Did Insects Kill the Dinosaurs?

Ponca City, We Love You writes "Asteroid impacts, massive volcanic flows, and now biting, disease-carrying insects have been put forward as an important contributor to the demise of the dinosaurs. In the Late Cretaceous the world was covered with warm-temperate to tropical areas that swarmed with blood-sucking insects. A theory explored by researchers at Oregon State suggests these bugs carried leishmania, malaria, intestinal parasites, arboviruses and other pathogens. Repeated epidemics may have slowly-but-surely worn down dinosaur populations while ticks, mites, lice and biting flies tormented and weakened them. 'After many millions of years of evolution, mammals, birds and reptiles have evolved some resistance to these diseases,' says Researcher George Poinar. 'But back in the Cretaceous, these diseases were new and invasive, and vertebrates had little or no natural or acquired immunity to them.' The confluence of new insect-spread diseases, loss of traditional food sources, and competition for plants by insect pests could all have provided a lingering, debilitating condition that dinosaurs were ultimately unable to overcome."

Comments

Bernard Werber

[Scrameustache]

A French sci-fi author suggested that ants deliberately waged war on dinosaurs and killed them all (by invading their natural orifices and killing them from the inside) because their large size was detrimental to ant nests.

But frankly, I don't think new diseases would wipe out an entire order of life, all over the world, in all ecological niches, without wiping out other unrelated orders of life. In their hundreds of millions of years of existence, dinos had to fight off insects and diseases that were there before them, it couldn't just wipe them (and just them) off the face of the Earth in such a short time.

Sounds plausible, but...

[zappepcs]

"We can't say for certain that insects are the smoking gun, but we believe they were an extremely significant force in the decline of the dinosaurs," Poinar said. "Our research with amber shows that there were evolving, disease-carrying vectors in the Cretaceous, and that at least some of the pathogens they carried infected reptiles. This clearly fills in some gaps regarding dinosaur extinctions." I think that in view of the asteroid disaster and limited sustenance material in its aftermath the diseased insects could do damage to already suffering species. In the short term this would be no major issue, but descriptions of the asteroid's damage show that it would have been decades of knock-on effects to climate and biology. If smaller (low on the food chain) animals suffered first, it would lead to shortages and starvation up the chain. Is that enough to cause mass extinction? Who knows, but it seems plausible enough to be worth counting in the list of causes.

You might ask what happened Mayan empire? http://en.wikipedia.org/wiki/Maya_collapse This insect thing might not be so far fetched as you think?

Re:Hold the phone

[Henry V .009]

It's not specific blood-bourne pathogens, it's blood-bourne pathogens in general. We have lots of complicated mechanisms that have developed over millions of years of evolution that provide a lot of protection.

And yes, there are a number of genes that code for malaria resistance in human beings; they exist wherever malaria is common. The most well known (and most common?) is the sickle cell gene. But there are a number of other mechanisms that have evolved independently that protect people from malaria. If your ancestors had a lot of trouble with malaria, you are probably much more resistant to it than someone whose ancestors came from Norway.

Flowering plants originated 70-90 mya too.

[140Mandak262Jamuna]

There could be something to this theory. Flowering plants originates at about the same time dinosaurs conked out. And to aid pollination by insects, the plants started making high octane fuels (nectar, is almost pure sugar) and the co-evolution of insects and flowering plants raced ahead. There could be something to it, but still we would need more positive evidence. We still have to explain the iridium layer in sediments too.

Re:Doesn't sound likely at all

[argent]

It's even more unlikely than that: pathogens have absolutely been part of the ecosystem since the days of single-celled life forms. There are organelles in a modern animal or plant cell, including mitochondria and chloroplasts, that are believed to have evolved from symbiotic organisms. These almost certainly started out as pathogens back when the whole multicellular complex organism schtick was just starting up.

