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The First New Zealanders and their rats David Winter Jul 29

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Crispin Jago has made a very cool thing, a periodic table of irrational nonsense. Rolling my eyes over the groups, wondering how people can believe some of these things, made me think about New Zealand’s unique ecosystem of kooky ideas. We don’t have to suffer creationists in any organised sense and I don’t think anyone is too into ear candelling, but those TV psychics have found themselves a niche to exploit and most people seem think chiropratric and homeopathy are normal parts of medicine. Then I was reminded about our very own, home grown cranks. There are people who believe that New Zealand was settled by Celts several hundred years before it was discovered by the ancestors of modern Māori. It probably goes without saying that these people are nuts, but the idea of a pre-Māori civilization in New Zealand is one of our culture’s enduring myths. It’s worth talking about why people who are serious about studying our country’s prehistory have discarded it.

People coming to this question for the first time my want a little bit of background. The settlement of the Pacific is one of the most interesting stories in our species’ history. I did the field work for my PhD (on landsnails, and not people) in the Cook Islands and you get a feel for the enormity of that achievement when you travel around that group. To fly from one island to another you walk out across the tarmac and meet your pilot, who is almost invariably sitting on the steps to his 12 seater plane, reading the paper through massive aviator glasses. Once you’re safetly stowed you get your safety briefing (”it’s gonna be pretty fine all the way, should be a good flight”) and you take off. The pilots don’t close the door to the cockpit, so you can see out the windscreen, but all you see is ocean and sky. You can fly for an hour without seeing land in front of you or out your window. Then an island looms. A few minutes later you land, and, even among the Cook Islands, you’re in a new culture. The Polynesian people who discovered and settled these tiny islands separated by such vast distances were master navigators. Without metal tools or written records, let alone maps and compasses, they very deliberately settled islands (taking livestock and crops with them), maintained trading relationships between island groups and almost certainly made it to South America (very likely beating Columbus in the process).

map of Pacific settlement based on language evolution

Schematic of the settlement of the Pacfic (this one is taken from a study of the evolution of Austronesian languages)

The “mainstream” view on the settlement of New Zealand fits nicely into what’s known about the settlement of the Pacific. There is good evidence that the bulk of Polynesia was settled in a stepwise fashion, moving west to east with the prevailing winds. Eastern Polynesia was settled by about 800 AD. The far reaches reaches of Polynesian – Hawai’i, Rapanui and New Zealand would require a different pattern of migration (upwind, or over vast distances) and remained, with Antartica, as the last uninhabited lands on earth for hundreds of years.

The first evidence for humanity in the New Zealand archeological record comes from the Wairau bar, where artifacts similar to those from contemporaneous sites in the Society Islands and the Southern Cooks have been dated to about 1280 AD. At the same time the pollen record shows New Zealand’s first wide scale deforestation, trees being replaced by bracken, scrub and charcoal. A few hundred years later the much sparser record of sub-fossil animals shows its first mega-faunal extinctions. Combined with evidence for “sattelite” settlements in the Kermadec islands (on the edge of the tropical Pacfic) you have exactly the pattern of evidence you’d expect to see with the settlement of islands as remote as Te Wai Pounamu and Te Ika a Māui – settlement as an extension of an ongoing process with clear evidence for human impacts starting from a date that makes sense in that framework

Compare that with the Celtic NZ people. The idea of Celts arriving in New Zealand without leaving any real evidence of their presence anywhere else outside of Europe hardly needs talking about. When we look within New Zealand, almost all the evidence supposed to support a pre-Maori celtic civilization amounts to big rocks that form, if you just imagine they used to be arranged slightly differently, a giant surveying network. Or astronomical observatories. Proponents of the Celtic NZ hypothesis spend very little time trying to find any evidence for the populations that must have lived, died, eaten, built, dug, farmed, and buried their dead in New Zealand to support these mad priests’ plans to move megaliths across the country. And when they do the results are less are less than convincing

By all accounts they treat the historical method with about as much respect as the scientific one, so academics don’t take them very seriously. In fact, you’d think these claims are so kooky that there was really no need to rebut them. Sadly, the Celtic NZ people seem to have convinced at least a few people that they are on to something. I’m sure part of the reason for that is New Zealanders were once taught that the ancestors of modern Māori did meet another people when they came to New Zealand.Up untill about the 1960s school textbooks said the Moriori were a Melanesian people that were driven off the New Zealand mainland by Māori, with a few survivors taking refuge on the Chatham Islands (called Rekohu in their language). That idea had been rejected by every scholar who’s addressed it since the 1920s because it’s clear that the Moriori descended from mainland Māori and the unique aspects of their culture were acquired during their subsequent isolation. Part of the reason the Moriori myth came about in the first place is that it fitted into a Victorian narritive view of history – a chain of never ending progress It was only right that Moriori hunter-gatherers were replaced my the adventurous and noble Māori, just as the advanced British settlers would in turn assimilate the Māori. We might have given up that story, but the Moriori myth is still tied to politics in New Zealand. For people who think the New Zealand government shouldn’t make reparations for its breaches of the Treaty of Waitangi the idea that Maori themselves were once colonisers looks like a get out of jail free card. Russel Brown quoted one example in 2004:

Leaders and academics that hark back to the pre-European days of Maori domination of New Zealand have driven this opportunism. They appear to conveniently forget that Maori violently conquered the Moriori, the original settlers, and their claims of tangata whenua status and demands for compensation for historical grievances appear to many to be ill informed.

