The Spacing of Generations
by Bob Brooke
Beginning genealogists often ask how many generations are likely to occur in a given
span of years, for instance, a century. Generally, three or four generations span one
hundred years, but in rare instances only two, in others five. The average span
between one generation and the next is about 25 to 30 years. So, over 350 years, the
researcher can estimate that there will be about 12 generations. At the 300th
anniversary of the landing of the Pilgrims at Plymouth, Massachusetts, most of the
applicants for membership in the Mayflower Society were of the 10th generation in
descent, few were of the 9th, few of the 12th.
There are, of course, exceptions to any rule. The tabloids often report of young
boys of 12 or 13 having children with girls the same age.
Throughout history there have been other instances of extraordinarily youthful
parentage. Marriages were often arranged, especially in English society, to increase
wealth or strengthen or stablize economic standing. Maurice Berkeley, who later
became Lord Berkeley, was born in 1281 and married in 1289 at the age of eight to the
heiress of considerable property who was also eight. Their first child, Thomas, was
born about 1291. He was 35 when he succeeded his father in the peerage. His son,
another Maurice, also married another heiress at the age of eight, but this young
couple wasn't permitted to live together for several years.
In the days of increasing longevity and youthful marriages, newspapers often publish
multiple-generation photographs. A common one is of a great-great-grandmother seated
in the center of a group, holding an infant in her arms. She's usually in her 80's,
if not her 90's, and the infant is a few months old. Five generations in less than a
century. True, but the span between each generation is still 20 to 30 years. The
great-great-grandmother may have been born in 1890; her son, the great-grandfather,
in 1915; his daughter, the grandmother, in 1937; her daughter, the mother, in 1958;
and the infant in 1980.
Birth dates of children usually occur in some kind of pattern. Sometimes a child is
born every 18 months, or every two or three years. Today, it's not uncommon for young
couples to have a child every 12 months and sometimes less. Also, if a researcher
finds a big gap between children's birth dates, it can sometimes signify an
unrecorded child, a stillborn child, a divorce, or the death of a wife and a
remarriage. It can also indicate a father who's serving in the military or away at
sea, or who's pioneering to find a suitable home for his family, or perhaps even away
prospecting for gold.
At the other extreme, it's not unusual for a man to be 40, 50, or even 60 before he
marries or produces his first child. In rare cases an 80-year-old may father
children. The late Richard T. Ely, a noted economist, born in 1854, married his
scond wife in 1931 when he was 77. Before he died in 1943, he had fathered a son and
a daughter by that wife, the youngest born when he was about 84 years old, making
only two generations in 84 years.
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