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December 2013 Archives

Around 14 months ago the husband & I were spending a lazy holiday in Rarotonga. We did quite a bit of snorkelling on the reefs, and especially enjoyed our experiences at Muri, where we saw a good range of reef fish in near-ideal conditions (as in, clear, calm, relatively shallow water). There were several moray eels, which were at first hard to spot - and then you saw them, loitering in a crevice, giving the impression of watching you rather closely and with their open mouths exposing some rather sharp, pointy teeth: "all the better to bite you with, my dears." We viewed them with caution.

But when you think about it, that wide-mouthed loitering would seem to pose a problem for the eels. This is because most predatory fish feed by opening their mouths wide from a closed position: water floods into the lower-pressure area inside the mouth & dinner comes along for the ride. Sitting around with your mouth half-open doesn't sound like a good strategy. I found the answer while reading The Book of Barely Imagined Beings by Caspar Henderson, under - you've guessed it - 'E for Eel'. (This wonderful book was recently reviewed on Sciblogs by Siouxsie Wiles.)

 

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'The' kiwi (Apteryx spp.) has always been a bit of an enigma, not least for the fact that it lays an absolutely enormous egg in comparison to its body size. In one of the essays in his book Bully for Brontosaurus (1991), Stephen Jay Gould argued that this differential in egg/body size was due to the impact of scaling: kiwi, he believed, had 'downsized' from a moa-like ancestor but had retained the large moa-type egg. This idea was quite widely accepted, even though later genetic evidence indicated that kiwi were in fact more closely related to the Australian emu than to NZ's now-extinct moa. But new research suggests quite a different evolutionary trajectory - and I rather suspect that Gould, great scientist that he was, would be delighted to see his hypothesis robustly challenged :)

The research reported in this news article from scoop.co.nz will be published in the Proceedings of the 8th International meeting of the Society of Avian Palaeontology and Evolution - you'll find the abstracts of the conference papers here. A newly-described fossil, from what's known as the 'St Bathans fauna' of Central Otago turns out to be a new genus and species of kiwi, but a tiny one by today's standards. Paul Scofield, one of the paper's authors, is quoted in the scoop report as saying that 

[this] fossil from the early Miocene, about 20 million years ago, shows us that it's a tiny bird about one third the size of a small kiwi today. It suggests the opposite [to Gould's hypothesis] is, in fact, the case - that the kiwi has developed towards a larger size, a trend that is seen in many birds from the early Miocene.

So, how would an ancestral kiwi have arrived in New Zealand? The suggestion is that they flew. This is based on the evidence that a) kiwi and emu are more closely related than kiwi and moa and b) the emu-ish early kiwi arrived here after NZ and Australia were separated by the developing Tasman Sea.

Finding the wing bones of this new fossil species would help to confirm/deny this proposal. Although - having read the abstracts for the conference, I can't help wondering if a proxy might be the size of a part of the brain known as the 'cerebellar flocculus', as suggested in another presentation by Walsh et al. It's an intriguing possibility, anyway! And I'm wondering - how may we then explain that anomalous kiwi egg? 

I'll look forward to getting hold of a copy of the paper by Worthy and his colleagues, once it's published. 

 

Gould, S.J., (1991) Of kiwi eggs and the Liberty Bell, pp 109-123 in Bully for Brontosaurus. Penguin Books, London. 

Walsh, S., Iwaniuk, A., Knoll, M., Bourdon, E., Barrett, P., Milner, A., Abel, R., & Dello Sterpaio, P. (2012) Can the size of the avian cerebellar flocculus be used as a proxy of flying ability in extinct birds? 8th Internat. SAPE Meeting, 11.-16. June 2012 Naturhistorisches Museum Wien

Worthy, T.H., Tennyson, A.J.D., Salisbury, S., Hand, S.J., & Scofield, R.P. (2012) A fossil kiwi (Apterygiformes) from the early Miocene St Bathans fauna, New Zealand. 8th Internat. SAPE Meeting, 11.-16. June 2012 Naturhistorisches Museum Wien

 
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One of my current favourite TV programs is Time Team - I enjoy learning little bits of history & Tony Robinson's happy enthusiasm is so contagious (but I still think of him as Baldrick). So you'll understand that I was happily distracted this morning when, while looking for something else (isn't that usually the way?), I stumbled across a fascinating piece about an ancient graveyard in the Italian town of Badia Pozzeveri.

