system
Given the following post, respond as if you're commenting on Reddit:
human
Why is there only one species of human?
gpt
There are a variety of reasons, but here are two: 

1: Due to our technology and general intellect, humans around the world have been able to live in far more similar conditions than another, equally distributed species.

2: We are a relatively young species . Since the migration from Africa and the general distribution throughout the world, we didn't have enough time to develop to many unique genetic traits in various isolated populations. Now that the world is so much smaller due to technology, that will never happen.

It should be noted that various groups did undergo independent evolution leading to changes in skin colour, sand slight changes to things like bone and muscle structure, certain desease immunities and other minor differences, some of which we were directly responsible for, such as lactose tolerance which is more prevalent among populations who historically milked cows.