
Evolution Runs Faster on Short Timescales - jonbaer
https://www.quantamagazine.org/evolution-runs-faster-on-short-timescales-20170314/
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Jach
Is this all that surprising? If mammals tend to have genome sizes of around
1-10 pg, and a mutation has a chance of around 10^-8 per base, then you would
expect around 10-100 mutations per generation. So if you were sampling random
members of a species at close periods in time, you would probably see a lot of
genetic variation, but over wider stretches of time, the later samples are
only descendants of the old genes that reached fixation and survived, plus
whatever new mutations centered around the later time. Fixation is slow and
depends on the mutation's positive selection benefits and the overall
population count, but some mutations happen every generation and most aren't
positive... With viruses their mutation chance is even higher... This is just
from references in the 90s, so is Ho's result just a nice math model to better
take into account time scales with samples?

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daxfohl
Agreed, I was surprised this was surprising. I saw some study where some moths
can evolve from white to black in a couple generations if they go from white
bark forests to black bark forests. But that doesn't mean they'll evolve into
something unrecognizable in a hundred generations.

I was just looking at Taylor expansions today (guid uniqueness...birthday
problem), so, this kind of reminds me of that. First you evolve, then you
evolve the ability to evolve, then you evolve the ability to evolve the
ability to evolve, etc. So maybe there's a formula.

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foota
What do Taylor expansions have to do with guid uniqueness and the birthday
problem?

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daxfohl
[https://en.wikipedia.org/wiki/Birthday_problem#Approximation...](https://en.wikipedia.org/wiki/Birthday_problem#Approximations)

~~~
foota
Interesting, thanks.

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joe_the_user
This seems entirely in harmony with Stephen Jay Gould's theory of punctured
equilibrium. [1] "Punctuated equilibrium (also called punctuated equilibria)
is a theory in evolutionary biology which proposes that once species appear in
the fossil record they will become stable, showing little evolutionary change
for most of their geological history. This state is called stasis. When
significant evolutionary change occurs, the theory proposes that it is
generally restricted to rare and geologically rapid events of branching
speciation called cladogenesis."

Species experience perturbations in their genetic expression constantly but
these only evolve into stable changes when the environment changes to require
it.

[1][https://en.wikipedia.org/wiki/Punctuated_equilibrium](https://en.wikipedia.org/wiki/Punctuated_equilibrium)

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keithpeter
As others have said, I found it surprising that the change in rate with time
scale compared was surprising. Simon Ho's paper is downloadable (link in OA)
and it has a mathematical framework for his discussion. I'm not sure if the
argument is accessible to non-specialists but I'll have a read.

Rabbit hole warning: Björn Kurtén the Finnish paleontologist whose work on
horse fossils was cited early in the OA turns out to be a very interesting
character. He wrote what he described as a 'paleonovel' about encounters
between CroMagnon and Neandertal people...

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veddox
This strikes me as a very hyped article. "It’s like Einstein’s theory of
relativity, but for viruses" \- seriously?! While the proposed explanation for
differing rates of evolution is doubtlessly interesting from a scientific
perspective, it is definitely not as big as this article makes it out to be.

Also the dig at the molecular clock is pointless - we have always known that
there are many unknowns involved when using a "standard mutation rate" to
calculate the time since the divergence between two species. That is nothing
new, and the estimates we have are consequently constantly being revised. The
time-dependent rate is a good addition to our methodologies, but it isn't the
revolution advertised here.

(Oh and by the way, the original paper is from 2005.)

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devoply
Does not seem to me to be like that. Seems to me what this is saying is that
on shorter time scales it tries out many different combinations that when you
look at them on longer time scales have settled into whatever wins that
process. It sort of settles on longer scales of time to the optimal solution
that survives, in shorter periods of time it's experimenting with the search
space. In longer periods of time it's decided on the answer so it converges on
that space. Putting it this way, evolution is just a search to find something
that works or works better, the results being tested continuously by the
environment.

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FullMtlAlcoholc
This makes sense. If a species is thriving and not under much selective
pressure, it does not have to be optimized for its environment to survive.
This allows for a larger amount of genetic variance. Most mutations either are
maladaptions, don't cause any significant change or lead to death while
relatively few confer an advantage. In addition, some adaptations may take
many generations of mutation to actually provide an advantage or may need time
to find a niche where a mutation that is a maladaptation in one environment
may be an advantage in others (Sickle cell anemia gives resistance to malaria,
Tay Sachs does the same for tuberculosis).

When selective pressures/shocks arise, there is a wider amount of genetic
variance that can adapt to the new environment... a larger menu of options for
survival, and this pressure acts as a feedback loop, further promoting that
more mutations in that direction. Think of the pressures that led to the
growth of the giraffe's neck. Perhaps it is this combination... allowing time
for a species to thrive and have genetic diversity and shocks which select for
and promote the evolutionary path

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GedByrne
Does genetic variation rise in response to selective pressure?

It seems to me that this is a two stage process.

1\. Variation is introduced at a fairly constant rate by mutation. 2\.
Variation is filtered out by natural selection based on how well it fits the
environment.

The shocks occur when the environment changes so that the criteria for fit
change and new variations survive for the long term.

So when we look at evolution we see a rate of change driven by the rate of
mutation.

When we look at the long term we see a rate of change driven by the
environment.

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FullMtlAlcoholc
I agree. When I look at the long term though, the environment and mutation are
just different parts of the same whole. Both are necessary for phenotypic
changes and speciation. Even that is simplistic. It doesn't take into account
the significance of viral transfer of dna and other epigenetic factors, how an
environment can cause normally dormant genes to express themselves, sexual
selection where attractiveness != most environmentally fit, etc.

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hNewsLover99
See also the link to "This might be the coolest visualization of evolution
ever" and comments re: "Wolf359" and "Microcosmic God" by Theodore Sturgeon
at...

[https://news.ycombinator.com/item?id=12467015](https://news.ycombinator.com/item?id=12467015)

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kmonad
Here are the first sentences of the first comments on this thread I read:

Is this all that surprising?

I was surprised this was surprising.

I think the issue is local optima.

Does not seem to me to be like that.

This makes sense.

...you guys ^^

