Glia
05-12-2012, 07:50 PM
We *still* can't fool Mother Nature!
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Natural Selection Is Still With Us
by Elizabeth Pennisi
30 April 2012
https://news.sciencemag.org/sciencenow/2012/04/natural-selection-is-still-with-.html
In a world where we've tamed our environment and largely
protected ourselves from the vagaries of nature, we may
think we're immune to the forces of natural selection.
But a new study finds that the process that drives
evolution was still shaping us as recently as the 19th
century.
The finding comes from an analysis of the birth, death,
and marital records of 5923 people born between 1760 and
1849 in four farming or fishing villages in Finland.
Researchers led by evolutionary biologist Alexandre
Courtiol of the Institute for Advanced Study Berlin
picked this time period because agriculture was well
established by then and there were strict rules against
divorce and extramarital affairs. The team looked at
four aspects of life that affect survival and
reproduction, key signposts of natural selection: Who
lived beyond age 15, who got married and who didn't, how
many marriages each person had (second marriages were
possible only if a spouse died), and how many children
were born in each marriage. "All these steps can
influence the number of offspring you have," says
Courtiol.
Natural selection was alive and well in all of the
villages the researchers surveyed. Almost half of the
people died before age 15, for example, suggesting that
they had traits disfavored by natural selection, such as
susceptibility to disease. As a result, they contributed
none of their genes to the next generation. Of those
that made it through childhood, 20% did not get married
and had no children, again suggesting that some traits
prevented individuals from obtaining mates and passing
on their genes to the next generation.
The numbers were about the same for landed and landless
individuals, indicating that wealth did not buffer the
environment enough to prevent natural selection from
culling or favoring individuals. "Although there is
agriculture and transmission of wealth, there is still
as much room for evolution to proceed as in other
animals," says Courtiol, whose team reports its findings
online today in the Proceedings of the National Academy
of Sciences .
The Finns were also subject to sexual selection, in that
men who were able to attract new mates had more
offspring. With one partner, the average was about five
children; with four partners, that jumped to 7.5,
Courtiol notes. Men benefited more than women in terms
of begetting more children, most likely because they
tended to remarry young women with good child-bearing
potential. Thus sexual selection was more important in
men than in women.
From the records they had, the researchers could not
tell which traits were being selected for, but the
variation in the number of offspring-from zero to 17-
indicates there was a large opportunity for selection to
occur. That variation is the grist for evolution.
The importance of sexual selection is well accepted in
birds and fish, "but this is the first time that sexual
selection has been so well documented in humans," says
Stephen Stearns, an evolutionary biologist at Yale
University. As for showing natural selection, "they are
providing additional, confirmational evidence."
"Without a doubt, natural selection occurs in modern
humans," agrees Jacob Moorad, an evolutionary biologist
at Duke University in Durham, North Carolina, who was
not involved in the study. He thinks this work will
inspire other researchers with large databases of data
on humans to look at how selection operates in
populations.
Courtiol is not certain how strong natural selection is
today, particularly in the developed world. But he says
that at the very least, the data show that even as
recently as 200 years ago, it still played a role in
shaping humans as a species. As such, he notes,
biological and cultural processes should both be
considered in understanding how humans are changing
through time.
--------
Natural Selection Is Still With Us
by Elizabeth Pennisi
30 April 2012
https://news.sciencemag.org/sciencenow/2012/04/natural-selection-is-still-with-.html
In a world where we've tamed our environment and largely
protected ourselves from the vagaries of nature, we may
think we're immune to the forces of natural selection.
But a new study finds that the process that drives
evolution was still shaping us as recently as the 19th
century.
The finding comes from an analysis of the birth, death,
and marital records of 5923 people born between 1760 and
1849 in four farming or fishing villages in Finland.
Researchers led by evolutionary biologist Alexandre
Courtiol of the Institute for Advanced Study Berlin
picked this time period because agriculture was well
established by then and there were strict rules against
divorce and extramarital affairs. The team looked at
four aspects of life that affect survival and
reproduction, key signposts of natural selection: Who
lived beyond age 15, who got married and who didn't, how
many marriages each person had (second marriages were
possible only if a spouse died), and how many children
were born in each marriage. "All these steps can
influence the number of offspring you have," says
Courtiol.
Natural selection was alive and well in all of the
villages the researchers surveyed. Almost half of the
people died before age 15, for example, suggesting that
they had traits disfavored by natural selection, such as
susceptibility to disease. As a result, they contributed
none of their genes to the next generation. Of those
that made it through childhood, 20% did not get married
and had no children, again suggesting that some traits
prevented individuals from obtaining mates and passing
on their genes to the next generation.
The numbers were about the same for landed and landless
individuals, indicating that wealth did not buffer the
environment enough to prevent natural selection from
culling or favoring individuals. "Although there is
agriculture and transmission of wealth, there is still
as much room for evolution to proceed as in other
animals," says Courtiol, whose team reports its findings
online today in the Proceedings of the National Academy
of Sciences .
The Finns were also subject to sexual selection, in that
men who were able to attract new mates had more
offspring. With one partner, the average was about five
children; with four partners, that jumped to 7.5,
Courtiol notes. Men benefited more than women in terms
of begetting more children, most likely because they
tended to remarry young women with good child-bearing
potential. Thus sexual selection was more important in
men than in women.
From the records they had, the researchers could not
tell which traits were being selected for, but the
variation in the number of offspring-from zero to 17-
indicates there was a large opportunity for selection to
occur. That variation is the grist for evolution.
The importance of sexual selection is well accepted in
birds and fish, "but this is the first time that sexual
selection has been so well documented in humans," says
Stephen Stearns, an evolutionary biologist at Yale
University. As for showing natural selection, "they are
providing additional, confirmational evidence."
"Without a doubt, natural selection occurs in modern
humans," agrees Jacob Moorad, an evolutionary biologist
at Duke University in Durham, North Carolina, who was
not involved in the study. He thinks this work will
inspire other researchers with large databases of data
on humans to look at how selection operates in
populations.
Courtiol is not certain how strong natural selection is
today, particularly in the developed world. But he says
that at the very least, the data show that even as
recently as 200 years ago, it still played a role in
shaping humans as a species. As such, he notes,
biological and cultural processes should both be
considered in understanding how humans are changing
through time.