Posts Tagged natureofscience

evolution supressed in new zealand? i think not Alison Campbell Mar 02

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While searching for some background on another post, I happened across this headline on the Herald site: University denies author’s PhD claim. I went on to read the story, as it’s always a bit of a concern to see people claiming credentials and the supposed awarding institution denying that this is the case. And a statement from the person making the claims caught my eye.

“During a period in which ‘evolution’ became a bad word [in New Zealand] punishable by revocation of credentials and confiscation of property [the 1980's], I refused an order from a department chairman to withdraw my books Darwin’s Universe and Time Gate from press,” he told a contemporary writers’ website.

Really? I have to say, that was news to me. The history of attitudes to teaching evolution in NZ has been quite well documented, most notably in works by Numbers & Stenhouse (2000), McGeorge (1992), & Peddie (1995), & it’s an area I’ve followed with interest.. Way bac,k in the 1880s there was an attempt by local creationists to get an Otago academic removed from his post for daring to mention evolution in his lectures (to no avail), and in the 1940s the creationist lobby was successful in getting a radio program for schools that talked about the evolution of life, taken off the air.

But to claim, as this person has done, that in the 1980s you could lose your credentials or even have property confiscated for mentioning the ‘e’ word?! This was the same time that I was teaching evolutionary biology to impressionable young minds in Palmerston North high schools – and I wasn’t run out of town or tarred & feathered ;-) Mind you, the fact that evolution wasn’t taught until the last couple of years of high school, thus exposing the smallest possible number of of impressionable young minds to this dangerous idea of Darwin’s, may have had something to do with that :-) Similar claims have been made in the US, around the infamous movie Expelled. And they’ve been shown to be similarly without substance. (Unless, in some alternate universe…)

Don’t get me wrong – there are problems associated with teaching evolution, particularly in some parts of NZ, as Peddie documented in his 1995 thesis. But they don’t manifest in people being pilloried or losing their belongings. Instead, as Peddie found, teachers may face pressure to skip that part of the curriculum (perhaps made easier to do by the fact that schools don’t have to offer the full number of achievement standards in a subject). Hopefully the fact that evolution is so prominent in the new science curriculum (beginning in primary schools) – being implemented this year, along with all the other curriculum areas – will make it that much harder to avoid teaching about this key biological concept, in state schools anyway.

But as for the claim that began this post? Pure fantasy.

 

 

C McGeorge  (1992) Evolution in the Primary School Curriculum. History of Education 21(2): 205-218

RL Numbers &  J Stenhouse (2000) Antievolutionism in the Antipodes: from protesting evolution to promoting creationism in New Zealand. The British Journal for the History of Science 33: 335-350

WS Peddie  (1995). Alienated by Evolution: the educational implications of creationist and social Darwinist reactions in New Zealand to the Darwinian theory of evolution. Unpublished PhD thesis, University of Auckland.

 

 

breadth vs depth Alison Campbell Feb 11

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One of the conflicts faced by probably every classroom teacher is the one between the amount of material one has to teach (& the students to learn about) and the time available. I face it myself: huge (though also very good) textbook, requests from my colleagues to make sure that the first-year course adequately prepares students to take second-year papers, students coming in with a range of backgrounds & prior experiences of biology – & a 12-week semester in which to accommodate it all. Reflecting on my teaching practice over the last several years in our A semester intro bio paper, I think I probably teach less content, less detail, than when I started in this particular paper, but have more of a focus on identifying (& dealing in depth with) big, or key, ideas. As you’ve probably guessed from my posts, I encourage my students to think critically about what they’re learning, and to gain an understanding of how those ideas & concepts relate to each other. And of course I’d like all my students to view science as fascinating, fun, useful, & relevant to them in their daily lives…

So of course I was interested in a paper by Marc Schwartz & his colleagues, entitled Depth versus breadth: how content coverage in high school science courses relates to later success in college science coursework. How would their findings relate to my own teaching approach? (And, is what I do in the classroom supported by empirical data, or is it a case of intuition & experience leading me up the garden path?) In a survey of 8310 students taking first-year biology, chemistry, & physics courses, the authors fround that students who said they’d spent at least a month studying at least one major topic in depth, while at high school, received higher grades in their university science classes than students who hadn’t done (or didn’t remember!) doing any in-depth work. Interesting! The team also looked at the outcomes for students who reported having broad high school classes that covered something on all major topics. The results here were equally interesting – these students didn’t seem to have any advantage over students who hadn’t ’studied everything’ in physics & chemistry, & were at ‘a significant disadvantage in biology’.

