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JonesP77 t1_j2f6kq0 wrote

Reply to comment by Shadowkiller00 in Why is Mitochondrial Eve dated to 150-170,000 years go? by jayhovian

I dont understand. I dont get the connection between differences in our mitochondrial DNA and the time we can follow it back. How do we get to that number? I really seem to miss something because i have no clue what youre saying.

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VoilaVoilaWashington t1_j2fkhph wrote

Say you have an heirloom poem that each member of your family has to transcribe. It's in Latin, so you have no idea what it says.

Even with all the checking, we know that every new generation makes minor mistakes transcribing it, which build up over time. The same poem has somehow spread all over the world because your family is all over.

How do you find out when it was written?

Well, you compare the last few generations' worth of poems and realize it's on average 1.75 mistakes each time it's transcribed. Now you compare your family's to another one elsewhere on earth, and there are 500 differences - how many generations ago did they branch off?

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jamesj t1_j2fc6c2 wrote

Differences in DNA that are neutral with respect to their effect on function accumulate at a roughly constant rate. This is genetic drift. So, by looking at the number of changes between two sets of DNA you can calculate roughly how long they've been drifting apart.

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