I’m quite tired of all the pop culture references to asteroids destroying the dinosaurs. You can find it referenced in kids’ movies and big budget films, all alluding to our certain demise in the future. There is a lot of scientific evidence which discredits the Asteroid Theory as the xenocidal bullet. The theory was perhaps a hasty conclusion, and a holdover from Catastrophism.
Gerta Keller of Princeton University performed an in-depth study of geologic strata, and has concluded: “We found that not a single species went extinct as a result of the Chicxulub impact.”
Originally, when the KT boundary was discovered and they identified spherules (which can only come from asteroids), it seemed a reasonable inference that a massive impact could cause ecological disaster. It’s a human bias to associate a massive extinction to a massive disaster. However, a more careful look at the Cretaceous Extinction, shows that it occurred in a more gradualistic manner, taking place over several thousands of years.
One must also consider what kinds of animals survived. Not all dinosaurs went extinct, because we still have birds, crocodillians, turtles and tortoises, etc. And of course, other animals still exist: the mammals, amphibians and invertebrates. The original theory proposed that a lack of adaptability to rapid climate change was the primary cause of extinction post-impact.
While a multitude of alternative theories have been proposed, most still hold on to a sense of enormity and global destruction. The tsunami theory for instance, is also inconsistent with geologic data. Extreme volcanism, and sustained droughts have been suggested. What I think is a viable theory, that I have heard almost nothing about but seems rather obvious to me, is invasive species.
If you take any amount of time to study modern ecology, you will discover how disastrous invasive species are. An invasive plant can potentially wipe out continental ecosystems, which we are witnessing today in North America with a variety of invasive plants. Invasive animals likewise, are a plague to the land. Because nothing predates on them, they can run free and consume all the precious resources that the rest of the ecosystem is dependent on. The best artificial control we can implement is the introduction of a foreign predator to bring the system back into equilibrium.
So if they are such a big problem now, why wouldn’t they be a big problem in the past? Most scientists would reply, “well we have airplanes now”. True, species are much more mobile now than they have been in the past, due to human activity. But it would only take a breeding pair, brought to a new area by a vector, to sustain an invasion. A hurricane, a land bridge, or drifting logs are all adequate vectors and theoretically it would only be a matter of time before a mating pair found each other and an invasion took place.
It also explains why certain animals survived, and others didn’t. There are two broad understandings of animal lifestyles. Generalists have a wide niche, they eat many things and perform many functions in the ecosystem. But specialists are extremely picky about where they live, and what they eat. If a particular species only eats one kind of food, if that food goes away, the species will go extinct!
This proposition makes more sense to me than the asteroid theory, given much of the evidence against it. The pieces of the puzzle fit together in my brain. Whether or not it is the mass killer I suspect still needs to be tested. But with the growth of endangered species, it may not take as long as another asteroid.