Scroll down to the ‘Australian’ section or read below, where I quote it:
Small families of Australian languages have been identified, but assembling them into larger families has proved frustratingly difficult. R.M.W. Dixon believes that the family tree model is not very useful in Australia; rather, hundreds of languages existed in a dynamic equilibrium, grammatical features and lexemes diffusing across different regions or the whole continent.
Many of the Australian languages have a limited set of numbers. (That doesn’t mean they’re simple languages– they tend to be quite complex.) Some number words, as shown, represent not a single number but a range.
I have to wonder when some languages, like Yir Yoront, have a full set of numbers, but we’re told that most Australian languages stop at 2, 3, or 4. As in many languages, the number words in Yir Yoront refer directly to the process of counting on the hands: 5 = “whole hand”, 7 = “hand entire, fingers two”, 10 = “hand-two”. It makes me wonder if most fieldworkers are asking the wrong questions.
Dude. No, it’s not that we’re all dumb. It’s that there were 250 languages on this rather large continent, and they differ. Some have systems beyond 4. Others don’t. Some, like the Thura-Yura languages, have birth-order names up to ten but numerals up to 4. Getting people to count when they have numeral systems beyond 4 is not exactly the most difficult enterprise in fieldwork. The Australian data itself is pretty poor. It seems to be from Capell, Curr, possibly Tindale, and other sources from more than 50 years ago.