Ignoring the gaps in the logic (the Treaty is between Maori and the crown, and is not contingent on Maori being the original inhabitants of New Zealand) such claims also face a pretty big evidence gap. The piece Brown picked up was from then Member of Parliament Muriel Newman. Dr Newman is no longer and MP, but she has set up a think tank (which shows about as much evidence for thought as any group with that name) and it seems she hasn’t given up on her politically motivated brand of crypto-history. Here’s her latest, in which she tries to argue New Zealand has no indigenous people:

Archaeologists agree that humans first settled in New Zealand well over 1,000 years before the main Maori migration, which is estimated to have arrived around 1200 AD. Their evidence is based on the exhaustive forensic examination of historic plant and animal remains. They believe that the settlement of New Zealand was most likely a continuous process, a view that is certainly consistent with early settler journal accounts (from the proceedings of the Royal Society of New Zealand) which indicate that not only did Moriori precede Maori, but that when they arrived in the Chatham Islands, “they found the country in the possession of aboriginal natives called Hiti”- inhabitants of the “Flint age”, who used not stone, but “chips of obsidian as cutting implements.” There is also strong evidence of an early presence of people of Celtic and Chinese ancestry as well as Greek, French, Portuguese, Spanish and others – in addition to settlers of Polynesian descent.

Breathtaking. But perhaps the most amazing bit of that bizarre paragraph is that somewhere, deep under the layers of crazy, there is just a little science peaking through. We’ve already seen that archeologists don’t agree that New Zealand was settled a thousand years before the Māori arrived. But there has been one little hint among the prehistoric “plant and animal remains” that humans might have got to New Zealand before the people that lived at Wairau Bar. Old Rat bones.

A Pacific Rat (photograph of museum specimen)

A Pacfic rat, image is CC 2.0 thanks to wikipedia user Tolter Alter Man

The Pacific rat (Rattus exulans or the kiore) is native to South East Asia and Melanesia, but it can be found everywhere Polynesian people visited. The kiore isn’t much of a swimmer so the presence of R. exulans bones on an island is unambiguous evidence for human contact. In 1996 Richard Holdaway published the first radiocarbon dates for kiore bones in New Zealand, and they were surprising. Holdaway published dates for 18 bones and all but two of them were older that the first archeological evidence for humans (at 1280 AD) and some of them dated to around 10 AD. Quite how the presence of the Pacific rat in New Zealand in 10 AD gives support to the wild claims of people like Newman or the Celtic NZ crowd I can’t imagine, but those results did fuel a genuine scientific controversy. Why were there rats in New Zealand almost a thousand years before there is any evidence for humans? At the time there were three answers; Holdaway himself argued that the bones were evidence that humans had visited New Zealand but either left immediately or failed to establish themselves, a few archeologists held that the bones were evidence the ancestors of Maori arrived in New Zealand a long time ago but didn’t leave a mark until they adapted to the colder climate, and others said the dates must just be wrong.

Atholl Anderson dedicated a lot of time to testing the reliability of radiocarbon dates from kiore bones. The bones Holdaway had used to establish the antiquity of New Zealand’s rats had come for so called “natural” sites, most notably laughing owl nests and caves, which offer little in the way of corroboratory evidence for the ages estimated from the rat bones. In contrast, Anderson focused on archeological sites (those associated with human habitation) which provide plenty of contemporaneous material to set the dates determined for rat bones in context. Anderson did indeed find the dates determined from rat bones often differed greatly to those determined from the contents of the same midden. They even found bones from well studied archeological sites that were estimated to be thousands of years older than the site! Clearly, there’s something odd about those dates. The real smoking gun for the “old rats” hypothesis came when Anderson looked at the relationship between the age estimated for a bone and the date of the labwork done to determine that age. Almost all the bones measured before 1997 were older than that magic mark at 1280 AD, and every single bone measured at the same facility since 1997 was younger (or at least, the error bars cross that date):

dot plot (with error bars) for dates estimated from rat bones. Dates clearly fall into two group, depending on when they were dated

Dates estimated from rats fall into two distinct groups, depending on when they were analysed. From Wilmshust et al (2008) cited below

There is no reason to think the real age of the kiore bones sampled over time will fall into two such distinct classes (it’s not as if the oldest bones will be the easiest to get to) and it’s easy to bias the date estimated by carbon dating by failing to prepare the bones properly (or by introducing contamination in the lab) so it looks like the surprising results Holdaway reported where actually a lab error which has since been taken care of. It’s (barely) conceivable that originally published dates were right, and that the Anderson’s archeological sites were biased in some particular way, but that hypothesis really doesn’t make sense given what we now know about the settlement of the Pacific. It’s widely accepted that Eastern Polynesian wasn’t settled until about 800 AD, meaning any earlier rats in New Zealand would have had to come from visitors from the Western Pacific. That’s against the main direction of settlement, but, more tellingly, genetic evidence has established that modern kiore in New Zealand come from Eastern Polynesia. Kiore also make their first mark on New Zealand’s faunal record around 1300 AD, when Plactostylus landsnails with gnawed shells show up for the first time. If you want to believe rats were in New Zealand 2000 years ago you also have to believe the first bones to be carbon dated were the oldest, dates estimated from archeological bones are more unreliable than those for bones sourced from “natural” sites and that those old rats left not descendants in modern New Zealand populations and left no mark on the New Zealand faunal record until just after Polyneisian settlement of New Zealand.

