There’s also the issue that if their “stem whale” had had a beneficial mutation that gave it skeletal pneumaticity it probably wouldn’t have evolved into a whale. It might have evolved into an aquatic bat-like creature instead.
2 Likes
I’m not sure if this is in the realm of relevancy, but Anton has a fascinating video on the Avalon explosion
all we can tell for sure is life on earth is definitely special and it definitely evolved in a lot of different complex ways but I guess more importantly, it also had so many chances to basically get nowhere yet somehow, for some reasons we had these periods of biodiversity that lasted for millions of years
1 Like
Ha! While listening to the video for a second time, I picked up that the weakened magnetosphere as determined by these crystals from Brazil, meant an increase in cosmic radiation could have corrsponded with the Avalon explosion.
That doesn’t pass the smell test for me. If we are talking about the Cambrian, the sudden availability of free oxygen probably drove the vast majority of evolution. Another example is the radiation of mammals after the K/T extinction event where there were open niches everywhere. I highly doubt an environmentally caused increase in mutation rate had much to do with it. [/IMHO]
1 Like
Check out the video. Avalon explosion 575 mya. Anton mentioned something about how the oxygen change doesn’t account. But I didn’t catch all of it.
Anton seems like a nice guy and has an entertaining YouTube channel. However, I prefer primary sources over YouTube videos when it comes to scientific findings.
1 Like
If there was an absence of the magnetosphere, why would you doubt that would have an affect on evolution?
1 Like
The magnetosphere is what protects against charged particles in the solar winds. Water is also a very effective shield against those particles. Since we are talking about life evolving in the oceans, the absence of a magnetosphere wouldn’t be noticed a few feet under the ocean surface. Even if there was an increase in radiation, I still don’t see why this would result in massive increases in evolutionary rates. The mutation rates we see today are way above the rates needed to produce the amount of evolution we are seeing. I don’t see how increasing mutation rates even more will increase evolutionary rates. What DOES increase evolutionary rates is the availability of niches.
2 Likes
By the way, this is the paper Anton references to question the oxygen theory
https://onlinelibrary.wiley.com/doi/10.1111/gbi.12557
Contrary to a classical hypothesis, our interpretations place the Shuram excursion, and any coeval animal evolutionary events, in a predominantly anoxic global ocean.
To be fair to Anton, after listening again, he draws the correlation between what happened to the earth for the magnetosphere to drastically decrease for over 20 million years and the Avalon explosion. He mentioned an increase in cosmic rays, but he did not draw the correlation between it and the increase in biodiversity.
At the very least, there is a big debate within the scientific community on what oxygen levels were during this period. I don’t think it is appropriate to cite one paper and sweep the whole thing under the rug.
This also doesn’t give credence to any other explanation that can be dreamt up. If increased radiation is the cause of these speciation events then it needs to stand on its own, and I don’t see how it does.
Just thinking out loud, the magnetosphere has fluctuated throughout history. It has weakened and completely reversed poles many, many times, and has done so in geologically recent times. If this does create a significant impact on molecular evolution then it could show up if one compares the genomes of living species with respect to when those lineages diverged.
1 Like
The quote I originally pulled from the video is true either way.
all we can tell for sure is life on earth is definitely special and it definitely evolved in a lot of different complex ways but I guess more importantly, it also had so many chances to basically get nowhere yet somehow, for some reasons we had these periods of biodiversity that lasted for millions of years
It’s also worth noting that it is an issue of the magnetosphere nearly disappearing for over 20 million years
1 Like
Agree with all this. Also, there is already no shortage of radioactive sources in the immediate sea water and actually within sea creatures, which is full of potassium 40 and contains dissolved metals such as uranium.
2 Likes
Any correlation between cosmic rays and increased biodiversity was my own naive takeaway. Anton was considering the correlation between whatever caused the magnetosphere to disappear and the Avalon explosion. These events do apparently coincide. He also casts doubt on the theory that explains increased biodiversity by increasing oxygen levels.
1 Like
I just was just thinking about this statement, which I agree with, but there may be a difference as it pertains to the beginning of complex life forms.
I’m confused by this
Even if there was an increase in radiation, I still don’t see why this would result in massive increases in evolutionary rates. The mutation rates we see today are way above the rates needed to produce the amount of evolution we are seeing. I don’t see how increasing mutation rates even more will increase evolutionary rates.
A statement I see frequently is that, “mutation is the ultimate source of genetic variation.”
If the mutation occured more or less uniformly across an entire species or biological environment, that seems like it could have a major effect on evolution and biodiversity.
1 Like
It is also worth noting that mutations caused by radiation have different patterns than the usual processes that cause mutations (e.g. copying the wrong base, CpG methylation). The “usual” processes produce transitions at a higher rate than transversions, but radiation appears to change the ratio of transitions to transversions.
IR is ionizing radiation, Ti are transitions, and Tv are transversions. So, they saw more transversions in cells that were irradiated than would be expected from natural processes. If radiation were making a significant contribution to mutations periodically through time then I think it could be detectable by looking at the ratio of transitions to transversions.
Also, take every chance to reference @glipsnort 's great article on the topic:
2 Likes
Mutations don’t occur uniformly across a population. The chances of the same mutation occurring more than once within a population are very small. In the same way, among 100 million lottery tickets there would only be a small number of tickets with the same numbers.
From my understanding, the observed mutation rates are usually well above that needed to produce the adaptive molecular changes we see over time. Mutations have to filter through a population generation after generation, and this can be a slow process. I would also suspect that haplotype blocks, linkage disequilibrium, and other factors in sexual reproduction play a role. To use an analogy, mutations are the gasoline that fuels the engine of evolution, but an engine can only use so much at any given time. Putting more gasoline in the tank doesn’t make the car go any faster.
There’s also the issue of the mutation rate exceeding the ability of natural selection to remove deleterious mutations.
Please forgive me in advance for asking a stupid question. If a population is being exposed to the same type of radiation or source of mutation, wouldn’t that increase the likelihood for mutations to be similiar?
Also, you may like to consider another question I am trying to get posted on r/askscience about the possible effect cosmic rays will have on the chemistry of seawater over a 20 million year period.
1 Like