Subject: Has earth's gravitational pull been constant over millions of years?

I was pondering why Dinosaurs were so large millions of years ago, and 
thought about the strength that their bones would have needed just to 
support the muscular structure of the animals.  I propose that the 
gravitational force on earth has become greater over time, causing living 
beings to become smaller.  Does anyone have a comment on this?

Re: Has earth's gravitational pull been constant over millions of years?