Question: when did the megafauna of north america go extinct
[{'answer': 'The Quaternary period', 'provenance': [{'wikipedia_id': '18783051', 'title': 'Quaternary extinction event', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 21, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]