Who should consider grad school in science?
There are more people qualified for faculty positions at research universities than there are openings. By "qualified" I mean having earned a PhD, done a postdoc, and published at least one senior-authored peer-reviewed journal article from each. By this definition, one can be qualified without necessarily being competitive in today's academic job market.
Those of us lucky enough to get such a research university position find that (as vwxynot put it):
"Even if you do make it big and get your own lab, you’re suddenly responsible for your whole team’s job security as well as your own. Grants depend on the quality of the researcher and their work, yes, but also on trends, fads, luck, nepotism, reputation, political interference and geography."
The importance of nepotism, politics, and geography probably varies among countries, but there's no doubt that only a fraction of good proposals get funded. And yet, getting grants is often an expectation for tenure.
So, if most PhD's won't get a research university faculty position (RUFP), then who should consider going to grad school in science?
1) those who expect to enjoy grad school itself, at least most of the time.
2) those who think they would be happy in some science-related job requiring a PhD, even if it's not an RUFP
There could be a third category: those who are confident of being among the lucky few that get those scarce faculty positions. But I suspect that these are a subset of category 1. Not everyone who enjoys grad school will get a RUFP, but those who do get one probably enjoyed grad school, mostly. They were smart and creative (and lucky) enough to pick important and interesting questions, and hard-working (and lucky) enough to answer them. They published two or more papers each from PhD and postdoctoral work, including one or more in prestigious journals. And they enjoyed this enough to make up for working long hours (reading, writing and thinking about science as well as lab or field work) for little pay.
I wrote "little pay", not "no pay." I strongly discourage anyone from running up major debts to go to grad school. It's too much risk for too little certainty of reward. If you are aiming for a research position, try to get a research assistantship or fellowship that will pay you (a little) while you work on your thesis research. If you are more interested in teaching at a 4-year college, try to get teaching assistantships. If you can't get either, at least for most years, that could be a sign of trouble. Your professor may not be good enough at getting grants or your university may be poorly funded; either way, they may not have the reputation that will help you get good postdocs and jobs. Or, if other students are getting assistantships and you aren't, that may be some indication of who's going to be most competitive for jobs later on.
Maybe someday the long-predicted scientist shortage will arrive and there will be great jobs for all qualified candidates, but don't count on it. Actually, the scientist shortage is already here in terms of important problems needing research, just not in terms of jobs and grants!
I don't think I would have regretted the years spent in grad school and two postdocs, even if I hadn't been lucky enough to get good research jobs afterwards, first with USDA and then at two great universities (UC Davis and University of Minnesota). But I can think of several fellow grad students and postdocs who didn't get as rewarding jobs, despite being at least as smart and hardworking as I was.
If you've been thinking about grad school in evolutionary biology and this hasn't discouraged you, the grant proposal I'm submitting in July includes funding for another grad student. Overall funding success is <15%, but grant panels have liked my last three proposals....