You might be wondering why someone hasn’t just gone back an re-analysed the bones that made for Holdaway’s original surprising results. Radiocarbon dating is a destructive process and rat bones are small, so, apparently there isn’t enough bone from the original samples to re-determine their age. Recently, a team from Landcare Research and lead by Janet Wilmshurst did the next best thing, and went back to sites that gave up the apparently old rat bones and re-excavated them. I’m sure you can guess what they found, none of the bones had a pre-1280 AD date. But they didn’t just look at rat bones. The subfossil record of plants is almost always more finely grained than animal records. Every year plants put out millions of seeds and pollen grains, some of which are recorded in pits and lake beds and soil horizons. The Landcare team took advantage of this high resolution record to look for the first appearance of distinctively rat-gnawed seeds, and they found them after 1280 AD, but earlier than the oldest rat bones. Importantly, some of the deposits with relatively old rat-gnawed seeds contain much older seeds, with no evidence of rats. The team plans to go on an use this high-resolution record to establish the dates of settlement for other Pacfic islands.

The sort of people who think the presence of the Pacific rat in New Zealand would be evidence for a pre-Maori Celtic population aren’t likely to let evidence get in the way of their stories. They already think the entire New Zealand acadame is par of a grand conspiracty (they’ve apparently never tried to organise a meeting between three academics let alone pull of a conspiracy among them…). But hopefully the long story of the first New Zealanders and their rats, only summarised above, and the kinds of evidence scientists use to test their ideas will help to make it clear what such “alternative” archeologists lose when they turn their backs on established methods

This post got way longer than I thouhgt it would, and I’m emdebted to a lot of excellent source on the web to get me up to speed on the subject.

Scott Hamilton and Matthew Dentith have written extensively about the Celtic NZ crowd and Te Ara has a nice article on historical ideas on of the orign of Māori (check out the galleries in particular to get an idea of European attitudes at different times)

The orignal paper with the old dates is:

  • Holdaway, R. (1996). Arrival of rats in New Zealand Nature, 384 (6606), 225-226 DOI: 10.1038/

Atholl Anderson’s critque of those is summarised in this paper:

  • Anderson, A (2000). Differential reliability of 14C AMS ages of Rattus exulans bone gelatin in south Pacific prehistory Journal of the Royal Society of New Zealand, 30 (3)

And the recent landcare paper is this one:

  • Wilmshurst, J., Anderson, A., Higham, T., & Worthy, T. (2008). Dating the late prehistoric dispersal of Polynesians to New Zealand using the commensal Pacific rat Proceedings of the National Academy of Sciences, 105 (22), 7676-7680 DOI: 10.1073/pnas.0801507105

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Sunday Spinelessness – A missed opportunity David Winter Jul 25

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I hate agapanthus. Really, district councils’ and home gardeners’ obsession with those dull plants must put them alongside geraniums as the most over-planted under-interesting plant in the country. So it’s with some chagrin that I tell you that a clump of these banal flowers is the abosolutley favourite hangout for spineless creatures in our garden. The ichneumon in this post is poised on an agapanthus leaf, and I’ve seen several others wasps, aphips, leaf hoppers, three species of jumping spider, lots of moths and a few beetles among those green swords. But the most interesting creatures to make their home among the agapanthus are these tiny green spiders.

At different times over the summer I could find five or six different imdividuals like that one, living on the the tip of agapanthus leaves. So I started sticking my head into the agapanthus plants a bit more often, and even keeping few notes to track what these guys were up to. In that time I managed to record a few interesting behaviours. Males and females cohabitate (the male is the one in focus here):

They eat aphids and small flies:

They spin a silk “retreat” to hang out in (though, this doesn’t appear to be associated with moulting as they are in some other spiders):

And they lay their eggs in in disc-shaped egg sacks with raised edges.

On one rainy day I saw a female running down to the water pooling inside her leaf, collecting a mouthful of the rain then scurrying back to her egg sack. Once there, she deposited the water around the outside of her egg sack before heading back for another mouthful and repeating the process.

All those observations are tiny little data points that might, if there were written up for a little journal like Weta, help anyone who decided to seriously take up the study of these spiders, or the distribution of these behaviours among spiders as a group. To be really useful those observations need to be tied to a name, after all, species are the fundamental units of biodiversity and each of the observations above are the property of a species. I just don’t know which species. These spiders are definitely from the family Dictynidae, and they fall into either the genus Paradictyna or Viridictyna. That’s where things get a bit interesting.

