Global warming affects cultivated cereal crops
New Worlds: Study claims to shed new light on early humans' adaptation to living on the ground.
Wheat Photo: Courtesy
Although farmers know better than ever how to grow food, global warming may
indirectly affect our diet by diminishing the amount of available nutritients. A
28-year comparative study of wild emmer wheat and wild barley populations has
revealed that these progenitors of cultivated wheat and barley, which are the
best hope for crop improvement, have been affected by climate changes, which
presents a real concern for their being a continued source of crop
Prof. Eviatar Nevo of the University’s evolution institute,
who has studied the phenomenon, notes that wheats and barleys are the staple
food for humans and animals around the world. Their wild progenitors have
undergone genetic changes over the past three decades that imply a risk for crop
improvement and food production, he said. Premature flowering time and genetic
changes that are taking place in these important progenitor wild cereals, most
likely due to global warming, can negatively affect them and thus indirectly
cause food production to decline.
Wheats are the universal cereals of Old
World agriculture, he said. The progenitor – wild emmer wheat and wild barley,
which originated in the Near East – provide the genetic basis for ameliorating
wheat and barley cultivars. Earlier studies have shown that they
themselves are under constant genetic erosion and increasing susceptibility to
Nevo’s new study, published in the Proceedings of
the [US] National Academy of Sciences (PNAS) set out to examine whether the wild
cereal progenitors are undergoing evolutionary changes due to climate change
that would impact future food production.
Ten wild emmer wheat and an
equal number of wild barley populations from different climates and habitats
across Israel were sampled first in 1980 and then again at the same sites in
2008 and grown in a common greenhouse. The results indicated that over the
relatively short period of 28 years, all 20 wild cereal populations examined,
without exception, showed a dramatic change in flowering time. All populations
sampled in 2008 flowered, on average, about 10 days earlier than those sampled
in 1980. These cereal progenitors are adapting their time of flowering to escape
the heat, Nevo explains.
The study also found that the genetic diversity
of the 2008 sample is for the most part significantly reduced, but that some new
drought-adapted variants have appeared that could be used for crop
Ongoing global warming in Israel is the only likely factor
that could have caused earliness in flowering and genetic turnover across the
range of wild cereals here, he says.
“This indicates that they are under
environmental stress that may erode their future survival. Multiple effects of
the global warming phenomenon have been observed in many species of plants and
animals,” he adds. “But this study is pioneering in showing its influence on
flowering and genetic changes in wild cereals. These changes threaten the best
genetic resource for crop improvement and thereby may damage food
A number of species did show positive adaptive changes
resulting from global warming, such as earliness in flowering or migration into
cooler regions. But overall, says Nevo, the genetic resources of these critical
wild cereals are undergoing rapid erosion and cannot be dismissed as a concern
for future generations.
“Wild emmer wheat is the world’s most important
genetic resource for wheat improvement, and it is up to us to preserve it,” he
said. “We are utilizing our institute’s gene bank for transforming genes of
interest to the crop. However, a much more extensive effort needs to be
made to keep the natural populations thriving, by preventing urbanization and
global warming from eliminating them.”
Study claims to shed new light on early humans' adaptation to living on the ground
Birds and squirrels nest in
trees – and so do many types of chimpanzees. But now researchers at the
University of Cambridge and Kyoto University have published the first study of
rarely-documented ground nesting by wild chimpanzees. They suggest it supplies
clues about the ancient transition of early hominins from sleeping in trees to
sleeping on the ground.
The article, published in the American Journal of
Physical Anthropology, focused on a group of wild West African chimpanzees that
often shows ground-nesting behavior.
UK primatologist Dr. Kathelijne Koops
studied the chimpanzee (Pan troglodytes verus) population in the Nimba Mountains
in Guinea, West Africa. All species of great ape build nests to sleep in.
Construction of these shelters takes minutes as the apes bend, break and
interweave branches into a circular frame, followed by tucking in smaller
branches to form a sturdy but comfortable sleeping platform.
that, like modern apes, the common ancestor of chimpanzees and humans also slept
in the trees six million years ago,” said Koops. “However, these nests are not
preserved in the fossil or archeological record, so it is impossible to study
directly the ancient transition from sleeping in trees to building shelters on
the ground. Recording this rare behavior in the chimpanzee, our closest
relative, may provide vital clues.”
As the Nimba chimpanzees do not yet
tolerate human presence at close range, the team used new molecular genetic
techniques to analyze hairs collected from the nests. This allowed the team to
establish the sex of chimpanzees displaying the behavior and to identify
individuals in the group.
The team showed that as chimpanzees sleep both
on the ground and in trees, the transition did not require a special
evolutionary adaptation. This suggests that early hominins may have slept on the
ground before the emergence of Homo erectus, the first species that was fully
adapted to living on the ground.
“This is intriguing as it has long been
believed that coming down from the trees was a crucial evolutionary shift,” said
Koops. “However, this chimpanzees’ behavior suggests a more deep-seated, gradual
transition from tree-to-ground sleep.”
Other theories for the
tree-to-ground transition have included the use of fire and the scarcity of
trees in open habitats. The team demonstrated that neither is a prerequisite for
ground sleeping, as the chimpanzees live in a plentiful evergreen rainforest and
do not create fire.
“These chimpanzees offer a rare opportunity to
investigate why a population of wild apes choose to sleep on the ground,”
concluded Koops. “We showed that ground-nesting was not caused by male
mate-guarding behavior, a lack of trees in which to nest, or because of fire.
This suggests that our direct ancestors were neither the only, nor the first,
species to come down from the trees.”