The study of wizarding genealogies is considered by many to be a prestigious area of magical study. There are three significant purposes for the study of wizarding genealogies.
1. Tracking pure blood in wizarding families. A wizard, curious about his blood status, will employ a wizarding genealogist. Usually, the wizard is wealthy and is convinced of the importance of being pure blood. In attempting to prove that his family is pure blood up to 16 generations previous (further back if they could) the wizard or witch will pay a vast amount of money to a wizarding genealogist.
This wizarding genealogist can find themselves very wealthy if they bring about results that are pleasing to the wizard or witch. If the results are not pleasing, they will still find themselves wealthier but not as reputable. A rich wizard has influence enough to bring disrepute to the wizarding genealogist, while still enforcing the facade of being truly, pure-blood. The wizarding genealogist, being defamed, may give up the study of wizard genealogy altogether or might rely more on the others areas of study within genealogy for their professional gain.
2. Connection to Name. A wizard will also employ a wizarding genealogist to find out if they are connected to wizards of renown. It has been rumored that Sybil Trelawney, a professor at Hogwarts school of wizardry and magic, only received her professorship because of her familial connection to famed seer, Cassandra Trelawney. That however, is only hearsay, no matter how truthful it sounds.
A relation to a wizard of renown, even an evil wizard such as Grindelwald, can be beneficial to the wizard's fame and even wealth. Recently, a distant cousin to the late Bathilda Bagshot was able to claim some of her leftover property, that was not designated by her will to any relation or entity. This claim was many years after Bagshot's death. I personally, know the wizard that worked on that case. His caseload has increased a hundred times since then. My focus in studying wizarding genealogies does not lend itself to wealth or fame because it delves in the realm of theory.
3)The Weighing of Magical Power. Powerful wizards have been known to have relations (close and distant) that are equally as powerful. However, greatness can be honed through practice and training. Hence, the draw of magical schools, apprenticeships and clubs. Therefore, it is not wise to depend on inherited talent alone. I study how magical power of wizarding families strengthen and weaken over time.
Theories are more widely used is this arena because of the ability to elevate one's own magical power through mastery of skills, which may nullify the affects of having a lineage lacking in strong magical power. However, many wizards have noted that having relations with high magical power may have an affect on one's own talent. Other wizards have contested to the complete opposite.
The late Professor Charity Burbage suggested that the breeding of magical and non-magical humans can produce strongly magical offspring. This is the Theory of Mingling, supported by much evidence throughout history and the recent increase in muggle-borns with significant magical ability. Professor Burbage also comments on the weakening of magical power in pure-blood families, where the gene pool has been narrowed and the magical sources have been depleted. This is called the Theory of Waning. This theory suggests an older and yet more commonly accepted theory, that all human beings were all magical or all non-magical at one point in time. This is the Theory of One-Blood. There are many ancient theories as to the reason for the division. All are fascinating and worthy of study because evidence is still being collected. But the funding for such studies is scant and only those who truly value knowledge and reason would seek out the answers.
As you can see, there are many reasons as to why this field would interest me. I am not a historian, but I am intellectually stimulated by the study of theories. As a Ravenclaw, I have surpassed many in the study of muggles. And, I have always been drawn to the most powerful, talented, and skillful wizards and witches of our time. My name is Cho Chang and I am a wizarding genealogist.