Viewing a single comment thread. View all comments

byllz t1_iv1rntu wrote

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

Mitochondria lines also die off just because of random chance. There was a woman who lived a couple hundred thousand years ago. Every woman alive is a direct female line descendent of hers. There were likely thousands of other women alive at the time, but every one of their female lines eventually died out, but hers survived. Why? No particular reason. Just random chance.

319

reeherj t1_iv2mn0u wrote

Exactly what I was thinkin! We know ALOT of maternal mitochondrial lineages were lost. So with hybridization, they were either lost, or never existed in the first place.

92

byllz t1_iv2pscv wrote

Also possible, there is some neandertal mitochondrial DNA in some family that hasn't been tested yet. Some dude in South Carolina about a decade ago got a genetic test and learned that his Y chromosome diverged from everyone else ever tested like 250,000 years ago. Turns out this one patrilineal family survived with few members in Cameroon. It is perfectly possible some ancient undiscovered matrilineal line with Neandertal mitochondria is alive and well in some remote corner of the world.

138

PracticalWallaby4325 t1_iv3ezj4 wrote

This kind of explains why we don't have any neanderthal mitochondrial DNA though, doesn't it? If we are all descendents of this woman & she did not have neanderthal mitochondrial DNA then we wouldn't either...

25

byllz t1_iv3h1xm wrote

Humans and Neandertals coexisted and interbred about 50,000 years ago. Mitochondrial Eve is thought to date back about 150,000 years ago. Of course, it is possible that there are as of yet undiscovered branches in the mitochondrial family, and Mitochondrial Eve dates back quite a bit further. Before the dude from South Carolina took his DNA test, Y chromosomal Adam was thought to date back about 150,000 years, but finding him pushes Adam back perhaps 250,000 years. And if some Neandertal mitochondrial lineages are found in humans, that could push Mitochondrial Eve back to more than 500,000 years or so, to before humans and Neandertals split.

58

d-a-v-e- t1_iv5eiit wrote

Meaning: neanderthal and sapiens mitochondrial dna could be very similar?

2

Q-uvix t1_iv4r3e3 wrote

There's no explanation there. If we did find Neanderthal mitochondrial dna in some human population, that would just mean mitochondrial eve would have lived longer ago than we thought (before Neanderthal and sapian lineages split.)

3

vrts t1_iv3d1uo wrote

Doesn't even need to be remote, if your line hasn't been tested it could be you!

24

mcr1974 t1_iv3h72s wrote

remote with the regard to the current discovered set, not the commenter.

5

cunninglinguist32557 t1_iv3sb6k wrote

Man, I wish discoveries like this were the only possible consequence of widespread genetic testing.

21

pursnikitty t1_iv3x2kf wrote

I mean, knowing if you have markers for certain medical conditions so you can make informed decisions for yourself are pretty good. Just as long as we don’t go gattaca with it

8

ab2377 t1_iv2ezrl wrote

can you give me some link so i can read more on that woman?

13

za419 t1_iv2pszj wrote

She's called Mitochondrial Eve. Her male counterpart is Y-chromosome Adam.

The correct way to read this is, all living women have an unbroken daughter-to-mother line with Mitochondrial Eve, and all living men have an unbroken son-to-father line with Y-chromosome Adam.

That doesn't mean there were no other women or men in their time, nor that none of the others reproduced, nor that none of the other's bloodlines survived - just that all of Mitochondrial Eve's female contemporaries' bloodlines either died out or was solely carried by sons at some point, and a similar deal for Y-chromosome Adam.

They also never met. Actually, if I remember correctly, they lived several hundreds of thousands of years apart.

We also don't know anything about the individuals, and there's nothing special about them - if you went back to the time of Mitochondrial Eve (assuming you could nail it down to a specific generation, which I don't think we have with absolute certainty), and found her tribe somehow, you wouldn't be able to tell her apart from the other women. Actually, who she is changes all the time - If a woman who's carrying the last copy of a mitochondrial branch (imagine Eve has two daughters, and one of their female lines has only one surviving woman) dies daughterless (either doesn't have surviving children or only has sons), then the title of Mitochondrial Eve might move down a generation (if Eve had two daughters and one line dies out, then the daughter who's female lines survive is the new Mitochondrial Eve).

It's more of a statistics thing than anything - it's just if you trace back all the women you must eventually find a common mother. That's Mitochondrial Eve.

97

Chemiczny_Bogdan t1_iv31t2s wrote

> all living women have an unbroken daughter-to-mother line with Mitochondrial Eve

Since all humans regardless of sex have mitochondrial DNA (unlike a Y chromosome), all living men also descend from the Mitochondrial Eve.

26

Lambsio t1_iv3kkmg wrote

What about mitochondrial Eve's mother?

11

za419 t1_iv3qa0v wrote

There's no word for her.

But Mitochondrial Eve is the most recent such woman - If her mom had multiple daughters it's entirely possible she used to be Mitochondrial Eve, but no longer is because one of her daughter's female lines was broken.

11

ab2377 t1_iv4djzk wrote

quoting @za419: Actually, who she is changes all the time - If a woman who's carrying the last copy of a mitochondrial branch (imagine Eve has two daughters, and one of their female lines has only one surviving woman) dies daughterless (either doesn't have surviving children or only has sons), then the title of Mitochondrial Eve might move down a generation (if Eve had two daughters and one line dies out, then the daughter who's female lines survive is the new Mitochondrial Eve).

