Why does every mammal get 1 billion heartbeats in their life?

How much LSD should you give an elephant? (mellow music) Well, to a reasonable person, the correct answer is probably none.

But what if you needed to do it for a scientific experiment? In the 1960s, the CIA was working on a top secret project known as MKUltra, and one of their main goals was to find out how drugs like LSD could be used to change human behavior.

And this is where elephants come in because elephants are normally quite docile, but sometimes they just snap.

And the hypothesis was that this change in behavior might be triggered by the release of an LSD-like substance that naturally occurs in their brains.

So if that's true, then administering LSD to a docile elephant might reproduce that behavior. So the real question was how much LSD should you give an elephant so that the dose is large enough to cause a psychological reaction, but not so large that it causes harm?

(mellow music) Well, the researchers didn't know, LSD had never been given to an animal that big, but they did know that the safe dose in cats was around 0.3 milligrams.

Now, since an elephant has around a thousand times the mass of a cat, they figured we'll give it a thousand times the dose.

They received approval to perform the experiment on Tusko, an Indian elephant at the Lincoln Park Zoo in Oklahoma.

And there they injected him with nearly 300 milligrams of LSD. But within five minutes, Tusko trumpeted, collapsed, fell heavily onto his right side, defecated, and went into status epilepticus.

They administered a few other drugs in an attempt to revive him, but Tusko died shortly thereafter.

The mistake they made was to assume that safe drug dosage scales linearly with mass. It does not. And it turns out there are a lot of things like this that don't scale in the way you'd expect.

(mellow music) For example, take the smallest mammal by mass, the Etruscan shrew, and the largest land mammal, the African bush elephant.