Another candidate for one of the first scholars to carry out comparative ethnographic-type studies in person was the medieval Persian scholar Abu Rayhan al-Biruni of the Islamic Golden Age, who wrote about the peoples, customs, and religions of the Indian subcontinent. According to Akbar S. Ahmed, like modern anthropologists, he engaged in extensive participant observation with a given group of people, learnt their language and studied their primary texts, and presented his findings with objectivity and neutrality using cross-cultural comparisons. Others argue, however, that he hardly can be considered an anthropologist in the conventional sense. He wrote detailed comparative studies on the religions and cultures in the Middle East, Mediterranean, and especially South Asia. Biruni's tradition of comparative cross-cultural study continued in the Muslim world through to Ibn Khaldun's work in the fourteenth century.