Presumably students spending a month or so on a single topic can really come to a good understanding of the area, mastering key concepts & able to understand how it all fits together. Taking a ‘deep learning’ approach, in other words.  In classrooms where there’s a drive to cover everything, it could well be that many students cope with the huge volume of material by using learning approaches that could be called ’shallow’ – rote learning techniques, for example, that don’t really aid a thorough understanding. (All this, of course, assumes that the tertiary assessment practices these students are encountering reward those taking the ‘deep’ learning approach to their studies…) And those with the learning skills developed by taking a deep learning approach to one topic can then apply those to the new material they learn in the following year, enhancing their learning outccomes there as well.

I guess my fondness for trying to focus on teaching methods that encourage ‘deep’ learning reflects my own philosophy that there is simply too much information potentially available. In ‘the old days’ it was probably quite possible to teach a subject such as any one of the sciences in fairly comprehensive breadth. But since then, particularly with the advent of modern technology, there’s been something of an explosion of knowledge. I know some of my students are quite daunted by the sheer size (& volume of content) of our textbook (the excellent Campbell [no relation!} & Reece). For me, & my colleagues in first-year biology, the question is, how to include it all? And,  should we cover it all? Schwartz et al quote another author as saying that '[to] be successful [in their learning], students need carefully structured experiences, scaffolded support from teachers, and opportunities for sustained engagement with the same set of ideas over extended periods of time." That ’sustained engagement’ part is the tricky one, when you’re teaching a ’service’ course that’s intended to prepare students for a range of paper options in their next year of study. I try to manage it by identifying common themes (eg the need for gas exchange, internal transport, energy) that apply across the living world, & tying things to those, so the themes recur even if the material attached to them is novel. But it’s a testing balancing act, nonetheless… Nice to know that at least one research paper suggests that I’m on the right track :-)

M.S.Schwartz, P.M.Sadler, G.Sonnert & R.H.Tai (2009) Depth versus breadth: how content coverage in high-school science courses relates to later success in college science coursework. Science Education 93: 798-826 doi 10.1002/sce.20328

but it does no harm… Alison Campbell Feb 09

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Over on Code for Life, Grant’s recently put up some posts concerning homeopathy (here & here, for example). He’s also suggested that homeopathic (& other) remedies should carry disclaimers to do with their active ingredients (or lack thereof) and what they can & can’t do.

Anyway, one of the common responses to articles critical of homeopathy & other ‘complementary & alternative medicines’** is that, even if they ‘work’ only via the placebo effect, at least they do no harm. I would argue that if the placebo effect masks an ongoing problem, then it is doing harm. And the same is true if patients are led to stop taking necessary medication. But – & I think more seriously – here’s an example where following a homeopathic prescription may do considerable damage: homeopathic vaccinations.

The article I’ve linked to (posted  by Peter Bowditch of ratbags.com, for purposes of serious critiquing) makes the following claim:

Homeopathic immunisation is effective against poliomyelitis, chickenpox, meningococcal disease, hepatitis (all types),Japanese encephalitis, Hib, influenza, measles, pneumococcal disease, cholera, smallpox, typhoid, typhus, whoopingcough, rubella, mumps, diphtheria, malaria, tetanus, yellow fever, dysentery, and many other epidemic diseases.

Well, they’re pretty safe in making this claim for smallpox as that’s been eradicated in the wild, but the rest are still with us in various parts of the world. These are pretty extraordinary claims for products that, by their very nature, usually contain no molecules whatsoever of their supposed active ingredients. Most of the diseases on that list can be fatal if left untreated, & can leave survivors with ongoing physical problems. So you’d expect to see some decent evidence that homeopathic ‘vaccines’ actually perform as claimed – good, solid evidence-based data on patient outcomes. Not vague statements that lack names, dates & other data, which is all the article provides. Yet hard evidence appears to be lacking.

