We could have evolved in any way. We could have grown wings, or gone back to the sea like the dolphin, but instead we chose a different path. (we, evolution, God, w/e you believe)
But why? Life as bacteria does just fine, and some say our intelligence will ultimately be our own doom.
I prefer a more optimistic point of view. What if we evolved to have intelligence because we seen that the earth underwent massive extinctions because of meteors, floods, pole-shifts, etc., and we're currently evolving to develop the ability to get off the planet?
Think about it. Similar to animals evolving to walk on land so they could survive, it would make sense that species would want to ensure it's survival by taking the next step, outer space.
To get around it, our bodies would have either needed to develop some sort of method that can escape the Earth's gravity and survive outer space, or become intelligent enough to develop the tools to do so.
We/evolution/God chose the second option.