Brown algae fossils have been dated to between 150 million and 200 million B.C. No evolution since then.
Science Daily: Brown Algal Genome Opens New Door to Understanding Multicellularity and Photosynthesis.
Brown algae were assumed to have arisen from the fusion of photosynthetically inactive colourless cells with a unicellular red alga. However, as discovered in a previous research project on single-celled diatoms, AWI researchers showed that brown algae also arose from the fusion of a green alga with a red alga and thus refuted a widespread theory among experts.