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Mathematical Modelling 101: Introduction & Viability Selection

July 12, 2010

I think the best place to start would be to state the following: Do not fear math. I spent far too long dodging equations and, when that wasn’t possible, freezing in a state of absolute confusion when faced with something like:

By the end of this post, you’ll hopefully be able to understand the above is not just a bunch of jibberish. Now before we get into the nitty gritty of the subject, I think a clarification of my assumptions is in order:

  1. That you’ll have a basic understanding of evolutionary biology. If not, then may I suggest Evolution as a very good, and highly comprehensive, introductory text. Failing that, you can always pop over to the wikipedia page.
  2. Although these posts will refer to evolutionary biology, my background is in linguistics and socio-cultural evolution — and as such, I will tend to default to the position of explaining these latter areas.
  3. It might sound insulting, but you’ll also need a basic understanding of math. You’ll be surprised by the number of people who, despite being very bright, lack even an elementary grasp of the fundamentals. A good place to start is with Kahn Academy’s wonderful online resource: http://www.khanacademy.org/.
  4. Having said that, I’m not really expecting anything beyond algebra level math, and I’ll do my best to try and clarify any confusions in the comments section. Also, I’m hardly a math guru, so I welcome anyone with a solid background in math to provide any hints, tips or suggestions, and, in the event I’m plain wrong, point out any mistakes.

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Some links #8: Are you WEIRD?

July 10, 2010

We agree it’s WEIRD, but is it WEIRD enough? Greg Downey at Neuroanthropology gives his take on Henrich et al.’s paper The weirdest people in the world? which looks at acronym WEIRD (Western, Educated, Industrialized, Rich, and Democratic) and how we may be extrapolating too much from this particularly narrow data set. Yet, despite this, we continue to use WEIRD individuals in psychological experiments, even though it may not be representative of, say, the large body of Africans. I mean, come on, you wouldn’t take genetic data from Western Europe and then make sweeping generalisations about populations in Western Africa…

The Human Penis Bone. From WEIRD to just weird. Scicurious reviews a very old journal article from 1913, which tells of a guy who actually grew a penis bone. Now, many mammals do have penis bones, but human males generally lack this ossified aid. However, if you’re curious about how to get one, then all you have to do is simply wear a particular type of corset (see below) and, here’s a downside for those of you planning on ditching the Viagra, get syphilis. As Scicurious explains:

The syphilis, combined with the constant irritation of the corset, had apparently caused a build up of desposits, which eventually ossified and turned in to bone. REAL BONE, with marrow and holes in it and everything! […] So the moral of this story is: if you’re a guy, and you’re vain about your appearance, get a flat front corset. You don’t want to be sitting down in something pointy.

Wild cat found mimicking monkey calls. Some clever vocal mimicry from a margay. ScienceDaily reports:

Researchers first recorded the incident in 2005 when a group of eight pied tamarins were feeding in a ficus tree. They then observed a margay emitting calls similar to those made by tamarin babies. This attracted the attention of a tamarin “sentinel,” which climbed down from the tree to investigate the sounds coming from a tangle of vines called lianas. While the sentinel monkey started vocalizing to warn the rest of the group of the strange calls, the monkeys were clearly confounded by these familiar vocalizations, choosing to investigate rather than flee. Four other tamarins climbed down to assess the nature of the calls. At that moment, a margay emerged from the foliage walking down the trunk of a tree in a squirrel-like fashion, jumping down and then moving towards the monkeys. Realizing the ruse, the sentinel screamed an alarm and sent the other tamarins fleeing.

Nongenetic selection and evolution: flies use bacteria to adapt to parasitic worms. Jerry Coyne has a fascinating post about nongenetic evolution occurring in a mushroom-eating fruit fly Drosophila neotestacea. But how is it nongenetic? Well, as Jerry explains:

A new paper by John Jaenike and his colleagues in Science, however, shows a form of biological evolution by natural selection that isn’t based on changes in genes. It’s based on changes in the presence of symbiotic bacteria that protect a species from parasites […] Some flies also carry another organism: the bacterial symbiont Spiroplasma, which is found in many insects.  In D. neotestacea, however, the presence of Spiroplasma protects the fly from the sterilizing effects of nematodes.  While flies with worms and no Spiroplasma are virtually sterile, the presence of the bacteria confers almost normal fertility on worm-ridden flies.  It’s not yet clear how this works, but worms in flies with Spiroplasma are much smaller than those without the bacteria. Presumably the bacteria does something to the worms (or to the flies) that makes the worms grow much more slowly.

Some Links #7

July 9, 2010

Deconstructing Chomsky — Rewriting the innate rules of grammar. Andrew Caines over at the Naked Scientist has a good, layman’s article on Chomsky’s conception of UG and Dan Everett’s recent book Don’t Sleep, There Are Snakes: Life and Language in the Amazonian Jungle. It’s quite a good introduction for anyone who is open to the possibility that  psycholinguistics doesn’t end with Chomsky (or Pinker for that matter).

New developments in AI. An in-depth article on artificial intelligence over at .CSV. I’m only half-way through the article, but I thought it was worth mention as, the first half at least, is pretty good. H/T: Mind Hacks.

Many English Speakers cannot understand basic grammar. Apparently, “Research into grammar by academics at Northumbria University suggests that a significant proportion of native English speakers are unable to understand some basic sentences”. Language Log and John Hawks have both picked up on the story. Once the paper is released I’ll probably write an in-depth post at GNXP.

