Varki’s Mind Over Reality Transition theory says that awareness of mortality is a barrier to evolving an extended theory of mind and this barrier can only be crossed by simultaneously evolving denial of reality.
Only one species has crossed this barrier and it used its extended theory of mind to take over the planet, while denying the consequences of its success.
One prediction of Varki’s theory is that all 7 billion humans will have descended from the individual that managed to cross the barrier.
Here is a short video that explains why it is generally accepted that all 7 billion humans descended from one woman about 200,000 years ago.
The usual explanation is that humans experienced a bottleneck caused probably by a changing climate.
I think Varki’s barrier explanation is more consistent with the evidence.