system
Given the following post, respond as if you're commenting on Reddit:
human
Are there any groups of humans who have difficulty interbreeding?

**EDIT**: I feel I haven't been clear enough in my question. Not "are there groups of people who have trouble reproducing", but "are there groups of humans where it's hard for someone from one group and someone from the other group to have offspring together". As in, not "Amish people's children have problems because of **inbreeding**", but e.g. "Japanese people and African people very rarely have children together because some protein in the blood causes the foetus to be rejected".

As far as I know, all humans around the world can interbreed. But are there any combinations of genes, immune systems, hormones, blood types or other factors which make it difficult for certain combinations to have offspring?

I'm just wondering if somewhere out there's, say, an Eskimo-African couple talking to their OB/GYN practitioner, being told that they're unlikely to become parents and it's a known issue.
gpt
Not in the sense that you're referring to. Human beings are not genetically diverse at all. We just seem to be because there is a fair amount of phylogenic variation. But this doesn't necessarily imply genetic variation. There was a population bottleneck around 70 000 years ago. Genetic evidence indicates that all humans are descended from around 1000-10 000 breeding pairs.