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byllz t1_iv3r0vs wrote

Reply to comment by truthseeker1990 in Why don't we have Neandertal mitochondrial DNA? by nodeciapalabras

It is just a natural effect of lots of time combined with a population that doesn't grow quickly (as human population didn't for the majority of its existence). Take all the women living at a specific time in history and track each of their lines. Over time, just by random chance, one line will grow in members, which means another line will shrink. Every so often this random growing and shrinking will mean a line will shrink to nothing. However, once it is gone, it is gone forever, and so will never grow again. One by one they are snuffed out, until only one remains. And then Mitochondrial Eve moves forward in time. Since populations started growing considerably, lines have been dying out less.

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truthseeker1990 t1_iv4fb4b wrote

I understand some lines will snuff out and some will progress but why would there be exactly one line that survives? Wont you expect a mixture of lines to survive?

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byllz t1_iv4g9lr wrote

The answer lies in time. In a given period of time, just from random fluctuations there is a chance the number of surviving lines will decrease, based on how many lines are left and the population. So, given enough time, assuming the population doesn't grow, the chance the number of lines will decrease eventually approaches 100% just like theoretically you can flip a coin as many times as you want and always get head, the chance you will eventually get tails approaches 100%

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