Translation:Human beings have different cultures.
In most contexts, you are correct, but the Oxford English Dictionary does feature several examples of "peoples". Yes, many are quite antiquated, but not the usage "b. In plural. Nations, races." It is accompanied by 20th examples: "The Ruthenians are a part of the family of east Slavic peoples." "The desert regions yield support only to nomadic peoples, such as the Tuareg."
Funny question, but it did get me curious. Menneske sounds very similar to the German/Dutch Mensch/mens, so I looked the etymology of that up. Mensch/mens/menneske apparently all derive from the same root word, where the -sch/-s/-eske part indicates similarity or type (i.e. menneske originally came about as 'something human-like' or 'something that is human'), a bit like the English -like/-esque. There doesn't seem to be a relation to the word for box, eske, and that doesn't seem to get used that way in taxonomy.
Thank you for looking into an answer for my question. The point you make that -eske appears to have originally indicated similarity or type will give me pause to consider other words where -eske may be acting like a suffix. At any rate, I won't forget the meaning of menneske too quickly now.
Have a lingot for your efforts.
Ok, I read here that you can’t translate "mennesker" by "people", but in the sentence I had just after, Mennesker ler og mennesker gråter." it was translated by "People laugh and people cry". Is that because the context is different, or is there a problem with duolingo here?