I think that any description about the human aspects in the Tagore short story would have to start with Ratan. There is something uniquely human about her condition. She is an orphan. When we first meet Ratan, she does not have any family and there is little else that makes her distinctive. However, she is loyal to the postmaster throughout his tenure of service. She tends to his every need and hangs on his every word as if it's the ground beneath her feet. The human condition that she displays is her forlorn condition matched with a hope to be included in something, anything. She is an outsider who longs to be an insider. She is someone devoid of connection who wishes for it. Ratan demonstrates human aspects in this regard, akin to a child waiting to be picked for sports teams on the playground. She displays human aspects because, on some level, everyone has experienced this predicament. Her desire to belong is a distinctly human aspect of her character.
Another human aspect of Ratan's characterization exists in the ending of the story. After dutifully serving the postmaster, she hopes to go with him when he leaves. In the end, she is betrayed as she is left behind. This is a human aspect in that everyone knows what hurt feels like. Ratan's willingness to be there for someone and then not be reciprocated are human aspects of charater. They are parts of her character that can apply to anyone. As the postmaster rationalizes his actions, which is another human tendency embraced when confronted with the painful horror of our behavior, Ratan is left without any such elements to console her. She simply wanders alone, yearning for what might have been. This is a human reality: sometimes, our pain is the only company we can find.