Take influenza, for example. Here’s an evidence review from our Ministry of Health – a meta-analysis of a number of studies examining claims for a homeopathic ’remedy’ called oscillococcinum (made from the liver of a dead duck, by the way, although it’s so highly diluted that you would be hard-pressed to find any evidence at all of duck in your liquid or pills). Oscillococcinum is prescribed by many homeopaths as both a prophylactic & treatment  for flu. The Ministry’s evidence summary examined data from a systematic review & a total of 7 clinical trials (representing 3459 patients). Three of the trials (2265 patients) found that the oscillococcinum preparation did not prevent the flu. The other 4 trials looked at its efficacy in treating flu – oscillococcinum shortened the length of the illness by about 6 hours. In other words, this particular homeopathic remedy didn’t do what was claimed for it; it acted as neither vaccine nor treatment. (There did appear to be some reduction in severity of flu symptoms, but as such data tend to be self-reported it’s hard to be sure how much represented actual effect of the preparation & how much reflected patient expectations that they’d get better.)

But that’s just the flu – what about the other claims made in that article? Since they’re extremely vague, & cite no evidence whatsoever in their support, it’s rather difficult to judge. But a scirus search for published data on the claimed efficacy of homeopathic treatment during a a supposed polio ‘epidemic’ in Buenos Aires turned up nothing. And frankly, if the stuff was that good I’d expect to see hard evidence of that fact. Given the potential severity of polio, I’m sure doctors around the globe would love to have an addition to the treatments available to them. But then, it seems that most individuals affected by polio don’t progress to the severe paralytic form of the disease – so many of those Buenos Aires patients claimed as success stories for the homeopathic ‘vaccine’ may in fact have had the less severe infection, easily confused with the flu. With no actual data in the article, how can we tell?

So it’s hard to see how the claims made in the article for homeopathy’s ability to prevent serious, potentially lethal, infectious diseases can be supported. What’s more, I wonder how those claims can sit with any code of conduct for homeopaths. After all, the Society of Homeopaths in the UK has a code of ehtics which clearly states that no advertising may be used which expressly or implicitly claims to cure named diseases. And another homeopathy site expressly states that TCAM practitioners are prohibited from… treating infectious, communicable diseases (which is pretty much everything on that list I cited). Where does the responsibility lie, if someone follows this advice, takes (for example) a malaria ‘vaccine‘, contracts the falciparum form of the disease, and dies?
…………………………………………………………………………………………………………………………………………………………………

PS CAM isn’t really the right term. If a treatment works, can be shown to work in a reliable manner, produces positive outcomes that can be confirmed by other workers in the field – then it’s medicine. If it doesn’t – whatever it is, medicine it’s not.

And Ben Goldacre has an excellent article on the subject here.

a quick lesson from statistics :-) Alison Campbell Jan 25

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Frm PHD Comics (via Pharyngula):

 

I couldn’t agree more :-)

mms revisited Alison Campbell Jan 24

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A while ago I wrote a post on the so-called ‘miracle mineral supplement’, aka MMS. I thought I’d re-post it following an article debunking this nostrum in the Sunday Star-Times. My original post attracted a couple of comments from people claiming that MMS will cure a multitude of ills; I’ve reproduced them, & my responses, after the re-post.

After reading & commenting on that letter, which attributed health benefits to sodium chlorite, I found my interest had been piqued. Just what has been claimed for this chemical? So I went looking…

 

… & found, among other things, a webpage claiming all sorts of things for this ‘miracle mineral supplement’.

Apparently it’s not the sodium chlorite itself, but the chlorine dioxide that is produced from it in slightly acidic solution. The acetic acid in vinegar is supposedly ideal as an acidifier, act[ing] like a blasting cap by lowering the pH of the chlorine dioxide without setting it off. Then – you drink it! (Although in miniscule quantities – 6-15 drops in a glass of water… Not quite a homeopathic concentration, then.)

This is where things get interesting, from a chemical & biological point of view. When a chlorine dioxide ion contacts a harmful pathogen, it instantly rips up to five electrons from the pathogen, in what can be likened to a microscopic explosion… harmless to us, but terminal to pathogens. The pathogen – an electron donor – is rendered harmless due to the involuntary surrendering of its electrons to the chlorine dioxide – an electron acceptor – and the resulting release of energy. Oxidised by the chlorine ion, the former pathogen becomes a harmless salt.

Hmmm. “Pathogen” = ‘an agent that causes disease, especially a living microorganism such as a bacterium or fungus.’ Now, chloride dioxide gas is used in killing bacteria on food – but this is in relatively high concentrations & a far cry indeed from killing bacteria/fungi within the body. (The belief that it can be used in this way sounds similar to the belief that if colloidal silver in an ointment on your skin will kill bacteria, how much better it will be for you if you drink the stuff. At least with ClO2, I guess you’re not likely to turn blue…) But it’s not nice stuff: If you were to breathe air containing chlorine dioxide gas, you might experience irritation in your nose, throat, and lungs. If you were to eat or drink large amounts of chlorine dioxide or chlorite, you might experience irritation in the mouth, esophagus, or stomach.

