Michael Pollan's book "The Bottany of Desire" tackles nearly this same question. He examines evolution and survival of the fittest from the perspective of the plant. He doesn't mention the poppy but does go into detail studying cannabis.
His suggestion is that as an evolutionary strategy for cannabis, getting people high might just be the ticket. We tend to look it from the perspective of "we domesticate the plants" but if you look at it from the perspective of the plant, few plants have spawned so many offspring as the poppy, cannabis, or even the lowly potato plant.
Quite interesting. He looks at 4 plants from this perspective. Potatoes, The Tulip (think about The Netherlands back in the 1600's, i think it was the 1600s), The Cannabis plant and finally the Apple. Interesting chapter in there about how Johnny Appleseed was really seeding the wild west with inedible apple plants, not to eat but to make cider in fact!