How historical are early Chinese (Shang dynasty and earlier) dynastic records?

The recent discovery of the Oracle Bones has been shedding more and more "Historical" light to many of the previous legends surrounding the Shang. Check out the awesome China History Podcast. Here is one of the episodes that cover some of this specific information you are asking about.

It is very difficult to know. To a similar question a few months ago, I weighed in and got rewarded with -8 votes (Chinese do not like having their history questioned), so the question to you is, do you want to know (A) What the official Chinese position is? (B) What the contrarian Chinese position is? (C) What Western scholars think? (D) What unaffiliated Western scholars think (ie, those who do not have to rely on grants)? or (E) What is probably true?

As a point of comparison, the genealogies can be compared to those of Ireland, which are similar in that they are based on oral tradition. Originally, Ireland supposed had many of these records written on deer skins and birch bark, etc, but they were destroyed during the Christianization in the 4th century. The first written records date from the 7th century and many manuscripts exist from the 9th century. The Irish records contain many inserts in verses called "ranns" that indicate usage in oral tradition. The earliest Chinese historical manuscripts were inscribed or block printed around the 12th century (more than 3 centuries after the earliest Irish mss), and most are much later.

The Confucian genealogies are in two primary sources: the Zuozhuan and Shiji which are the basis of a sort of cult of people who wish to show the antiquity of their lineage. The Zuozhuan is widely considered an obvious forgery, even by Sinophile scholars, so I will not consider that further. The Shiji ("Records of the Historian") exists in small fragments dated to the 8th century. The earliest complete MSS is 11th century. However, the edition actually used today is a "palace edition" printed in 1598, which differs considerably from the 11th century edition. If you consider, the scope of changes which took place from 1100 to 1598, a 500-year difference, it is hard to believe that the changes from 100 BC to 1100 AD (a 1000-year difference) would be anything other than extreme.

There was a project earlier called the Xia-Shang-Zhou Chronology Project, but because it's a sensitive matter for Chinese, as well as the political situation regarding the People's Republic of china, there's a ton of dispute about it.

Even in Chinese texts, it doesn't all agree. The Shiji, for example, paints a starkly different picture than the Bamboo Annals about the circumstances of Taijia's Reign and the Role of Yi Yin.

The two main schools of thought regarding the Xia is that one believes it was just a fabrication made by the Zhou to justify conquering the Shang, so the Xia's customs and metrics are diametrically opposed to the Shang. On the other hand, people didn't believe that the Shang existed either until the oracle bones were unearthed.

Note that this is not necessarily racism, as the first people to start this kind of doubt wwas actually chinese. They were known as the Doubting Antiquity School, started by the famous Hu Shi.

However, it is notable that a similar situation occured in Sumeria, also having a lot of written history that was not corroborated by archaeology. However, for whatever reason it wasn't questioned nearly as much as the Xia. In the end, it's arguable that the two are about as equal in historicity.

As for Confucius's family tree, you have to remember one thing. All family trees are prepared by the members of their family. For any and all kinds of political reasons, it may be altered without any way of proving that it has been done. You can literally dig up his family tree buried next to him in the tomb and still not be sure that it hasn't been doctored, perhaps even by Confucius himself.

Note that Confucius was not well-respected until well after the start of the Han Dynasty, before which the Qin Dynasty practiced hard control over text and Xiang Yu burned most of the records in Xianyang. It's just not possible to zero in on anything as a 100% accurate "family tree" of Confucius.