
New paper claims that evolution has stopped in a bacterial species. Is it true? - tokenadult
https://whyevolutionistrue.wordpress.com/2015/02/04/a-new-paper-claims-that-evolution-has-stopped-in-a-bacterial-species-is-it-true/
======
Udo
> _if there’s no selection pressure on the organism, it will not evolve_

This is (and the article agrees) a statement not compatible with modern
evolutionary understanding. Primary school-level knowledge about biology
should be enough to debunk this claim: a set of genes survives if there are
organisms that pass those genes on, it's as simple as that.

If there is a mutation in a homogenous group of individuals, and that mutation
is not lethal or otherwise causes the individual to die before procreation,
that mutation survives - selection pressure or not.

There are also genomes that remain highly preserved over long stretches of
time, which should likewise not be surprising. This occurs even at the gene
level: there are genes in all of us pretty much unchanged compared to early
eukaryotes, mostly because the proteins they produce work well, but also
because mutations to those sequences are generally lethal.

While most mutations are lethal, it's not true that the remaining ones are
beneficial either. This means there are lots of individuals with sometimes
distinctive properties which are still causally disconnected from selection
pressure.

Anyone who spent some time experimenting with evolutionary models on a
computer should know this, because those are intrinsic properties of genetic
systems. We _expect_ them to behave that way. We expect ancient versions of
organisms to stick around if there was no reason for them to die out. That
doesn't mean the reverse is true in the sense that no change in selection
pressure leads to genetic stagnation.

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lotsofmangos
Even if it had stopped in this bacteria, and it sounds as though there is
nowhere near enough evidence to make that claim, it doesn't mean it cannot
start again.

Evolution is an event driven process and given there is time between events,
there can be a long time between events.

And if there were no possibility of time between those events, everything
would look like the end of Akira.

------
tsomctl
There are so many different species of bacteria that it is hard to estimate
how many there even are, but according to Wikipedia, it might be between 10^7
and 10^9. I'd be willing to bet that there is a healthy species of bacteria
that has stopped evolving, that perfectly copies its dna when it divides, and
never transfers dna horizontally. There's no technical reason not to, and the
numbers are so huge that they almost guarantee it.

~~~
chrisamiller
> I'd be willing to bet that there is a healthy species of bacteria that has
> stopped evolving, that perfectly copies its dna when it divides, and never
> transfers dna horizontally

There are several flaws in your argument: 1) There is no known polymerase that
has a fidelity of 100%. There will always be some number of replication errors
when DNA is synthesized. 2) There are lots of mutagens in the environment. UV
light, mutagenic chemicals, hell, even radioactive decay of mostly-stable
elements will occasionally hit a base and cause a mutation.

So, no, there is certainly no species that meets your criteria for non-
evolving.

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Houshalter
Well organisms do get stuck in local optima all the time. If you only climb
up, eventually you will get to the top of the hill and stay there.

Second, sexually reproducing organisms, _theoretically_ , will decrease their
mutation rate over time until eventually they no longer mutate at all. And so
no longer evolve.

Most (non-neutral) mutations are harmful. So any gene that decreases mutations
(e.g. better DNA copying or repair) will have fewer unfit, mutant children.
These children will than propagate the gene more. Even if a gene that causes
higher mutations eventually creates beneficial mutations, they will just mix
into the general population after a few generations, and not provide a fitness
advantage.

~~~
GuiA
1\. The notion of "local optima" for biological species is ill conceived. The
world is complex and extremely dynamic; "local optima" isn't a very meaningful
concept in the context of evolution.

2\. "Most mutations are harmful" -> this is patently false. A lot of mutations
are inconsequential, some are harmful, some are beneficial.

3\. "sexually reproducing organisms, theoretically, will decrease their
mutation rate over time" -> this isn't true. Mutation rate is variable over
species and over time.

