How do the old man and the girl defy the odds in the novel, West With Giraffes?

Though the Old Man does not have use of his hand, he still learns to accept himself and leads a life in communion with animals that he is proud of. Similarly, no-one believes that Girl will survive the trip across the country because of her splinted leg. She proves them all wrong and becomes the first giraffe to make the trip, giving birth to a healthy calf shortly thereafter.