A Reader Asks: Can Microevolutionary Changes Add Up to Macroevolutionary Change?

After my recent article on microevolutionary changes in lizard toepads, a reader wrote to us here to ask whether there is any real distinction between microevolution and macroevolution. It's a reasonable question. In other words, could thousands upon thousands of small microevolutionary changes accumulate and add up to "macroevolution"? In response, I pointed out that there are good reasons to understand that many biological features cannot be built simply by adding up small changes.

I assum...