Slashdot Mirror
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?"
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.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.
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.
...