How can the testers know the names and lifespans of your whole family tree from just a hair sample? I know they have databanks, but there’s no way they’ve existed long enough to have info on that many people from all over the world. I’ve always thought it was cool, but never understood the mechanics.
In: Biology
They can’t tell that from a hair sample, it’s a combination of sources to do all that. A hair sample gives you someone’s DNA, which can be used to find close relatives already in the data bank. Once you have a few closer family members figured out, you can then go and use the enormous amount of genealogy information that’s out there to fill in more of the family tree.
Genealogy has been a popular human interest for a long time, people study things like old census data or marriage records to build family trees, which are then held in huge databases like you can find on ancestry.com.
When I tried doing my own family history I only had to go as far back as my grandparents before ancestry.com could fill in the gaps going back many generations.
edit: Just wanted to add one more thing regarding this part of the question
> I know they have databanks, but there’s no way they’ve existed long enough to have info on that many people from all over the world.
Maybe the digital data banks haven’t existed for a very long time, but the data itself absolutely has. Don’t underestimate the popularity of genealogy and the absolutely enormous amount of record keeping that countless people have been doing for a very long time. There’s more data than you realize, and your family isn’t as unique as you think, going back just a few generations links your family tree with TONS of other people, and there’s a very good chance at least some of them have helped research their own family trees.
They don’t.
If you’re doing a tree on Ancestry for example the hints are just based on trees built by other people.
For example, if X and Y are siblings and X says his grandmother is Phyllis who was born in 1930 Ancestry will suggest Phyllis born 1930 as a potential grandmother to Y
But the hint will only be correct if X had the correct information to begin with.
Your genealogy test can match your DNA with other people who have also taken the test but other information like traits, ethnicity and your ancestors is just extrapolation based on who you matched with and what information they have given ancestry. This information is often wrong or incomplete.
DNA is a really useful tool but you need to use a document trail as well to confirm facts.
Yes to the commenters who point out that they’re supplementing the DNA data with traditional genealogical data that goes back centuries. But, also, note that [Ancestry.com](http://Ancestry.com), for instance, does have the DNA of 25 million people at this point. It’s likely they can find a close match to your DNA from someone in their database already.
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