☛ The rat that’s ‘immune’ to acid

This is a very interesting article about why the naked mole rat can’t feel pain from acid burns. Apparently it was already known that they don’t feel the pain; their hypothesis about why it happened—that the acid sensing ion channels that tell neurons to transmit pain would be missing—was not true.

Because it turns out that mole rats — despite being the only known vertebrates that are insensitive to the painful stimulus of acid — have the same two fully-functional, acid-sensing channels regulating their pain receptors as the rest of us, and even produce the channels in similar quantities. And this is where things get interesting.

Now they know the actual reason. There’s another way neuron-firing can be controlled, and it is this (sodium) channel that is highly inhibited in the naked rat mole. Similar phenomenons are observed in humans too:

Furthermore — and this doesn’t happen often — humans lacking the Nav1.7 channel have been known to feel no pain whatsoever.

Very interesting, yes, but my question is this: the naked rat mole is insensitive to pain due to acids; but does that mean that it is in fact unaffected by acids? It does not seem so—the phenomenon is purely neurological, and there seems to be nothing physiological that would protect the rat against acids.

Does this not make this a counterproductive adaptation? Why would this adaptation survive? Is it because the natural environments of these rats are entirely devoid of harmful acids, thus making that pain sensation redundant? (Is this also why they’re “naked”, rather than furry?)


It’s all in the Statistics!

As is well known, Earth plays host to numerous meteors, some of which are big enough to reach the Earth’s surface as meteorites. What scares us, the human species as a whole, of course, are the ones large enough to cause significant damage—especially the ones that can cause mass extinctions.

Are the rates at which meteorites arrive at Earth cyclic? Can we predict when the next mass extinction (meaning almost certainly the end of the human race as we know it) will be upon us? It’s all in the statistics!

Of course, there’s no other way make predictions, other than to watch for patterns and extrapolate the timescales involved into the future. Based on past records, there are certain hypotheses about when and why some big rocks hurl towards the Earth—and the most interesting of them involves a phantom solar companion. Christened “Nemesis”, this hypothetical star is supposed to be lurking at the outer edges of the solar system, and like a classical villain hurling chunks of rock from the [Oort Cloud][linkoort] into the inner solar system. Essentially, he’s made out to be playing Duck Hunt, with Earth as the Duck, of course.

But all of this story (and other cyclical hypotheses) depends on a robust analysis of data, which involves robust statistical methods. Everything is a question of probability, of course—you can’t get absolute numbers in situations like these—and it’s no easy matter to set limits to what the error tolerances are. To understand how difficult the whole process is, consider the data in this case: cataloguing previous impact craters on Earth against how old they are. There are numerous craters, of course, but there are also erosion processes that make life difficult.

Well, according to this article by Ian O’Neill, there isn’t much statistical evidence after all for Mr. Nemesis. Researchers at the Max Plank Institute of Astronomy turned to Bayesian probabilities to look at the data, and concluded that there isn’t periodicity in the data as previously thought. Bayesian probabilities are a little more complex implementation of probability theory, where the question asked is: “What is the probability of event A, given that event B precedes it?” Event B, of course, has its own probability of occurring. (There are other complexities, of course, but that’s the simplest case.)

We’re not doomed by Nemesis after all! Apparently robust statistics has saved the day once again. :)

Or has it? The scientists did not find cyclical evidence that would point to Nemesis, but they think they’ve found evidence for an increasing rate of meteorites over the past 250 million years. And before you say “erosion!”–which would decrease the number of older craters—apparently the same trend is observed on the Moon, where there is, of course, no erosion going on.

So—we’re not out the woods yet! ;)

(In case you’re seriously wondering—no, there isn’t a serious chance that we’d be hit by a big one soon. There isn’t even a less serious chance. Doesn’t mean it’s impossible, though!)