microbes living in people's guts are much less diverse than those in humans'
closest relatives, the African apes, an apparently long evolutionary trend that
appears to be speeding up in more modern societies, with possible implications
for human health, according to a new study.
Rate of change accelerating
an analysis of how humans and three lineages of ape diverged from common
ancestors, researchers determined that within the lineage that gave rise to
modern humans, microbial diversity changed slowly and steadily for millions of
years, but that rate of change has accelerated lately in humans from some parts
of the world.
non-industrialized societies have gut microbiomes that are 60 percent different
from those of chimpanzees. Meanwhile, those living in the U.S. have gut
microbiomes that are 70 percent different from those of chimps.
Read more: You and your digestive system
took millions of years, since humans and chimpanzees split from a common
ancestor, to become 60 percent different in these colonies living in our
digestive systems," said Howard Ochman, professor of integrative biology
at The University of Texas at Austin and co-author of the study. "On the
other hand, in apparently only hundreds of years – and possibly a lot fewer –
people in the United States lost a great deal of diversity in the bacteria
living in their gut."
rapid change might translate into negative health effects for Americans.
Previous research has shown that compared with several populations, people
living in the U.S. have the lowest diversity of gut microbes. Still other
research has linked a lack of microbial diversity in human guts to various
diseases such as asthma, colon cancer and autoimmune diseases.
More meat and fewer plants
results of this latest study, carried out by researchers from The University of
Texas at Austin, Yale University, the University of Pennsylvania and elsewhere,
appear this week in the journal Proceedings of the National Academy of
Sciences. The lead author is Andrew Moeller, a visiting scholar at The
University of Texas at Austin and a graduate student at Yale University.
possible explanation for humans evolving to have less diversity in their gut
microbiomes is that they shifted to a diet with more meat and fewer plants.
Plants require complex communities of microbes to break them down, which is not
as true for meat.
Read: Stress bad for good bacteria
why Americans have experienced much more rapid changes in microbial diversity
compared with people in less industrialized societies, some experts have
suggested more time spent indoors, increased use of antibacterial soaps and
cleaners, widespread use of antibiotics and high numbers of births by Caesarean
section all may play a role.
Antibiotics and antimicrobial cleaners can kill
good bacteria along with the bad, and C-section deliveries prevent babies from
receiving certain bacteria from the mother typically conferred during vaginal
diversity in the gut has been a trend for a long time," said Ochman.
"It's tantalizing to think that the decrease in microbial diversity in humans
is due only to modern medical practices and other lifestyle changes, but this
research shows other factors over time also must have played a role."
researchers analyzed the genetic makeup of bacteria in faecal samples from
humans, chimpanzees, bonobos and gorillas to draw their conclusions.
Gut bacteria affect health and obesity
How your digestive system works
Chocolate cravings explained
Image: Female gorilla from Shutterstock