You won’t like my answer: We’re human because human’s have said ‘we’re human’ — Yes, we are genetically distinct from other animals but I don’t know if that really makes us human. If humanity is just genetic, could we alter someone (genetically) and would that make them unhuman? How different would they have to be before those lost their humanity?
Many people would say our consciousness, morality, intelligence, is what makes us human. Those concepts are harder to define. If we made a really really really smart computer, could it be human?
A species like humans are considered a species if they can mate and produce offspring (babies). Over evolution different species can no longer mate- changes in their DNA makes them different enough to not be able to make babies. We are humans because we are a species that can only mate with itself and not other species like apes. About 1% of our DNA has changed since we shared a common ancestor with apes and that 1% is what makes us human.
From a neuroscience perspective, what makes us distinctly human is complex frontal lobe development. We are very similar to all mammals, and even more so to primates, genetically. Our complex and unique frontal lobe development gives us the ability to think in extremely abstract ways – like replaying past events in our minds, planning future events in our minds, using symbols and language to represent complex concepts such as emotion and mathematic principles. Your humanity is in your frontal cortex! 😀