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Scientist Says Our Oldest Ancestor May Have Been Only ‘Half Alive’

Home, sweet home in the heat and chemical chaos of a hydrothermal vent. Image credit: NOAA Vents Program via Wikimedia Commons // Public Domain

Here are some things we think we know about the first organism to ever appear on Earth: Its name was LUCA. It lived on the hot sea floor about 4 billion years ago. And although it eventually gave rise to every person, plant, and virus alive today, scientists now say LUCA itself might only have lived a sort of half-life. They published these controversial findings in Nature Microbiology.

LUCA (our Last Universal Common Ancestor) may have been cruder than a single-celled bacterium, but that doesn’t make it uninteresting. Quite the opposite, in fact: This older-than-old organism could teach us volumes about the appearance of life on Earth as we know it.

The tricky part of studying an ancient, formless organism is that it could leave no footprints, feathers, or bones behind. Fortunately, LUCA left something better: its genes, moving forward through time.

Researchers at Heinrich Heine University (HHU) in Dusseldorf, Germany set out to find LUCA’s genes in its single-celled descendants, bacteria and archaea. They combed the genomes of 1847 bacterial and 134 archaeal species, looking for shared genetic material. Any proteins that appeared in at least two groups of bacteria and two groups of archaea would likely signify a common parent.

The team found 355 overlapping protein clusters out of the 286,514 they examined. The shared proteins suggested that LUCA was even more primitive than scientists had previously imagined. The genetic lines drew a picture of an organism getting by in the dark of a boiling, oxygen-less hydrothermal vent, feeding on hydrogen gas and metals.

The life LUCA led was so very different from our own that study co-author William F. Martin told The New York Times it could be considered just “half alive.”

If you consider LUCA a biological bridge between a lifeless planet and the life forms that came after it, this framework makes sense. But that theory has its detractors.

Biochemist Steven Benner, a distinguished fellow at the Foundation for Applied Molecular Evolution, told the Times that if LUCA could synthesize proteins—and the genetic analysis suggests it could have—the organism could likely synthesize other, simpler things as well, even if the HHU team didn’t find them. “It’s like saying you can build a 747 but can’t refine iron,” he said.

Chemist John Sutherland of the University of Cambridge had his own objections. He says that LUCA’s dependence on its environment was not as extreme as Martin makes it out to be. “It’s like saying I’m half alive because I depend on my local supermarket.”

Sutherland and Benner don’t disagree with the HHU researchers’ conclusion that LUCA was, well, our LUCA, and they’re fine placing it on a hydrothermal vent. But they don’t think LUCA was the first life form, and they say a lot more research is needed before we can really pin down just what that ancient little weirdo was up to. 

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People Listen (and Remember) Better With Their Right Ears, Study Finds
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If you’re having trouble hearing in a noisy situation, you might want to turn your head. New research finds that people of all ages depend more on their right ear than their left, and remember information better if it comes through their right ear. The findings were presented at the annual meeting of the Acoustical Society of America in New Orleans on December 6.

Kids’ ears work differently than adults' do. Previous studies have found that children's auditory systems can’t separate and process information coming through both of their ears at the same time, and rely more on the auditory pathway coming from the right. This reliance on the right ear tends to decrease when kids reach their teens, but the findings suggest that in certain situations, right-ear dominance persists long into adulthood.

To study how we process information through both our ears, Auburn University audiologists brought 41 adult subjects (between the ages of 19 and 28) into the lab to complete dichotic listening tests, which involve listening to different auditory inputs in each ear. They were either supposed to pay attention only to the words, sentences, or numbers they heard in one ear while ignoring the other, or they were asked to repeat all the words they heard in both ears. In this case, the researchers slowly upped the number of items the test subjects were asked to remember during each hearing test.

Instructions for the audio test read 'Repeat back only the numbers you hear in the right ear.'
Sacchinelli, Weaver, Wilson and Cannon - Auburn University

They found that the harder the memory tests got, the more performance varied between the ears. While both ears performed equally when people were asked to remember only four or so words, when the number got higher, the difference between their abilities became more apparent. When asked to only focus on information coming through their right ear, people’s performance on the memory task increased by an average of 8 percent. For some people, the result was even more dramatic—one person performed 40 percent better while listening with only their right ear.

"Conventional research shows that right-ear advantage diminishes around age 13, but our results indicate this is related to the demand of the task,” one of the researchers, assistant professor Aurora Weaver, explained in a press release. In other words, when the going gets tough, the right ear steps up.

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Pigeons Are Secretly Brilliant Birds That Understand Space and Time, Study Finds
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Of all the birds in the world, the pigeon draws the most ire. Despite their reputation as brainless “rats with wings,” though, they’re actually pretty brilliant (and beautiful) animals. A new study adds more evidence that the family of birds known as pigeons are some of the smartest birds around, as Quartz alerts us.

In addition to being able to distinguish English vocabulary from nonsense words, spot cancer, and tell a Monet from a Picasso, pigeons can understand abstract concepts like space and time, according to the new study published in Current Biology. Their brains just do it in a slightly different way than humans’ do.

Researchers at the University of Iowa set up an experiment where they showed pigeons a computer screen featuring a static horizontal line. The birds were supposed to evaluate the length of the line (either 6 centimeters or 24 centimeters) or the amount of time they saw it (either 2 or 8 seconds). The birds perceived "the longer lines to have longer duration, and lines longer in duration to also be longer in length," according to a press release. This suggests that the concepts are processed in the same region of the brain—as they are in the brains of humans and other primates.

But that abstract thinking doesn’t occur in the same way in bird brains as it does in ours. In humans, perceiving space and time is linked to a region of the brain called the parietal cortex, which the pigeon brains lack entirely. So their brains have to have some other way of processing the concepts.

The study didn’t determine how, exactly, pigeons achieve this cognitive feat, but it’s clear that some other aspect of the central nervous system must be controlling it. That also opens up the possibility that other non-mammal animals can perceive space and time, too, expanding how we think of other animals’ cognitive capabilities.

[h/t Quartz]

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