  JWST observations of high redshift galaxies are used to measure their star
formation histories - the buildup of stellar mass in the earliest galaxies.
Here we use a novel analysis program, SEDz*, to compare near-IR spectral energy
distributions for galaxies with redshifts 5 < z < 7 to combinations of stellar
population templates evolved from z = 12. We exploit NIRCam imaging in 7 wide
bands covering 1-5 mu m, taken in the context of the GLASS-JWST-ERS program,
and use SEDz* to solve for well-constrained star formation histories for 24
exemplary galaxies. In this first look we find a variety of histories, from
long, continuous star formation over 5 < z < 12 to short but intense starbursts
- sometimes repeating, and, most commonly, contiguous mass buildup lasting ~
0.5 Myr,possibly the seeds of today's typical, M* galaxies.
