nation development-- nation
's(put an apostrophe)man kind--
mankind(one word)be laid upon researches
But several researches in the past have proved devastating.
-- You mention the term " proved". Now, how would you make the readers believe to that, since it's a strong stand? This is a generalized sentence which lacks specific supporting details.
People during that era thought diseases were a curse or it is punishment from god
Black plaque in England
during the 16th century exemplifi
ed ( should be past tense) how ..
But nowadays plaques would have practically vanished not to ...
In relation to this sentence,
But several researches in the past have proved devastating.
As what I said, it's a generalization so you better place it on the third para since you have enumerated there all the details supporting it..
keep in check of these kinds of researches and put restriction on them.