There was indeed an old wood beam under this wall but it was so chewed up by termites that it was functionally useless. I had an engineer take a look at it and he said that beam existed mainly to take some bounce out of the floors.

Before I started on the kitchen I replaced that basement beam with a steel I-beam. I didn't want any flex in this wall with a couple of hundred pounds of bricks over a thousand dollar granite countertop. There's a 4x10 header over the brick to transfer the upstairs load to that I-beam.