As I'm sure you're all aware, human beings at some point in their lives -- generally post-puberty or so -- stop growing. As a result, there's some easily-predictable measures, such as the average height of a human, and some pretty consistent standards in our society, such as the height of a typical door or a ceiling.
This, however, relies on some sort of bizarre internal biological mechanism that basically, at some arbitrary point in our development, says "Okay, we're done growing." And while there are a few examples of genetic abnormalities where that mechanism fails, by and large that's a constant across virtually all life on our planet.
But what if it weren't?
What if this biological mechanism simply had never existed? Clearly there are some upper-bounds on physical size due to the infamous Square-Cube Law -- such as reaching the point where our bones fail under our own weight, or where our heart simply can't keep up with the vastness of our circulatory system -- which would likely take the place of generic "old age" as putting in place the upper limit on how old we could get. But what would be the more subtle impacts on our biology? And how would this change the face of our society?