The Stand to Reason blog had a short article a while back on the classic creationist argument about microevolution versus macroevolution.
Sure, everyone believes those examples of “evolution.” That’s microevolution. That’s not controversial.
Perhaps the reason so many Americans are unconvinced of evolution is because these examples hardly explain what needs to be explained – macroevolution. This is the process by which a single cell evolves into the myriad of living organisms that exist today without any intelligent intervention.
I’d like to illustrate what’s wrong with this argument using streams, creeks, rivers, lakes and oceans.
The fundamental problem with the creationist “micro vs macro” argument is that the terms microevolution and macroevolution refer, not to different processes of evolution, but to the results of evolution as seen across different timescales. That is, there is not a microevolution process and a macroevolution process, there is only an evolution process, whose results are called “micro” when you compare samples that are relatively near to each other, and “macro” when you compare samples that are more widely separated.
The process is analogous to the relationship between tiny streams, larger creeks, even larger rivers, and even larger bodies of water like lakes and oceans. We have different names for these phenomena, but in a way they’re all the same process: water flowing downhill. It would be silly to treat rivers and oceans as being something categorically different from creeks and streams, just like it’s nonsensical to treat microevolution and macroevolution as though they were categorically different.
Trying to accept microevolution while denying macroevolution is like trying to admit that creeks and streams exist while denying the existence of rivers and oceans. A river is just the result of many smaller streams flowing together, so you can’t really accept the stream and then deny the consequence of the streams’ existence. In the same way, macroevolution is simply the consequence of many microevolutionary changes accumulating over time. You can’t (legitimately) accept the fact of microevolution and then credibly deny its consequences.