Re:extremely suspect

[flyingsquid]

The end-Cretaceous mass extinction did not just target the dinosaurs. It resulted in the extinction of dinosaurs, pterosaurs, the vast majority of birds, many mammals and lizards, a few turtles and crocodilians, frewshwater sharks, freshwater clams, large marine reptiles (mosasaurs and plesiosaurs), ammonites (shelled cephalopods similar to the modern chambered nautilus), marine plankton, many species of plants... and ironically enough, some insects. The insect fossil record isn't good enough to look at extinction patterns, but if you look at fossil leaves, a number of distinctive feeding traces disappear 65 million years ago, at the same time as the dinosaurs, indicating that whatever plant-eating insects made them went extinct.

In short, it is unlikely that biting insects could be responsible for all this chaos. The extinction was simultaneous, worldwide, and (in geological terms) instantaneous, it hit animals and plants, and it hit organisms on land and in the sea. Now, it turns out, probably not coincidentally, that at the same time all of this happens, a huge asteroid or comet impact- one of the biggest in the past half-billion years- takes place in the Yucatan, blasting dust into the stratosphere, sending tidal waves across Texas, and probably igniting much of North America in the process. An asteroid impact is probably capable of causing an extinction like this. Its doubtful that gnats, mites, and mosquitos could.

Another theory that ignores the evidence...

[Monkey_Genius]

Dinosaurs were on their way out by the end of the Cretaceous
anyway. In N. America they had declined from about 35 genera
to about 12 genera by the end of this period. The #1 reason
for their decline was the dropping O2 levels in the atmosphere
caused by the intense volcanic activity that was occurring
due to the breakup of Pangea. O2 levels were about 35% at the peak
of the Cretaceous and are about 21% today. Dinosaurs got big because
they had lots of O2 to breathe. They also didn't need to be warm-blooded
because everywhere it was warm, anywhere from 5 to 10 degrees C. higher
on average than it is today. Big animals take a long time to heat up and
longer to cool off, so no need to be homeothermic.

The number two reason was probably cooling due to increased levels of
aerosols and particulites in the atmosphere from all the volcanism.
So it's getting harder to be a big animal when you can't breathe,
it's getting colder (and you can't regulate your body temp),
and your food supply is changing or disappearing.

Then along comes this pesky meteor that blasts a few billion cubic
meters of dust into the atmosphere and turns out the lights for a
year or two. No heat, no food, no O2, no survival if you need these in
quantity. That's one situation that our mammalian ancestors could cope with
though, because their survival demands were lower.

Re:Seems odd

[iroll]

Not so much "funny" as "insightful."

In fact, since insects had been *The* animal ecosystem on land for millions of years before the first vertebrates skulked out of the ocean, it's pretty plausible that all manner of mites and parasites had existed and passed around proto-diseases--lets not forget that even today, our insects are covered with even tinier insect parasites. Parasites of all sorts also existed in the oceans where the vertebrates were evolving. Parallel evolution makes much, much more sense.

Insects

[Mark_MF-WN]

I think the claim is that instigating event was the evolution of flowering plants. That triggered an explosion in the biodiversity of plants, insects, and small fast-evolving animals like wee lizards and mammals. Animal biodiversity leads invariably to pathogen diversity, as there are more combinations of organisms between which pathogens can transfer and which can participate in parasite life-cycles.

The vast majority of flowers are intended to attract insects. Think about the most notorious disease-spreading insect: mosquitoes -- which are primarily nectar feeders (the males exclusively so). So it's not as if flowering plants only support the existence of cute fuzzy little insect species like butterflies and honeybees. Flowering plants form the base for a sizable percentage of the entire insect population, including many of the ones that spread diseases and parasites.

Insects aren't much better at eating cellulosic biomass than animals are, and blood alone isn't a particularly practical food-source. In fact, are there ANY insects that can subsist entirely on blood? Some arachnids do, but no insects. It's easy to see how the emergence of nectar-producing plants would give rise to vast array of new types of insects, some of which would then be willing to take a bite out of passing dinosaurs to supplement their diets.