11 December 2021 | New Scientist | 19FOR most of our history,
humans have been short, a
study has found. Until around
150 years ago, few people grew
taller than 170 centimetres –
not even the most privileged
individuals, who had ready
access to food.
The discovery adds
to growing evidence that
stunting – being unusually
short – isn’t a wholly reliable
indicator of malnutrition.
Instead of being a sign of a
good diet, growing taller may
instead reflect competition for
dominance in some societies.
Christiane Scheffler at
the University of Potsdam
and paediatrician Michael
Hermanussen in Altenhof, both
in Germany, have spent several
years studying the height
of people from a wide range
of populations. In their latest
paper, they combined an
existing data set of more than
6000 prehistoric human
skeletons with multiple studiesof more recent historical
populations from Europe and
the US. They also included their
own data on 1666 present-day
schoolchildren from Indonesia.
In the prehistoric populations,
the maximum height for men
was 165 to 170 centimetres, while
women topped out at 160 cm.
Today, by comparison, men
in England have an average
height of around 175 cm, while
for women it is about 162 cm.The average heights of men and
women are several centimetres
higher in Germany.
The pair found that similar
patterns to the prehistoric
heights held in the historical
populations. Even a group of
upper-class German boys from
the late 1800s were all much
shorter than modern children,
so much so that over half of
them would be considered
stunted by modern standards.
But there is significantvariation between modern
countries. The Indonesian
schoolchildren in the study
were shorter than similarly
aged children from the US,
despite being well-nourished
(American Journal of Human
Biology, doi.org/g75k).
If food availability isn’t
the key to height, what is?
Scheffler and Hermanussen
argue that height can be a signal
of dominance, so in societies
where it is possible to move
up through the social classes,
evolution favours individuals
who reach a greater height.
Growing tall, says Scheffler,
“is more or less associated
with the hope of a better life”.
S. V. Subramanian at Harvard
University isn’t convinced by
the pair’s interpretation. His
team previously showed that
the best predictor of a child’s
height is the height of their
parents, indicating that the
trait is highly heritable. This
suggests that the influence
of other factors, such as social
mobility, is limited.
Scheffler also argues that
stunting is a poor indicator of
whether a child is malnourished.
“We don’t find any association
between signs of nutritional
status and height,” she says.
Subramanian agrees that
stunting isn’t a perfect indicator
of malnutrition. After assessing
nearly 163,000 children living
in 55 low and middle-income
countries, his team found that
42.9 per cent had poor nutrition
but no sign of stunting or other
physical indicators of this fact.
This implies there is a lot
of hidden malnutrition that
doesn’t reveal itself through
stunting. A person’s nutritional
status should be assessed by
looking at their diet not their
height, says Subramanian. ❚The best predictor
of a child’s height is
their parents’ heightPhysiologyMichael MarshallWERA
RODS
AWANG/GET
TY
IMAGES170 c m
Maximum height discovered
in prehistoric humansHumans were relatively short
for thousands of years
THE timing of when ice forms
on lakes in the winter can have
big knock-on effects on life in the
water the next spring and summer.
As the climate warms, lake ice is
forming later and thawing earlier.
But not much research has been
done on what happens in lakes
during the winter, partly because
the ice-covered period has long
been considered a dormant season
for freshwater organisms.
“This is rather alarming given
that we do not know much about
under-ice lake ecology, so it is
even harder to anticipate the
consequences of ice loss and predict
future changes,” says Marie-Pier
Hébert, an aquatic scientist at McGill
University in Montreal, Canada.
To find out more, Hébert and her
colleagues conducted a unique
experiment to manipulate the
timing of ice onset in a lake
in Canada. They constructed a
floating platform with several
deep containers extending below
it, essentially turning columns of
water into giant test tubes. Then,
once the lake froze, they broke up
and melted the ice in each container
twice a day at dawn and dusk,
delaying the onset of winter ice
cover for 8, 15 or 21 days.
This had a profound effect on
life in the water below. A later
freeze meant that algae could
continue photosynthesis for longer,
which allowed some of the tiny
zooplankton that feed on the algae
to fatten up more and so survive
throughout the winter under the ice.
Those surviving zooplankton then
got a head start on eating the new
batch of spring algae once the ice
started to melt, leaving less food
available for species that only
become active once the ice is
gone (PNAS, doi.org/g78g).
These changes in the population
of algae and zooplankton could
cascade through the food
web, says Hébert. ❚EcologyBrian OwensWeb of life in icy
lakes faces turmoil
in a warming world
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