Unraveling the Evolutionary Puzzle
By PEERJ
Throw a tantrum. Threaten, shove aside, or
steal from your colleagues. Science confirms, yet again, that brutish behavior
can be an effective path to power. And not just in humans, but in chimpanzees,
too.
Getty Images
A new study published on April 24 in the
journal PeerJ Life and Environment found that male chimps
with more bullying, greedy and irritable personalities reached higher rungs of
the social ladder and were more successful at siring offspring than their more
deferential and conscientious counterparts.
But if that’s the case, researchers ask, why isn’t every chimp a bully?
A research team led by scientists at
the University of Edinburgh and Duke University followed 28 male chimps living
in Gombe National Park in Tanzania.
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| Known as a bully, Frodo the chimpanzee was Gombe’s alpha male for five years. Credi: Ian C. Gilby, Arizona State University |
A previous study of Gombe chimpanzees led by Edinburgh’s Alexander Weiss along with Duke professor Anne Pusey and colleagues showed how some chimpanzees are more sociable, while others are loners. Some lean towards easy-going, while others are more overbearing or quick to pick fights.
Tanzanian field researchers who knew the
chimpanzees well performed the personality assessments, based on years of
near-daily observations of how each chimpanzee behaved and interacted with
other chimps.
In the current study, researchers found that
male chimps with certain personality traits — in this case, a combination of
high dominance and low conscientiousness — tend to fare better in life than
others.
“Personality matters,” said Joseph Feldblum,
assistant research professor of evolutionary anthropology at Duke and the other
lead author of the study.
It may not be shocking to learn that bullying
has its perks. But for some researchers, findings like these pose a conundrum:
If males with certain personality tendencies are more likely to rise to the top
and reproduce, and pass the genes for those traits on to their offspring, then
shouldn’t every male be that way?
In other words, why do personality
differences exist at all?
“It’s an evolutionary puzzle,” Feldblum said.
One long-held theory is
that different personality traits pay off at different points in animals’
lives. Even if being aggressive gives young male chimps an edge, it might
backfire when they’re older. Or perhaps certain traits are a liability in youth
but an asset in old age.
“Think of the personality traits that lead
some people to peak in high school versus later in life,” Weiss said. “It’s a
trade-off.”
But when the team tested this idea, using 37
years of data going back to some of Jane Goodall’s early work at Gombe in the
1970s, they found the same personality traits were linked to high rank and
reproductive success across the lifespan.
The findings suggest that something else must
explain the diversity of personalities in chimpanzees. It might be that the
“best” personality to have varies depending on environmental or social
conditions, or that a trait that is beneficial to males is costly to females,
Feldblum said.
If that were true, then “genes associated
with those traits would be kept in the population,” Weiss said.
Not too many years ago, the mere suggestion
that animals have personalities at all was considered taboo. Jane Goodall
herself was accused of anthropomorphism when she described some of the Gombe
chimpanzees as “bolder” or “more fearful” than others, some as “affectionate”
and others “cold.”
Since that time, scientists studying
creatures ranging from birds to squid have found evidence of distinctive
personalities in animals: quirks and idiosyncrasies and ways of relating to the
world that remain reasonably stable over time and across situations.
Weiss says personality ratings for animals
have proven to be as consistent from one observer to the next as
are similar measures of human personality.
“The data just don’t support the skepticism,”
Weiss said.
Reference: “Personality traits, rank
attainment, and siring success throughout the lives of male chimpanzees of
Gombe National Park” by Alexander Weiss, Joseph T. Feldblum, Drew M. Altschul,
D. Anthony Collins, Shadrack Kamenya, Deus Mjungu, Steffen Foerster, Ian C.
Gilby, Michael L. Wilson and Anne E. Pusey, 24 April 2023, PeerJ Life and Environment.
DOI:
10.7717/peerj.15083
This research was supported by grants from
the National Science Foundation (#BCS-9021946, #BCS-0452315, #BCS-0648481,
#BCS-9319909, #IIS-0431141, #IOS-1052693, #IOS-1457260, #EF-0905606 and
#DGE-1106401), the Carnegie Trust for the Universities of Scotland, the Jane
Goodall Institute, the U.S. National Institutes of Health (R01-AI058715),
Harris Steel Group, the University of Edinburgh, University of Minnesota, Duke
University and the British Academy (PF20/100086).
