My personal view on adaptivity (M.Lautsch)
1982 ordinary differential equations, Runge Kutta, Error estimation, stepsize control = 1D adaptive meshing,
1983 - 1987 partial differential equations, Finite Element, fast linear Multigrid solvers, but no adaptivity
1987 - 2006 automotive CAE
1987 Engineers say: Tetras do not work
1990 Zienkiewicz Error criterion at MEDINA
1994 3D Delaunay meshing, Engineers say: linear tetras do not work
this disabels the simplest error control - by the quadratic add on.
1992-2000 mesh coarsen, refine, improve at MEDINA
2006 LFE
2016 MMT's adaptivity is the fundamental principle of mesh generation.