When Old Man Warner says, "Lottery in June, corn be heavy soon," what does that tell you about the original purpose of the lottery?

The townsfolk in "The Lottery" appear to be pagans. In many ancient pagan societies, it was believed that in order to ensure the success of the harvest, sacrifices of one kind or another had to be made to the gods. Good harvests were essential for such communities; if they failed, widespread starvation could ensue. So it was considered absolutely crucial to do whatever was necessary to appease the gods, even if it meant resorting to human sacrifice.
And that's what happens in "The Lottery." The annual lottery is held in June to make sure that once the human sacrifice has been made, a bumper harvest will inevitably follow. That's what the old man means by "Lottery in June, corn be heavy soon." What makes the annual ritual sacrifice especially disturbing is that it takes place in a modern town. Indeed, it is ironic that the townsfolk feel the need to resort to such primitive rites in order to maintain a modern standard of living. They firmly believe that if human sacrifices aren't made every year, then the crops will fail, and if the crops fail then the community will be forced to revert back to a more primitive standard of life.

Old Man Warner's comments suggest that the Lottery ritual may have started as a human sacrifice to the gods of the harvest and fertility. He seems to tie the labor of farming and cultivated crops with the better lifestyle the community has enjoyed since they stopped, as he puts it, living in caves. But he insinuates that giving up the Lottery could thrust the community back into poverty and starvation, into the days of eating "stewed chickweed and acorns." Such a diet would signify a hunter-gatherer type of society rather than an agrarian-based culture. When other people mention that some neighboring villages have discontinued the Lottery, or are contemplating discontinuing it, Old Man Warner insists that is "foolishness" and "nothing but trouble." He seems more tightly connected to the superstition that keeps the Lottery in place than some of the younger townspeople. That superstition is that bountiful harvests depend on the sacrifice of one randomly chosen human each year.