Mitochondrial DNA can be inherited from fathers, not just mothers
nature.com
nature.com
Maybe this happens a lot more often than documented. In this case, it can throw the field of mtDNA testing and implications into question.
Conversely, maybe it happens extremely rarely and only in pathological cases (in the mathematics/statistics sense, if not the medical sense). In this case, it's just a medical curiosity and only important insofar as a doctor treating a patient with a rare disease may want to consider the remote possibility of this.
But it does indicate that more research is needed to understand the implications of this, especially on genetic screenings.
Also mitochondrial eve isn’t a hypothesis, but rather stub for the most recent common genetic ancestor of modern humans before the divergence of the mitochondrial DNA groups.
Also it’s important to note that mitochondrial eve isn’t a “fixed individual” in say 50,000 years the mitochondrial eve candidate would be shifted to someone who lived well pass the current one as lineages die out.
It is possible to imagine several different single cells being our ancestore. If we pretend a lightning strike in the ancestor primordial DNA soup sparked life, then it could have sparked life in millions of cells with a single lightning bolt. There could even have been several different puddles of DNA soup.
An interesting aside is everyone who lived more than 2000 years ago is either your ancestor or has no living descendant. This wasn’t true before 1803 because the Tasmanian aborigines had been genetically isolated since the end of the last ice age [0].
0. https://en.wikipedia.org/wiki/British_colonisation_of_Tasman...
Actually you only have around 1000 effective ancestors from that time as you don't inherit DNA from every ancestor.
It's like seeing a human as the root of its ancestors tree, and saying that this tree is well balanced all the way to the nodes at depth 100 or so. But surely it's not a well balanced tree, more like a directed graph with many sideways connections. There could be multiple clusters, lineages, more or less narrow, coming from the bottom and reaching the top.
Single Eve: still holds; given the small population size of humans in the past, at some point there was a female ancestral to us all, as other lineages would have stochastically died out.
Human dispersal and Neanderthal-modern human crosses: both have been examined via autosomal DNA. Reconstructions of dispersal may be skewed in the following manner: since we use X- Y- and mtDNA to look as sex ratios of admixture events (such as in modern Caribbean populations, where there is more European male influence and African/Native American female contribution), our reconstruction may be skewed by these selection due to incompatibilities. We expect there to have been some incompatibilities between modern humans and Neanderthals/Denisovans—no doubt some were mitochondrial. But autosomal DNA bears the evidence of our admixture. Likely some lineages (including those with prehistoric-human mt- and Y-DNA) were lost, either due to selection, stochasticity, or likely, both.
It does not seem we understand the mitochondrial inheritance mechanism during conception.
If all paternal mitochondria were transferred every time (unlikely‡), then a child's mitochondria would be ~99.99% inherited through the mother.
‡ Unlikely because sperm mitochondria are located toward the flagellum in order to power locomotion, and the capsule at the head is normally the only part which fully penetrates the cell membrane.
Ref: https://www.quora.com/How-many-mitochondria-are-there-in-hum...
"Although biparental inheritance of mtDNA and heteroplasmy coincided with disease symptoms in some of the individuals studied by Luo et al., the authors’ data do not demonstrate a causal link with disease. In fact, we cannot be certain that the study participants have mitochondrial disease, because no specific examinations to confirm this diagnosis are reported. Further study is needed to identify more cases of potential paternal mtDNA inheritance, and to determine the functional consequences of such heteroplasmy."
So no, it is not definitively linked with mitochondrial disease. If anything, the article suggests that the inheritance may be due to an abnormality in the host DNA:
"Previous work has shown that mitophagy, the process by which cells ‘eat’ their own mitochondria, has a role in the selective elimination of paternal mitochondria. Given our rapidly expanding knowledge of mammalian mitophagy in vivo16, these rare instances of paternal mtDNA transmission might be attributed to defective mitochondrial turnover. The inheritance pattern of paternal mtDNA in Luo and colleagues’ study suggests that a yet unidentified gene on one of the autosomes (non-sex chromosomes) is involved in eliminating paternal mitochondria."
https://news.ycombinator.com/item?id=18559212
(Ars Technica article points to same PNAS article as this Nature article does).