All of Jannia's Comments + Replies

Maybe predators are wary of rattles and don't step on the snake. Or maybe the rattle diverts attention from the snake's head.

The point of a rattle, as I understand it, is that it's metabolically expensive, and time consuming, to produce poison. A snake that can chase off a dozen threats a day by wagging its tail is much better off probability-of-producing-offspring-wise than one that can only bite and poison three threats before being left defenseless for a few days.

It does leave me wondering what benefits the intermediate mutations provide though, since going from a normal snake tail to a rattle seems like it would take more than one step.

Intermediate mutations don't necessarily need to provide any benefit at all, they just need to not have any detrimental effects. As I recall, a rattlesnake's rattles are formed more-or-less by its skin failing to shed perfectly cleanly.  That costs practically nothing and is exactly the kind of weird mutation that can crop up in an isolated segment of the population where it doesn't take long for genes to stabilize. Then the isolation ends, and it turns out that the weird new trait has some amount of benefit over the population at large, so it spreads.
even if poison were cheap, every fight has a risk. better to neither fight nor flee.

I have observed that more ordinary snakes that have not developed a rattle often vibrate their tail in a similar manner, which often makes a warning buzz that is merely somewhat quieter than a rattlesnake's rattle. So incremental improvements to this rattling mechanism, which started with a regular tail, would just slowly increase the loudness, and thus warning ability, of a snake's tail.

Interesting. That corresponds remarkably well with the best advice I've ever gotten for estimating software schedules: take your best guess as to when you'll be done, then double it.