Question: where did the idea of a unicorn come from
[{'answer': 'Greek writers of natural history', 'provenance': [{'wikipedia_id': '43236', 'title': 'Unicorn', 'start_paragraph_id': 7, 'start_character': 94, 'end_paragraph_id': 7, 'end_character': 126, 'bleu_score': 1.0, 'section': 'Section::::History.:In antiquity.\n'}]}, {'provenance': [{'wikipedia_id': '43236', 'title': 'Unicorn', 'start_paragraph_id': 0, 'start_character': 0, 'end_paragraph_id': 0, 'end_character': 0, 'bleu_score': 1.0, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13117173888083965502}, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '43236', 'title': 'Unicorn', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 496, 'bleu_score': 0.933064252843217, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13117173888083965502}, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '43236', 'title': 'Unicorn', 'section': 'Section::::History.:In antiquity.\n', 'start_paragraph_id': 7, 'end_paragraph_id': 7, 'meta': {'evidence_span': ['Unicorns are not found in Greek mythology, but rather in the accounts of natural history, for Greek writers of natural history were convinced of the reality of unicorns, which they believed lived in India, a distant and fabulous realm for them. The earliest description is from Ctesias, who in his book "Indika" ("On India") described them as wild asses, fleet of foot, having a horn a cubit and a half () in length, and colored white, red and black.', 'Unicorns are not found in Greek mythology, but rather in the accounts of natural history, for Greek writers of natural history were convinced of the reality of unicorns, which they believed lived in India, a distant and fabulous realm for them.', 'Unicorns are not found in Greek mythology, but rather in the accounts of natural history, for Greek writers of natural history were convinced of the reality of unicorns, which they believed lived in India, a distant and fabulous realm for them.']}}]}, {'provenance': [{'wikipedia_id': '43236', 'title': 'Unicorn', 'section': 'Section::::Abstract.', 'start_paragraph_id': 1, 'end_paragraph_id': 1, 'meta': {'evidence_span': ['The unicorn is a legendary creature that has been described since antiquity as a beast with a single large, pointed, spiraling horn projecting from its forehead.', 'The unicorn was depicted in ancient seals of the Indus Valley Civilization and was mentioned by the ancient Greeks in accounts of natural history by various writers, including Ctesias, Strabo, Pliny the Younger, Aelian and Cosmas Indicopleustes. The Bible also describes an animal, the re\'em, which some versions translate as "unicorn".', 'The unicorn was depicted in ancient seals of the Indus Valley Civilization and was mentioned by the ancient Greeks in accounts of natural history by various writers, including Ctesias, Strabo, Pliny the Younger, Aelian and Cosmas Indicopleustes.']}}]}]