(a) The information which is of most value is exactly that which genealogy ordinarily does not furnish. Dates of birth, death and marriage of an ancestor are of interest, but of limited biological importance. The facts about that ancestor which vitally concern his living descendant are the facts of his character, physical and mental; and these facts are given in very few genealogies.
LINE OF ASCENT THAT CARRIES THE FAMILY NAME
Fig. 40.—In some pedigrees, particularly those dealing with antiquity, the only part known is the line of ascent which carries the family name,—what animal breeders call the tail-male. In such cases it is evident that from the point of view of a geneticist practically nothing is known. How insignificant any single line of ascent is, by comparison with the whole ancestry, even for a few generations, is graphically shown by the above chart. It is assumed in this chart that no cousin marriages took place.
(b) Genealogies are commonly too incomplete to be of real value. Sometimes they deal only with the direct male line of ascent—the line that bears the family name, or what animal breeders call the tail-male. In this case, it is not too much to say that they are nearly devoid of genuine value. It is customary to imagine that there is some special virtue inherent in that line of descent which carries the family name. Some one remarks, for instance, to Mr. Jones that he seems to be fond of the sea.
"Yes," he replies, "You know the Joneses have been sailors for many generations."
But the small contribution of heredity made to an individual by the line of descent carrying his family name, in comparison with the rest of his ancestry, may be seen from Fig. 40.
Such incomplete pedigrees are rarely published nowadays, but in studying historic characters, one frequently finds nothing more than the single line of ascent in the family name. Fortunately, American genealogies rarely go to this extreme, unless it be in the earliest generations; but it is common enough for them to deal only with the direct ancestors of the individual, omitting all brothers and sisters of those ancestors. Although this simplifies the work of the genealogist immensely, it deprives it of value to a corresponding degree.
(c) As the purpose of genealogy in this country has been largely social, it is to be feared that in too many cases discreditable data have been tacitly omitted from the records. The anti-social individual, the feeble-minded, the insane, the alcoholic, the "generally no-count," has been glossed over. Such a lack of candor is not in accord with the scientific spirit, and makes one uncertain, in the use of genealogies, to what extent one is really getting all the facts. There are few families of any size which have not one such member or more, not many generations removed. To attempt to conceal the fact is not only unethical but from the eugenist's point of view, at any rate, it is a falsification of records that must be regarded with great disapproval. At present it is hard to say to what extent undesirable traits occur in the most distinguished families; and it is of great importance that this should be learned.