16 | New Scientist | 3 October 2020
News
MicrobiomeMichael Le PageA NEW way of calculating our
biological age based on gut
bacteria has thrown up some
surprising results. Among other
things, it suggests that people
following the paleo diet are
nearly two years “older” on
average than people who aren’t.
“It is striking,” says Guruduth
Banavar at Viome, a Californian
company that sells tests that
measure gut bacteria. “In our
population, people on a paleo
diet were younger, but their
biological age is actually older.”
In the past decade, many
groups have developed ways to
estimate people’s age based on
biomarkers, such as the length
of structures called telomeres
on the ends of chromosomes.
These biological ages are
thought to show whether people
are ageing slower or faster than
normal, though it has yet to be
shown that they can accurately
predict life expectancy.
Several groups have been
trying to estimate age by using
machine learning to analyse
microbiome data. Viome’s
approach involves looking
at which genes are active
in gut bacteria, not simply
which genes are present, as
other groups do, says Banavar.
Its findings are based on
90,000 stool samples from
customers analysed by the firm,
making it by far the largest such
study to date. Having so many
samples has allowed the firm’s
researchers to look at how
various lifestyle factors affect
biological age as estimated by
their method. For example, they
could examine the effects of the
paleo diet, in which people eat
as our Palaeolithic ancestors
are supposed to have done.
“For the paleo diet, the
finding is quite strong,”
says team member Hal Tily.“It’s unambiguous that
something is going on.”
However, this could be
because people with poor health
are more likely to try the paleo
diet, rather than this being a
result of the diet itself, cautions
Cara Frankenfeld at George
Mason University in Virginia.
“We can’t identify whether
something about a person’s
health made them decide to
change their diet or whether the
diet preceded and influenced
the biological age,” she says.
The team also found that
people on the low-carb, high-fat
ketogenic diet had biological
ages nearly two years older on
average, but this finding isn’t
as robust as the paleo diet one,
says Tily. Women who reported
drinking more than a unit of
alcohol a day, and men who say
they drink more than two units
a day, were nearly a year olderon average. People who say
they eat organic food were
around half a year older
(bioRxiv, doi. org/d97t).
Vegetarians fared best,
being around a year-and-a-half
younger biologically than
non-vegetarians on average.
This finding isn’t surprising
given all the evidence that a
vegetarian diet is beneficial,
says Banavar, but he stills
thinks it is significant.
“This is the first time that
anybody has shown through
biological ageing modelling that
this effect is true at a population
level,” he says. Vegans were also
younger biologically, but not
quite as much as vegetarians.
“From a machine-learning
perspective, the methods
look sound,” says James Cole
at University College London,
who has estimated biological
age from brain scans. However,
Cole says the microbiome
method is much less accurate
at estimating actual ages than
other techniques. ❚Paleo diet may cause
you to biologically age
XSANDRA/GETTY
IMAG
ESThe paleo diet is
supposedly that of
early hunter-gatherersClimate changeMichael Le PageEVOLUTION normally helps
organisms positively adapt to
changing circumstances, but climate
change may turn that on its head.
A model of how some species
could rapidly evolve in response
to increasingly extreme events,
such as storms, has found that
mutations could actually drive
some populations to extinction.
This is because traits that help
the animals or plants that survive
extreme events can be a hindrance
in normal situations. “By the nextgeneration, the environment has
already gone back to normal,” says
Kelsey Lyberger at the University
of California, Davis. “You never
get to benefit from the change.”
It is already clear that extreme
events fuelled by global warming,
such as more extensive wildfires,
can drive vulnerable populations
to extinction. Those extreme events
can also produce rapid evolution.
Lizards on the Caribbean island of
Dominica evolved a superstrong
grip after category 5 Hurricane
Maria in 2017 –probably because
only lizards that managed to
cling onto branches survived.
Such observations inspired
Lyberger and her colleagues
to create a mathematical
model comparing the effects of
environmental changes of different
durations (bioRxiv, doi.org/d97h).
The results suggest that brief
changes, such as storms, can reduce
the fitness of survivors in normal
conditions to such an extent that
their numbers decline rather than
recover. The size of the effect
depends on how extreme an event
is, how often such events happen
and how much genetic variation
there is in a population. ❚Extreme weather
events could make
evolution backfire“Lizards on the Caribbean
island of Dominica evolved
a superstrong grip after
Hurricane Maria in 2017”