Dry air might be the answer but honestly I’m not sure if it is
I believe it’s Australopithecus
Answer:
The brackish water adaptation is clearly necessary because the aquatic snails need to live in an environment in which the river system has a higher quantity of salt than what land snails can take. I can determine that the environmental factors influenced the inherited adaptations because the second population has a higher salt concentration in their habitat compared to the initial population.