Your question is a little flawed because there were at least four different human species that lived more recently than 70,000 years ago. Newer evidence suggests if not proves that Neanderthals never died out completely. Instead, they hybridized with some homo sapien populations in Europe. Most people of European ancestry have a significant contribution of Neanderthal ancestry in their genome (1% - 5%+ percent is common). There was also the Denisovansfound in the area that is now Siberian Russia. Little is known about them except that they were also genetically distinct and possibly interbred with some homo sapien populations as well.
Finally, there is Homo floresiensis which is also a rather recent discovery. Their remains were found on an island on Indonesia and they were called the Hobbit People because they were very short. The researchers that found them were astounded because the remains found were only 9,000 years old but the native islanders were not surprised at all. They firmly claim that they were around in the last few hundred years until they killed them off on purpose.
The point to all of my comments is that modern human evolution is a quickly evolving science and a lot of what you think you know isn’t true. It is most likely true that homo sapiens went through an extreme population bottleneck at one point but that was only one of a few very similar species that also survived and hybridized during that time.
It is a fascinating question in general and new scientific tools can help answer it over time but the true story is still far from complete.