Published on Science magazine's site, the article tells the story of the ongoing excavation of a medieval graveyard. The dig is providing a wealth of information on things like the dietary differences between nobles, monks, & peasantry (based on isotope analysis of their teeth) & the impact this had on health. What's more, using ancient DNA (aDNA) techniques, the scientists leading the dig are hoping to identify the presence of various pathogens, such as Yersinia pestis (the bacterium linked to the Black Death, and which still causes cases of plague in the US today) and Treponema pallidum, which causes syphillis and has already been found in 16th-century mummies from Naples.

And like many episodes of Time Team, the tale has a twist at the end: a bit of fashion-based detective work showed that at least some of the burials were not medieval at all.

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One of the questions that often comes up in my first-year bio classes relates to natural selection and human evolution. Does the fact that modern medical science keeps alive people who in previous centuries might have died, mean that we're countering the effects of natural selection? As you can imagine, this generates quite a lot of interesting discussion that spans ethical issues as well as the obvious biological ones.

Next year I think I'll give the class a new paper to read: one that examines such a question in the context of the Chatham Island black robins (Petroica traversi) (Massaro et al, 2013). 

As many New Zealand biology students may know, by 1980 the breeding population of this little bird was reduced to a single pair, in a total population of seven. Things were not looking good, but dedicated conservation workers - led by the late Don Merton (there's a lovely obituary for him here) - managed to turn things around by careful management of the population, including fostering the robin's first clutches under another species (thus inducing the robins to lay again), and translocating the small population from Little Mangere Island to the better habitat on Mangere Island. However, it seems that at the same time, the conservationists were also unwittingly selecting for a distinctly maladaptive behaviour - that of laying eggs that were left teetering on the very brim of the nest.

After that initial bottleneck event the population slowly started to recover. However, the researchers working with them noticed that in 1984 one of the five breeding females laid a sinlge egg were laid at the edge of her nest, with more females following suit in subsequent years. Left alone the eggs didn't hatch, mainly because they weren't incubated (although I suspect some could simply fall off the edge). The obvious thing to do was to reposition the eggs in the nest, & this resulted in an increased in chicks hatched & subsequently fledged. However, Massaro & her colleagues report that by 1989 18 of the 35 females (51%) were 'edge-layers', a behaviour that would leave the population completely reliant on human intervention if edge-laying continued to spread.

The research team suspected that this was an example of inherited rather than learned behaviour, and hypothesised that

[if] rim-laying [had] a genetic basis, and its spread [had] been facilitated by human intervention through egg repositioning, the frequency of this trait would be predicted to decrease following cessation of intervention.
Conservation workers stopped moving rim eggs in 1990, which then meant that the researchers could subsequently compare data sets: 
we therefore compared egg-laying data from three years before cessation of repositioning (1987–89) with a three year period almost two decades after management stopped (2007–09)

and found that the number of rim eggs being laid decreased significantly between those two periods. They next looked at the many years' worth of data to see if the 'rim-laying' behaviour had any effect on individuals' evolutionary fitness, and discovered that

[when] rim eggs were not repositioned, females that laid rim eggs had significantly reduced clutch sizes (i.e. number of eggs laid inside nests that were incubated), and decreased hatching and breeding success compared to normal-laying females, demonstrating that rim laying substantially reduces fitness.
The final step was to confirm that this maladaptive behaviour did have a genetic underpinning. This part of the study was aided by the fact that there's an extensive genetic pedigree available for this closely-studied species. Examining that pedigree, Massaro & her co-workers found that a) the behaviour first showed up in the grand-daughters of the 'founding' female, 'Old Blue'; and b) that the population was highly inbred. A detailed analysis of the pedigree led them to determine that the rim-laying trait was an autosomal dominant trait that's inherited in a Mendelian manner (ie no evidence of sex-linkage). Their final message:
This episode yields an important lesson for conservation biology: fixation of maladaptive traits could render small threatened populations completely dependent on humans for reproduction, irreversibly compromising the long term viability of populations humanity seeks to conserve. 

 

You'll also find information on the study here on the University of Canterbury website.

