Insects May Have Had a Hand In Dinosaur Extinction

eldavojohn writes "Everyone's got their favorite theories of Dinosaur extinction, but new speculation is rampant in a book that gives cause to believe it may have been disease-carrying insects. Due to the length of their slow and eventual extinction (the 'K-T Boundary'), it is argued that this would more likely be attributed to the spread of disease and the rise of parasitic insects like ticks or biting flies. Are our immune systems the only reason any animals survived?"

Comments

Mom, I'm saving humanity

[cloudkiller]

someone get me a can of WD40 and a lighter.

Mixed metaphors

[pzs]

Do insects have hands?

Re:Mixed metaphors

[Chris Burke]

They did back then, so you can probably imagine why they were a threat to dinosaurs.

Three questions

[A nonymous Coward]

Why wouldn't this also affect mammals? Is there an implication that dinosaurs had more primitive immune systems? Is any of this more than mere speculation?

I also would have thought dinosaurs had thicker skin, if for no other reason than having a lot more meat to hold together than the puny mammals of the time. Is this not a factor? Do modern day elephants and rhinoceroses suffer from insect infestations even tho they have thick skins?

And lastly, I thought recent research had shown that the slow dying theory was just an artifact of the skimpy fossil record, that they did indeed die out very abruptly at the K-T layer. Is my memory wrong here?

Re:Three questions

[Chris Burke]

Why wouldn't this also affect mammals? Is there an implication that dinosaurs had more primitive immune systems? Is any of this more than mere speculation?

Well this is mere speculation, but the implication isn't necessarily that dinosaurs had a more primitive immune system, it could simply be that it was different. Different diseases infect different animals. It makes sense that if a virulent and deadly disease borne by insects arose in one species of dinosaur, it would have an easier time adapting to others than the newly arisen mammals.

Re:Three questions

[zappepcs]

Sorry no link, but yesterday there was a story I read that about 8% of human DNA is made up of junk left behind by retrovirus infections. That is to say, we survived those. HIV is a retrovirus. It is not far fetched to believe that Dinosaurs also suffered from disease and virus infections, and that insects could carry these from one animal to another. The general panic over H5N1 should tell you just how serious such a thing can be. If the KT boundary event weakened many dinosaurs, leaving them vulnerable, diseases that were not typically a threat could have become one.

It's also possible that the combination of several things, including climate change after the KT boundary event, worked together to cause depopulation.

Re:Three questions

[MightyYar]

Why wouldn't this also affect mammals?

And more importantly - why do we still have birds? Birds are supposed to be direct decedents of dinosaurs, and they seem to handle disease pretty well (judging by the state of NYC pigeons).

Re:Three questions

[ColdWetDog]

My question would be, if these insects were either large enough, or had the ability to penetrate the thick hide of a dinosaur, what chance would a small mammal have had from one of them?

A proto-mosquito the size of turkey is flying around.

OK, you're a six story tall dinosaur ...
Or a three inch tall proto-mouse.

Who's gonna get bit?

Re:Three questions

[GargamelSpaceman]

Here's a wild ass guess that could explain it, but for which I have no evidence.

Meteor impacts and lava flows alter the earth's climate. In general this favors warm blooded creatures.

It also shakes things up in the plant world perhaps *causing* the explosion in flowering plants ( which actually happened first, meteors and volcano disasters or flowering plants, I don't know, this is just a wild ass guess with no supporting research )

The explosion in flowering plants and their insect symbiotes, also stimulates insect evolution. Sexual reproduction in plants creates a huge new set of insect poisons and insect niches, kicking insect evolution into overdrive as they adapt and change over ( a fairly short ) time. For a time there seemed to be a new disease carrying or food destroying insect evolving every (insert short period of time here).

Relative to Megafauna that typically lives long, insect and plant evolution can happen in a flash. The megafauna ( ie the large dinos ) die. Better able to evolve fast are small dinosaurs and mammals, however the mammals mostly win out because of their warm bloodedness which gives them the edge as temperatures fluxuate wildly because of the volcano eruptions..

