For starters, biologists acknowledge that the basic mechanisms for biological intelligence are still not completely understood, and as a result there is not a good model of human intelligence for computers to simulate.
Indeed, the field of artificial intelligence has a long history of over-promising and under-delivering. John McCarthy, the mathematician and computer scientist who coined the term artificial intelligence, told his Pentagon funders in the early 1960s that building a machine with human levels of intelligence would take just a decade. Even earlier, in 1958 The New York Times reported that the Navy was planning to build a “thinking machine” based on the neural network research of the psychologist Frank Rosenblatt. The article forecast that it would take about a year to build the machine and cost about $100,000.
The notion of the Singularity is predicated on Moore’s Law, the 1965 observation by the Intel co-founder Gordon Moore, that the number of transistors that can be etched onto a sliver of silicon doubles at roughly two year intervals. This has fostered the notion of exponential change, in which technology advances slowly at first and then with increasing rapidity with each succeeding technological generation.
At this stage Moore’s Law seems to be on the verge of stalling.