Question

Why is the genetic ancestry of microbes much more difficult to ascertain than the ancestry of animals?

Answer 1

Genetic ancestry of microbes much more difficult to ascertain than the ancestry of animals because microbes are much more dominant on earth in terms of mass and volume than animals. They are very diverse and vary in size, cell structure etc. Therefore, one diverse group arise from one set of two (or more) species and another different group will from different set of species.

It is explained that this diversity "come" from different organisms. So there is direction of movement from one specific organism to another. Therefore difficult to ascertain their ancestry as to identify genetic homologies...

All animals are related and their cells depend on each other to sustain the life of the organism. Therefore, the common ancestor of all animals was a single cell and this single-celled organism gave rise to multicellular organisms.