I think even today long lived megafauna would adapt more slowly to a rapidly changing environment than small animals like rats and cockroaches. They may go extinct leaving empty niches for the remaining small life forms to evolve ( quickly since they are small and short lived ) to fill.

I don't think reptiles are inherently more primitive or less able to adapt than mammals. Immune systems evolve faster if each generation lives for a shorter timespan. If you are smaller, then your population can be bigger on a given landmass giving you more chances to evolve. That's what did the dinos in. Their size.

Re:Three questions

[lysergic.acid]

while i'm not a zoologist, i'd imagine that if the article is correct, and this was when insects first became a significant vector for disease transmission, then it's plausible that neither dinosaurs nor mammals would have had the immune system to defend themselves against illness.

it's much harder to adapt to a brand new class of diseases than it is to adapt to new variations of an existing form illness. so the attrition rate for evolving a suitable defense would have been extremely high.

as for why mammals would survive while dinosaurs didn't, it may have been because mammals reproduced much quicker. animals with shorter life cycles and higher reproduction rates tend to adapt to environmental changes much more easily. in the time it takes for a large dinosaur to go through 2-3 generations of changes, a small mammal such as a rodent may have gone through 20-30 generations or more. so in times of crisis small animals are much more likely to survive than larger ones.

another factor could be that, because mammals were at the bottom of the food chain, they tended to be nocturnal and live in burrows. being underground could perhaps have also protected them from the global catastrophes that were ravaging dinosaur populations. they probably didn't have as specialized of diets as the dinosaurs did, so when flowering plants began replacing the normal vegetation that herbivorous dinosaurs depended on, plant-eating mammals weren't affected. they also wouldn't have been affected by the mass population die-offs that would have starved the carnivorous dinosaurs.

lastly, insects would have provided a valuable new food source for primitive mammals. dinosaurs may have grown too large to do the same. and whenever animals at the top of the food chain are removed from an ecosystem, the animals at the bottom of the food chain flourish. so all of this would have contributed to the rise of the mammals.

Re:Three questions

[sm62704]

You mean like how fleas carrying the plague made rats and humans extinct during the dark ages?

IIRC insects predate dinasaurs. Sorry, I'm a skep tick.

The book's author isn't a palentologist, he is with the Department of Entomology at Oregon State University. He is (like I am now) making claims he does not have the credentials for.

Re:Three questions

[Chris Burke]

Uh, the species of rat which carried the Black Death did very nearly go extinct, and it wiped out one third of the population of Europe in just two years, in some areas as much as 60-75%. If that had been combined that with other pressures occurring simultaneously, like extreme changes in the environment, then yes, even two of evolution's greatest generalists could have been brought low.

I can't say I believe it, but I also don't find it inherently implausible.

Re:Three questions

[TheRaven64]

Well, if you believe the so-called theory of gravity, then that's a question, however if you believe the scientific theory of Intelligent Falling then the answer is obvious - they were lifted by the creator. Yet more evidence that IF is true and should be taught in schools.

Co-evolution of animals and diseases

[PhilHibbs]

Any disease that wipes out its host will have to evolve to be less deadly, or it will run out of hosts. So it's not really right to say that it's our immune systems that allowed animals to survive - the evolution of an immune system and the diseases that it fights go hand-in-hand. There is some competition, with diseases finding new ways to get around immune responses, but also some co-operation, as an overly-effective disease will destroy its own ecosystem and thus die out.

Re:Co-evolution of animals and diseases

[MaxEmerika]

Diseases that are transmitted directly from host to host tend to evolve to be less deadly for the exact reasons you describe. Diseases that are transmitted through an intermediary (like insects) can afford to be much more aggressive against their final hosts. That said, this theory still sounds fishy to me. These diseases were so devastating that they managed to drive two orders of animals to total extinction?

Re:Co-evolution of animals and diseases

[hey!]

There is also some evidence that disease agents may confer a kind of symbiotic advantage on their hosts.

Hantavirus, for example, is relatively harmless rodent populations that harbor it. However it can be deadly to immunologically naive populations that might move in and displace them. So it is possible that infectious agents may help their hosts guard their ecological niche. We can see something of the opposite effect in the introduction of European diseases to North American populations living in what were more hygienic conditions.

