The capacity for symbolic thinking was the last great evolutionary innovation that made possible human ultrasociality. People now did not need to know personally another individual in order to determine whether to cooperate with him, or treat him as an enemy. Particularly good diagnostic features are religious observances and ritual actions. However, one could also look at the details of his clothing and ornamentation (including such permanent markings as tattoos or caste marks). One could listen to his dialect and observe his behavior.
