The 'human evolution' achievement standard expects you to be able to discuss trends in cultural evolution. You need to be aware of evidence relating to: use of tools (stone, wood, bone), fire, shelter, clothing, abstract thought (communication, language, art), food-gathering, and domestication of plants & animals. The earliest evidence for culture is the presence of stone tools, and the oldest such tools come from sites in Africa (Omo, Turkana, & the Middle Awash) that date date back to around 2.3 million years ago. But - is this likely to represent the earliest tool manufacture and use?
The answer is almost certainly 'no'.
For starters, hominins aren't the only primates known to make tools. There's an increasing amount of data available on culture in chimpanzees, something that was first observed by Jane Goodall. Chimps modify twigs and use them to extract termites from their burrows, chew and crush leaves to act as sponges for getting water out of hollows in trees, and use rocks to crack nut shells. And there are cultural differences between different chimp groups. So it's reasonable to assume that early hominins also used such simple tools.
But the odds of us finding evidence of this are minimal, for the simple reason that tools of wood or crushed leaves are highly unlikely to leave any traces. What's more, even before our primate ancestors started modifying natural objects, however simply, they probably used unaltered materials - the chimps' nut-crushing hammerstones would be a case in point. Because these 'opportunistic' tools are essentially no different from natural objects, how would we recognise them?
This question may have a partial answer in some archaeological research into chimpanzee living sites, where scientists have found an accumulation of stone fragments broken from hammerstones as they are used (Mercader, Panger & Boesch, 2002). Such accumulations in ancient hominin sites could also signal the opportunistic use of stone tools by our early ancestors. Mercader & his colleagues studied chimpanzees living in the Ivory Coast's Tai forest. At one site they found around 4kg of stones and stone flakes, which had accumulated over a lengthy period of use by the local chimps. They also discovered that the chimps had carried the stones in to the nut-cracking sites.
What does this imply for our interpretations of early hominin sites? Mercader's team comment that chimpanzees engage in cultural activities that leave behind a stone record that mimics some Oldowan occurrences and invite us to speculate whether some of the technologically simplest Oldowan sites could be interpreted as nut-cracking sites or, more generally, if some subsets of artifacts from the more sophisticated Oldowan assemblages could be interpreted as evidence of hard-object feeding by early hominins.
Perhaps Louis Leakey's nickname for Australopithecus boisei, 'Nutcracker man', wasn't so far off the mark after all!
J. Mercader, M. Panger & Christophe Boesch (2002) Excavation of a chimpanzee stone tool site in the African rainforest. Science 296: 1452-1455