Geology

Idea rubbished at the time because nobody could imagine an engine to move continents, and the continuous geography and geology was explained by 'land bridges' which had since sunk.

Then, in 1940's and 50's they began mapping the Atlantic for military and for telegraph cables, and found the Mid-Atlantic Ridge, where lava constantly extruding and pushing the sea floor away like a conveyor belt on either side. And they found that the supposed land bridges weren't there at all.

(Then a whole lot of research involving earthquakes, fault lines, displaced geology such as Baja Peninsula etc, super accurate laser measuring of how landmasses changing position etc etc)

Conclusion that the continents constantly moving, very slowly, but covering immense distances.

For example, India ramming into Asia, bulldozing up the Himalayas in front of the collision zone, and propagating fault lines and earthquakes up into Nepal and China in northeast, and across Middle East.

Similarly, Africa ramming into Europe, pushing up the Alps, squeezing the Mediterranean and popping up bits of the seafloor in islands like Cyprus.

Explaining all sorts of anomalies such as the N America-Europe and S America-Africa connections, strange fossils such as the tropical palms and ferns found in rocks at South Pole, marine fossils in sedimentary rocks high up Mt Everest.

All of which, of course, implies enormous time periods.

(and so that gave the 'deep time' for evo to have happened)