When a gibbon is on the ground it almost always walks on two legs. Using it's arms to stabilise itself. Youtube thinks this is very funny and has many videos of gibbons walking "like a human". It's not that they have "learned to walk like a human", that's just what they do on the ground. Note even the great apes adopt bipedalism when wading in water.
So there is a fallacy here. The fallacy tells us that the chimp is our closest genetic relative, so our ancestors must have been chimp-like (hiding in their somewhere is the assumption that chimps are "primitive" animals and that only humans evolve). But our ancestors were not chimp-like. Chimps, gorillas, and orangutans evolved knuckle walking, humans never did. Nor did gibbons.
The modern view of evolution is that all organisms currently alive have been evolving for exactly the same amount of time. So just because a bacteria looks archaic, does not mean that it is archaic. Everything currently alive is modern. Evolution doesn't stop for living things.
Chimps and humans have evolved for equal lengths of time. And neither of us is more like our common ancestor than the other.
This means that there are no "primitive" tribes. Hunter-gatherers living now are not necessarily representative of pre-historic humans unless we know the conditions they live in have not changed (and given the intervention of the last ice-age this is extremely unlikely).
Yes, humans arrived in Australia as long ago as 60,000 years before the present, but they constantly changed. The evolved literally hundreds of languages for instance.
In my field of study, modern schools of Buddhism, whether Theravāda or Tibetan or Zen are often seen are representative of some previous era. This is the same fallacy. All forms of Buddhism currently being practised are modern (though not all are modernist). No amount of social conservatism can prevent changes from accumulating over dozens of generations.
I'm not sure what to call this fallacy.