Saying "does start" is the same as putting "starts" in caps or italics. Italics are more polite than caps, but this platform doesn't support italics, so it is the same as: "It STARTS with people questioning"

This is a good question. The grammar of this sentence only makes sense in relation to a previous sentence or question. For example, If your friend says to you: "I just looked out the window and I saw many people with umbrellas. DOES this mean that I need an umbrella?" You could reply: "It DOESN'T mean that you need and umbrella, but it DOES mean that you should check the weather report." "it DOES mean that you should check the weather report." = This structure references the previous sentences. I also agree with Jonathan's answer. "Does" adds a feeling of emphasis to a statement. I hope this helps. Good luck!

"Does" is just being used to make the statement more emphatic. You can do a web search for "emphatic form" or "emphatic do" to see some other examples.