Question: when did the first bacteria appear on earth
[{'answer': 'about 4 billion years ago', 'provenance': [{'wikipedia_id': '9028799', 'title': 'Bacteria', 'start_paragraph_id': 10, 'start_character': 119, 'end_paragraph_id': 10, 'end_character': 144, 'bleu_score': 1.0, 'section': 'Section::::Origin and early evolution.\n'}]}, {'provenance': [{'wikipedia_id': '9028799', 'title': 'Bacteria', 'start_paragraph_id': 10, 'start_character': 0, 'end_paragraph_id': 10, 'end_character': 808, 'bleu_score': 0.956047202777158, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 4204366125200211825}, 'section': 'Section::::Origin and early evolution.\n'}]}]