I really cannot answer that, as humans are a very versatile species. It is likely though, that over time, we have evolved as such because we have not needed to have enclosed rib cages and retinas that aren't prone to detachment
Both are design flaws, when would we not need our eyesight? Why would we have no need to protect our most vital organs? Man's brain evolved, so the night vision that Owls have in order to hunt for food and survive, did not evolve in humans as we learned, via our superior brain, to grow food and the create devices that made hunting for food easier.
For what reasons? I couldn't say. But we obviously haven't needed those features and features similar to them, otherwise we would have evolved to fit them into our function.
As stated above, our brains evolved so physical features such as night vision, acute sense of smell and hearing, camouflage, and other evolutionary traits were not needed.
We expect to die from all sorts of causes. If I'm faced with a gun, I expect to die from a bullet. If I find the concrete rushing up to meet my head because I just swan dived from a 40 story building, I expect to die from a collision. When considering death, we as a race take more than old age into account.
And humans aren't all that fragile. People can survive falls from planes.
Human are indeed that fragile, a slip on your front steps can kill you, children have been known to drown in less than a foot of water, a dive into a pool can break your neck, and I won't go into all the evil microorganisms this divine being populated the earth with.
I've actually never heard the "be fruitful and multiply" mindset.
It's certainly part of the Catholic religion, remember no birth control, it's a sin, so they tell the poor and uneducated, and the babies just keep coming, they can't feed the children they have, but the church says keep them coming. On condoms the Pope comments were, "Aids is bad but condoms are worse"
Population is exponential and will continue to grow as long as people have children, even ONE child.
No with proper management humans can control the earth wide population, but they don't stand a chance with religion standing in the way.
The human need to reproduce is biological, not theological. As long as people have biological urges, we will reproduce, and the population will exponentially grow.
It seems I have more faith in our species than you do, biological urges can be controlled, hell I do it in the college all the time. In many cases it is Theological, spend some time with the poor and the uneducated, especially those with religion, the South American countries come to mind as most are of the Catholic faith.
We could implement population control, but that usually involves forcing people to stem biological urges or killing people off.
No you don't have to "stem" biological urges, just educate them on various means of birth control, of course you have to get by the church telling them that the copulation should only be to produce offspring, and no we don't have to kill them off, it's amazing what a little education will accomplish.
We learn from out mistakes. If a child burns himself on a stove, he learns that stoves are hot and not to touch them when they're on. With no negative experiences, we wouldn't experience growth. So what you define as "Unnecessary" suffering, may actually be necessary for growth.