Poverty
Poverty is a major theme in this film. Poverty is what creates the street gang, it's a core reason why many of these kids have been abandoned by their parents, why they turn to someone with such poor character, as El Jaibo does. All they know is that they are hungry, they want to have money and they are tired of being beaten at home, or being unloved. Jaibo gives them the false belief that he is empowering them by paying attention to them, when in reality he is preying on their poverty of heart that comes from their lack of love in their homes in order to get what he wants. This is an epidemic that Luis Buñuel is revealing about the cause and effect of poverty across the world.
Sins of the Father
These kids we see in the film are paying for their parents' inability to be parents, to be a mother and a father. We see Julian's drunk father having to be pulled out of a bar by his son, we see that many of the street kids don't have parents at all, and Pedro's mother doesn't trust him and thus shuns him. We see the price that these kids must pay for the inattention their parents give to them, for the lack of responsibility the parents take in raising their kids. The price, horrifically is paid with the lives of these kids.
Cost of Building a City
The opening of the film shows the big cities across the globe before we see Mexico. Luis Buñuel creates the theme that with the demand for expansion and growth in a city, from the need for the city to be big and great is created a deranged cycle that crushes the human spirit. As the bricks climb higher and higher into the sky, the basic needs are more and more deprived from the lower classes. The pockets of the rich are being lined by the building of these monuments to men, while the men who build them are being left behind by being paid as little as possible. This creates a corrupt society where the pain is perpetrated with booze as it kills their pain, but causes them to abandon their family in their misery.
