Invalidating conclusions: not particularly; these results suggest that under rare circumstances (in a few sorts of mitochondrial disease), mitochondria can be transmitted paternally. It makes the matrilineal model slightly less definitive, but, overwhelming often, accurate (note that people with mitochondrial diseases rarely exhibit this feature, and are less likely to reproduce anyway due to the disease).
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.
Doesn’t the paper specifically say that they really have no idea of the impact because not enough attention has been paid to determine the amount of paternal inheritance? You sound awfully sure of yourself considering maternal inheritance of mtDNA has been practically gospel for 50 years.
I agree. I wouldn't rush to draw any conclusions, as this paper changes the status quo. We can not say anything about the rarity of transmission events in the past really. This work is focused particularly on heteroplasmy -- it doesn't rule out other causes.
It does not seem we understand the mitochondrial inheritance mechanism during conception.
We can set an upper bound on paternal mitochondrial inheritance: there are hundreds of thousands of mitochondria in an egg, and tens in a sperm.
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.
Does that not assume that the mitochondrial from both parents are treated equally in terms of inheritance? It seems to me that biological systems do not tend to use random chance most of the times if there is a evolutionary benefit, thus if there is such benefit I would predict that those "tens" would be treated differently from those hundreds of thousands.
I was mostly talking about the concept of mitochondrial incompatibility, which is significantly more common than what is discussed in the paper, which is paternal inheritance. I made a note of it being doubly rare (female must survive to reproduce age with a specific mitochondrial sort of defect)
>these results suggest that under rare circumstances (in a few sorts of mitochondrial disease), mitochondria can be transmitted paternally.
"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."
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.