People had had to try for thousands of years before they knew how to put together days, weeks, months and years.
I'd like to know if the usage of "had had to try" in the sentence is correct. I think my question is different from the duplication you mentioned here. My question is "had had to+Infinitive (V1)" not "had+Past Participle (V3).So I'd like to know what the difference between them is.
In this sentence, "People had to try..." would be sufficient to convey the meaning ("People needed to try...").
"Had had" emphasizes that [the period of needing to try] preceded [the time when they knew how to put together days, weeks, months, and years]. In this case, it's a redundant emphasis that unnecessarily complicates the sentence, though it does not seem to significantly obscure the meaning.
