I want to know the answer to the following question:
What higher-level is constantly up for debate and research?
All the background I'm provided with is that "In 2008, researchers at Tufts University uncovered what they believe is the world's oldest known full-body impression of a primitive flying insect, a 300 million-year-old specimen from the Carboniferous period.". Is that enough to answer the question?
Answer: no