As technology develops and progresses, it tends to leave behind many predecessors. A short look at history will show this. I'm afraid I'm not as knowledgeable about this as some here, so forgive any mistakes I might make in the following example: One might look at early mechanical computing devices, later followed by electromechanical devices such as those used to break the Enigma code, followed by vacuum tubes, followed by the transistor, followed by the integrated circuit, etc.

Each one of those steps had a predecessor, much as living creatures have fossil ancestors. Each step is accompanied by huge amounts of documentation, research, theory, budgets and spin-off technology.

Can anyone show us one example of technology, whether we take it for granted or not, that just suddenly sprung into being without such backing? If so I'd really be interested in hearing about it.

As for our ability or inability to backwards engineer alien technology... I think we can take it as a given that any civilization advanced enough to traverse interstellar distances would have to be far more advanced than us. Let's say by 500 years at least. Go back 500 years into our past and give Galileo a nuclear powered aircraft carrier and ask him to reproduce it. How do you think that would work out?