What makes us human is our unique DNA signature. Every animal has the same types of DNA made of the same building blocks or nucleotides ATGC. the way these are arranged to form different genes and the different types of genes that a living thing has makes it its unique signature. Even though almost all animals have some or the other form of the same parts/ same type of mechanism, they are different in their own ways.
One key characteristic that is not just our DNA related that makes us human is the fact is our social structures and its complexities. We can read and write and we are curious and try to always discover and invent new things!
Good question! If we’re being literal, I would say the 3 million or so nucleotides that make up the human genome. As a comparison, we share about 96% of our genes with chimpanzees, 60% with mice and 50% with bananas!
If we’re being more philosophical than that, I think that our ability to make and create art, through whatever medium, is one thing that sets us apart from the rest of the animal kingdom. Another is our ability to not only use, but create fire – Ray Mears discusses this in his ‘what makes us human?’ article in the New Statesman here: http://www.newstatesman.com/culture/2014/03/ray-mears-catching-fire.