Question: the ultimate source of new variation in nature is
[{'answer': 'mutation', 'provenance': [{'wikipedia_id': '364423', 'title': 'Genetic variation', 'start_paragraph_id': 1, 'start_character': 128, 'end_paragraph_id': 1, 'end_character': 136, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]