Do spider monkeys and lemurs evolve at the same time?

It's not quite accurate to say spider monkeys and lemurs evolved *at the same time*. They both evolved along different branches of the primate evolutionary tree, at different times, over millions of years.

Here's a simplified explanation:

* Lemurs: These primates are part of the Strepsirrhini group, which diverged from the rest of the primate lineage around 65 million years ago. They are native to Madagascar, and their evolutionary history is distinct from the other primates.

* Spider Monkeys: These belong to the New World Monkeys group (Platyrrhini), which diverged from the Old World Monkeys (Catarrhini) around 40 million years ago.

So, while both groups have been evolving for a long time, their evolutionary timelines are different. They did not share a common ancestor recently enough to say they evolved "at the same time."

It's more accurate to say that they have both been evolving independently for millions of years, with different adaptations and responses to their environments.