Why is sweet potato the main food in Papua New Guinea?

It's not entirely accurate to say that sweet potato is the main food in Papua New Guinea. While it's an important staple food, there are other key food sources in the country.

Here's a more accurate picture:

* Sweet potato (kumala) is indeed a very important staple food in Papua New Guinea. It's highly adaptable to the country's diverse climate and terrain, and it's a good source of carbohydrates and vitamins.

* Other important staples include taro, yams, bananas, and sago palm. These crops provide essential nutrients and are widely grown throughout the country.

* Protein sources like fish, pork, and poultry are also vital. Access to these varies depending on location and resources.

* Rice is increasingly becoming a staple, especially in urban areas. It's widely available and affordable, though it's not traditionally grown on the same scale as the other staples.

Therefore, it's more accurate to say that Papua New Guinea has a diverse food system with various staples, and sweet potato is one of the most important. The specific diet of people in Papua New Guinea depends on their location, resources, and cultural preferences.