I think we're a long way off before reaching that limit. In research fundamental discoveries can take a genius many years of his career, but once it has been di

I think we're a long way off before reaching that limit. In research fundamental discoveries can take a genius many years of his career, but once it has been discovered the basic theory can often be taught an undergrad within a few months and adjacent discoveries will improve our understand and things easier to explain. Textbooks explaining it in 5 different ways will be written and our tooling improves etc. etc. You don't have to be fleming to grow penicillium, you don't have to be einstein to calculate relativistic corrections to GPS satellites. Eventually such diminishing returns might be reached if everything remained the same, but you also have to consider that IQ and lifespans are slowly ticking upwards over the decades and eventually we may be able to build a better researcher.