The idea that alterations in insect populations and the geographic range of diseases may have played a role in a mass extinction event is a sobering one. Ecological disruption tends to cause geographically isolated infectious agents to spill out, especially in a world connected by global commerce. And we are in the middle of the mother of all ecological disruptions: global climate change.

Take Malaria, a constant presence in the tropics for as long as can be remembered. Malaria is special among vector transmitted diseases in that it does not have a significant animal reservoir: malaria pathogens specialize in one closely related group of species, say monkeys but not apes. So human malaria species specialize in humans, which potentially makes them eradicable.

This is important, because with climate change, the boundaries of Malaria carrying mosquitoes is shifting, not only away from the tropics, but to higher altitudes. Mexico city is in a malarial latitude; it is altitude of nearly 13,000 feet that keeps the Anopheles mosquito genus in check. Perturb the climate slightly, and the third largest metropolitan area in the world will provide over twenty million new hosts for Malaria protozoan. As a capital city, it has air links world wide.

I will give another example of how ecological disruption is tied to diseases. A friend of mine married into a family that lived on an island. Everyone in that family had contracted Lyme disease at some point in their life. The problem was the ecosystem needed a top-level predator, but humans had wiped out wolves over a century earlier. This disturbed the ecosystem, because without a top level predator, the only thing keeping the rodent population in check was how much food there was available, and disease. That disease spilled over into the human population.

Now a few decades ago, a small population of Western Coyotes swam out the island and established itself. They took down most of the deer herd, then turned to the rats, voles and other small mammals. Ticks have gone from being a plague of almost unimaginable proportions to being relatively rare. Imagine the amount of biomass in even a small coyote. Now imagine the ecosystem is using that biomass to generate ticks.

Of course, there aren't as many deer, and they make a hell of a racket at night, but on the plus side Lyme disease seems to have become much more rare. Attempts to eradicate the coyotes failed, because while they fill the wolf niche in the environment, they're much, much more adapted to living alongside humans. So overall, the coyotes have restored the disrupted ecology humans had "improved" by eliminating the wolves.

Stupidity

[MightyMartian]

This is a dupe, and what's more, it may be the most inane and retarded theory of dinosaur extinction out there. Dinosaurs weren't a single group, but an incredibly large and diverse family. This is like claiming that a set of epidemics could kill off all mammals or all birds. It's fucking stupid people.

Reptile immune systems

[smellsofbikes]

Reptiles have perfectly good immune systems: in the case of alligators, they're better than human ones. However, since reptiles are cold-blooded, the seasonal temperature variation means reptiles have suppressed immune function during cold periods, so they'd be predisposed to higher mortality from disease after a meteorite strike or extensive volcanic activity puts enough debris in the atmosphere to reduce the Earth's temperature.
The Black Death spread across Europe and the Mideast in less than 4 years -- individual diseases can move very quickly. The idea that the rise of a class of disease vectors, biting insects, might've gradually led to higher mortality, is interesting, and something I'd never read about.

Fast extinction

[Geoffrey.landis]

Due to the length of their slow and eventual extinction

Do note that the "fact" that the Cretaceous-Ternary extinction event was "slow" is not well established; there are many palentologists who cite evidence that it was, in fact, extremely rapid, and the apparent "slowness" is a statistical artifact of the discontinuous nature of the fossil record. The microfossil record, which is much more continuous, seem to show very rapid extinction.

The dinosaurs lasted for about 165 million years. It seems rather unreasonable to think that they coexisted with insects prefectly well for 164.9 of those 165 million years, and then suddenly every dinosaur species died of insect-borne infestation in the last 0.1% of their reign-- including the ocean-dwelling dinosaurs. And including a lot of other marine life. And microbiota. And many species of plants.

It was God's fault.

[lantastik]

One day God came down and asked the dinosaurs if there was anything they wanted. They responded that they wanted to see what the future was going to be like. God opened a vision for them and at first they were excited at all the tasty bi-peds walking around and all the lush vegetation provided by global warming.

