An Anthropologist On Mars: Seven Paradoxical Tales is a collection of essays about extraordinary people, for sure. “An Anthropologist on Mars” is the seventh, and last, essay in the collection by Sacks. In regards to your question, the “disadvantageous aspects of life” according to Sacks here are almost always some kind of neurological aberration. As should be expected from the title, each story contains a definite paradox and most often deals with mental illness and how it can be overcome.
There are seven different essays about different individuals, but the most known of the seven characters is that of Temple Grandin: an autistic woman who defied her malady and society by becoming a successful academic. Grandin has a definite disadvantage: autism. This causes Grandin to flee from being touched. Knowing that the concept of “squeezing” helps Grandin tolerate the touch of others, she creates a “squeeze box” that helps her with that issue. Grandin realizes that this invention could also help others. Grandin uses this idea as the impetus to move her life forward and, sure enough, she catapults into the world of academia.
Keep in mind that Sacks values his abilities as a neurologist over those as a writer. This helps us to understand the importance of his characters. In fact, Sacks asserts the following:
Defects, disorders, diseases [are able to expose] latent powers, developments, evolutions, forms of life, that might never be seen or even be imaginable, in their absence.
In conclusion, using Temple Grandin as a perfect example, you can see how “disadvantageous aspects of life can have upsides.” The book, then, is about more than people with some kind of mental handicap. Instead, it becomes about all disadvantages in life and how they can be turned into positive forces.