Question: why are birds such as kiwi and penguin unable to fly
[{'answer': 'through evolution', 'provenance': [{'wikipedia_id': '927476', 'title': 'Flightless bird', 'start_paragraph_id': 1, 'start_character': 32, 'end_paragraph_id': 1, 'end_character': 49, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '927476', 'title': 'Flightless bird', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 528, 'bleu_score': 0.914785462162765, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 549219123688724285}, 'section': 'Section::::Abstract.'}]}]