*Though they appear similar to humans, the species encountered on PJ2-455 in the episode "One False Step" has a very different physiology. These life forms respond to sound waves and have a symbiotic relationship to the planet's other primary life forms, a vast network of plants. The plant life emits low frequency waves, which when altered, can harm their humanoid counterparts. These primitive "people" are curious in nature, but seem easily frightened. Although they do not speak as humans do, they show signs of some intelligence.
*Source: back of card.