Thanks to Jonah Choiniere who is currently on a long term trip to the IVPP I was able to get my hands on “What bugged the dinosaurs?” this week. A recent book by husband and wife team George & Roberta Poinar, it puports to show how insects and diseases wiped out the dinosaurs (or so the hype went). I have wanted to read this for a while as the premise seemed intriguing, if very far fetched. However, as you may have guessed from the title above, I was far from impressed.
The book is a myriad of overstated and / or unsupported claims, poor English (they might be non-native speakers, but both work in the US and this is their third book in the language!), and most startlingly a frightening lack of knowledge about dinosaurs. Some 27 people are listed in the acknowledgements and not one do I recognise as working on dinosaurs, and it shows. Worse than that, it seems like even the authors did not bother to do any research on the subject and the errors are numerous and obvious. If you are working well outside your field, you need to do the work, or get help and there is no evidence that either occured. The thrust of the book is of course about ancient insects (and other parasites) and pathogens something the authors do work on, but of course in order to relate it to the dinosaurs, they will need to know about them and get their facts right, and here they fail badly. In most cases, I doubt the corrections would have made much difference to their arguments, but the errors are so frequent and obvious, it makes one wonder about how the rest of it was put together, and some of the arguements are incredibly tenuous. A few examples follow:
- Dinosaur taxa are misplaced in time and space (e.g. no sauropods in the Cretaceous outside of South America).
- Names used include the “Garudimimidae”, “coelurids” and “hypsilophons”.
- A reconstruction of the therizinosaur included an ‘allosaur’ head, no beak (despite it being mentioned in the figure caption) a short neck, a long body and tail, the manus was normal but with one enlarged claw (a la spinosaurs) and the three toed feet included a raptorial claw! Where did they get this from? Igananodons are shown in the ‘kangaroo’ pose, abandonned decades ago, and sauropods are shown as tail draggers and later described as living in water! Oh, and the authors drew the illustrations themselves, so excuses there!
- The following ideas are all given without citations or supporting evidence (paraphrased): dinosaurs shed their skin like lizards, most if not all juvenile dinosaurs ate insects (implied exclusively), pterosaurs were gliders, dinosaur skin was no thicker than that of modern lizards, no dinosaurs (except birds) were arboreal, hadrosaurs could feed up to 30 feet into a canopy, but ignaunodontids were limited to the bottom 10 feet, some troodons [sic] ate ants as did some dromaeosaurs, and insect diversity was 4 times higher in the Cretaceous compared to the present.
From here we get to the crux of the book – did the insects (and other vectors and parasites and pathogens) have a serious detrimental effect on the dinosaurs? There is much here of interest, if only as a catalogue of known mites, mosquitoes, ticks, bugs, nematodes and more (along with some incredible preservation of pathogens inside the amber imprisoned insects) and the evidence that they were present in the Cretaceous and that they may have (or probably did) feed on dinosaurs and cause both injuries and transfer parasites. Again though, a lack of hard evidence is obvious, while it would be silly to suggest that dinosaurs somehow avoided ticks, mites and diseases throughout their reign, it would have been nice if the authors could have demonstrated that there insects out there with mouthparts capable of piercing dinosaur hides, or that dinosaur skin was vulnerabe to the insect known at that time, or that there were skin traces with wounds known, or bones showing pathologies that could be traced to insect vectored pathogens. Perhaps this evidence simply does not exist, but surely they could have looked, and in places (like dinosaur skin thickness) statements are made, but without backups or citations.
Fully half the book consists pretty much of “parasite X existed in the Cretaceous, we know they transport diseases like Y and modern versions of X feed on reptiles, therefore dinosaurs suffered from diseases like Y”. I am being a bit over harsh here, but it really does read like that. I was more interested in the existence of these insects, their evolution and preservation, but the authors wasted their efforts trying to tie them to dinosaurs and not talk about the insects themselves. Ultimately, they propose three key issues why these animals would have been a serious threat to the dinsoaurs: 1. they would have competed for food (insects eating leaves etc)., 2. they would have spread diseases, weakening some animals and which ultimately 3. could have killed them in some cases.
