This is an astoundingly stupid and self-defeating argument. "Famines never happened except when they did", really? Famines happened every time a major disaster (like a volcanic eruption) occurred or more commonly because the country got invaded and all the men got conscripted and the other side stole all the food. Like just go look at a list of premodern famines, and notice the actual written accounts discuss peasants starving because they couldn't grow enough and someone demanded food they couldn't spare (because your landlord needs to pay his taxes). So yes, if you by some chance had a large natural disaster in a region (which inevitably happens every 30-50 years or so) and didn't have modern agriculture, fertilizer, and pesticides, then yes, you will look like those malnourished people in Africa and you will possibly get sick and die.