The actual patterns of dna variation in humans show that african populations contain:

The actual patterns of DNA variation in humans reveal that those from African populations also contain almost all of the common DNA found in other races such as Asians, Europeans, and other novel variants. 

African populations were shown to contain alleles (genetic variations) not present in non-African populations but nearly all of the alleles common in non-African populations are present in African populations. Thus, although externally, different races may present various physical characteristics, our genes dictate that we are more similar than we actually think/believe. 

The short-term effect of tar on the body is increased blood pressure.