middle Eastern, and folks in neighboring Pakistan turn out 98-100% S Asian in speculative mode.
This naturally is unrealistic and uninformative, because you don't need a test to tell you that. Conservative mode is better with regards to inflation of major components and underestimation of minor components, but the trouble here is that people get 5-70% unassigned. This is where your minor components are hidden.
The above translates to 23andMe being useless for figuring out your minor components to any degree of accuracy.