What can you infer about london's beliefs from this line: "its instincts told it a truer tale than was told to the man by the man's judgment"?

When London says that, he is referring about the dog's instinct. When we are fighting Nature, we can only survive by battling Nature exclusively with our own set of skills. Because of his innate instincts, the dog is a survivor, while the man, a greenhorn, have no survival skills, and instead they die.