Also – I really want to know – how would the ClO2 distinguish between a pathogen, & normal body cells? According to the site’s author, ‘toxic’ or ‘diseased’ body cells are more acidic than normal cells, & this underlies the ClO2 effect. A pity, then, that normal cells, happily respiring away, also acidify their surroundings as they release carbon dioxide – a necessary effect that triggers release of oxygen from the haemoglobin in circulating red blood cells (the Bohr effect), thus allowing the cells to continue respiring. Can the ‘miracle mineral supplement’ tell the difference here? And how does it get round the body, anyway?

Apparently by being picked up by the red blood cells, instead of oxygen… Red blood cells … do not differentiate between chlorine dioxide & oxygen. Therefore, [after you've drunk the sodium chlorite solution], red blood cells pick up chlorine dioxide ions that are deposited on the stomach wall where it normally gathers nutrients of various kinds before journeying through the body. Then, when the red blood cells armed with chlorine dioxide encounter parasites, fungi, or diseased cells that all have low pH and a positive ionic charge, the ‘aliens’ are destroyed along with the chlorine dioxide ion.

Hmm. Chlorine dioxide is certainly used as a sterilising agent for red blood cells. But in high enough quantities it can markedly reduce your blood’s ability to carry oxygen – hardly a Good Thing. Just as well, then, that the stuff isn’t all that likely to enter the bloodstream, given that it’s supposed to be taken in miniscule quantities & that the odds of it being picked up by red blood cells is vanishingly small. Far more likely that it will be consumed by some other redox reaction in the gut.(Oxygen saturation of haemoglobin is usually around 98%, so there isn’t much spare capacity there.)

And, of course, your body already has a perfectly good way of dealing with parasites, fungi, & so on – it’s called an immune system :-)_______________________________________________________________________________

The comments:

I am a Medical Laboratory Scientist, and I am surprised at your attitude. Your theorising about MMS, without backing it up with your own personal experience, is unscientific to say the least.
From what I can gather, you are quite prepared to dismiss MMS… even as a last resort. I am not surprised though. Your apparent indoctrination by allopathy is akin to religious intolerance.
Allopathy kills thousands of New Zealanders each year with ineffective toxic drugs. Iatrogenesis is ignored. Sooner or later the public will discover the widespead scams of the medical industry. Then the penny will drop and how will they explain their failures?
I have some advise for you. Have an open mind about MMS, try it yourself and don’t pre judge.

My ‘own personal experience’ would amount to no more than anecdote. Anecdote = data, so it would in fact be unscientific to base my statements on personal experience. There is no scientific underpinning to the claims made for MMS & its proposed mode of action is improbable in the extreme.

I would have to agree with Emanuel’s previous comment. Don’t draw conclusions from what you read;…try it first.
I have personally used MMS for a couple of years now and have had great results.
I have recommended it to many others, and know of people completely cured of cancer (among many other things), using only MMS; no other treatments. One was a lady with a 6cm pancreas cancer tumor, sent home to die. Two months on, her daughter tells me she is completely cured. Another friend of a friend cured himself of prostrate cancer using only MMS. I have a cousin currently trying it for a brain tumor. Although(to my knowledge), no-one seems to have carried out ‘approved clinical trials’ on this product; positive reports are poping up around the world.
The point is, results speak louder than the closed minded, bias opinions that you will find pasted all over the internet.
I hope you will give it a try before you speak any further negative words about this amazing product. It is available from www.miraclemineral.co.nz if you want to test it for yourself,

The problem here, though, is that we’re dealing with anecdotes rather than actual data. For example, was the friend of your friend formally diagnosed with prostate cancer, or was it a self-diagnosis? If the latter, then the ‘cure’ may not be what it first appears. Similarly, where is the medical diagnosis of a complete cure for a pancreatic tumour? (Hearsay evidence isn’t sufficient.)
In addition, there is no mechanism by which MMS does what is claimed for it – basic chemistry & physics mean that it cannot act as described on many of the websites promoting its use.
If it does have an effect for some people then we are almost certainly looking at the placebo effect. Which would mean MMS wouldn’t work to me, as I wouldn’t expect it to :-) And the big worry with the placebo effect is that it may simply mask underlying conditions, rather than making them go away…

asking the right questions Alison Campbell Jan 20

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A colleague sent me advance notice of an upcoming protest: a ‘mass overdose’ of sugar pills being organised as a protest against ‘homeopathic remedies’. (Grant picked up on this & has blogged on it over at SciBlogs. This got me thinking (as these things do) about an interesting podcast by Mark Crislip, who focuses on supplements & ‘complementary & alternative medicines’. This particular episode concerned claims that a particular food, supplement or treatment ‘boosts the immune system’. There are a few questions you should ask when you hear such statements.

