Origin of current earth?

While we know that there have been massive glacial melts, one in N America and the larger in Asia, with moraines and channels, we politely gloss over the causes. The latest theory sets out astronomical involvement based upon those micro-diamonds embedded in creatures and objects all buried at once, it seems. The brush of a planet would give rise to orogenesis and massive friction. Add the expanded earth then we may have had a direct hit, causing all sorts of gravitational anomalies, continental movements and wave action worldwide. The DNA geeks suggest we had a choke point 70,000 years ago when humans faced extinction, based presumably on some hypothetical common ancestor scenario. We are aware of vulanism at that time, but again that would be merely a symptom of a direct collision. The isotopes could all be off due to electrical incidences at the same time caused by "thunderbolt" action. I wonder what our ancestors, now buried under glacial waters 300 feet higher than when they lived, thought about this? We will only know when we seek out the answers at those depths.