The only obvious answer to this is: so what? Modern herbivores compete with insects for food and don’t suffer for it. Sure, animals get sick and die from diseases, but they tend to evolve resistence to pathogens, and behavioural or anatomical defences against parasites (e.g. thicker skins, tail swishes, seeking shade, mud wallows etc.). How is this any different to a modern ecosystem? How does a pathogen evolving some 100 million years ago seriously threaten the dinosaurs who only struggled on for another 35 million years at this point? The arguments put forward are hardly convincing:
We are shown how diseases affect animals (especially humans) and can cause deaths in large numbers. Other examples of blue tongue in domestic livestock, and the loss of Hawaiian birds of avian malaria are cited. But humans are known as poor models for such things, having only recently evolved and spread quickly, we are vulnerable to all kinds of diseases that others are not (look at HIV vs SIV). Domestic livestock are massively inbred and the tactic of slaughter every time a disease rears its head hardly help immunity evolve, and groups of small populations in isolated areas like Hawaii will always be vulnerable to newly introduced pathogens. Coming from someone who was an advisor for WHO, I am worried that this is the best they can come up with as models of dangerous pathogens (in terms of death) – are there no better examples in the literature, and if so why are they not cited? Pathogens killing off vulnerable or newly evolved taxa is no surprise. Sure, being sick is no fun, and it brings with it an increased risk of mortality (from other infections, predation etc.) but again, this is true of all wild animals – they have a parasite load, and some are worse than others. But the idea that some pathogens suddenly arose and wiped out dinosaurs seems ridiculous, and indeed it is as we shall see below.
One is left to wonder how such invertebrates could have wiped out all dinosaurs, on all continents, from all habitats at one point in time. It is suggested that land bridges and wind dispersal would soon allow vectors and dieases to spread quickly, but I am not convinced. Would a tropical disease in the equatorial African forest quickly spread to the American arctic, Australia and the Mongolian deserts? Really? Why did birds survive this onslaught? Did not some dinosaurs have big enough populations (and thus the variation) to make them immune?
This last point is challenged by the idea that insects outdid dinsoaurs in the r-selected vs K-selected arena, but the idea is poorly argued. Dinosaurs are far less at risk of this factor than mammals or birds. They are about as un K-selected as they could be given their size – they have large numbers of offspring (large egg clutches) could potentially lay multiple times a year, and yet still had long lifespans. An elephant that lives to 80 might have 15 young in her lifetime, a medium sized sauropod might lay several clutches of 50 eggs, four or five times a year. They picked the worst possible group to argue this point with.
Finally we reach the last few pages and the denoument – did these pathogens really take out the dinosaurs. Well, no. What we are told is that with the deccan traps activity (possibly combined with a meteorite impact) and other factors, dinosaurs would have been in big touble and with collapsing ecosystems. Would then, the effect of parasites and pathogens have helped them on their way? Yes. Well, obviously. I fail to see why this is news. It has perhaps never been explicitly suggested, but the book could really be summed up as “dinosaurs probably had all kinds of parasites and if the ecosystems were doomed, then this might have killed some of them”. Thanks. For. That. Page after page of devastating scenarios have been presented with dinosaurs being outcompeted for their very greenery, huge numbers of new pathogens arising and being transported by new vectors, but the conclusion is far from the drama of previous pages – the result is a whimper, not a bang. It is not like the idea is even new in this context, I think any reasonable palaeontologist would agree that many dinosaurs must have suffered from parasites and diseases and during an extinction event might be still more critical. In fact in 2005 David Unwin made note of the same idea in his pterosaur book with a little piece of fiction – the last survivng pterosaur slowly dying from an excess of ticks worrying at her skin.
Even here we are still subjected to more unsupported hyperbole namey that “Anytime an ecosystem is challenged…virulent pathogens appear and epidemics run rampant”. Really? Since when? You might think an expert on parasites and pathogens who works as a WHO advisor could provide a few examples of such spontaneously generating pathogens in stressed environments, but if he can, they were not cited. Thus we are left with entirely hypothetical ‘new’ pathogens (or ones that are already 10s of millions of years old) arising during the KT extinction and somehow helping to deliver the “knockout blow” to a group that was apparently already doomed.
I really do suspect that much of this is a result of editorial pressure. It is far easier to sell a book on dinosaur extinction than on Mesozoic ticks and fleas, but the outcome is a disaster. The dinosaur science is horribly mangled and gives off a very false impression of the current state of research, huge and sweeping (and sometimes critically important) statements are made without support or even explanation, and the one thing that should be of interest (the exceptionally preserved insects and bugs and the evidence for them carring dieases) is overlooked in trying to relate everything to dinosaurs, (and dinosaurs alone), as victims.
There is the germ of an excellent popular account of fossil insects here, and if it has to be related to dinosaurs to sell it, so be it. But that can still be done by focusing on the insects themselves: what were they like, what are they related to, how does amber preserve, are they any dinosaur-specific adaptations preserved, how do these things affect modern animals? All of these issues are largely ignored or glossed over in an attempt to make it sound like the dinosaurs were doomed through the presence of these animals, yet the denoument is that they may have contributed in some way to an already doomed race. It is hardly a dramatic and exciting conclusion after a litany of suggestive comments about the power of the parasite which themselves I think provided little real support.
So what bugged the dinosaurs (and me)? A frightening lack of research, and indeed a lack of respect for my field, and the outcome is an unsupported and unconvincing mess. The book that should have been written would have been fascinating, the book that was written is poor, and the science it communicates is inaccurate on the dinosaur front, limited on the insect front, and misleading or unconvincing on the actual extinction front.