Both Paradictyna and Viridictyna were described by New Zealand’s preeminent arcahnologist, Ray Forster, who lived right here in Dunedin. The two genera are actually pretty easy to differentiate, “virid” means green and Viridictyna are green with white chevrons on the top while Paradictyna can have purple markings on their abdomen (Forster actually calls them “one of New Zealand’s most handsome spiders”). If you look up there you’ll see “my” spiders have purple on their abdomen, so they must be Paradictyna right? Well it’s not quite so simple, Paradictyna hasn’t been recorded south of about Christchurch (close to 400 km away). New Zealand spiders might be chronically under studied but remember Forster lived in Dunedin, the original descriptions of these spiders include collections from all over the city and if they’d been common in Dunedin gardens at that time surely he would have found them!

So, what are these spiders? They might be one of the Viridictyna species Forster described, in which case the simple rule (purple = Paradictyna) will have to be updated, it’s probably more likely that Paradictyna have moved south to Dunedin, it’s even conceivable these guys are undescribed species. To really work out which of these cases is true you’d have to look at internal and microscopic anatomy of spiders, and I’m certainly not qualified to do that. This is the bit where a dedicated scientist, as opposed to someone poking his head in a bush once a week, would say he took a couple of these spiders dropped them in 70% ethanol and sent them to someone who knows there way around the inside of a spider. Taxonomists are sometimes criticised for their willingness to kill the creatures they study and fill museum shelves with specimens that might never be looked at again. But the major pieces of research I’ve been involved have relied utterly on being able to go to collections that were dealt with by pioneering systematists like HB Baker and JT Salmon (you can tell they’re old because they have initials for names) and apply tools those scientists couldn’t have dreamed off to their samples. Even if I’d simply put my spiders in ethanol with a descriptive tag and sent them to museum the location, date and behaviours of these spiders would be linked to a specimen that could be inspected by anyone who was interested. Who knows, maybe it would help someone PhD student in 60 years time!

But of course I didn’t sacrifice any of these spiders. It was too much fun for a geneticist like me to be playing field biologist for a while and I kept thinking, “I’ll just keep watching them a bit longer”. And now they’re gone, I don’t know if the wasps that hang out in the agapanthus did for them if they’d just done their job, seen their eggs will hatch, and shuffled off. The eggs have hatched now, so I’ll keep sticking my head in those boring leaves, but for now it’s an opportunity lost.

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Sunday Spinelessness – Behold, the Future Worm! David Winter Jul 18

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Ok, I let my Sunday get completely out of control, so here’s a very quick Sunday Spinelessness. Behold, the Worm of the Future!

Err, actually I found this little caterpillar in one of the smaller paths in Stanely Park in Vancouver. As every schoolboy knows, all insects hae six legs, but most caterpillars supplement their “true legs” with a set of porlegs along the length of their body. The prolegs are quite different to the jointed true legs, they act more like the legs of onchyphrans, moving in ripples down the body to move the caterpillar . But caterpillars like this one, which grow up to become geometer moths, don’t have prolegs along their whole body, just a few at each end. They get around by alternatively extending their bodies forward with the hindlegs clasping a surface and dragging themselves forward with their forelegs hanging on. This unique way of moving makes geometer caterpillars look like they are measuring out the set distance along a twig, which has earned them the name “inchworm” (and in fact, geometer means “earth measurer”, making these moths among the very few insect groups named for their larvae)

I framed this photo to try and show one of the inchworm’s characteristic behaviours; when they feel threatened the cling to a branch with one set of lets and extend themselves out. Impersonating a twig. Once I realised there was going to be no way of getting the shot without getting a bit of lens flare I decided to go all out for the science fiction movie meets mid 2000s web design look. I quite like it.

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Sunday Spinelessness – Love and deception in Vancouver David Winter Jul 11

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I think I’ve finally got back into the rhythm of life in Dunedin after The Big Trip, so it must be time to get back to spending a little bit of my weekend documenting some of the goings on in the spineless world. Thankfully, having gone to visit the summer I’ve got quite a cache of bug photos to keep the series going

Let’s start by interrupting this couple, who I found enjoying summer amongst the flowers on the University of British Columbia’s very impressive campus:

At first glance I thought I’d stumbled across a pair of mating bumblebees. But it’s really the wrong time of year, bumblebee mating is usually restricted to the end of summer. As the days get shorter and cooler the flowers that keep a bee hive become in short supply. Honeybees get through the winter by hunkering down, but bumblebees skip it altogether. The sisterhood that runs a bumblebee nest sends out queens and males (drones) towards the end of summer, once she’s mated the queen hibernates and emerges in the spring ready to set up a new nest. So, not quite sure what I was looking at, I took a closer look.

Hmmm, thats odd. Those big eyes …

… those little, hairy antennae …

These are flies! I think, in fact, that they are hover-flies. The bee-like appearance is no coincidence, these flies are an example of something biologists call Batesian mimicry. Despite a widely held belief to the contrary, bumblebees pack a pretty mean sting and at least some would-be predators stay away from them as a result. By appearing enough like a bumblebee to fool birds these flies get the benefit of bumblebee’s sting without having to pay the cost of making the venom. Hover-flies in particular make good mimics, there are species that specialise in aping wasps and honeybees and indeed there are other bumblebee mimics.

I’m afraid I can’t say very much more about these particular flies, after all the Pacific North West’s fauna is entirely new to me. Perhaps the dipterous and the British Columbian wings of the of the bug-blogosphere can at least give them a name. As always, the images link to higher resolution versions.

