Android : android - onStart and onStop called in weird places

I'm getting this very weird log, and I can't seem to find anything to explain this behavior (my notes are after the hyphen):

D/LifeCycle﹕ onStart - old activity - first activity started for the first time
...
D/LifeCycle﹕ starting new activity  - a button triggers starting the second activity
D/LifeCycle﹕ onStart - old activity - ??????
D/LifeCycle﹕ onStart - new activity - second activity is starting
D/LifeCycle﹕ onStop - old activity  - first activity is stopped
...
D/LifeCycle﹕ onStart - old activity - pressing the back button, returning to the first activity
D/LifeCycle﹕ onStop - old activity  - ??????
D/LifeCycle﹕ onStop - new activity  - second activity is stopped

In addition, when I call findViewById in the question marked functions, I get null. Can anyone explain why I'm getting this log?

BTW, I'm running on an emulator, but when I ran it on my nexus 5 it seemed to behave the same.