Simply stated, an AI that writes AI.(Forget the halting problem for a moment) How many iterations can it create in 3 hours?
Imagine a massively parallel optical computer with the same transistor density as the human brain, the size of an olympic swimming pool running at the speed of light, and networked with 1000s of other similar computers around the world.
Foomp, superintelligence, you won't even be able to pinpoint the source.
So certainly you would get the baby situation first, but going from manageable baby to astral foetus could potentially happen rapidly and unexpectedly as the rate of progress accelerates to unfathomable speeds, which is what's happened already in going from tribal man to modern civilization, and if you extrapolate that very consistent and reliable trendline, it leads to progress happening in a foomp step perceived as a foomp in real time. Really, all life is just one big accelerating foomp.
We don't need to rely only on humans to design every aspect of neural networks. We are already computationally searching for AI designs that work better. In a recent paper, hundreds of variations of design for the neuron of the LSTM network have been tried to see which one is the best and which of its components are important.
Also, we can play with networks like clay - starting from already trained networks, we can add new layers, make layers wider, transfer knowledge from one complex network into a simpler one and initialize new networks from old networks so as they don't start from scratch every time. We can download models trained by other groups and just plug them in (see word2vec for example). This makes iterative experimenting and building on previous success much faster.
I don't think evolving a super intelligence will happen by simple accident, it will be an incremental process of search. The next big things I predict will be capable robots and decent dialogue agents.
I don't think the big breakthroughs in artificial general intelligence are going to come from well funded scientific researchers anyways, they are going to come out of left field from where you least expect it.