The main claim for this thesis is the depiction of Mayella Ewell. The novel as a whole is much concerned with debating family origins and background. This often takes a humorous form with the likes of Aunt Alexandra endlessly harping upon the importance of good breeding and pointing out various hereditary faults in the neighbours:

Everybody in Maycomb, it seemed, had a Streak: a Drinking Streak, a Gambling Streak, a Mean Streak, a Funny Streak. (chapter 13)

However, the more serious implications of this are explored as well, with the case of the Ewell family. The Ewells are seen very much to be a bad family; certainly a disadvantaged one. Known long in Maycomb as poor white trash, they are looked down upon and frankly despised by most of Maycomb society. This constitutes a form of social prejudice like racism, which of course is also explored in the novel.  The Ewells certainly have unpleasant traits, but one wonders how much of this is due to the prejudice and neglect that they suffer. It is true, though, that Bob Ewell, Mayella's father, appears innately mean and vicious, as he is capable of such a vile and cowardly act as attacking children in the dark.

Although not villainous as her father, Mayella, when she appears in court, similarly comes across as coarse, ill-mannered and hostile. She is also instrumental in having Tom Robinson unfairly convicted. However, while Bob Ewell is presented in an unsympathetic light, a sense of understanding for Mayella's situation is advanced in the novel. Although Bob Ewell is seen to be pretty much beyond redemption, there are hints of a better character in Mayella. She does a lot of hard work around the house, she has to look after her siblings, and the geraniums she keeps in her window are a symbol of how she tries to brighten her miserable life. Scout realises how lonely and neglected she must feel, and how nobody but Tom Robinson was probably ever kind to her. Yet, Mayella is intimidated by her brutal father into colluding against Tom and sending him to his death. 

Mayella's situation, then, seems to point to a belief in the novel that one ultimately cannot overcome being born in a bad family. She might try to strive for better things but she ends up on the same low level as her father, as she is cowed and brutalised by him and neglected by society at large. It really seems as though she has little choice, and there does not seem to be much hope that she can ever break out of the vicious cycle of poverty and meanness to which she has been condemned by birth.