We are descended from mammals who are by nature selfish, as that was what was necessary to survive. But what makes us human is our caring for the welfare of our ‘tribe’; nurturing those in our group (family, neighbours, nation) who need help to survive. Some other animals do this too though, to varying degrees (elephants for one).
These two drivers are sometimes in conflict, and I think it’s nurture and life experience rather than nature that determines which side we prioritise. There’s probably an innate leaning though - not all toddlers are naturally selfish.