Mice’s facial expressions can reveal a wide range of emotions
Although it’s tricky for us humans to see, mouse feelings
are written all over their furry little faces.
With machine learning tools, researchers
reliably spotted mice’s expressions of joy, fear, pain and other basic
emotions. The results, published in the April 3 Science, provide a field guide for scientists seeking to understand
how emotions such as joy,
regret
and empathy
work in animals other than humans (SN:
11/10/16; SN: 6/9/14; SN: 12/8/11).
Using machine learning to reveal mice’s expressions is “an extraordinarily exciting direction,” says Kay Tye, a neuroscientist at the Salk Institute for Biological Studies in La Jolla, Calif. The findings “lay the foundation for what I expect will be a game changer for neuroscience research on emotional states.”
Neuroscientist Nadine Gogolla of the Max Planck Institute of Neurobiology in Martinsried, Germany, and colleagues gave mice experiences designed to elicit distinct emotions. Sugar water evoked pleasure, a shock to the tail triggered pain, bitter quinine water created disgust, an injection of lithium chloride evoked a nauseated malaise, and a place where shocks previously had been delivered sparked fear. For each setup, high-speed video cameras captured subtle movements in the mice’s ears, noses, whiskers and other parts of the face.
Observers
can generally see that something is happening on the mouse’s face, Gogolla says.
But translating those subtle clues into emotions is really hard, “especially
for an untrained human being,” she says.
Machine
learning techniques handle the job beautifully, the researchers found. The
methods were able to spot subtle face movements that came with good or bad
experiences. For instance, on the face of a mouse drinking sweet water — and
presumably happy about it — the ears move forward and fold at the back toward
the body, and the nose moves down toward the mouth. A mouse tasting bitter
quinine sends its ears straight back, and the nose curls slightly backward,
too.
Activity of
nerve cells in the mice’s brains also changed with distinct emotions, other
analyses showed. These cells reside in the insular cortex, a deeply buried spot
known to be involved in human emotions, too.
By prodding these cells to fire signals, the researchers could prompt the mice to display certain facial expressions. These connections among brain activity and facial expressions may lead to insights about the neural basis of emotions, and what goes awry in disorders such as anxiety, the researchers suggest.
Southern Africa may have hosted a hominid transition 2 million years ago
Members of three
different hominid lines clustered at the bottom of Africa around 2 million
years ago, signaling an evolutionary swing propelled by the spread of a highly
successful, humanlike species, new fossil discoveries suggest. It’s unclear,
though, if the three ancient populations inhabited the region at precisely the
same time.
Excavations at Drimolen, a set of caves in South Africa,
uncovered two fossil braincases, one from Homo
erectus and the other from Paranthropus
robustus, say paleoanthropologist Andy Herries of La Trobe University in Melbourne,
Australia, and his colleagues. Both finds date to between 2.04 million and 1.95
million years ago, the scientists report in the April 3 Science.
The H. erectus
fossil comes from a child who displayed a long, low braincase typical of adults
from that species. The P. robustus
braincase is that of an adult.
Researchers previously determined that two Australopithecus species, A. africanus and A. sediba (SN: 7/25/13),
inhabited nearby parts of South Africa approximately 2 million years ago.
Taken together, these discoveries indicate that a major
transition in hominid evolution occurred in southern Africa between around 2.1
million and 1.9 million years ago, Herries’ team says. During that stretch,
climate and habitat fluctuations drove Australopithecus
species to extinction. H. erectus and
P. robustus weathered those
ecological challenges, possibly outcompeting Australopithecus for limited resources, the researchers speculate.
It’s unclear whether members of the three hominid lines ever
encountered each other during that transition period.
“These spectacular discoveries confirm what some of us have
expected for some time, that three genera of [hominids] coexisted in southern
Africa,” says paleoanthropologist Darryl de Ruiter of Texas A&M University
in College Station, who was not involved in the research.
Earlier work at several other South African cave sites had
suggested that H. erectus, P. robustus and A. sediba all dated to nearly 2 million years ago. But many fossils
from the first two species are fragmentary, and precise dating of cave
sediments that held those finds has proven difficult.
