"Back in 1985 Alex
Shoumatoff wrote an account of kinship and genealogy called The
Mountain of Names, A History of the Human Family (A
Touchstone Book published by Simon & Schuster, Inc., New York.) He
speaks about an amazing paper by Robert C. Gunderson called Tying
Your Pedigree into Royal, Noble and Medieval Families. Gunderson
invented the term ‘pedigree collapse’. This is a phenomenon which is
ubiquitous and makes every genealogist's life a little easier. When
one's pedigree collapses, one has a reducing number of ancestors to
search for. Here is how it works.
We all are blessed with two parents, four
grandparents, eight great grandparents and so on. If the average
generation is twenty-five years, in 1200 years (back to 800 AD, the time
of Charlemagne) each person has 281.5 trillion grandparents. That's the
way geometric progressions work. The number of grandparents doubles
every 25 years and in 12OO years or 48 generations, 281.5 trillion names
would be on your pedigree.
But hold on, you say! In 800 AD there were not
that many people on the whole planet. How could I - or any person - have
that many grandparents? The answer is that while you must have this number
of grandparents, given the imperatives of human
procreation, they are not all different people. Some names
on your pedigree appear twice, three times or even hundreds of times in
the 1200 years. Cousins have married and, if they were first cousins,
their offspring will have only six great grandparents rather than the
normal eight. Those offspring will have pedigrees which have
"collapsed" from 8 to 6 or 25% in the 4th
generation back. That 25 % collapse will be present in each and every
one of the 44 generations back to 800 AD. The same phenomenom occurs
when 2nd, 3rd, 4th or 5th
cousins marry although the percentage ‘collapse’ is not as dramatic.
A dramatic collapse occurs when siblings marry as was the norm for
Egyptian pharaohs and Inca kings. In those cases there is a 50% collapse
(from 4 to 2) at the 3rd generation, the grandparents.
In the 1990s we may not think that this is a
common occurrence but the impact on our pedigrees must be significant or
the population on the earth in the past must have been much larger than
it was. The facts speak for themselves. There could be no other
explanation for how the number of one's grandparents can be reconciled
with known population figures.
Studies in various parts of the globe have
confirmed this and provide us with some case studies:
In 1964 it was found that a third of the
marriages in Andhra Pradesh, southern Indian, were between first
cousins and that almost 12% of marriages were between uncles and
their nieces.
In 1875 in England 7.5 % of Jewish marriages
were between 1st cousins, a result of their society being
relatively isolated from the main stream community.
King Alfonso XIII of Spain (1886-1941) had
only eight different people as his great great grandparents rather
than the normal sixteen, a 50% collapse of his pedigree at the 5th
generation.
Prince Charles' pedigree has been examined
by Gunderson who found that 17 generations back when Charles should
have had 65,536 progenitors, he only had about 23,000, a collapse to
35 % of the theoretical.
A great deal is known about the family
histories of the Amish who came to North America from Switzerland in
the 18th century. It is estimated for one family about
whom a very complete genealogy has been compiled that 21.5 % of 627
marriages in this family were between 2nd cousins or
closer.
Mr. K. W.
Wachtel, a demographer cited by Shoumatoff, built a probability model for a child born in England in
1947. Around the time of King John who reigned from 1199 AD to 1216
AD, this 1947 child would have about two million grandparents in the
same generation. This represents about 37% of the progenitors
required 30 generations back. This is the first type of pedigree
‘collapse’ that occurs. The child would be descendant from 80%
of all the people in England at that time.
But now a ‘collapse’ in the absolute
number of progenitors starts to occur for this 1947 child. The
actual number of different grandparents would start to decrease at
this point - 30 generations back. Theoretically the further one goes
back from this point the smaller the number of different
grandparents there would be until one reached one's theoretical
‘Adam and Eve’. Put in graphical terms and viewing the child's
pedigree from the bottom (now) to the top (early), the number of
names creates a diamond with one person at the bottom in 1947, two
million people in the generation 700 years earlier and then an
ever-decreasing number dwindling to the original ‘Adam and Eve’,
say, several thousands of years before that at the very top of the
chart.
There are, of course, many genetic, medical and
hereditary aspects of kinship. All of these are made more
fascinating and complex by the intermarriages within families and small
tribes that have been taking place." |