On a cloudy morning this past April, more than eighty men and women, dressed in matching red windbreakers, stood in orderly lines in front of the train station in Kashgar, a city in Xinjiang, China.

Step-by-step process of taking fish teeth impressions: The researchers took teeth molds from Polypterus fish (about 20 cm long); (A) setting up the materials; (B) carefully sedating the fish; (C) ...