Herries’ team dated the fossil braincases at Drimolen using
two techniques for calculating the time since sediments formed just below and
above where the specimens were found. Evidence of previously dated reversals of
Earth’s magnetic field in Drimolen sediment helped to confirm age estimates for
the fossils.
The South African H.
erectus fossils may be slightly older than those of A. sediba, but a controversial proposal that A. sediba was an ancestor of the Homo genus remains in play, de Ruiter says. Researchers don’t know how
much earlier than 2 million years ago A.
sediba originated or how far it ranged beyond its one known fossil site in
South Africa. Even so, some other researchers consider A. sediba a dead-end species and regard East Africa as the best bet
for where Homo originated.
Unearthing an H.
erectus fossil dating to around 2 million years ago in South Africa
considerably expands that species’ range at an early stage of its evolution,
says paleoanthropologist John Hawks of the University of Wisconsin–Madison.
H. erectus fossils in western Asia date
to about 1.8 million years ago (SN: 10/17/13).
And H. erectus may have made
2.1-million-year-old stone
tools in China (SN: 7/11/18).
“It’s possible that this child from Drimolen is the
earliest-known representative of the first global [hominid] species,” says Hawks,
who did not participate in the new study.
H. erectus’ last known appearance
was as late as 108,000 years ago on an Indonesian island, meaning it survived
about 2 million years (SN: 12/18/19).
The H. erectus
fossil found at Drimolen “marks the beginning of the most successful species of
Homo ever known — present company
included,” writes paleoanthropologist Susan Antón of New York University in a commentary
published with the new Science report.
Just breathing or talking may be enough to spread COVID-19 after all
The coronavirus that causes COVID-19 may
spread through the air in tiny particles that infected people exhale during
normal breathing and speech.
Until now, experts
have said that the virus, called SARS-CoV-2, doesn’t spread through the air
in that way, but rather through relatively large droplets released when people
cough or sneeze. Those droplets can contaminate surfaces or objects and infect people
who touch the surface and then touch their faces.
Large droplets are still a means of
infection, but researchers now say that tiny airborne particles may also carry
infectious virus. “Currently available research supports the possibility that SARS-CoV-2
could be spread via bioaerosols generated directly by patients’
exhalation,” researchers from the U.S. National Academies of Science,
Engineering and Medicine wrote in an April 1 report to the White House Office
of Science and Technology Policy.
If the coronavirus is airborne, that could help explain why it is so contagious, and can spread before people have symptoms (SN: 3/13/20).
As of April 2, more than 1 million
people worldwide are confirmed to have COVID-19, with nearly a quarter of those
cases in the United States, according to tracking by Johns Hopkins University.
More than 50,000 people have died worldwide, including more than 5,600 people
in the United States.
Wearing surgical masks can cut down on the
amount of virus that infected people spread, the expert panel says, citing an
unpublished study from the University of Hong Kong. The letter does not address
whether wearing
a mask will protect the person wearing the mask from catching the illness (SN: 3/27/20). How much virus a person
must breathe in to get infected isn’t known.
The report also notes that genetic material from the virus was detected more than two meters (six feet) away from patients’ hospital beds. That finding could indicate that physical distancing by at least two meters may not be enough to limit spread of the virus. Whether infectious virus could be carried that far or if the genetic material is from dead viruses isn’t yet known.
The U.S. has resisted the metric system for more than 50 years
Ten years to metric, Science News, April 4, 1970 –
Australia is taking its first brisk steps toward conversion to a fully metric system of weights and measures over the next 10 years…. The arguments for conversion to metric in Australia have been similar to those given elsewhere: The metric system is used by countries representing 90 percent of the world’s population; three-fourths of world trade is carried out in metric measurements.
Update
Five years into Australia’s metrication, the U.S. Congress passed the Metric Conversion Act in a bid to move the country away from an imperial system based on measures such as the foot and the pound. But the voluntary process failed to gain public support.
Some U.S. industries along with science agencies made the switch, but inconsistencies have led to mishaps. In 1999, the Mars Climate Orbiter burned up in the Red Planet’s atmosphere because of a unit mix-up between NASA and Lockheed Martin (SN: 10/9/99, p. 229). Today, only the United States, Liberia, Myanmar and a handful of island nations use versions of the imperial system.
