Steve Monfort, John and Adrienne Mars Director of the Smithsonian''s National Zoo and Conservation Biology Institute, speaks during an interview at the Smithsonian''s National Zoo in Washington, D.C., the United States, Aug. 22, 2020. Mei Xiang, who''s of an advanced maternal age, gave birth to a cub at Smithsonian''s National Zoo here on Friday. (Xinhua/Liu Jie)