3

MaineSnowangel t1_iv3uisg wrote

I believe mitochondrial Eve’s mother would be a singular mitochondria outside of a human cell.

−1

byllz t1_iv3tw9u wrote

Mitochondrial Eve likely hasn't changed in quite a while. With rapid population increases since agriculture became a thing, lines are much less likely to die off.

5

za419 t1_iv3yty3 wrote

Ehhhh... Maybe.

Fertility rates among some demographics is dropping pretty quickly, which could easily end a line.

And lines end by chance too - even with an increasing population, an endangered line just needs a few accidents, or a few lesbians, or a few child free daughters, or even just a random generation of sons to come to an end.

Now, most lines that end won't be ancient enough to move mitochondrial eve - since it can only move down if exactly one of her daughters has a surviving female line.

But, the point is that "Mitochondrial Eve" isn't a permanent title, or one specific super important person - it's flexible. Who she is changes with time.

A lot of people overstate the importance of Mitochondrial Eve - not that she isn't important to our development, obviously everyone on earth literally has a part of her in us - but she isn't unique. If you went back in time and shot her, another woman would take her place, and you'd come back to an earth that's probably very different, but probably also is still populated by many humans - And there are probably plenty of humans back then you could have shot and changed history even more.

Indeed, any given woman alive today who has/will have multiple daughters could become mitochondrial eve at some point in the very distant future - It's not impossible, though it's kind of unlikely at this point.

5

byllz t1_iv4038c wrote

It isn't just the growth, it is the sheer population. Suppose you had an ancient generation that was down to 2 women with matrilinear descendants. One line accounts for 99.9999% of the current population, and the other the rest. If your world population is 1,000,000, then the likelihood you will have a new Eve pretty soon is high, as there is currently only 1 woman left of the minority line, and the chance of any given woman not having daughters, or her daughters not having daughters is pretty high. But if the world population is 8,000,000,000 then the chance of a new Eve is low any time soon as you would need 8000 such occurrences.

2

Ok-disaster2022 t1_iv31q3s wrote

If were going to extend biblical metaphor, it's better to also use the names of Noah and Namaah.

A y chromosomal male is better identified as Noah, whereas a mitochondrial Eve is Eve. After all Noah's sons brought their wives in the genetic bottleneck.

1

za419 t1_iv38tsb wrote

Eh, probably.

I think the Bible metaphor sucks because it gives the impression that no one else was around or passed on their genes, and that's very not true. It works on the surface level (in a "everyone's ancestors" sense), but it lends itself to being misunderstood and requiring a huge comment to clarify what it means.

I believe the original name was "lucky mother", which... Lost out for obvious reasons.

15

truthseeker1990 t1_iv3lpi0 wrote

Isnt that odd? Or maybe just seems strange at face value. Nature rarely does anything in ones, why would all other lines vanish rather than have a mix of many lines

3

byllz t1_iv3r0vs wrote

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.

7

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?

1

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%

2

KaliCalamity t1_iv4noj9 wrote

At one point, it's believed the total worldwide population of "modern" humans dropped to around 10,000 people. This was only around 74,000 years ago and correlates to the eruption of what is now Lake Toba in Sumatra. It was so massive, the world was thrown into a literal volcanic winter for around ten years, and likely effected the world climate for a millenia.

3

RhabarberJack t1_iv2uu9q wrote

Does that mean that every living human on this planet has the same mitochondria?

2

byllz t1_iv2wsb4 wrote

It is one family of mitochondria, but there are random mutations that happen regularly. Through tracking these mutations, you can tell how closely different people are related to each other, matrilineally speaking.

20

poop_face_monster t1_iv39hcf wrote

Do any of these variations [edit: mutations] change the form/fit/function of the mitochondria?

It seems to me that any marginal improvement there would yield a pretty significant boost to fitness.

(Thank you for fielding Qs. I’m only a moron, but this thread is brilliant.)

5

PontificalPartridge t1_iv3gjd8 wrote

Probably. Some mutations are good, some bad. If it provides selective advantage for ATP exchange then over a long period of time that mutation could become prevalent if that ATP exchange could become more common if it meant more breeding.

It’s worth noting that modern humans don’t necessarily rely on ATP exchange for “breeding” at this point. The movie idiocracy is an extreme example. But our survival selection method is pretty close to societally based at this point

Edit: for most of human history there are probably some tangible selective advantages to some mitochondrial mutations, just like anything else. I don’t have any specifics

4

morgrimmoon t1_iv4gyjt wrote

Quite a few of these mutations impact mitochondria in a negative way. For example the LHON mutation often causes blindness, but only in about 30% of carriers (so there's probably some environmental or non-mitochondrial DNA factor that "activates" it).

Since cells have multiple mitochondria, and since the non-mitochondrial DNA rules most of the cell, it can be tricky to determine what any mutation does and having it may not cause a change for all carriers. So it won't have as strong a selection pressure as it may intuitively seem, and any fitness improvement may still take a long time to spread thru a population.

1

Ok-disaster2022 t1_iv3149p wrote

Successive generations and larger population dominance would eventually result in a singular case. The fact that mitochondrial eve isn't close in time probably indicates sufficient mixing and lineages.

1