.30-06 was not developed from the .45-70. It may have been developed because of the -70, but the development of the .30-06 was from the .30-03, from the 6mm Lee Navy, from the .30-40 Krag, as a result of the new Mauser bottlenecks that was kickingass on the .45-70.
Ballisticly the .30-06, .308 or 7.62x51 are similar. The .308 was developed from the .300 Savage or T65 research, it is not a cut down .30-06. The reason they went with the Savage round had to do with case capacity and taper of the case for ejection in full auto fire, and political issues with Britain.
Thanks for calling him on that, I was going to but decided not to bother but I think it needed to be said. As I said in another comment, I was always puzzled why they didn't just use the .300 savage right out of the box, except they probably wanted to get a little more power. Mistake IMO, it was powerful enough, was even lighter than the .308 and was more akin to the Russian 7.62X39, would have been easier to hold on full auto. That M14 was a bear to shoot full auto!