I've modified the tech cost function, if you use that option, so that if anyone is too far ahead or too far behind in terms of techs from where it should be (compared to our real world timeline), you get respectively hindered or helped in terms of tech costs. I.E. if you're around 400AD and you are already getting to gunpowder, it will cost you a LOT more than if you were around 1000AD. Or, if you're around 1600 and you still don't have gunpowder, it will cost you very little in terms of tech cost. In practice, that won't almost ever happen. With this function you prevent having tanks around 1200AD or having longbows around 1900AD. So you will hit and develop each era more or less in the timeframe experienced in our world. This also means that it might be better to research some older techs that you would have skipped otherwise than to beeline straight to the most modern techs. For example, Renaissance should start around 1300-1500AD; if you're in year 1000AD and you could research Gunpowder (hence moving to Renaissance) it would cost you many turns. It might be better to get some older techs in the meantime and research Gunpowder once you reach 1200AD because you'll be able to research it faster. I've made it an option that you can turn off because in some scenarios you might want some civs to stay behind while with this function most civs are more or less on the same technological level (hence making harder for humans to overrun other AI civs, which are usually left behind in terms of techs once you reach Renaissance/Industrial).