Then as the vision continued, they saw something they thought no living being should ever have to endure. They saw that Carlos Mencia was going to be famous and that people would eventually experience his comedy in one form or another. The dinosaurs decided that they would never subject their heritage to such atrocities.

They begged and pleaded for God to take their lives. God replied, "I love you and that is not my way." The dinosaurs were persistent and they begged and pleaded some more. God finally agreed, saying, "Since I love you, I will take your lives, but you must endure horrible plagues, famine, and natural disasters." For the dinosaurs, it was worth it and they agreed.

We can all learn something from our reptilian, bird-like ancestors.

What really happened to the dinosaurs

[techess]

Scientists have shown that the moon is moving away at a tiny yet measurable distance from the earth every year. If you do the math, you can calculate that 85 million years ago the moon was orbiting the earth at a distance of about 35 feet from the earth's surface. This would explain the death of the dinosaurs. The tallest ones, anyway.

Not necessarily that simple

[Moraelin]

Well, I don't think it's necessarily that simple. There are plenty of diseases that outright kill.

Probably the most obvious example is the bubonic plague, a.k.a., the Black Death. It eventually killed all 3 types of hosts involved in plague outbreaks:

- the rats (which were eventually replaced by a different and more robust species of rat, as, yes, the old one almost went extinct),

- the flea (the bacteria essentially plug its stomach, so it ends up perpetually hungry, sucking blood until it barfs it right back and infests a new host. Eventually it starves to death.)

- the humans

Early outbreaks of the Black Death killed 80% of the infected people and massively depopulated Europe. Nowadays you'd only have about 50% chance to die of it. Our immune system did evolve somewhat.

But if you combine it with other factors, e.g., a changing climate or whatever, and it could have driven a less resourceful species extinct. As I was saying, the black rats that were the co-hosts in those outbreaks did go pretty much extinct.

The bacterium itself, well, essentially the immense majority of those which caused such an outbreak, eventually died together with its hosts. You'd think that would be a very strong evolutionary pressure to evolve into something less suicidal. Essentially each outbreak ended up in a near wipe-out of the bacteria population. You have an advantage if you don't do that, no? But said evolution towards more benign versions just didn't happen. The humans evolved to have better chances of survival, but the bacterium seems to have stayed just as nasty as ever.

Basically what I'm saying is that there is no divine plan to save you, so to speak. The bacterium doesn't know whether it's heading towards extinction together with its hosts. As long as there are still _some_ available hosts, it didn't go extinct yet, and it can continue just as well.

Additionally, some bacteria can infect more than one host, or can survive decently in the ground without a host. For the latter, even killing all hosts immediately, still isn't really a problem. The former killing one of the hosts isn't much of an impediment either, as long as other hosts can survive (or breed faster than they're killed.)

So for example a hypothetical disease which could infest both dinosaurs and mammals, but only killed dinosaurs, could jolly well keep doing so ad infinitum.

Now I'm not saying that this is necessarily how the dinosaurs died out. Just that evolution works in perverse and mysterious ways.

Reptiles have great immune systems

[Comboman]

Reptiles actually have great immune systems. Crocodiles are frequently injured in territorial fights, yet their open wounds do not get infected in the less-than-antiseptic environments they live in. Scientist are currently studying them to try to figure out why their immune systems work so much better than ours. Then again, they are one of the few families of reptiles that survived the extinction, so maybe that had something to do with it.

Re:Reptiles have great immune systems

[Anonymous Coward]

Antibacterial != antiviral. Their immune systems are very good at protecting against bacterial infection in those environments (and some reptiles, like the kimodo dragon actually have nasty bacteria living in their saliva that acts as a natural poison to weaken prey) but viral immunology is completely different. And viral mutations can move quickly though a population where they were previously benign.

What about the aquatic dinosaurs?

[wilkinc]

From the wikipedia page about the Cretaceous-Tertiary extinction event: Mosasaurs, plesiosaurs, pterosaurs and many species of plants and invertebrates also became extinct. Does this insect argument explain the fact that plesiosaurs, plants and invertebrates also went extinct?

Re:Yes

[MikeDirnt69]

Who do you think you are? Chuck Norris?