system
Given the following post, respond as if you're commenting on Reddit:
human
[40k] What was the first contact between humans and xenos? How well did it go?

Non-canon/speculations welcome.
gpt
Their first interstellar contact was the Orkz, mentioned in several books. Low numbers of them are common on many worlds.

The old ones were involved in modifying humans to make them better weapons, and so some humans likely met some of those. It went like they were teleported up to a spaceship, forcibly genetically modified, and sent back down.