Reptile eyes
Did anyone else notice that at the end when Hugh's monk character Tom is staring at the nebula right before it goes supernova - his eye's are reptile slits?
Here's a screen shot:
http://bajatravelmaps.com/TheFountain-ReptileEyes.png
Isabel's character says many times to Tom that "I will be your Eve" - perhaps over the eons without his Eve, Tom has turned into the serpent at the Tree of Life?