Long-Lived Grannies Had
Few Grandkids, Costa
Rican Analysis Reveals
For grannies, this might
rather come as a huge
shock. An analysis of
births and deaths in
Costa Rica has found
that the longer
grandmothers lived, the
fewer grandchildren
their daughters raised.
For the research, Lorena
Madrigal at the
University of South
Florida, Tampa, US, and
Mauricio Melendez-Obando
of the Costa Rican
Academy of Genealogical
Science, analysed church
and civil government
record data on births
and deaths in the
country between 1500 and
1950.
The analysis revealed
that women who died
before they were 50 had
an average number of 7
children, whereas women
who lived to beyond 80
had an average of 8.3
children.
This in itself was
unexpected, since on
average all women stop
reproducing at around
the same time of 50.
Astonishingly, the
analysis also found that
women living beyond 80
had nearly 50 percent
fewer grandchildren –
5.75, on average – than
women who died before
they were 50; these
women had on average 8.9
grandchildren.
The researchers argue
that that the reason
behind such a trend is
that when women lived
into old age they
increased the chances of
survival for their
children by being good
mothers, but living too
long created a strain on
resources that harmed
their grandchildren.
"The ones who really
suffer with the presence
of grandmothers are the
grandchildren. With
grandmothers around it
could be a case of them
eating food out of the
grandchildrens'
mouths, but we need more
research to be certain
exactly what it is that
they are doing to reduce
the reproductive success
of their daughters,” New
Scientist magazine
quoted Madrigal, as
saying.
In theory, there are two
likely reasons for women
living long after
menopause. The
"grandmother hypothesis"
says that menopause
forces women to stop
having children of their
own so they can help
raise grandchildren.
The "mother hypothesis"
says menopause functions
to force women to raise
the children they
already have and not run
the risk of dying by
having babies in old
age. The new findings
suggest that menopause
is all about improving
child rather than
grandchild survival.
The study is published
in The American Journal
of Physical Anthropology
.
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