I have no accurate knowledge of my age, never having seen any authentic record containing it. By far the larger part of the slaves know as little of their ages as horses know theirs, and it is the wish of most masters within my knowledge to keep their slaves thus ignorant.
He goes on to say that his master "deemed all such inquiries [about dates of birth] on the part of a slave improper and impertinent, and evidence of a restless spirit." To know one's date of birth means that it is a date worth acknowledging. A birthday is a celebration of life, an acknowledgement of value and a place of worth.
It is likely that slave owners simply didn't value the lives or the births of slave children enough to make a note of the date. The fact that they owned slaves capable of the necessary work was enough. What practical or economic purpose could knowing an exact date of birth serve these owners? Since they had almost nothing to personally gain from keeping track of these records and viewed their slaves as merely acquired property, the date of birth was insignificant.
If masters did know a date of birth, they likely didn't share this knowledge with their slaves because doing so would create a feeling of significance regarding this date. Most slave owners tried to belittle and demean their slaves in order to maintain the sense of order they desired, so they didn't want to create a sense of individuality.
Parentage was kept quiet for other reasons. Douglass, for example, believes that his father was one of his white owners. This situation happened frequently and was not a source of joy or celebration for slave owners. While they might have gained one more slave to own, they certainly did not claim these offspring as their children. It was also common for masters and owners to disperse biological families across different plantations. After all, families make sacrifices for...
each other and form bonds that could overcome powerful obstacles. By breaking apart families, slave owners weakened the collective power of the slaves on their plantations.