
Urban Evolution: How Species Adapt, or Don't, to City Living - Thevet
https://www.edge.org/conversation/jonathan_b_losos-urban-evolution
======
kwhitefoot
I think that was a rather confusingly written article. It uses the word
evolution in several different senses which means that it is hard to see if
the writer really understands the subject. Yet, he is a professor at Harvard
so I think it is safe to assume that he really does understand it.

The problem is that a careless reader could quite easily skim the article and
conclude that the moths, for instance, had undergone genetic changes as a
result of the environmental changes when all that had happened was that the
proportion of the population that was darkly pigmented had increased,
presumably because predators were able to see the lighter variants more
easily. If it had continued long enough it is quite possible that this
variation in frequency could have become fixed by driving the light coloured
variants out entirely.

But evolution, as I understand it anyway, is the combination of mutation plus
the fixation of that mutation through differential survival; that is we have
to include the origin of the light and dark varieties as well as the
differential survival of them.

Lastly this:

> The moths evolved to become dark in order to match the background of these
> trees.

That's backwards. The dark variants already matched the trees, selection
pressure (differential predation) caused that variant to become more frequent
in the population when the environment changed.

It would make sense to say:

The moth population evolved to become dark because they matched the background
of these trees thus resulting in fewer of them being eaten by birds.

But even that is open to misinterpretation because not everyone will
distinguish between the moths and the population.

There is no shortage of well written works on this subject so it is a pity to
see a confusing one mentioned on HN.

I personally recommend Almost Like a Whale: The 'Origin of Species' Updated by
Steve Jones for a popular rendering and The Blind Watchmaker and The Extended
Phenotype by Richard Dawkins for those wanting a more technical explanation.

A disclaimer: unlike itchyjunk I really am not an expert, just a moderately
well read engineer with physics degree.

------
itchyjunk
"The moths evolved to become dark in order to match the background of these
trees." "Those guppies evolved to be very colorful, over the course of just
two years." "Over ten years they evolved significantly shorter legs."

Remember, the variation already existed. There were already white and dark
months in the population and natural selection caused increase or decrease in
the ratios. The black moth did not evolve into white. The variation for short
and long legs already existed. Short legs probably increased reproductive
fitness in once case and not the other. Causing the number of individuals with
certain trait to increase or decrease. My professor has repeated this the
entire semester and she wants us to never forget that mutation is the only
source of variation. If the variation is not already present, natural
selection cannot trigger it. This is how some species go extinct. Natural
selection is one source of evolution. Also, distinction between micro vs macro
evolution is important here. [0]

"But there's no reason to believe this. Why shouldn't they be adapting to our
conditions just like any other evolutionary situation?"

Because natural selection doesn't cause variation. Mutation is the only source
of variation. Variation must already exist in a population for natural
selection to work on it.

"What she found was that in each case they had changed. The lizards in the
city had evolved longer legs—presumably useful for hanging onto broad
surfaces, like walls—and they had evolved bigger toe pads—again, presumably to
hang on to the smooth surfaces in cities. "

Giraffe's neck get longer with usage is a Lamarackian theory which is an
outdate model because we know only changes in the sex genes are passed on to
offspring. [1]

"Evolutionary biologists have become very interested in recent years in a
higher-level analog of this, and that is the mixing of different
species—hybridization—when two different species interbreed and are able to
successfully reproduce."

Depends on your definition of species, there are many. [2] The biological
definition is one where if they fail to see each other as potential mate
naturally and produce sterile offspring, they are different species. So I am
not sure which of the 13ish popular definition I am supposed to apply to this.
And genetic definition always considered more variations to be good. So that
one won't work here either.

"When wolves were around, coyotes were small. But, you get rid of the wolf,
suddenly, there's this great opportunity for coyotes to evolve to get bigger
and eat the bigger food that the wolves aren't taking, such as deer."

There is no selective pressure so both big and small coyotes would increase in
number. I know where this is from though, we watched the video in class. It's
called "How wolves change the river."[3]. It's really good, please watch it.

"Are they just mutations for larger size that then get taken advantage of by
natural selection? That can happen, it might play a role, but it seems more
likely in the case of a coyote that it's the result of hybridization"

So the author is aware of the concepts but it just brushing them off?

"Think about weightlifters, for example. If you spend your life lifting
weights, you'll develop very big muscles and thick bones. But that is not a
genetic change. You have not evolved. "

Correct, it means that variation "genotype[4]" is already present. "Those
differences will not be passed on to your offspring."

Incorrect. there is a change that the genes that allowed for larger muscles in
you will be passed on. Just the "phenotype" won't pass. The kid wont be born
with big muscles, but like you, if he exercises, he might get similar muscle.

I don't see citation for any of the claims on the articles. If I missed it, I
apologize. I am not an expert and these are just my opinions based on my very
limited understanding on the subject matter. Feel free to correct me.

\-------------

[0]
[http://evolution.berkeley.edu/evolibrary/article/evoscales_0...](http://evolution.berkeley.edu/evolibrary/article/evoscales_01)

[1]
[http://natureinstitute.org/pub/ic/ic10/giraffe.htm](http://natureinstitute.org/pub/ic/ic10/giraffe.htm)

[2]
[http://evolution.berkeley.edu/evolibrary/article/evo_41](http://evolution.berkeley.edu/evolibrary/article/evo_41)

[3]
[https://www.youtube.com/watch?v=ysa5OBhXz-Q](https://www.youtube.com/watch?v=ysa5OBhXz-Q)

[4]
[https://en.wikipedia.org/wiki/Genotype](https://en.wikipedia.org/wiki/Genotype)

Edit: Added white space for clarity as suggested.

~~~
imartin2k
May I ask: If you are not an expert and only have opinions and "very limited
understanding on the subject", and if we consider this subject to be extremely
complicated and research-heavy, why do you then put so much effort in writing
a lengthy comment and what's the value of it for others?

Or are you actually an expert and were just trying to be humble?

~~~
itchyjunk
I came across evolutionary theory in an Anthropology class. I am not asking
anyone to take my word for it, but maybe at least inspire some to double check
the information provided. I get a lot out of HN comments and this is just my
attempt to give back.

~~~
kwhitefoot
Having taken, and paid attention to, an anthropology class makes you
considerable more expert than most people, including I think most of us on HN.

I'm not totally familiar with US terminology, I presume this means a course in
anthropology, perhaps lasting one term or semester?

But, "came across", sounds a bit accidental. Isn't evolutionary theory central
to anthropology?

I'm just an interested layman in this field (with a book shelf full of Richard
Dawkins, Charles Darwin, Stephen J. Gould, Daniel Dennett, Steve Jones, as
well as sundry textbooks).

~~~
itchyjunk
Yes, the course is called Introduction to Physical Anthropology (1020). It's a
1 semester 3 credit class. Yup, most of the course introduced what evolution
is, how it's studied, variation, macro-micro evolution etc. It than applies
this to living primates and Hominin remains. I phrased the way I did because
our professor said that other than some fundamentals, no one agrees completely
on anything and there is a lot of school of thought. So the author might
subscribe to some other school of thought, I wouldn't know. But it contradicts
a lot with what I was taught so I felt I should point it out.

