No offense to anyone intended, but this is a ridiculous question and it should not have as many serious replies as it does. Precisely what are you changing about people that would yield the result of there being "no Fe" ? Its just GONE without anything to supplement its status? What else are you fundamentally altering about people/brains to get the result of "no Fe"? Seeing as functions work cohesively/together and opponent to one another, are the other cognitive functions going to be fundamentally altered by there being no Fe?
I guess its a "fun question" but to me it's akin to asking "what would the universe be like without the Carbon atom"? It's like Uhhhhhmmm......precisely what did you change about the universe to produce the result of there being no carbon? Did you fundamentally change the nuclear forces and mechanisms for ALL atoms, or perhaps you wiped out all atoms in series 14 of the periodic table? What happens to the characteristics of Nitrogen and Oxygen when you pull the existence plug on carbon?
There's absolutely no way to answer such a question unless you elaborate on what you are changing in the system to produce said result.