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The End of Evolution … David Winter Jul 04

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… well, the end of Evolution 2010 anyway. The silence that you may very well have failed to notice around here over the last couple of weeks has come about because I’ve been away attending my very first Proper International Conference in Portland. I haven’t been as deligant a communcator of science as the guys behin Denim and Tweed or Evolution Development and Genomics who blogged, tweeted and even podcasted the meeting but I thought I’d share a few of my experiences

On the face of it flying half way around the world to talk for twelve minutes about what you’ve been doing for the last three years is surely insane, but I found the whole experience incredibly useful. Being based in New Zealand I’ve spoken to some of the very best evolutionary biologists in the world, but we are small country and I’ve never been exposed to such a great diversity of topics, or to such great depth of expertise within the topics that I’m most interested in as I have over the last week. It turns out even the rock star scientists whose name you know as the last one on author lists on Nature papers are just people, and nice ones at that (although my first attempt to introduce myself to Jerry Coyne failed because he was mobbed by fans who wanted autographs and photos) and that some of the most interesting and well executed studies come from people you’ve never heard off.

So, flying back to New Zealand with a head full of ideas and a little bit more knowledge about the wider world of evolutionary biology has made the trip well worth it. But it get’s better than that. I can’t find any seemly way of bringing this up so I’m just going to blurt it out: I won a freaking award! The Ernst Mayr award goes to the best student presentation at the meeting by a member of the Society of Systematic Biologists (one of the three societies that host the meetings) and this year I shared it with Jeremy Brown from Berkley* . The award will find a nice place on my CV and my wall, but it’s particularly neat for me to have won something that bears Ernst Mayr’s name. Mayr was one of the most important contributors to the consilience of ideas that formed the theoretical basis to modern evolutionary biology, the modern synthesis. Unlike most of the other names we associate with the modern synthesis Mayr was not a mathematician but a naturalist, and he was particularly interested in the nature of species and the process by which they arose. As it happens, I disagree with quite a lot of what Mayr had to say and my talk was about a subject he is famously not a fan of (as you read his work it becomes clear he disagreed with himself quite a lot, so I guess this is OK), but the innovative way Mayr thought and the clarity and force with he expressed his ideas helped but speciation at the heart of evolutionary biology and his contribution to our field of study was immense. So, yeah, I’m quite stoked!

You can expect some more detailed about talks and ideas that I really like over the next couple of weeks, but for now I better go check in to my next flight.(PDX->LAX->SYD->CHC->DUD might actually be insane…)

*To underline what I said about the strength of evolutionary biology in New Zealand, two other kiwis made the finalists, Gillian Gibb and Simon Hills from Massey

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Sunday Spinelessness – Protecting the katipo David Winter Jun 13

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New Zealand has a pretty benign fauna. We have no snakes, no carnivorous mammals bigger than our little bats and, ever since Haast’s Eagle was the driven to extinction, the apex of our natural food webs has been occupied by the karearea. The karearea is the native falcon, and a fierce predator, but it holds no threat to humans. In fact, we only have one native animal capable of doing people any harm, a venomous spider known as the katipō. So, some people were a little surprised to hear the katipo had been added to list of “absolutely protected” animals included in the wildlife act, the same level or protection offered to kiwis and the tuatara.

A female katipō, photograph is CC 2.0 from Jon Sullivan


The katipō’s name is a testament to the punch its bite packs, it translates as “night stinger”. Actually, the fact the species has a māori name at all sets it apart from our other spider species, the rest of them fall under the name pūngāwerewere. The katipō certainly deserves special recognition, it’s a cousin to the black widow and the redback and its neurotoxic venom can produce the same suite of symptoms that make those spiders feared the world over.

Although the katipō’s bite is excruciatingly painful, the spider’s unique ecology means they seldom bite humans. The katipō is very closely related to the Australian redback (the two can still hybridise) but whereas the Australian species is a generalist that lives in amongst rocks and logs and human debris, the katipō has become a specialist. It builds its web in driftwood and grass on sand dunes. That specialised lifestyle has been the katipō’s undoing. In the last hundred years the total area of sand dunes in New Zealand’s coastline has decreased by 70%. Not only has most of the katipō’s habitat been destroyed in the last hundred years, most of the the remainder has been degraded. We introduced marram grass to sure up dunes that have been disturbed by agricultural and urban development. While that grass does a great job of collecting sand and holding up dunes, it’s also very invasive and the katipō doesn’t much care for it (preferring the relatively sparse growing native sedge pingao).

Marram grass isn’t the only invasive species driving the katipō’s decline, a distantly related South African spider called Steatoda capensis has become widespread in New Zealand. S. capensis is another generalist which has not trouble getting by in marram filled dunes and breeds more quickly than the katipō. Add the damage done by recreational activities like quad bike riding to the pressures already listed and you start to realise why there are eight populations of katipō left it the South Island.

There is no doubt that the katipō is threatened with extinction. Adding it to the list of species protected under the Wildlife Act* gives DoC the ability to post scary sounding warnings around remaining habitat, and to prosecute people who willfully damage that habitat. But it’s clear from a few comments around the web that not everyone is on board with saving the katipō. Why should we try and hold on to our only dangerous animal? The risk posed by the katipō is really infinitesimal, they aren’t living on your downpipes or your living rooms. Even if you wander into the sand dunes you’ll have to go out of your way to find a katipō and get it scared enough to bite you. New Zealand’s biota is already so depleted by human enduced extinctions, it really would be shamefull to lose another species because of ill informed fear.

