I would imagine that increasing crop yields would do social good primarily via decreasing the amount of cultivated farm land, especially since we're well past Jevons paradox territory with calorie intake I imagine.

While the pharmaceutical industry is large, the marginal researcher does still seem to have a pretty positive impact from an outside view.

The most positive use of human time probably looks something like antiwar advocacy, but I don't really think that most quants have the social skills for that tbh.

>decreasing the amount of cultivated farm land

I have good news and bad news for you. Good news: we've known the solution to that for more than a century, which is to reduce livestock consumption, a cause which many smart people have dedicated their lives pushing vegetarian/vegan culture and producing alternatives. Bad news: from my point of view, the masses are not going to give up meat and eggs faster with each additional alternative meat.

to stop war we need to stop being lazy, greedy and most important: envy, which is impossible.

>While the pharmaceutical industry is large, the marginal researcher does still seem to have a pretty positive impact from an outside view.

From this outsider's point of view it's failed to have a positive impact; people nowadays are far less healthy and happy than they were half a century ago when the pharmaceutical industry barely existed.