In particular, look at the extent to which humans, unlike apes, have been able to shape and change our environment. Perhaps they are hiding their light under a bushel, since there is such minimal evidence of awareness in the wild. Take their use of tools. It takes chimps up to four years to acquire the necessary skills to select and adequately use the tools to crack a nut. Given the amount of time and effort the young invest in attempts to crack nuts, this raises serious questions about their ability to reflect on what they are doing and to learn from their 'experiences'.
Nuts are, after all, an important part of their diet.
The accomplishments of apes in captivity look more impressive. What is probably more impressive than the achievements of the apes themselves are the persistent efforts of the trainers who manage to get them somewhere near to the level of a toddler. Most importantly, apes never develop the ability to use language to regulate their own actions. It is when thought and speech come together that children's thinking is raised to new heights and they start acquiring truly human characteristics. Language becomes a tool of thought allowing children increasingly to master their own behaviour.