- From https://www.quantamagazine.org/extra-dna-may-make-unlikely-h...
The distance in time from the point when some evolution lineages have split is a very poor predictor of the genetic distance between them.
While no living being from today is really a "living fossil" that is identical to some ancient ancestor, there still exist both conservative evolution lines, where those who live today do not have any obvious differences from ancestors living even 500 million years ago, and progressive evolution lines, where after switching to a different way of life and after even only one million years the descendants may have changed beyond recognition.
> American paddlefish (Polyodon spathula), which are diploid, have 60 pairs of chromosomes, while Russian sturgeons (Acipenser gueldenstaedtii), which are tetraploid, have four sets totaling about 250 chromosomes (the chromosomes are so numerous and some are so small that it’s hard to count them reliably). Nearly 200 million years of independent evolution should have seeded the two species’ DNA with countless genetic mismatches and incompatibilities — from missing and added genes, to rearrangements and relocations of genes, to mutational tweaks to gene expression. It seemed certain that hybrid cells would struggle to figure out how to line up their chromosomes during cell division and what genes to turn on or off.
As the researchers said:
> “We never wanted to play around with hybridization,” said Mozsár. “It was just a negative control, which found, somehow, a way to live.”
It seems to be a very good predictor with some extreme outliers yeah? It's reliable enough that this event ran against the intuition of specialists who are trained and experienced in this domain.
It's easy to look after the fact and say "oh ya 180m years but they didn't change much" it's another thing to have predicted this as a likely outcome. They didn't, I wouldn't have, I doubt you would have either?
This is where I started getting suspicious about how accurate the article was. The paddlefish is vulnerable, but not endangered. They're doing pretty well in the Missouri, all things considered.
>Researchers in Hungary conducted experiments designed to test if either species could be bred in captivity.
This is where the wiki lost me. Paddlefish are relatively easy to produce in captivity. We've been doing it for decades. It generally doesn't involve sperm from an unrelated species either. I'm curious what the real story is.
> During an experiment to produce gynogenic Russian sturgeon progeny, a negative control was initiated using non-irradiated American paddlefish sperm and eggs from the Russian sturgeon. Unexpectedly, the control cross resulted in viable hybrids.
I'm not a biologist, but I guess it's the "gynogenic" part that's hard to do?
> The initial goal of the study was to encourage the critically endangered sturgeon to reproduce asexually. That isn’t quite how it went.
The focus of the study was the critically endangered sturgeon.
The other species was needed since:
> in gynogenesis, the DNA of the sperm specimen isn’t supposed to transfer to the offspring.
They deliberately picked a distant species (not in the same genus, and not even in the same family) to use as a negative control. But, accidentally, their negative control group "found a way to live" (in their words)!
For the description of the American paddlefish as "endangered species", this may have come from, e.g., https://en.wikipedia.org/wiki/American_paddlefish -
> American paddlefish are also protected under Appendix II of the Convention on International Trade in Endangered Species (CITES) meaning international trade in the species (including parts and derivatives) is regulated
Of course.
It doesn't even mean the authors think there is any actual implication for CO2 or that they are being dishonest, in many cases the system has to be gamed like this if you want to be able to do research at all.
