I felt like this video series needed more exposure, it really is shaping up to be quite excellent in my opinion:
I really hope @Jon-Perry eventually gets around to talking about how we can infer, from structural and sequence-comparisons, that many of the individual proteins that make up the flagellum are actually homologous to proteins found in other, simpler structures (and interestingly, how numerous individual proteins in different parts of the flagellum are homologous to each other).
In other words, a video on what you might call the case for homology of similar protein sequences. In particular I find it worth going into the topic of increasingly dissimilar protein sequences and how this is a straightforward prediction of evolutionary divergence over time.
Innumerable examples could be given from so many other systems and structures, from enzymes families, globin-family proteins, through immunoglobulins and so on, where we can trace their evolutionary relationships to increasingly dissimilar proteins. Take your pick, I like table S3 in the supplementary information from this paper which shows a huge list of increasingly dissimilar protein sequences in basically 0.1% intervals all the way from 45.455% to 4.545% sequence idenity for the DPBB superfamily.