4\. DNA duplication is a complex biological process with many moving parts.
There isn't such a straightforward thing as a "gene that decreases mutation".

~~~
Houshalter
>The notion of "local optima" for biological species is ill conceived. The
world is complex and extremely dynamic; "local optima" isn't a very meaningful
concept in the context of evolution.

Changing environments can help organisms break out of local optima, but that
doesn't imply they don't exist. There are countless examples of organisms
getting stuck in local optima. E.g. horseshoe crabs haven't changed in
hundreds of millions of years.

Most traits in general are stuck in local optima. Theoretically large changes
could improve them, but it's unlikely to happen by random chance.

>"Most mutations are harmful" -> this is patently false. A lot of mutations
are inconsequential, some are harmful, some are beneficial.

Who are you quoting? I never said that. I said most _non-neutral_ mutations
are harmful. Neutral mutations don't do anything and so don't matter.

>Mutation rate is variable over species and over time.

>DNA duplication is a complex biological process with many moving parts. There
isn't such a straightforward thing as a "gene that decreases mutation"

There are many mechanisms that control mutations, like DNA repair and copying
mechanisms, or shielding from radiation and mutagens, etc. Of course it's
probably very difficult to reach perfection, which is why organisms still
evolve. I just said theoretically, evolution is always pushing towards less
evolution.

~~~
GuiA
> E.g. horseshoe crabs haven't changed in hundreds of millions of years.

No. They may have barely changed in morphology, but that doesn't mean they are
"stuck in local optima". And even then, it seems they have changed
morphologically in some ways.
[https://whyevolutionistrue.wordpress.com/2012/09/14/horsesho...](https://whyevolutionistrue.wordpress.com/2012/09/14/horseshoe-
crabs-arent-living-fossils-2/)

> I said most non-neutral mutations are harmful.

That is just false, and I don't know how you came to that idea.

> Neutral mutations don't do anything and so don't matter.

Again, false. Mutations can have no impact on a population until that mutation
interacts with another mutation (e.g. because the population bred with another
population that has other mutations), resulting in a net evolutionary
advantage for the species over time.

> Of course it's probably very difficult to reach perfection, which is why
> organisms still evolve.

There isn't a notion of "reaching perfection" in evolution. That's a
fundamental misunderstanding of how it works.

> I just said theoretically, evolution is always pushing towards less
> evolution.

No. There is no "theoretically"\- evolution is a well observed and documented
process. And if you observe and document the real world, you will notice that
the evolutionary process is certainly not pushing towards "less evolution".

Please stop posting misinformed comments that may confuse or mislead readers
who take them to assume you have a good understanding of the topic. If you
wish to comment on the topic, please take the time to inform yourself first
from scientists who work in the field, rather than from your own baseless
speculation. A good start is here:
[http://evolution.berkeley.edu/evolibrary/misconceptions_faq....](http://evolution.berkeley.edu/evolibrary/misconceptions_faq.php)

~~~
Houshalter
>They may have barely changed in morphology, but that doesn't mean they are
"stuck in local optima".

That's exactly what that means. Their morphology is stuck in a local optima at
the very least. And unless you really believe horseshoe crabs are the ultimate
form of life and it's impossible for organisms to improve at all, then it is
"local".

>That is just false, and I don't know how you came to that idea.

And I don't know how you disagree with it. Do you really believe that most
mutations are beneficial? Really? If so, exposing yourself to radiation would
be beneficial for your health. Or your childrens fitness.

This is just utterly ridiculous and defies all logic. Mutations are almost all
negative.

>Again, false. Mutations can have no impact on a population until that
mutation interacts with another mutation (e.g. because the population bred
with another population that has other mutations), resulting in a net
evolutionary advantage for the species over time.

Then, by definition, it's not a neutral mutation. It's slightly positive, or
slightly negative, or really positive, or really negative, but if it has an
effect at all, it's not neutral.

>There isn't a notion of "reaching perfection" in evolution. That's a
fundamental misunderstanding of how it works.

Perfect as in having the best fitness possible. A global optima. Where no
mutation could improve it at all.

>No. There is no "theoretically"\- evolution is a well observed and documented
process. And if you observe and document the real world, you will notice that
the evolutionary process is certainly not pushing towards "less evolution".

I'm sorry you don't know what the word "theoretically" means. My hypothesis is
"If there is a gene that decreases mutation rates in a sexually reproducing
population, it should be selected for over time."

This hypothesis would be difficult but not impossible to test in the real
world. If we could find a gene that decreases mutation rates and introduce it
to an animal that doesn't have it, and observe them for many generations. It
could also be easily tested in computer simulations.

>Please stop posting misinformed comments that may confuse or mislead readers
who take them to assume you have a good understanding of the topic. If you
wish to comment on the topic, please take the time to inform yourself first
from scientists who work in the field, rather than from your own baseless
speculation.

Please stop being pedantic and misinterpreting everything I say.