Birth Months of World Cup Players. A short, but interesting, post over at GNXP debunking the relevance of your birth month in regards to sporting achievement. I never thought there was any controversy over the issue… But it turns out I was wrong.

Mathematical Formula Predicts Clear Favorite for FIFA World Cup. Keeping with the football theme, and apparently this formula predicts a Spanish victory. The psychic Octopus appears to think so too. I disagree. Go Netherlands!

How many Zombies do you know? Applied Statistics links to yet another Zombie-inspired study.

Dr Evan Harris. Not a link to a particular article, but it’s just nice to see Dr Evan Harris back writing his blog after being defeated in the recent UK elections.

PepsiCo has been expelled. For those of you who don’t know what this headline’s about, don’t worry, it was all just a very bad dream.

Can linguistic features reveal time depths as deep as 50,000 years ago?

July 8, 2010

ResearchBlogging.orgThroughout much of our history language was transitory, existing only briefly within its speech community. The invention of writing systems heralded a way of recording some of its recent history, but for the most part linguists lack the stone tools archaeologists use to explore the early history of ancient technological industries. The question of how far back we can trace the history of languages is therefore an immensely important, and highly difficult, one to answer. However, it’s not impossible. Like biologists, who use highly conserved genes to probe the deepest branches on the tree of life, some linguists argue that highly stable linguistic features hold the promise of tracing ancestral relations between the world’s languages.

Previous attempts using cognates to infer the relatedness between languages are generally limited to predictions within the last 6000-10,000 years. In the present study, Greenhill et al (2010) decided to examine more stable linguistic features than the lexicon, arguing:

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What we’re not talking about

July 8, 2010

Without trying to sound too sensationalist: ScienceBlogs is seeing a mass exodus of writers. The main reason revolves around Seed Media, the parent company of ScienceBlogs, selling blog space to advertisers. As MarkCC, of Good Math, Bad Math, notes:

Seed has, in its corporate wisdom, decided to let Pepsico buy its way into a blog on ScienceBlogs. Pepsi writes SMG a nice check, and suddenly their content gets mixed in to the ScienceBlog RSS feeds, the ScienceBlog feed to Google News, etc., exactly the way that my blog posts do.

This is not acceptable.

For now, I’m suspending my blog for a few days. If Seed decides to back out of this spectacular stupidity, then I’ll start posting here again. If not, then I’ll go looking for a new home for GM/BM. The money that I’ve made from the ads that Seed has sold has been nice – but it’s not worth my integrity.

If Blogs here are for sale, then I’m gone.

The blog in question is Food Frontiers. What’s it all about? Well, as the opening article itself states:

On behalf of the team here at ScienceBlogs, I’d like to welcome you to Food Frontiers, a new project presented by PepsiCo.

As part of this partnership, we’ll hear from a wide range of experts on how the company is developing products rooted in rigorous, science-based nutrition standards to offer consumers more wholesome and enjoyable foods and beverages. The focus will be on innovations in science, nutrition and health policy. In addition to learning more about the transformation of PepsiCo’s product portfolio, we’ll be seeing some of the innovative ways it is planning to reduce its use of energy, water and packaging.

Is it just me, or does that paragraph leave a sickly taste in your mouth? Maybe I’m just a synaesthete for blatantly corporate PR gimmicks. There are, of course, many arguments to be had about the role of advertising on blogs — it needs to generate money, after all. Still, whether you care or not about the ethics of the situation, I think ScienceBlogs made a very bad move not to consult their writers before going ahead with this.

N.B. If you’re worried about who has left and, more importantly, where they’ve gone, then Skulls in the Stars is keeping track of the situation: The Sciencebloggosphere is a changing. Of the blogs I regularly read, only one of them has made the move: Neuron Culture. The other blog I read, Laelaps, is still undecided as to where he’s going to take up permanent residence. You can, however, follow his twitter feed: http://twitter.com/laelaps.

There’s definitely something wrong with your model when Serbia are finalists

July 7, 2010

I came across this rather amusing model for predicting football results using mostly economic data (click on image for full screen):

Now, we all know Brazil aren’t going to win the world cup, but most of us would’ve predicted they’d fare quite well, and possibly win it (my own failed prediction was with Argentina). What’s dubious about the algorithm their using is it predicted Serbia to be finalists! How the hell did they arrive at that conclusion? Well, to give you an indication they do discuss some of the factors included in the model. I’ll definitely be coming back to this when I’ve got a spare moment… They did, however, predict Germany would face, and subsequently knock out, England in the last 16.

Some Links #6: We are all Keynesians now. Yeah, but which type?

July 7, 2010

If you think economic cuts are necessary, you’re being fooled. Martyn Winters (known to me as dad) writes about Joseph Stiglitz’s thoughts on George Osborne’s attempts to reduce the deficit:

You may have heard of Professor Joseph Stiglitz – he’s the Nobel laureate economist who correctly predicted the global crash. He’s distinctly unimpressed with Osbourne’s budget. This, he predicts, will make Britain’s recovery from recession longer, slower and harder than it needs to be. The rise in VAT could even tip us into a double-dip recession. He took time to offer George Osbourne a bit of advice – which will probably go unheeded, because Osbourne’s objectives aren’t necessarily to improve the economy. They are an ideological attack on the state, with the intention of shrinking it by forty percent.

The basis for this is part Keynesian, and has been echoed by other commentators such as Johann Hari, in that we must spend our way out of economic woes. Now I must admit I’m not too fond of how Osborne is going about reducing deficit (raising VAT… huh?), but, for reasons that’ll become apparent below, I do think we need to tackle the deficit.

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