Question: when did the first fish appear (answer with era period)
[{'answer': 'late Cambrian', 'provenance': [{'wikipedia_id': '37824359', 'title': 'Evolution of fish', 'start_paragraph_id': 1, 'start_character': 345, 'end_paragraph_id': 1, 'end_character': 358, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '37824359', 'title': 'Evolution of fish', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 704, 'bleu_score': 0.9587365925518061, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 18143731218037832264}, 'section': 'Section::::Abstract.'}]}]