This is yet another question I was asked. The idea was that bacteria aren’t becoming complex organisms “on the way”, so what is the point?
This is like another question often asked by sceptics “If humans evolved from monkeys, how come there are no monkeys becoming humans nowadays?” The Earth is a rich place, rich with resources, rich with diversity. Humans did not evolve from monkeys, it’s not like monkeys are living in the past and we are living in the present. We all live in the present, and monkeys have spent time evolving like we have. Monkeys are adapted to their environment, and we are to ours, and bacteria are to theirs. Could you live off bananas, in a tree? Could you turn water, carbon dioxide and light into food? No. There are many different niches on Earth, each of which is inhabited by different organisms. Hot springs, dry deserts, deep oceans, high mountains and an airplane are all very different places. Why would there only be one species?? We are complex for our environment, but we are not universally adaptable to anything. We CAN live in deep oceans, but that’s not our home address.
Back to the question. The point of evolution in bacteria is to have bacteria live. If that so happens to increase their complexity due to their environment and the selection pressures present (which are due to more basic, chemical or physical factors and properties), then that’s just a side effect. Food for thought.