The question "why are we built like this", appears to imply a builder, of which there is none. We evolved this way, along with many other species. And on some level that actually had some randomness which in combination with real world fitness testing drove our evolution. Or you could take a short term view and say that you were "built" like this because your parents had sex, and these were the genes that combined to make you.
Dementia is a state of failure that is unlikely to have severe negative effects on ability to reproduce.
Are you aware of the means by which natural and sexual selection occur and ultimately lead to speciation or are you simply applying Christian thinking to atheism?
Yeah? So why is my pleasure noodle, and my piss faucet the same organ? Why is my partners faeces dispenser an inch away from her baby cannon? When she gave birth, why did it rip open? Why, as a man, do I have nipples?
If this was all "built like this" I would like to have a go, because this seems like a beta test which received a failing grade.
Hey, I'm an ideas guy, not an engineer. When I say combine the waste organs and leave the sex organs to be sex organs, that's the engineers job to figure out.