How does it boost the immune system? Your immune system has a number of inherent control mechanisms that regulate its responses. Which of these mechanisms does the food/supplement/treatment affect, and how?

Which part of the immune system does it target? After all, the mammalian immune system is a thing of many parts: non-specific & specific responses; cellular & ‘humoral’ components (eg antibodies); the many different types of white blood cells; signalling & regulatory chemicals such as cytokines, interleukins, & interferons… – which of these, specifically, does the food/supplement/treatment target?

What is the evidence in support of these claims? Is it based on ‘in vitro’ studies ie of cells that have been isolated from the system & grown & studied in the test tube? These aren’t necessarily going to behave as they would in the actual organism. (I’m reminded of a study I read some years ago now, that supposedly demonstrated that drinking chicken soup really was a good thing to do when you’re sick. But it didn’t look at the impact on patient health of drinking chicken soup – the researchers looked at the effect of samples of soup on the activity of isolated white blood cells: specifically, whether or not it inhibited the cells’ abiltiy to generate an inflammatory response. But this doesn’t mean it will translate to a similar effect in the body.) In fact, it turns out that white blood cells will often generate an ‘inflammatory response’ in the presence of some pathogens, but this doesn’t necessarily translate into an elevated body-wide immune response.

And that segues nicely into the final question: Is ‘boosting the immune system’ necessarily a good thing? If that response is a generalised inflammatory response, the answer is, quite possibly not. Because chronic inflammatory responses may be related to increased risk of blood clots, and those in turn can carry nasty health risks. For example, a 2006 study published in the Lancet found that people who’d had a urinary tract infection, with accompanying inflammatory response, had a heightened risk of developing a thrombosis (blood clot) in the four weeks immediately after the infection. There are similar findings from other studies. This apparent inflammation-thrombosis link hasn’t yet been shown to be a causal relationship, & we do need to be careful in attributing causality (it’s all too easy to get it wrong NB warning, this is humour!), but it’s certainly one to consider.

In fact, in people who are in good health & do all the common-sense things needed to stay that way (ie get sufficient sleep, exercise, & food), it’s neither necessary nor possible to ‘boost’ the activity of their immune systems. It’ll work just fine all by itself :-)

communicating science – an example of good practice Alison Campbell Jan 18

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The following is from the Young Australian Skeptics website – I’ve copied the whole post across because it’s a brief one (& I’ve added links to book reviews):

We probably have all encountered scientifically ignorant people, for some people knowing the complexities of the universe is simply not interesting. This ignorance is generally spawned within the Medias interpretation of science and scientists; however a scientist known as Len Fisher is doing something about this by communicating science to the general community. Earlier in Brisbane  this year (as part of the BrisScience and BWF Festival) he held a seminar on how science should be communicated to the public. Len Fisher is best known for his ignoble prize for physics; it related to the topic why biscuits go soggy when you dip them in your tea.

He was contacted by a biscuit company to conduct this research, much to the derision of his colleagues; however his aim was to show to the media how real scientists think about everyday problems. He made it very clear to the reporters that the research was not really “life or death” serious research but it was to illustrate that science is not just a collections of immaterial facts and figures, but the study of reality. This was also seen in his desire for the motto and aim of the ignoble prize completion to be changed; it was originally an award for “Science that should not and cannot be reproduced”, he morphed this to “Science that first makes you laugh, then makes you think”.

This aim was to elevate respect for science within the community and to inspire interest in education. Len fisher has also authored several novels on a variety of topics: Rock, Paper and Scissors: Game Theory in everyday life, How to dunk a doughnut: The science of everyday life, Weighing the soul: The evolution of Scientific ideas, The perfect swarm: The science of Complexity in everyday life. By illustrating common science to the community Fisher is attempting to stir interest within the community, young and old, and this approach might help fellow communicators to attract and maintain interest in how the world works.

