Question: when did the prehistoric period start and end
[{'answer': 'c. 3.3 million years ago', 'provenance': [{'wikipedia_id': '18994022', 'title': 'Prehistory', 'start_paragraph_id': 1, 'start_character': 66, 'end_paragraph_id': 1, 'end_character': 93, 'bleu_score': 0.668740304976422, 'section': 'Section::::Abstract.'}]}, {'answer': 'c. 5,300 years ago'}, {'provenance': [{'wikipedia_id': '18994022', 'title': 'Prehistory', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 197, 'bleu_score': 0.53530329295014, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15124900569053505034}, 'section': 'Section::::Abstract.'}]}]