It's not just about brain size. Even though you might not believe it on a crowded subway train, humans have a unique set of social skills that set us apart from other animals. And new research says it could be down to all the extra dopamine we have in our brains. Dopamine is a neurotransmitter - a chemical messenger in the brain - linked with our mind's reward centre and our mood, memory, and movement. Scientists think it may have made us friendlier and less aggressive than most primates as the millennia went by. While it's found in both humans and animals, a team of international researchers found "dramatically increased" dopamine levels in samples of brain tissue taken from humans when compared to apes and other primates, and it's perhaps this chemical mix that has given us a leg up in evolutionary history. "Humans are characterised by remarkable demographic success relative to our nearest relatives and by advanced social traits such as language, empathy,