Common sense tells you that there were 10s of millions of bison across the USA, Africa was covered in large herbivores, as was Europe, far in excess of cattle today.

You would think that would mean elevated levels of atmospheric methane in the past then too, right?

Nope.

The University of Nebraska on cow burps & methane on climate change:

“They have not accounted for the capture part; they only account for methane being released.

Carbon capture in soil and grass - helped out by cow grazing and manure - can far outweigh the emissions from cattle.

Grasslands can take up more CO2 and carbon in the soil and plants, which offsets the CO2 that cattle are producing, but it also offsets the methane."