As a result of reading the above I’ve come to a number of conclusions: a) I want to meet Len Fisher & learn stuff from him! b) I need to keep an eye open for future BrisScience events; & c) there isn’t enough time in the future timespan of the universe to read all the good science books I come across. (Well, OK, that last is pure exaggeration, but you know what I mean!) 

on the shoulders of giants Alison Campbell Jan 13

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One of the things that sets science apart is the way that it operates, building on the work of others and accepting, rejecting or altering understandings as new data come to hand. The idea that science is so open to change seems to be one of the hardest things to get across, in the classroom & in society at large: there seems to be constant surprise that scientists might alter their conclusions on an issue in the light of new information, and that each generation of scientists builds on the work of those who have gone before them.

That last point is perhaps exemplified by this quote from Isaac Newton: ‘If I have seen further it is by standing on the shoulders of giants‘ (Newton was writing to his colleague, Robert Hooke, at the time, & I have heard it said that he was being rather snarky; Hooke was a small man.) Now Orac has a wonderful post about stepping back into the past in the medical world – how much of what doctors do today is dependent on the discoveries & advances of previous generations. You could substitute ’scientists’ for ‘medical doctors’ & the message would be the same. [Warning: there is a graphic description of a pre-anaesthesia operation on a malignant breast tumour - perhaps not best for reading over lunch...]

(Orac’s post could be a good basis for a classroom thought experiment; some of his commenters give some good supporting reading material, in the form of science-fiction novels based on the back-in-time premise. Now, if I could only think of a way to fit this into my lectures…)

owlcat. definitely not coming to a place near you, any time soon Alison Campbell Dec 15

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Owlcat:

owlcat - why evolution is so interesting.jpg

Makes me chuckle when I think about it. Not just because Lolcats make me LOL (they do), but also because the idea of an owlcat epitomises a standard creationist argument. It goes something like this: if evolution is true, how come there aren’t any crocoducks/owlcats/<insert laughable hybrid here>?

This is an example of the ’straw man’ argument. No evolutionary biologist would suggest – except in jest – the concept of a crocoduck, or an owlcat (no matter how sweet this hypothetical beast might look). This is because ducks & crocodiles, cats & owls, are all modern species, far removed from any last common ancestor.

(In the case of owls & cats, very far removed indeed; mammals & reptiles (including birds) last shared a common ancestor around 300 million years ago, & have followed divergent evolutionary paths since then. Birds appeared on the scene much more recently, evolving from a group of dinosaurs known as maniraptors during the Jurassic period.- and (contrary to what this straw-man claim implies) there is a rather nice series of transitional fossils that lets us trace the ancestry of this clade.)

Thus true transitional fossils will not look like some fusion of their modern descendants – there is too much time & too many gradual transitions between them. As Richard Dawkins puts it:

The demand for a crocoduck is based on the misunderstanding that there should be intermediates between modern animals and other modern animals.

Unfortunately (for the creationist camp) this isn’t how it works. Dawkins again (using leopards & rabbits as his pair of modern species):

You start with any modern animal you like, such as a rabbit, and put her next to her mother and then her mother in a chain that goes back in time a very long way until you hit the common ancestor with some other animal such as a leopard. It would no longer look like a rabbit but more like a shrew.

You call that the hairpin bend and you turn round and start going forward in time. You just keep taking the fork that leads to the leopard and in time you’ll get to the modern animal.

So, while owlcats are cute, & crocoducks giggle-making, any request that evolutionary biology should produce an actual animal simply betrays a profound misunderstanding of how evolution operates.

moa evolution & new zealand’s geological past Alison Campbell Nov 30

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The Level 3 & Scholarship examiners often ask you to discuss the evolutionary history of a group of organisms (Hebe, cockroaches, cicadas etc) in relation to the geological history of New Zealand. Geological changes such as the widening of the Tasman Sea, and the uplift of mountain ranges including the Kaikoura ranges & the Southern Alps, can drive evolutionary change through the isolation of populations (the Founder effect, genetic drift) & changes in selection pressures.

A new paper just out  has done just this for the moa (Bunce et al., 2009), combining "mitochondrial phylogenetic information from 263 subfossil moa specimens from across NZ with morphological, ecological, and new geological data to create the first comprehensive phylogeny, taxonomy, and evolutionary timeframe for all of the species of an extinct order." This includes evidence that for much of the last 30 million years or so, the North & South islands were geographically isolated, which would have provided the basis for allopatric speciation of the fauna & flora on those 2 landmasses.

