Ages of plants - Rocks versus clocks

During a recent interaction with a student who expressed doubts about evolution, they contended “that the fossil record just doesn’t support evolution; it just doesn’t add up.” Translation: I really don’t know anything at all about the fossil record, but most people won’t argue with me because they don’t know any more than I do. Well, that isn’t the case with the Phactor. Do you have an example of where the fossil record just doesn’t add up? “There are too many gaps,” he answered. Like where? “Well, fossils just suddenly appear in the Cambrian,” he said. Do you know that the fossil record of life, microscopic organisms, actually extends back to well over 3 billion years? No, he didn’t know and was only parroting what he had been told, and as a pre-med student he had avoided all those organismal courses where he might have learned some of this. The issue of potential medical students who don't understand or accept evolution is another matter.
Most undergraduate students really don’t know just how extensive our historical knowledge of life is. Some of the publications can be rather overwhelming for undergrads, and especially for amateurs, but if you want to peek at one to give yourself some idea of what is actually known, and in what detail, the AoB Blog provides a description of some work published just a bit ago along with links to the papers. The particular paper highlighted attempts to compare ages of plant lineages based on the earliest known fossils (the minimum age) with ages estimated by various molecular clocks (rates of change in DNA) , which generally provide an earlier age, e.g., rocks versus clocks. A tremendous amount of scholarship is represented in this 45 page long scientific article. It takes me an entire semester to explain enough about plant diversity for this all to make sense.