Propound on why a library is said to be the memory of the human race?

Let's look at the phrase " the memory of the human race?".

Memories are usually belonging to one specific human, and stored in their brain. The human race doesn't literally have a memory, so this must be a metaphor.

This metaphor might mean what the human race, as a total, can remember and have access to.

So just like we remember what happened last Tuesday, the human race can find the information in a library about what happened in 1912 - in this way, a library and a memory are similar, so a library is truly a memory of the human race.