Most of the work in hard science is done by people
between the ages of 21 and 30, grad students and post
docs. The ones with positions and tenure choose the
projects, conceive of the broad strokes, and assign
the work; the kids then burrow into the workface and
do the heavy lifting. Same profile mostly applies for
archaeology, which isn't always quite "hard", but often
can be, these days, lots of math and interactions with
chemists, physicists and geologists. With arch. though,
you can still do the field work as long as your body
still works, lots of senior project leaders into their
seventies and eighties, still digging along with the
kids, whereas in the math oriented sciences, the work is
passed to the kids because the old brain often can't
do that stuff as fast any more.

And the young ones get quite a lot of respect. When
you see someone particularly young looking, working
at the professional level, it usually means they got
there by being highly precocious, and such minds are
highly valued, as they can see more deeply. If they
don't crash and burn (a hazard with intellect outpacing
emotional maturity), they are likely to have a big
impact on the field. Anyway, I know a youngster who
got to work at a paleo dig in east Africa while still
an undergrad, as she was judged pretty exceptional.