That’s common knowledge — so common that it isn’t even true.
It is, of course, true that most cultures count in base ten, with some obvious and well-known exceptions from the ancient world, such as the use of base 60 in ancient Mesopotamia and base 20 in the Maya culture. Surely, however, that can’t be a culture that counts in base six!
Or can there be?
Who counts in base six?
The Ngkolmpu do!
And who, you ask, are the Ngkolmpu? I’m surprised you have to ask. They are of course a tribe of a couple of hundred people on the Indonesian side of the border in southern New Guinea. (No, I had never heard of them either.) If you follow the link, you’ll learn that the Ngkolmpu and their neighbors use base six, not base ten. Author Matthew Carroll says the only cultures that use base six are found in New Guinea, and I’ll take his word for it. The number 8, for example, is written one-six-two (naempr traowo yempoka); there are special names for powers of 6, such as ptae (36, or 62), tarumpao (216, or 63), ntamnao (1296, or 64), etc. Read the linked article for some informed speculation about why the shape of yams (see image above) might lead to counting by six. It’s not that the Ngkolmpu have six fingers — but you probably figured that out yourself.