Health & Science NEWS^21
A sedan-size turtle
Paleontologists have unearthed the remnants
of a colossal turtle that patrolled northern
South America some 10 million years ago.
The Stupendemys geographicus grew up to
13 feet long and weighed 1.25 tons, and
inhabited a giant wetland that once covered
the region. These creatures were built for
battle, reports Reuters.com. Fossils dug up in
Colombia’s Tatacoa Desert and Venezuela’s
Urumaco region—including a 9½-foot-long
shell, the biggest ever found—show that
males had front-facing horns on their shells
that they may have used to tussle with other
males over mates. Some Stupendemys fos-
sils have bite marks and punctured bones,
evidence of skirmishes with giant croco-
dilians. The enormous turtle’s diet “was
diverse, including small animals—fish,
caimans, snakes—as well as mollusks and
vegetation,” said lead researcher Edwin
Cadena, from the Universidad del Rosario in
Colombia. The turtles died out about 5 mil-
lion years ago, after the formation of the
Andes dried out their watery habitat.Deadly cross-state pollution
Half the premature deaths linked to air pol-
lution in the U.S. are caused by dirty air thatblows in from other states, new research
shows. The study is the first to detail the
sources and effects of two major harmful
airborne pollutants, ozone and fine airborne
particles, in the lower 48 states. By plug-
ging pollution data from 2005 to 2018 into
computer models, researchers were able
to work out exactly where and how much
pollution was traveling in the atmosphere.
They found that in 30 states, the majority of
premature deaths linked to poor air quality
were caused by out-of-state pollution. New
York was the largest “net importer” of early
mortality, with nearly two-thirds of prema-
ture deaths attributable to out-of-state pol-
lution. The states whose exported pollution
led to the most deaths were in the Northern
Plains and Upper Midwest. Interestingly,
the scientists found that pollution regula-
tions have reduced the number of cross-state
deaths from electricity generation and road
transportation, and that residential and
commercial emissions are now the leading
cause of premature deaths. “Future research
and future policy are going to have to bear
down on these emissions,” coauthor Steven
Barrett, of the Massachusetts Institute of
Technology, tells The New York Times.Jellyfish with ‘grenades’
If you’re scared of jellyfish, you’ll definitely
want to avoid Cassiopea xamachana, a
species found in the Caribbean, the Gulf
of Mexico, and the warmer parts of the
Western Atlantic. Scientists have discovered
that these so-called upside-down jellyfish
emit tiny balls of mucus-
surrounded cells
that swim
around sting-
ing anything
in their path.
Lead author
Cheryl Ames, from
Tohoku University
in Japan, says these“self-propelled microscopic grenades” are
designed to stun and kill small fish and
other prey; once the target is neutralized,
the jellyfish sucks it in by pulsating. “It’s
a real evolutionary novelty,” Ames tells
New Scientist. She and her team put brine
shrimp into a tank with the jellyfish. The
jellies released their stinging proxies, named
cassiosomes, which killed the brine shrimp
in under a minute. Cassiosomes can survive
outside their hosts for up to 10 days in the
lab, likely because the algae within them
generates energy through photosynthesis.
The discovery explains why divers have
reported feeling “stinging water” in the
vicinity of upside-down jellyfish.Health scare of the week
Promiscuity and cancer
People who have had more sexual partners
appear to have a higher risk of developing
cancer—especially women. Some sexually
transmitted infections are linked to cancer, so
researchers had expected to find an associa-
tion between the disease and an individual’s
number of partners. But they were surprised
by the starkness of the gender divide, reports
USNews.com. The study involved 5,722 men
and women, with an average age of 64.
The women who had had 10 or more lov-
ers were 91 percent more likely to have had
cancer than those who said they had either
one or zero. Among men, the risk among
those with the most partners was 64 percent
higher than those with the least. Women
with higher numbers of past partners did
tend to drink alcohol and smoke
cigarettes more frequently—habits
that elevate cancer risk. Still, study
coauthor Lee Smith says the gender
divide is “interesting” and suggests
it may be because “the link
between certain STIs and can-
cer is stronger in women, such
as HPV and cervical cancer, com-Science Source, Edwin Cadena/University of Zurich, Minden Pictures pared to HPV and penile cancer.”
Scientists say they have found evidence
of a “ghost population” of ancient
humans whose existence was previously
unknown—further complicating the pic-
ture of how modern humans evolved.
Unusually, evidence of these mysteri-
ous ancestors doesn’t come from bones
or ancient DNA but from the genes of
modern West Africans, reports NPR.org.
Our own species, Homo sapiens, lived
alongside other groups of hominins such
as Neanderthals and Denisovans for thou-
sands of years and sometimes mated with
them. The legacy of those relations can be
found in modern humans: Most people out-side Africa have about 2 per-
cent Neanderthal DNA. But
this new “ghost” DNA, signs
of which researchers found in
hundreds of people in Nigeria
and Sierra Leone, isn’t associ-
ated with any known species.
The researchers believe that
the mystery population split
some 1 million years ago
from the lineage that led to
modern humans, and that the
Homo sapiens ancestors of
West Africans bred with the ghost species
about 50,000 years ago. That’s roughly thesame time that Neanderthals
were breeding with humans
in Europe and Asia. Scientists
are unsure what happened
to the ghost population, and
why no fossil records have
been discovered. Lead author
Sriram Sankararaman, from
the University of California
at Los Angeles, says more
ghost populations might be
discovered in coming years.
“It’s almost certainly the case,”
he said, “that the story is incredibly com-
plex and complicated.”The ‘ghost’ DNA that complicates our evolutionary story
The massive shell of Stupendemys geographicus.Skulls of early hominins