In my research on American slavery, I’ve come across frequent references to slaves and freed blacks of extraordinary age. Part of the reason for this, I suspect, is that many people did not know in which year they were born. Census takers engaged in “statistical heaping” when old people estimated there age at “about 100”.

Given that life expectancy was much lower 200 years ago, one would not expect to find so many slaves of such advanced age. What are some other reasons for this? What other cultural, social, or statistical effects might be at play in reporting such old age?