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Spitting image

Saliva study highlights differences between apes and humans

Western lowland gorilla iStock/Alan_Lagadu

Spitting image

A recent study in the journal Molecular Biology and Evolution identified one small but significant difference between humans and apes: their spit. The results enlarge the widening gap observed between humans’ and nonhuman primates’ physiology.

The scientists studied the saliva of humans alongside two species they believe are closely related—chimpanzees and gorillas—looking for unique features. They also included Rhesus macaque monkeys as an “outgroup,” or unrelated species, for comparison.

While chimpanzees and gorillas have very similar saliva, human spit has a distinct composition, the researchers found. The amounts of different proteins in the human samples differed markedly from the ape samples, and the human saliva contained proteins that didn’t exist at all in gorillas, chimps, or macaques. Human spit was also waterier.

“Certain properties and components of human and nonhuman primate saliva might have evolved in a lineage-specific manner,” the studies’ authors wrote. Though they suggested evolutionary pressures like diet and disease could have caused the differences, they did not rely on evolutionary theory or say their findings supported it in any way. They only examined and described differences. The researchers said the trends they observed “raise the possibility that salivary protein profiles of humans may be more unique than expected solely based on phylogenetic distances of species.” If humans and apes were related as closely as evolutionary theory suggests, their saliva is more different than expected.

While evolutionary biologists hunt for similarities between humans and apes, this study adds to the physiological differences that researchers have identified over the years. The gentle, shapeshifting evolutionary journey from apes to humans often illustrated in museums cannot bridge the vast physical gulf between the species. On the podcast ID the Future, biologist Ann Gauger, a researcher with Discovery Institute, listed the many complicated biological systems that function differently in humans and chimpanzees, which evolutionists believe are our closest animal relatives. Neither the reproductive systems nor teeth nor thyroid and metabolism function nor immune systems nor brain structure and development work the same way in humans and chimps.

Gauger pointed out that chimps differ so much from humans that the National Institutes of Health advised against using them as models in medical research. The list of more obvious anatomical differences was just as long, and that’s to say nothing of the self-evident behavioral differences. “The list goes on and on,” she concluded. “Our capabilities are orders of magnitude beyond anything a chimp can do.”

A Mars lander is tested at a facility in Huailai, China, on Thursday.

A Mars lander is tested at a facility in Huailai, China, on Thursday. Associated Press/Photo by Andy Wong

A red flag on the Red Planet?

China unveiled a spacecraft Thursday that it hopes to send to Mars next year. The China Aerospace Science and Technology Corporation demonstrated how the landing vehicle can hover, avoid obstacles, and decelerate.

“After the probe is launched, it will take about seven months to reach Mars, and the final procedure of landing will only last about seven minutes, which is the most difficult and the most risky part of the whole mission,” said the Mars mission’s chief designer, Zhang Rongqiao.

The country is coming from behind in the space race, having conducted its first manned mission in 2003. This year, it landed a rover on the far side of the moon. It has sought international cooperation with space agencies from Europe and elsewhere. Only the United States has had success with missions on Mars so far, and it declined to work with China because of national security concerns. China is not allowed on the International Space Station, but it says it is working on building its own. —Lynde Langdon

A Mars lander is tested at a facility in Huailai, China, on Thursday.

A Mars lander is tested at a facility in Huailai, China, on Thursday. Associated Press/Photo by Andy Wong

Nature’s light show

Scientists and collectors are hunting for pieces of a meteorite that streaked down to Earth in a fireball on Monday, lighting up the Midwestern night sky. Security cameras in the St. Louis area picked up numerous images of the falling rock, which likely was the size of a baseball, said Ian Redmount, an associate professor of physics at Saint Louis University. People from Oklahoma to Wisconsin reported seeing its brilliant descent, the St. Louis Post-Dispatch reported. It was one of 27 widely seen meteors worldwide so far this year.

“For an individual person, seeing one that bright is a once in a lifetime thing,” said Mike Hankey with the American Meteor Society. “But as a planet it’s not all that rare.” —L.L.

Rachel Lynn Aldrich

Rachel is a former assistant editor for WORLD Digital. She is a Patrick Henry College and World Journalism Institute graduate. Rachel resides with her husband in Wheaton, Ill.

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