Lucy’s species heralded the rise of long childhoods in hominids
Lucy’s kind had small, chimplike brains that, nevertheless,
grew at a slow, humanlike pace.
This discovery, reported April 1 in Science Advances, shows for the first time that prolonged brain
growth in hominid youngsters wasn’t a by-product of having unusually large
brains. An influential idea over the last 20 years has held that extended brain
development after birth originated in the Homo
genus around 2.5 million years ago, so that mothers — whose pelvic bones and birth
canal had narrowed to enable efficient upright walking — could safely deliver babies.
But Australopithecus
afarensis, an East African hominid species best known for Lucy’s partial
skeleton, also had slow-developing brains that reached only about one-third the
volume of present-day human brains, say paleoanthropologist Philipp Gunz of the
Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and his
colleagues. And A. afarensis is
roughly 3 million to 4 million years old, meaning slow brain growth after birth
developed before
members of the Homo genus appeared,
perhaps as early as 2.8 million years ago (SN:
3/4/15).
Too few A. afarensis
infants have been studied to calculate the age at which this species attained
adult-sized brains, Gunz cautions. The brains of human infants today reach
adult sizes by close to age 5, versus an age of around 2 or 3 for both chimps
and gorillas.
In the new study, Gunz and colleagues estimated brain
volumes for six A. afarensis adults
and two children, estimated to have been about 2 years and 5 months old. The
kids had brains that were smaller than adult A. afarensis brain sizes in a proportion similar to human children’s
brains at the same age relative to adult humans.
The new data suggest that, for Lucy’s species, “infant brain
size [relative to that of an average adult] may have been proportionally even
smaller than in human infants,” says biological anthropologist Zachary Cofran
of Vassar College in Poughkeepsie, N.Y., who did not participate in the new
study. If so, that pattern would strongly point to an extended period of brain
growth for A. afarensis.
Gunz suggests the extended post-birth brain growth among A. afarensis may have eased the physical
and nutritional burden on mothers caring for infants, especially if food was
scarce. It also “likely provided a foundation for the evolution of long
childhoods in the human lineage,” he says.
His group used high-resolution CT scans to study fossilized
braincases from an infant A. afarensis
and six adults, including Lucy, all found at Ethiopia’s Hadar site. A second A. afarensis infant braincase came from Ethiopia’s
Dikika site (SN: 9/20/06). The
scans helped the researchers create 3-D digital reconstructions, or endocasts,
of impressions made by the brain on the skull’s inner surface. Endocasts
display signature folds and creases in brain tissue typical of humans or
chimps, although preservation of these neural landmarks varies.
CT scans also let the researchers determine the infants’
ages by revealing microscopic layers of dental enamel that form daily during
childhood, which can be counted like tree rings.
The Dikika child’s well-preserved endocast retained a crease
and a set of grooves toward the back of the brain that are found in chimps, but
not in humans. These impressions mark a prominent neural area involved in
vision. Human brain surfaces lack these markings due to expanded neural tissue
that integrates visual and sensory information. A
South African Australopithecus skull
was previously revealed to have signs of a chimplike visual area in the brain (SN: 1/10/19).
Neither of the A.
afarensis infants showed evidence of humanlike frontal brain organization,
as has been reported for an approximately 300,000-year-old South African
hominid, Homo naledi (SN: 4/25/17).
Anthropologist and neuroscientist Todd Preuss of Emory
University in Atlanta agrees. Endocasts of the Hadar A. afarensis skulls contain many preserved features from the
brain’s visual area that resemble those on an Australopithecus child’s skull from South Africa that dates to
about 2.8 million years ago, says Preuss, who was not part of Gunz’s team.
Much remains to be learned about the pace of brain growth in
A. afarensis, says
paleoanthropologist Aida Gomez-Robles of University College London. Researchers
can’t track brain sizes of A. afarensis
individuals from infancy into adulthood, so the new results don’t conclusively
determine growth rates, she notes. And earlier interpretations of hominid brain
organization based on endocasts have sparked frequent debate, leading
Gomez-Robles to withhold judgment on the brains of Lucy’s kind.