Isn't it obvious that Zira switched the baby??

I'm amazed at how many people on this thread never seemed to pick up on this. I thought it was made pretty obvious that, while in the Circus, Zira switched her newborn, baby Milo, with Heloise's baby Salome. When Zira says she wants to "say goodbye to Heloise," you can tell what she's thinking as she closely examines the 2 babies. (Cornelius, of course, does not know she does this, because later, at the oil rig, she says the baby - "HE," she says - wants feeding.) Now, if you happened to miss it there, surely the very end of the movie must make it clear what Zira did, yes?

Please tell me that there are other people out there who had no trouble grasping this on the first viewing.