Question: which eon was the first in earth's history
[{'answer': 'Hadean', 'provenance': [{'wikipedia_id': '12967', 'title': 'Geologic time scale', 'start_paragraph_id': 3, 'start_character': 64, 'end_paragraph_id': 3, 'end_character': 70, 'bleu_score': 1.0, 'section': 'Section::::Terminology.\n'}]}]