Our world is perfect because it's had 5 billion years to clean up it's act. Life has been on earth and has been developing for a good chunk of that time. We've existed for about a blink of an eye of that time. In fact, we haven't been the only sentient beings on the planet with emotions. When homo sapien sapien developed, it was alongside Neanderthals - they are not from the same strain as us. They lived in different areas, so it's unlikely HSS had much interaction with them, but they lived for a very short time and died off. We can't say we were the only ones, nor are we the last step in our evolutionary chain, we just haven't seen the next step. The next stage in human evolution will likely be even more well adapted to the earth than we are.
So. Uh, I'll likely get shit for saying this, but it's also very possible that our arrival on earth was an experiment or an accident.
Take into account the various plants and animals of this world. Each ecosystem is very specific, if a new predator, or a new plant is introduced to a system with no way to check it, the species will grow and grow and grow and grow and eat and eat and eat. Biologists see these species as 'Alien' to the new ecosystem.
Take a good look at the bottom of Mediterranean sea.
It used to be a lively reef on the bottom with a wide variety of species and life. If you look now, you'll see a wide foreboding expanse of green. That green is a plant genetically engineered by humans to foliage aquariums. The plant got introduced into the sea when a large scale Aquatic museum in Italy accidentally dumped it. What the plant did, was it covered coral, the coral couldn't get to it's food, and the coral died, fish couldn't hide in, eat or live in the new foliage, so the fish migrated, as the plant took over more and more of the reef, the fish had less places to go and they all died.
It is very likely that we are the 'Alien' introduced onto Earth. Our population is both wide spread, and ever expanding. We have the same symptoms that the non native pythons in Florida face-- too much prey to not constantly breed and expand. Our presence had contributed to the eradication of a large number of species.
@Kai: There was mass before the big bang, there were nebulae of dust and chemicals that were so vast that our minds cannot comprehend how large they were. Gravity existed too. Gravity has always existed. It's likely that the universe started the same way a new solar system starts. Time is purely a human invention to explain one day to another and to keep track of it. There is no time. Also, I'd very much like to live my life like just another animal, enjoying life, eating, fucking, not worrying about death till that brief moment of terror and pain that ends it, but I can't. Because I'm human, and we're all cursed to have higher brain function, I can't just let all the questions in the world go. Not for any reason actually.