This story might cause some sleepless nights in the taxonomy world:
5 Likes
Once again, the real world doesnāt always fit into the nice, neat boxes we humans try to force on everything.
5 Likes
Everythingā¦. including ourselves!
4 Likes
Theyāre both Messor spp, notwithstanding the millions of years of divergence. Iām more impressed by grasses being able to actually exchange genetic material without sex no matter how far away they are from each other phylogenetically.
https://poasession.blogspot.com/2021/06/frankensteins-plants-natural-genetic.html
2 Likes
Wow! Thatās super interesting. Itās amazing how common cloning actually is in the animal world.
Just a thought: How do you get the number five million years ago? What methods are used to figure this out? Are we trusting the number is correct with no thought that it might not be?
1 Like
I would assume someone did a molecular phylogenetic dating on that genus or set of related genera.
Which means that it might be about as accurate as me saying āthe other dayā¦ā, meaning some time in the last several years. 
From what Iām reading, molecular phylogenetic dating (like most dating techniques) is fundamentally flawed for the single reason of extreme assumptions. How can anyone possibly know how fast differences in DNA supposedly accumulated? It is a major and most likely flawed assumption that means the number five million years is meaningless, as @mftasp pointed out. The two species may have diverged one hundred years ago, for all anyone knows. And Iām not doubting that they are different species, they seem pretty east to differentiate.
https://answersingenesis.org/evolution/phylogenetics/
That said, this is quite amazing. Itās a reminder that no one actually knows what a species is. There are dozens and dozens of different species concepts ranging from incredibly detailed to one sentence: whatever the taxonomist thinks.
1 Like
There are two methods that phylogeneticists can use to calibrate molecular clocks.
The first is based on pedigree analysis. A biologist either breeds an organism in the lab or tracks the pedigree of an organism in the wild. After several years/generations, they sequence the DNA of the original organism and its descendants. Then they just count up the mutations that have happened in that known time period and get an estimate of the rate. This is repeated across many different individuals to check how consistent it is. This is a very time consuming process, but in general the rate estimates tend to line up reasonably well, with some consistent differences between different taxa, and with some other caveats about extrapolating short-term mutation rates over long time scales.
The second method is to use time calibration with known divergence dates. This may be geological events of known age, like the time that an island formed, or divergence dates known from the fossil record. This is used to calculate rates of DNA divergence that can be used for related species of unknown age. How well this works depends on the species - some have very good fossil records and very consistent mutation rates, others donāt work as well.
Often those two methods are combined, using information from fossil calibrations, geological calibrations, and pedigree-based mutation rates to come up with the best estimate and a confidence interval around that estimate. There are assumptions that need to be made, but these assumptions can be tested and some degree of mutation rate variation can be accounted for by recent methods.
The 5 million year date was estimated using some standard recent methods that incorporate time calibrations from another paper that estimated divergence times for ants. That paper used time calibrations from fossilized ants to estimate DNA divergence rates - luckily ants seem to leave a decent fossil record that allow these rates to be estimated.
So, there is not much reason to be skeptical about the ~5 million years date unless you have reason to distrust the ant fossil ages (Iām not an ant palaeontologist/taxonomist so I have no comments about that). (of course it is not actually an estimate of exactly 5 million years, there is a range of uncertainty centred around 5 million years - could be 4.5 or could be 7, but probably not too much lower or higher than that)
7 Likes
Great succinct summary, thank you.
2 Likes
I find that both methods, though valid in theory, fail.
How do we know that the rate of mutation does not change, has not changed or will not change?
This is the exact kind of assumption Iām talking about. Just because the mutation rate has stabilized in recent years does not mean that fifty years ago something happened that caused the mutation rate to accelerate.
The second method is even worse. The methods for calculating geological age (radiocarbon dating) are grossly tolerant of major assumptions.
Sometimes assumptions do need to be made, but when they accumulate into a giant mountain, its time to consider how many supposed facts are skewed or outright false.
A thing of note: the article stated the date of the divergence with no room for further research. They could have said āit is thought that the two species divergedā¦ā or ācurrent research suggests that the two species divergedā¦ā but instead they stated it as an absolute.
It all comes down to your preconceived notions and your worldview. āfive million yearsā is no problem for someone who believes the Earth is billions of years old. I believe the Earth is no older then 10,000 years (but probably 6,000), so I highly doubt any date that goes beyond those.
1 Like
This topic was automatically closed 60 days after the last reply. New replies are no longer allowed.