Let's do a little math, before I start preaching.
Firstly, let's think about new jobs. These are back of the envelope calculations. Order of magnitude of the problem. For the purposes of discussion.
There are ~180 medical schools in the US. As for biology departments, according to Wikipedia:
As of 2012, the latest figures available in 2015, the US has a total of 4,726 Title IV-eligible, degree-granting institutions: 3,026 4-year institutions and 1,700 2-year institutions.
Now some of these schools have more than one "biology" department. Certainly medical schools have multiple departments that hire PhD's. But let's just say 5000 departments? 10000?
How many PhDs in "life sciences"? Over 8000 a year. Other sources (NSF) have other, even higher numbers: ~12,000.
So the number of PhDs each year, in life sciences, is about equal or greater than the number of departments. This makes sense: most of those (non-SLAC, non-CC) departments have multiple faculty, churning out PhDs. Even if every single department hired one more faculty person, that would still have an excess of many, many PhDs.
Let's say that again, there are, roughly, each year, as many PhDs generated as there are departments that could hire these faculty.
I know people are waiting for "Boomers to retire", but I want to remind you that, again, that the youngest boomers are only 52. People do not retire at 52. Or 55. Or even 60. I'm mid-boomer, 62. When I talked to my chair about being on a 4-6 year retirement trajectory, he was shocked. I was surprised he was shocked. (but for me, damn there are other things I want to do).
I know people argue all the time about "alternative careers". I wrote about this years ago, when I started blogging with Mama Isis (and can't find the post). But no one starts a PhD program thinking "Oh, this is a good path to an alternative career".
Back to the problem. There are many reasons we, the mentors of academia, train people. Some of them are what economists would call "market pressures". We need trainees to survive. We need trainees to generate data to finish projects, write papers, get grants, and, well, survive. Some of us (yes, we all know these dudes, although they are not always dudes) who need trainees because their egos can't stand a small lab. They are competing for new students.
So what to do?
I think senior people need to make a commitment to finding trainees/support/help that does not involve bringing more mouths to the trough. I think senior people need to make a commitment to supporting the existing junior faculty in ways that do not require them to have enormous labs to succeed. This, in fact, will require education at the decanal level and above. NIH is the cash cow of many schools. Everyone needs to commit to education about NIH and the need to support research in the US, let alone elsewhere in the world.
Yet, expanding NIH is only kicking the can down the road. Supporting more trainees now, giving jobs to all the PhDs now will just mean this crisis will come back either come back in 10 years, if money is jolted into the system now, and current PhDs get funded, get jobs, and start training an even larger next generation. Or if money is dribbled in, there will just be the continual pain that we see now.
It is not the scheme is unsustainable: it's just a matter of where the selection and sorting (in the evolutionary sense) occur in the life history of a scientist. Although my GenX friends (and yes, I have one or two who do not perceive me as the devil incarnate) will be skeptical, this was an issue debated as I was finishing my PhD in the early-80s. There weren't a lot of jobs to go around then, even to people (and yes, you may laugh heartily here), who perceived themselves as the cream of the crop (I didn't, but that had more to do with my identity at the time). Academia had undergone an expansion in the 60s, and those people were the Boomers of the time. They were hanging on to jobs (in our view) and didn't care that they were training more people than there were jobs. Places weren't hiring (imagine that). I remember long discussion about whether it was better to restrict entry into grad school, and let selection occur earlier, or to expand postdocs (in ecology/evolution/organismic science PD's were relatively rare at the time) and push selection down the road. In those days (and to some extent now), in those fields, grad students were PI's, and lab or mentor affiliation was a weak tie, and certainly not necessary for the faculty, except as ego-props. The numbers of grad student admissions was more fluid, and often based on teaching assistant needs. I don't remember what I thought, except that I was tremendously relieved to get a postdoc.
But back to what to do? Please do not think that retiring the boomers will change the situation. Do you not think that the GenXers who do get jobs will see their survival as justification for doing what they need to do to survive? Do you not think the millennials who make it will turn into the boomers of 30 years hence? The boomers I knew back then were good people who would never ever ever abuse trainees, or promise things, or even inadvertently be part of the problem. We are all destined to become our parents, our mentors, and partly what we despised when we were young.
The solution? For me, right now, is to be aware, and work towards a change. Commit yourself to things be different, better. Reach out that hand, dammit.