Massaro M., Sainudiin, R., Merton, D., Briskie JV, Poole, AM, Hale ML (2013) Human-Assisted Spread of a Maladaptive Behavior in a Critically Endangered Bird. PLoS ONE 8(12): e79066. doi: 10.1371/journal.pone.0079066

 

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This is something I originally wrote for my 'other' blog over at Talking Teaching.

Last week I spent a couple of days down in Wellington, attending the annual symposium for the Ako Aotearoa Academy. The Academy's made up of the winners of the national Tertiary Teaching Excellence Awards, so there are around 150 or so of us now. While only 35 members were able to make it to this year's event (& the executive committee will survey everyone to see if there's a better time - having said that, everyone seems so busy that there's probably no date that would suit everyone!), we had a great line-up of speakers & everyone left feeling inspired & energised. I'll blog about several of those presentations, but thought I would start with one by Peter Coolbear, who's the director of our parent body, Ako Aotearoa.

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The latest PISA results are out, and NZ - despite remaining in the 'above the average' group for OECD countries - has nonetheless  slipped in this measure of achievement in reading, maths administered by the Programme for International Student Assessment . This is of concern, & there are probably multiple complex causes for our decline. Certainly the previous PISA commentary (2009) recommended that we pay attention to matters of inequality (There's interesting commentary here, & also on the RNZ website.)

This morning's Dominion-Post (I'm in Wellington at the moment, at a teaching symposium) carries a story giving a primary-teaching perspective.There are two key issues here: many primary teachers lack a science or maths background; and primary teachers in general are not well supported to teach these specialist sujects. (The removal of specialist science advisors - something I've commented on previously - did not help things.) This is important, because if students don't gain a good understanding of these subjects - and good experiences of them! - during primary school, then they'll basically be playing catch-up when they arrive in specialist secondary school classrooms.  Sir Peter Gluckman's suggestion (in his report Looking ahead: science education in the 21st century) that each primary school have a 'science champion' would help here, but in the medium-to-long term it would probably be even better if intending primary school teachers received much greater exposure to the STEM subjects to begin with.

Should we worry? Yes, but I definitely agree with Fiona Ell, from the University of Auckland, who's quoted in this morning's Herald as saying:

People get very hung up on the ranking ... because it's like a Top of the Pops top 10 thing. I don't think they should be ignored ... but knee-jerk reactions to rankings are really dangerous in education systems.

So, there are issues that we need to address, and as Fiona's pointed out, there are no quick fixes - we need to deal with them in a considered way that includes as many variables as possible (i.e. not just practices in schools).

One of those issues is highlighted by Sir Peter Gluckman, the Prime Minister's Science Adviser, who's said:

What's worrying is that there seems to have been a decline in the people represented in the top end of the scale and an increase in the number of people at the bottom end of the scale.

And socioeconomic status may well play a part in this. From the Herald story:

New Zealand was one of just two countries in which socio-economic status had a strong connection to a student's performance. Some countries' education systems made up for social disadvantage, but this was not the case in New Zealand.

So any solution addressing the PISA results will of necessity be complex. It's not going to be sufficient to look only at what's going on in schools. Yes, support and professional development for STEM teaching across the compulsory sector will be needed. The quality of teaching is definitely important (for a student's perspective see the Herald article). But without also seriously considering and attempting to deal with the social inequalities in this country, I suspect changes in the educational sector alone will not be enough.

 

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In posting an item about the 'pig-ape hybridisation' suggestion for human origins, the Daily Mail is a) coming rather late to the story (a slow day in the newsroom, perhaps?) and b) showing more regard for sensationalism than for good investigative journalism.

The story's one I've posted about before (& I've reposted my original piece below). Seeing it again really makes me think that the originator of this particular idea is trying to have it both ways. If our morphology is as similar as he claims to that of pigs, and different from chimps, then the differences should show up in our genes. Yet they don't; genetically we are much closer to chimps than to swine. He claims that this can be explained by repeated back-crossing with early humans - which is effectively no more than special pleading (& conveniently ignores the issue of significant differences in chromosome number between the two taxa). 

 

The internet is a wondrous place: a source of information, of amusement, and - alarmingly often - of material that elicits a combination of 'say what?' and <head-desk>. And a hat-tip to PZ Myers for this particular example...

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