I’m currently reading William H. Calvin’s A Brief History of the Mind. Calvin writes really well, and puts together an absorbing and convincing story of how the human mind has developed. While he traces the development of the human species, starting about 7 million years ago when hominids shared a common ancestor with chimpanzees and bonobos, it appears that the evidence for the modern mind only appears as little as 50,000 years ago. And that’s even though Homo sapiens has been around for at least 100,000 years.
So something caused (in Calvin’s phrase) "the mind’s big bang" to occur around 50,000 years ago. He posits a number of candidates for the trigger, for example, the use of the structured planning that is necessary to throw things accurately being applied in other modalities and time scales. He also argues that "if children are exposed to structured stuff can softwire their brains to better handle it, and if the younger they are exposed, the better they do as adults, then the more precocious children will soon double the amount of structured speech heard by the next generation of youngsters… So the transition might be language, acting like a contagious disease over a few generations’ time."
This is EvoDevo, when evolution interacts with the development via the einviroment. Today, I ran across an interesting article in Seed magazine: Why Do Grandmas Exist? This points out that the menopause is something that is unique to the female Homo sapiens – none of the other primates have this. Other primate females are capable of becoming pregnant until they die. So the menopause might also be one of the triggers of the big bang: females who are no longer capable of child bearing have more time to babysit or to forage for food. And the babysitting might help the children be "exposed to structured stuff".
Food for thought.