July 21, 2007

Science, sort of

I spend too much time reading stuff on the web, especially science news, but occasionally I feel like I'm actually getting something out of it. Two times in particular, I've read different science stories, put them together, and come up with something new.

Story #1: Toxoplasmosis, a protozoan parasite that infects a wide range of mammals, but especially cats, is widespread in the US (and practically everywhere else, too). Studies estimate between 20-35% of adults in the US are infected.

Story #2: Toxoplasmosis causes significant behavioural changes in infected mice and rats. Specifically, they lose their aversion to cat pheromones, and actually become attracted to them! This helps the parasite, because it breeds only in cats, so it's good for an infected rat or mouse to get eaten by a cat.

Possible conclusion: this parasite infects a wide range of mammals, and causes very specific behavioural changes in some of them. Could the cat-people vs. dog-people conflict be caused in part by toxoplasmosis? Evidence is needed, but it should be easy to collect: test people for toxoplasmosis and ask them to describe themselves as cat-people or dog-people. Correlation may not be enough: people who like cats would be more likely to get infected. Really solid evidence could be obtained by tracking some people who don't have pets, and testing them repeatedly over a few years to see whether those who catch the parasite from eating infected meat subsequently get a cat.

Story #1: Chicxulub Crater, dated to 65.5 million years ago, is the most likely candidate for the asteroid impact that might have finished off the dinosaurs. One of the main pieces of evidence for the asteroid impact theory is the high concentration of iridium 65.5 million year old rocks. Iridium is rare on Earth, but relatively abundant in asteroids.

Story #2: The Deccan Traps, a massive basalt formation in India, was formed from 60-68 million years ago by volcanic activity that was definitely strong enough to cause extinction. (Think lava covering half of India.) This is the second-strongest theory for the dinosaurs' extinction. Key evidence includes the steadily decreasing number of species of all kinds over several million years preceding the presumed asteroid impact.

(There are advocates of both theories, of course, plus people who think the Deccan traps started the ball rolling, and Chicxulub finished it off.)

Story #3: One of the biggest impact craters in the solar system is the Caloris Basin on Mercury. The impact was so large, seismic waves from the impact are thought to have converged on the opposite side of the planet and ripped up the terrain there.

Possible conclusion: other great examples of impacts causing damage on the opposite side of a world exist. The two largest impact craters on Mars, the Hellas and Argyre Impact Basins, are on the opposite sides of the planet from the two largest volcanic regions on Mars, Tharsis Montes and Elysium Planitia, respectively. It isn't beyond reason to expect large impacts on Earth to have caused volcanic activity on the opposite side of the planet, though tectonic activity would move and erase the evidence, unlike the situation on Mars.

65.5 million years ago, Chicxulub was on the opposite side of the planet from the Deccan Traps. (Image of world geography 65.5mya.) Oh, and two-thirds of the Deccan Traps' output occurred 65.5mya.

Taken together, it looks like the Deccan Traps were active for a few million years before Chicxulub, but the impact triggered a massive increase in activity. The combined effect caused one of the "Big Five" extinction events. Incidentally, this might also explain why other large impact events didn't cause equally large extinctions.

Do I really believe either of these theories? I haven't got enough evidence. But who knows, maybe the evidence will eventually prove me right or wrong.

Are these original ideas? I don't know. Other people are almost certain to have come up with them independently, and before I did. But that doesn't diminish the satisfaction I've gotten from coming up with them on my own.