That's just street/slums/ghetto behavior. Such heavy selection pressure selects the most adaptive and the most lucky (on the contrary to the popular misconcepti

That's just street/slums/ghetto behavior. Such heavy selection pressure selects the most adaptive and the most lucky (on the contrary to the popular misconception that the strongest and the smartest are selected). One could find a whole countries with this kind of society - Russia and some African states are good example. Highest level of corruption and crime produce such street-gang social norms. Such practices are plainly stupid and based on misconception and uneducated common sense and primitive memes. Every serious professional athlete will tell you that too much stress and pressure will dramatically diminish one's performance and health instead of making one "stronger". Relaxed self-control, proper habits and just enough of exercises will do. Any highly such competitive and stressful societies of assholes and jerks characterized by high turnaround, very short lifespan for participants, high injury and mortality rates, and hence adaptations, such as earlier reproductive age, smaller body sized, quicker but lower quality development, etc. It is just biology.