* Reading the actual law really does my head in, I think it means for the purposes of that act terrestrial vertebrates are protected unless other wise noted, and inverts are not unless specially picked out.

And a wee note for all the spineless fans (there are some, right?..), next Sunday I will be in a series of airports on my way to the USA for the Evolution meetings in Portland. So, Sunday Spinelessness will take a break ’till early July.

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If some of us have Neanderthal genes, are Neanderthals us? David Winter Jun 08

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I got a little bit starry eyed writing about the Neanderthal genome the other day. I chose to retrace the arc of scientific progress that links the initial description of Neanderthal man as something different than modern humans to the point reached last month, where we are able to tag some of those differences to a single gene. Most of the news stories about the Neanderthal genome focused not on the genes that made us different from them, but a small percentage of the genome that reinforced the continuity been them and us. Genetic evidence that Neanderthals interbred with the ancestors of some modern humans. The revelation of these ancient assignations has caused some quite sensible people to say some quite silly things about what species are and what Neanderthals were. So, perhaps I can compliment my slightly hazy earlier piece with a more hardheaded take on why Neanderthals remain a species unto themselves.

Let’s start with the evidence that Neanderthals interbred with the ancestors of modern humans. Modern humans (Homo sapiens) arose in Africa about two hundred thousand years ago, all modern human populations outside of Africa descend from a relatively small number of migrants who left that continent between eighty and fifty thousand years ago. When those migrants first left Africa and entered the Middle East they would have met other humans. The ancestors of the Neanderthal had moved out of Africa and established themselves in Europe and Central Asia thousands of years before. Until now we haven’t known which of the four ‘F’s (fighting, fleeing, feeding or reproduction) followed that first contact, the Neanderthal genome has given us a clue.

When you compare individual DNA bases that are variable within modern human genomes to the corresponding sequences in the Neanderthal genome you find that non-African sequences match the Neanderthal sequence slightly (but significantly) more often than African sequences do. It’s possible that this pattern is an artifact of our poor sampling of African genomic diversity (that observant nerd Christie does a good job of explaining how here) but for the sake of argument let’s take it for granted that his pattern is the result of ancient interbreeding. The authors of the paper describing the Neanderthal genome estimate people with no recent African ancestry inherited between one and four percent of their genome from Neanderthals. That number is the same for Papuan and East Asian populations as it is for Europeans despite Neanderthals having lived alongside Europeans for thousands of years, suggesting any interbreeding that contributed to modern human genomes was limited to that first period of contact.

This is where the problems start. Having heard the news that Neanderthals and some of our ancestors might have once swapped genes some people remember that nice easy test of species-status from high-school biology. Something like “if two animals can interbreed then they’re part the same species.” So, are we Neanderthals; or are Neanderthals us? No. In fact, the Neanderthal genome serves to highlight some the mistakes we commonly make when start trying to define species.

Biologists have spent a lot of time arguing about just what a species is and how can delimit species from the creatures that we study, too often we’ve forgotten that those are two different arguments. DeLene from Wild Muse has a thoughtful overview of some of the factors that contribute to the “species problem” in her review of Jody Hey’s book on the same topic. You should read her piece because the species problem really is a fascinating philosophical question, but I think most of the fights that erupt around competing definitions of species come from a failure to understand that defining species and organising critters into species are two different tasks. We’ve been studying speciation, the process by which new species arise, for a while now and we’ve developed a pretty good idea of how it works. Two populations stop interbreeding with each other, during that period of “reproductive isolation” genetic changes in one population can’t effect the other so natural selection and random changes (called genetic drift) change each population independently. Species are populations which are on independent evolutionary trajectories.

Reproductive isolation drives the independence that is at the heart of what species are, but it’s not the sine qua non of a species. James Mallet from University College London has made a special study of hybridisation, and he reckons 10% of animal species and a whopping 25% of plants interbreed with other species from time to time. As molecular tools have been applied to non-model organisms it’s become increasingly clear that the “species barrier” is more porous than we’d thought, and species can maintain their independence even in the face of the occasional injection of genes from other species.(If you’re interested in the wider question, I’ve written a bit on the species problem here. The short version is we should see competing “species concepts” as operational tools that might be used to help delimit species, but not as definitions).

Now, think about the results from Neanderthal genome. Most sequences in that genome are separated from their human counterpart by a split that happened over five hundred thousand years ago. There is pretty good evidence that Neanderthals and the ancestors of non-Africans interbred when they met each other in the Middle East about four hundred and fifty thousand years after that initial split. That gene flow had the potential to homogenise the two populations into one, but it didn’t. Each lineage maintained its identity. For the twenty or so thousand years that Neanderthals continued to exist they retained identifiable morphological traits. There are fossils in Europe that some argue show a mixture of characters, but any interbreeding in that continent left no mark on modern European genomes, which have no more Neanderthal DNA than Papuan and Chinese genomes do. At the same time, the authors didn’t detect any flow of modern human genes into Neanderthal genomes (so it’s not a case of of modern humans swamping Neanderthal populations and erasing any trace of genetic admixture in the process). The available evidence seems to point o Neanderthals and modern humans as separately evolving populations, and a little bit of gene flow between them wasn’t enough to upset that pattern.

