20 March: evolution and devolution, big cats and other things.

Jerry Coyne has an interesting post on mimicry in nature: this happens when one animal evolves to resemble something else; for example, sometimes an animal can evolve to look like something that preys on its natural enemies. However, read the post all the way down; there is a case in which the females evolved more mimicry than the males: though more mimicry might help the males live longer, it might have cost them potential mates if the females retained preferences for the “lesser evolved” males.

Here is a case in which swallows are evolving smaller wings….and at the same time, we are finding that fewer swallows are becoming roadkill:

A new study out of the University of Tulsa in Oklahoma seems to suggest that the cliff swallows there are adapting to their modified environments in an interesting way. Researchers found their wings may be getting shorter to help them take get out of the way of traffic.

“We found that by picking up dead birds killed by vehicles over the last 30 years, the wing lengths on these birds has changed, and we’re finding many fewer dead birds now than we were finding 30 years ago,” said Professor Charles Brown of University of Tulsa in Oklahoma. “So it looks like something is going on in the population enabling these birds to better avoid being hit by cars.”

According to data collected in the study, the swallows’ wing span decreased about 10 percent. Though that is not a large number, Brown says it’s significant because it’s happening in birds.

“It’s actually quite a bit as bird morphology goes,” said Brown. “Bird morphology is fairly static, it doesn’t really change much in response to selection, and this is actually a very dramatic change in a morphological trait.”

Though scientific evidence points to how natural selection allowing swallows to avoid being killed by vehicles, there are many other environmental factors that can contribute to such a evolution. For instance, Brown says that a change in the availability of insects, the bird’s natural prey, and changes to their habitat are factors to consider. Also, natural selection fluctuates over time, so adaptations we’re seeing now could cease to exist in the long term.

We shall see. Interesting, no?

I don’t get this behavior
I am not a Big Cat person (at all) but this is an awesome short video. It shows a cheeta paying a visit to some tourists in a tourist truck. It doesn’t really threaten the people in the truck, but it gets up close and personal; it “almost” behaves like a pet….a standoffish pet.

(hat tip: Jerry Coyne)

This is sort of random, but Jeffrey Shallit posts about a recently deceased mathematician and gives one of his results:

Here is a very simple, yet little-known result that proved useful to me recently. I’m surprised it is not better known, since it seems to be a natural question.
Suppose you have a directed graph G = (V,E) with n vertices that is strongly connected (so there is a directed path from every vertex to every other vertex). Consider the length of the shortest closed walk W that visits every vertex. In the worst case, how long can W be?

Here, as usual, by a “closed walk” we mean that we start at some vertex and return to it, and we are allowed to repeat vertices and edges. We measure the length of W by the number of edges, and write it as |W|. Such a walk is sometimes called a “Hamiltonian walk” in the literature.

The answer is floor((n+1)2/4). This simple result was apparently first proved by Yahya Ould Hamidoune, in Proposition 2.1 of his paper published in Discrete Mathematics 26 (1979), 227-234. Hamidoune just recently passed away; he was apparently one Mauritania’s most famous mathematicians, and proved many deeper results than the little proposition above. But his graph inequality might prove useful to others, so I reproduce his proof here.

Surf to Shallit’s blog to see the proof; it is one that, even if you aren’t a specialist, you can get something out of (with some intellectual effort).

Paul Krugman
He gets just a little bit snarky and I love it.
First, he cautions people:

Some readers have asked me to reply to this Steve Keen piece claiming that I don’t understand the IS-LM model. Sigh. I really don’t want to spend time fighting against people with whom I don’t really have a current policy disagreement — and this is so silly, besides. But to satisfy those who are for some reason nervous, here’s a brief explanation of why somebody doesn’t understand IS-LM.[…]

He then says, aha! The IS market is out of equilibrium when we’re in a liquidity trap, but Krugman writes as if it were in equilibrium! Gotcha!

Um, it pays to read the labels. Those savings and investment curves are what the supply and demand for funds would be if the economy were at full employment. They’re not the curves that actually apply when the economy is operating below full employment. In the IS-LM model, the quantity of funds supplied is always equal to the quantity of funds demanded — because the level of output adjusts. This is true both when the zero lower bound applies and when it doesn’t. […]

So what Keen thinks is a big logical fallacy on my part is just a failure of reading comprehension on his part.

Look, IS-LM could be all wrong; but I am accurately reflecting the way that model works. And while I am not infallible, I have done a lot of economic modeling in my time; if you think that I’ve made an elementary logical error, you might want to check your reasoning very carefully before going with it.

Seriously folks. These smart, famous people are sometimes wrong about conjectures or sometimes make mistakes. But they almost NEVER make “elementary mistakes” such as these. If you think that your “common sense” has found an elementary flaw in their work, YOU are almost certainly wrong.

Now what about conservative critics (mostly non-specialists): Krugman has little patience with them:

All of which raises an interesting question: why don’t people like Hinderaker who have been wrong about everything for years and years — demonstrably wrong, in ways that would have lost anyone who believed them a lot of money — ever reconsider? Shouldn’t the thought at least enter their minds that maybe economic analysis is not their strong point? Shouldn’t they at least entertain the notion that they are talking to the wrong “experts”?

So why doesn’t this happen? Part of it, surely, is the Dunning-Kruger effect: the truly incompetent are too incompetent to realize that they’re incompetent. Part of it, also, is the Madoff “affinity fraud” effect: people trust someone they perceive as part of their tribe — in this case the tribe of liberal-haters — and are blind to evidence that they are being taken for a ride.

The surprise, I’d say, is just how strong the Dunning-Kruger-Madoff effect has proved in the face of economic crisis. Year after year in which the predictions of their crowd have gone totally astray haven’t shaken their faith at all. They still believe that reading the WSJ editorial page and watching Fox are the way to know what’s going to happen to the economy, and nothing will change their minds.

Here is what I think that Krugman misses (remember, this is NOT economic policy but a conjecture as to why Fox and company stays in business despite getting just about everything wrong):

The Wall Street Journal and Fox are more about entertainment than anything else. People(*) often see “truth” as “what makes sense to me” and “what confirms what I already think”. These media outlets cater to that crowd. Accuracy is of no importance; it is about keeping the reader entertained.

(*): I used to think of this as a characteristic of conservatives, but have found that it really isn’t “just” conservatives. I am prone to making this mistake too and therefore have to be vigilant.

Michele Bachmann
She doesn’t appreciate it when she gets called out for just making stuff up. This is just over 9 minutes (from CNN) and is hilarious.


March 20, 2013 - Posted by | economics, economy, evolution, mathematics, media, politics, politics/social, science | , ,

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