From where does culture come? Culture is an expression of some aspects of the nature of the people who create it. Do black cultural expressions such as mob attacks have at least some genetic precursors? I think so.
Do males exhibit more aggression than females because male behavior is cultural or innate? The options aren't mutually exclusive. What about teenagers? Are they impulsive and rebellious because of culture or something inherent in being a teenager? The law (rightly) presumes that 18-year old men can choose not to engage in crime just as absolutely as 40-year old women can. But that doesn't entail any belief that the crime rates in those groups will ever be equal. Choice is exercised within an individual's own context, and that context includes innate and environmental inputs.
Blacks everywhere, from South Africa to Britain to Brazil to the U.S., exhibit high rates of violent crime relative to other races in those same countries. Different cultures around the world don't seem to produce different results -- at least not different enough to make racial crime disparities go away.
But the strongest evidence for black crime being partly explainable by genetics are actual physiological characteristics associated with blacks. They include differences in skull shape and size which correspond to differences in brain structure, which help explain why blacks have an average IQ of about 80, compared to 100 for whites and 105 for East Asians. (Black IQs are closer to 70 in most sub-Saharan African countries, where negroid genetics are purer than in blacks in the U.S., who average around 25% white/other admixture.) Lower IQ is correlated with less rational, more impulsive behavior. Also, blacks tend to have higher testosterone levels, which correlates positively with aggressiveness.
Variation exists in the distribution of the hormones, brain size and shape, and other factors that correlate with statistical variation in crime rates among races. As Heather MacDonald of the Manhattan Institute reports: "The face of violent crime in New York, in other words, like in every other large American city, is almost exclusively black and brown... Blacks committed 80 percent of all shootings in the first half of 2009. Together, blacks and Hispanics committed 98 percent of all shootings. Blacks committed nearly 70 percent of all robberies. Whites, by contrast, committed 5 percent of all violent crimes in the first half of 2009."
The premise of innate racial differences predicts the persistency and consistency of racial crime disparities across time, culture, politics, geography. The premise of innate racial equality has zero predictive value and no scientific basis. It is a pre-Darwinian notion that supposes human traits appeared suddenly from some source other than the adaptive process which gave different human populations in different parts of the world different traits, some of which pertain to cognitive abilities and behavioral tendencies. Variation in the distribution of hormones, brain size and shape, and other factors correlate with observable variation in crime rates among races and help explain incorrigibly high rates of black crime in particular.