I should stress, by saying H. neanderthalensis and H. sapiens are different species we aren’t saying very much about how different Neanderthals were from us. Species are not defined by a degree of difference, or an essence that was missing in Neanderthals but is present in us, they’re just another human population that was moving in a different direction (and eventually extinction). If some of us do have Neanderthal genes, then it only goes to show how fuzzy the line between our species and the rest of the biological world is.

Green RE, and many, many others (2010). A draft sequence of the Neandertal genome. Science (New York, N.Y.), 328 (5979), 710-22 PMID: 20448178

James Mallet’s bit on the frequency of hybridisation is taken form here:

Mallet, J. (2005). Hybridization as an invasion of the genome Trends in Ecology & Evolution, 20 (5), 229-237 DOI: 10.1016/j.tree.2005.02.010

The ideas about species and species delimitation presented above are pretty similar to Kevin de Quieroz’s take:

De Queiroz, K. (2007). Species Concepts and Species Delimitation Systematic Biology, 56 (6), 879-886 DOI: 10.1080/10635150701701083

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Sunday Spinelesness – One for the arachnophobes? David Winter Jun 06

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It occurs to me that some readers might be put off by my affection for spiders. I’d be interested to see which creature, the wasp or the spider, you find yourself cheering for at the end of this post. Let’s introuduce them. First, the large black hunting wasp Priocnemis monachus emerging from its burrow in one of the steps on our garden path (I messed up the focus, but nature has a way of refusing to re-pose):

pomp1

And the creature the black hunting wasp has been hunting, one of the native tunnelwebs Porrhothele antipodiana:

spider1

Po. antipodiana is pretty cool spider, it’s one of very few that are capable of eating snails. Snails usually avoid the attentions of ground dwelling spiders by being too slimy to get a hold off and being able to retract into their shell. Po. antipodiana get’s around those defenses by hooking its fangs into the snail’s body and holding on while the snail struggles, produces tonnes of mucus and finally succumbs to the spider. A couple of months ago I gave a talk to a local school who wanted someone to help their study of invertebrate lifestyles and one of the kids told me that he’d seen a tunnelweb eating a snail. The budding naturalist didn’t seem at all proud when I told him that he’d observed a behaviour that was only recognised by scientist 30 years ago. I guess 30 years seems an impossibly long time when your 10!

If this particular spider looks a bit bedraggled it’s because it has already been anesthetised by the wasp. Pr. monachus is a member of the family Pompilidae which, like the ichneumonidae that featured here last week, use the living bodies of other arthropods as incubators to grow their young. While most of the ichneumonidae use caterpillars to grow their larvae the pompilids specialise in spiders (which has earned them the name spider wasps). There are ten described species of spider wasp in New Zealand, each targeting a range of spider species. Pr. monachus the largest of our spider wasps, and by choosing Po. antipodiana to provision her nest this one has taken on of New Zealand’s largest spiders:

Pomp3

Pr. monachus follows the typical pompilid nesting behavior, which means they go hunting before they set up their nest. As I watched these two the wasp would drag the spider a few centimetres then drop it and scurry back up the step and into its nest for a few seconds before returning to the spider, checking it was still incapacitated (and giving it another sting if it showed a fight) and repositioning it again. I don’t know how much of that behavior was down to the wasp setting up its nest and how much was the wasp struggling with having bitten off more than it could drag up the sheer surface of the step it built its nest in.

Pomp5

The wasp was definitely seemed to be having a hard time hefting the spider up the step. I spent about half an hour watching her grab and the spiders legs, its spinnerets or its even its head while clinging to the sheer face of the concrete step. In the end, it started raining and I decided I should probably do something else with the rest of my weekend so I left her to her work. I came back about an hour later and both spider and wasp were gone. I don’t know if the wasp gave up; or if it achieved its Herculean task and the spider’s body is, even now, nourishing the next generation of these impressive wasps.

Pomp4

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Sunday Spinelessness – The Wasp That Did For Darwin’s Faith? David Winter May 30

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I own that I cannot see as plainly as others do, and as I should wish to do, evidence of design and beneficence on all sides of us. There seems to me too much misery in the world. I cannot persuade myself that a beneficent and omnipotent God would have designedly created the Ichneumonidae …

- Charles Darwin writing to Asa Gray

Here’s one the Ichneumonidae, the family of wasps that Darwin couldn’t fit into a world with a loving god.

ichn2

What could Darwin find so abhorrent about such a fine looking creature? It was their unique approach to parenting the put Darwin off. Ichneumon are diligent parents, to make sure their offspring have all the food they could ever need the wasps lay their eggs in the bodies of other insects. The larva develops within the host insect, carefully keeping the doomed creature alive as it eats its way through first its fat stores then its non-essential organs. Finally, with the larvae almost fully grown it turns its attention to the host’s essential organs before it eats its way through the skin. The ichneumon life-cycle was the inspiration for the chest bursting aliens in the Alien movies.

