From researchers at Harvard, here is stunning time-lapse photography of something that (as far as I can see) might or might not be evolution. A bacteria colony spreads out across a giant Petri dish, hits an area with a high concentration of antibiotics, appears to be stopped in its tracks, but then slowly breaches the boundary in a limited area and is soon spreading as before until it reaches an area with an even higher concentration of antibiotics, and the story repeats:
According to the narrator, the barrier is being breached by a small number of antibiotic-resistant mutants, which then reproduce like crazy, at least until they come into competition with other mutants, etc. In other words, evolution.
Now I’m sure this is an extremely naive question, but I hope someone can offer an answer that will leave me less naive: How do we know this is evolution as opposed to learned behavior?