I'm not actually quite sure it is needed to have the same level of technology anyway. Mind you, technological differences are often determined by many factors. Among these factors are the history of the culture in question. A culture which has a less violent history and has worked together more often will have more advanced tech. But, that doesn't mean that all cultures with less violence will have more advanced tech. There are many things that have to be considered when looking at tech levels. We will always have varied tech levels. Just because some people have a higher tech level at the beginning doesn't mean that they will have a higher tech level in the future. In fact, I would expect the cultures with low tech levels to focus mostly on gaining tech rather than fighting. 

As for history, just because it is 4,000 BC doesn't mean that we can't have history. Around 4,000 history is when we first saw written history. Before that, it would have been told orally. The history of our cultures are basically the legends of our people, we aren't even quite sure that the history is exact. I know that the history in my culture is quite possibly only true in the case of the names. Nobody can actually tell where history begins and the stories end. 

But, what you have been suggesting is that we should have the same tech level . I can't say I disagree but the tech levels will vary per culture. A war like culture would have developed defensive architecture and weaponry faster. A trade culture would have developed more in the area of trade tech and transports. Our cultures will in not always have the same tech levels as each other as we advance on with this roleplay. Truth is, I would be disappointed if we did have the same tech. It shouldn't be our world's history which effects what level our tech should be because, as Captios said, this is a blank slate. We shouldn't be trying to base our tech levels off the tech levels of our world's cultures at the same time.