so, after however many years they've been studying bacteria, they would have seen how many millions of generations of bacteria? and after those millions of generations, aren't the bacteria still just that: bacteria?
Bacteria, as evidenced through their presense in or on just about everything and everywhere are masters of their own little niche; there's little need for them to evolve beyond a biological specification that works best for them.
Same with sharks or any other animal that has had little evolution over the past few hundred million years.
