Gradual or punctuated? Read every interval
- The idea
- Predict
- See it
- Why
- Check
The idea
“A big total change means gradual. A jump or a flat stretch means punctuated.”
Flat stretches and jumps really are part of punctuated equilibrium, and a big change sounds like it must have taken ages. So the first clue you spot feels like proof.
The short version
The mistake: A big total change means gradual. A jump or a flat stretch means punctuated.
What's actually true: Gradual and punctuated change differ in how change is spread over time, so you compare the change in every interval.
- Gradualism is small, steady change in most intervals. Punctuated equilibrium is long stasis, with little change, broken by change that is quick compared with it.
- A jump between two layers only counts if they are close in time. If rock is missing between them, the change could have been slow or fast.
- Flat stretches are only half of punctuated equilibrium. The change between them also has to be quick.
On the exam: Check how much changed in each interval, and how long each one was.