My friend recently had her mid terrace house gutted and a supporting wall taken down between 2 rooms downstairs. The entire upper part of the house was completely done after gutting but she noted that a wooden beam was put in where the supporting wall was to support the upstairs.
She was advised this should have been an RSJ but her engineer said this was a grey area and open to interpretation.
They used timber for support in old buildings and they are still standing. I've seen old beams in a bad way still supporting big weights. Depends on type of wood, size of beam and the builder.