If key wars never happened, how different would Earth look today?

Humans will always fight and wage war with each other. But if certain wars were not fought, what would Earth look like?

Like the Greeks sacking Alexandria. If they never burned down the library there and all of that knowledge didn't go away.

Or, the internal fighting of Rome. We could have had indoor plumbing for thousands of years instead of almost 200 years. And all the engineering knowledge that went away. (I am glad the sea sponge poop brushes went away)

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I'm not saying "ALL WARS" didn't happen. I'm talking about the loss of knowledge, not cultures or people. But if the Library of Alexandria had been kept intact and the knowledge had survived. Could we have advanced faster than we did?
If key wars never happened, how different would Earth look today?
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