The quote that started this post is often presented as an observation unique to Darwin, or even as a sort of epiphany that did for Darwin’s faith. In fact, Darwin was repeating what had become an old saw by the time he wrote it. The ichneumon lifecycle was widely discussed by Victorian naturalists and theologians. At that time there was a great deal of interest in an idea called natural theology, which amounted to learning about god by studying his creation. But some pats of nature don’t seem to reveal a beneficent god. The natural theologians managed to convince themselves that the lion hadn’t yet laid down with the lamb because predators saved their prey a worse fate, but the idea of ichhneumon larvae rasping away at their hosts from the inside out proved a greater challenge.

Stephen Jay Gould wrote an essay on the problem of the ichneumon which lists some of the ways natural theologians tried to deal with it. William Kirby, the great entomologists who also happened to be a reactor, emphasized the great dedication of the wasp to her offspring and praised the larvae’s sustainable approach to eating their hosts while saving mroe live tissue for later. For modern readers it seems very odd to be describing wasps as virtuous. By and large we’ve come to realise that nature doesn’t provide moral lessons, but we haven’t quite given up the naturalistic fallacy that drove the natural theologians. How many times have you hear peddlers of snake oil claim their product was safe “because it’s natural”? Or people object to genetic engineering or vaccines because they are unnatural?

We even still look on nature as a source for morality, proponents on either side of the debate for gay rights swap statistics on how common homosexuality is among other animals – as if the sex lives of bonobos or prairie voles had anything to do with human rights. If there is a lesson to learn from the gruesome life-cycle of the Ichneumonidae it’s that nature just is, and we need to turn elsewhere for moral lessons.

Hold on, these posts are meant to be about celebrating weird bugs. Let’s end with the great David Attinbrorough on the Ichneumonidae.

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Living up to our name David Winter May 28

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Homo sapiens means “wise man”. Sometimes it’s hard to think that Linnaeus was right in honouring our species with that name. We’re the reason the earth is going through its sixth great extinction; people are still routinely killed for belonging the wrong race, religion or sexuality and the prospect of taking action on climate change makes a significant proportion of the population behave like children. So it’s nice to be reminded every now and again about the sorts things our species can do when we put our minds to it. I’ve been trying to find time to write a proper post about the Neanderthal genome, but here’s something to think about on a rainy Friday afternoon.


Neanderthal 1, the first human fossil to be described

In 1857 an anatomist and a school teacher, Hermann Schaffhausen and Johann Fuhlrott, described a set of bones that had been discovered in a limestone quarry in what was then called the neanderthal region of Germany. Amazingly, the neanderthal region was named after Joachim Neander whose own name translates as “new man”. A new man was exactly what Schaffhausen and Fuhlrott saw in the bones that they described. They were at once human and something “other” Chief among the characters that set the neanderthal samples apart from modern humans was the thick brow ridge that we now think of as characteristic of primitive humans. Thanks to these differences the school teacher and the anatomist concluded that the neanderthal samples were human but something quite different than modern Europeans.

“Neanderthal Man” was the first pre-human fossil to be described. At the time science had no convincing mechanism by which species might change over time and no idea of how organisms passed on traits to their offspring. Within in a couple of years Darwin had published The Origin and Mendel his Experiments on Plant Hybridization (which was promptly ignored, and only cited three times in 30 years). In time scientists discovered more human fossils; Neanderthal man showed up all over Europe and took the name H. neanderthalensis, Euguen Dobois uncovered H. erectus in Asia and host of anthropologists have since added characters like the Turkana boy, H. habilis, Ardi and a whole cast of Australopithecines to our family tree.

The science of heredity moved on too. In the 20th century geneticists, especially Hugo deVries, rediscovered Mendel’s work and set about building a particulate theory of inheritance. TH Morgan showed that genes resided on chromosomes, Fisher, Wright Haldane and others synthesized Mendelian genetics with Darwin’s ideas on evolution, MacLeod and McCarty showed that DNA (a chemical initially identified by Miescher) contained genetic information (though no one believed them until Hershey and Chase demonstrated it again) and, of course, Watson and Crick showed us what DNA looked like thanks to Rosalind Franklin’s x-rays. It took a little over 20 years to get from Watson and Crick’s double helix to first complete virus genome and another 30 to scale the 5 orders of magnitude in size between that one and the human genome.

Last month, scientists published a first draft of the Neanderthal genome. 60% of the genetic make up of species of human that has been extinct for thirty thousand years. Thanks to the work of all those scientists listed above, and countless others who go unremembered, we now have a pretty good idea about the genetic basis of the thick brow ridge that convinved Schaffhausen and Fuhlrott than neanderthal man something different than other humans. The Runx2 gene is in a region of the genome that has been selected for in the H. sapiens lineage. We know from the work of yet more scientists that Runx2 is one of the most important genes regulating bone growth in humans and is associated with malformations of the skull. It’s no great stretch to imagine that our species lost the brow ridge that that we associate with primitive humans thanks to changes in the expression pattern of Runx2.

It some ways that’s a trivial piece of information, we’ve known for a long time that most morphological change is likely due to changes in the expression pattern of development genes. But isn’t it wonderful to think that in the span of two human lifetimes we’ve moved from knowing nothing of our species’ history to the point that we are developing hypothesis on the molecular basis of the changes that made us different from the host of human species we’ve since discovered.

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