
Chicken study reveals evolution can happen faster than thought - dnetesn
http://www.ox.ac.uk/news/2015-10-28-chicken-study-reveals-evolution-can-happen-much-faster-thought-0
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ppod
I never really understand the view that evolution can only happen over long
timescales. From a theoretical perspective, natural selection can obviously
have a huge effect over a single generation.

Imagine that the ability to swim was an extremely heritable, genetically
determined trait. A flood on an island could select for the swimming gene in
about 30 minutes.

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astazangasta
Selection cannot act over a single generation, if by 'act' you mean that an
allele fixes in the population (reaches 100% frequency). If a new mutation
appears in a single individual, it cannot in the next generation be present in
every individual, unless the founder's progeny replace everyone else's. In any
event this would be a disaster for overall fitness, since the level of genetic
diversity would collapse.

In general selection propagates a variant exponentially fast based on the
reproductive advantage it confers. If you make 1000 progeny and I make 1001,
my reproductive advantage is 1.001 - every generation the frequency of my
variant relative to yours goes up by this factor. If I start at frequency f
and my advantage is s, it will take n=ln(1/f)/ln(s) generations to fix
(approximately). For the example above with f=1%, this gives about 4607
generations.

There are other factors, notably population size. For a population of size N,
the initial f will be 1/N. If N is small, f will be larger and selection will
take less time. On the other hand, in a small population, genetic drift is
stronger, and weakly selected variants are more likely to be eliminated by
drift before they can fix.

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mutagen
Paper:
[http://rsbl.royalsocietypublishing.org/content/11/10/2015056...](http://rsbl.royalsocietypublishing.org/content/11/10/20150561)

What are the implications for dates obtained with mitochondrial DNA? I suppose
the answer for anything beyond chickens or maybe other birds is "More research
needed".

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pluckytree
The chicken crossed the road to speed up the process of evolution and natural
selection.

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legulere
> Previously, estimates put the rate of change in a mitochondrial genome at
> about 2% per million years. At this pace, we should not have been able to
> spot a single mutation in just 50 years, but in fact we spotted two.'

Doesn't sound as spectacular as the rest of the article.

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taneq
So basically n=12, and they saw 2 instances of one thing and 1 instance of
another. Sure, maybe p<0.05 but a larger sample size wouldn't go astray.

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kirushik
Previous discussion:
[https://news.ycombinator.com/item?id=10462246](https://news.ycombinator.com/item?id=10462246)

~~~
dang
Not a dupe because it didn't get significant attention (and since it looked
good, we invited dnetesn to repost it). But we did merge the two comments
there into this thread.

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dang
Url changed from [http://phys.org/news/2015-10-chicken-reveals-evolution-
faste...](http://phys.org/news/2015-10-chicken-reveals-evolution-faster-
thought.html) to a more original source.

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DonHopkins
Then how fast is thought?

How do you even measure the speed of thought?

And who cares what chickens think?

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just_curioussss
_A new study of chickens overturns the popular assumption that evolution is
only visible over long time scales._

And yet the popular assumption remains the same, because it is the ignorance
of the general public that perpetuates it and not the lack of research.

The solution: stop calling it popular assumption and start treating it as
fact, journalists.

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PepeGomez
I've read your comment three times and I still have no idea what it's supposed
to say.

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dwc
It's been known for a long time that much of evolution happens in spurts. When
the environment is fairly stable evolution is a slow refinement toward local
maxima. When the environment changes there's much more selection pressure and
evolution happens much more quickly.

So, this one study doesn't tell us much new about the speed of evolution
(because we already knew), and there's no reason to think _this_ study will do
any more to correct common misconceptions than previous science.

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PepeGomez
Maybe that's what just_curioussss meant, but he wrote the opposite.