You may be reasonably familiar with the idea of adaptive radiation in relation to moa & other ratites, as it’s a common example of this pattern of evolution in senior biology textbooks in NZ. At the moment scientists think that ratites first evolved around 80 million years ago (mya) in Gondwanaland, diverging – as the supercontinent broke up – into groups that gave rise to the modern ostrich, emu, rhea, cassowary, kiwi, & the extinct elephant birds and moa. As a taxon, moa also show considerable adaptive radiation, although until recently it was difficult to tell just how many species there actually were. On the basis of morphological & aDNA data, Bunce & his colleagues suggest some changes from the till-now current taxonomy for moa, shown in the following figure (they reduce the number of species from 11 to 9, for example).moa systematics bunce et al.png

Fig.1 from Bunce et al. (2009): Systematics, dimensions and approximate distributions of moa in the three family, six genera, nine species taxonomy advocated in this study. doi/10.1073/pnas.0906660106

The data from ancient mitochondrial DNA also allowed the team to study the time-frame of moa evolution. Earlier studies have suggested that the moa radiation occurred about 15 mya, but Bunce et al.’s data indicate that the two main groups of moa (the Dinornithidae & Emeidae) happened just 5.27 mya - much more recently. (The 2009 paper discusses the reasons why their figure differs so significantly from the earlier one, which was also based on aDNA, & suggest this is related to how the data were calibrated.)

What was happening in NZ during that period, in ecological terms, that might have driven this divergence? One factor is the rapid orogeny (mountain-building) that we know was happening at around that time. This would have provided a range of new, untapped habitats for moa & other species to exploit – and new selection pressures as well. For example, as the Southern Alps rose up, they increasingly blocked the predominant westerly airflows, favouring the development of wet rainforests on the West Coast and a warmer, drier environment on the eastern side of the mountains, opening the way for niche specialisation and speciation. This could have been quite complex, as during glacial periods glaciers extended to the coast on the western side of the island & well down into the eastern low country, further subdividing habitats & providing additional barriers to gene flow.

In addition, from about 2 mya relatively short-lived land bridges linked the main land masses, allowing movement between the two islands. (This partly reflects the impact of glacials during the last ‘ice age’, at their peak lowering sea levels around NZ by at least 100m.)

moa evolution & changes in NZ geography.png

Fig.2 from Bunce et al. (2009) A spatial & temporal context for the evolution of moa. Molecular phylogeny and date estimates of the moa radiation… compared with the new paleogeographic model of Neogene New Zealand. doi/10.1073/pnas.0906660106 NB the authors caution that the timings of divergence for the various species are provisional – it would be useful to have data from many more moa specimens, to improve the accuracy of the calculations.

A great deal of new work has gone into developing those maps, particularly in the King Country, Taranaki, & central Hawkes Bay, plus data from exposed onshore marine sediments and oil exploration drill sites. During the Oligocene (> 25mya), the New Zealand land mass was reduced to a string of low, well-separated islands. Bunce et al. comment that, even when the northern landmass was re-emerging, it was still completely separated from the South Island by the Manawatu Strait (see maps above) until roughly 1.5-2 mya. Thus any land animals (& plants!) that couldn’t cross the strait were geographically isolated for that entire time. But – the moa genetic data don’t show any indication of divergence that far back, which means that the various lineages probably descended from ancestors on a single island. Fossil evidence fingers the South Island as the ancestral home, which means that moa couldn’t have colonised the North Island until less than 2 mya, only to be isolated again when Cook Strait first formed 450,000 years ago. (This interpretation is supported by data from other vertebrate remains.)

But there’s still a lot to learn! The authors conclude by saying that this "important new geological model of Neogene NZ emphasises our current lack of knowledge about the pre-Pliocene landscape, and raises important questions about the role of marine barriers and the biotic diversity of the north and south islands. The combined geological and genetic data suggests that the NZ Neogene terrestrial record is likely to have been marked by the significant loss of terrestrial endemics from a highly unusual environment, which is only just beginning to be characterised."

Bunce, M., Worthy, T., Phillips, M., Holdaway, R., Willerslev, E., Haile, J., Shapiro, B., Scofield, R., Drummond, A., Kamp, P., & Cooper, A. (2009). The evolutionary history of the extinct ratite moa and New Zealand Neogene paleogeography Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0906660106

 

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