Question: when did muhammad ali start his career in boxing
[{'answer': '1960', 'provenance': [{'wikipedia_id': '63747', 'title': 'Muhammad Ali', 'start_paragraph_id': 2, 'start_character': 167, 'end_paragraph_id': 2, 'end_character': 171, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]