Adaptation never stops: Study challenges long-established evolutionary theory

Oct. 19 (UPI) — Scientists in Australia claim to have debunked a long-held evolutionary theory — the assumption that in a simple, static environment, organisms will eventually reach a “fitness peak,” a plateau of adaptation, and stop evolving.

New research out of Monash University suggests there is no such thing as a fitness peak.

To better understand the molecular details of adaptation, scientists at Monash tracked the evolution of E. coli bacteria across 67,000 generations — one of the longest-running evolution experiments in science history.

The ongoing experiment has been managed by Monash scientists for the last 30 years.

“In our study we found that even though the E. coli populations in our experiment have been evolving in a very simple environment for a long time, they are still adapting to their environment,” Monash researcher Mike McDonald said in a news release. “In other words the fit get fitter.”

The findings of McDonald and his colleagues — detailed in the journal Nature — run counter to the long-held assumption of evolutionary theory.

“The established theory tells us that adaptation should have stopped by now,” McDonald said. “Our work shows that this is not the case.”

Researchers hypothesize that as the bacteria adapts, evolves and changes, it alters its environment, thus inspiring more adaptations. If true, evolution may inspire a feedback loop of never-ending adaptation.

During the experiment, researchers were able to use high-resolution genomic sequencing technology to track more than 33,000 mutations over the coarse of thousands of generations — the equivalent of more than a million years of human evolution.

Because many diseases and medical problems are adaptations gone awry, an improved understanding of the mechanics of molecular adaptations could help scientists anticipate and combat cancer and other maladies. Such knowledge could also be used to thwart the adaptive abilities of bacterial strains with antibiotic resistance, or to anticipate the impacts of climate change on vulnerable species.

“The insights we provide into the rate, repeatability, and molecular basis of adaptation will contribute to a better understanding of these evolutionary processes and challenges,” McDonald said.

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Genomic survey reveals source of sea cucumber's regenerative abilities

Oct. 12 (UPI) — New genomic analysis is helping a team of scientists unravel the secrets of the cucumber, including its ability to regenerate tissue.

The genomic survey may also help scientists better understand how the unusual marine animal evolved a skeletal structure so different from its closest relatives.

Sea cucumbers — of which there are 1,717 species — form a class of the echinoderm phylum. Other echinoderm classes include sea urchins and sea stars, which are markedly different in structure and appearance.

Like their relatives in the phylum Chordata — which includes all vertebrates, as well as sea squirts and lancelets — echinoderms are deuterostomes, which means they develop an anus before a mouth. But unlike most other echinoderms, sea cucumbers don’t form a hardened calcium exoskeleton. They can also quickly and efficiently repair and regrow damaged or lost body parts.

To locate the source of the sea cucumber’s regenerative powers, a team of Chinese scientists sequenced 92 percent of the genome of the Japanese sea cucumber, Apostichopus japonicus. The researchers surveyed more than 30,000 of the species’ genes.

Their analysis suggests sea cucumbers diverged from a group of hemichordates, a small group of marine invertebrates including acorn worms, some 533 million years ago. Some 54 million years later, sea cucumbers split from the rest of the echinoderm classes.

Over time, sea cucumbers minimized the expression of genes related to biomineralization, which explains the organism’s soft body.

The new research also revealed sea cucumbers to host a unique set of duplicated genes, called PSP94-like genes, which allow them to regenerate their internal organs. This evolved alongside the sea cucumber’s ability to eject its innards to ward off predators.

Scientists found the expression of another set of duplicated genes, fibrinogen-related proteins, were also linked with regeneration.

Researchers published their findings in a new paper, published this week in the journal PLOS Biology.

“The sea cucumber is a particularly promising model animal for regenerative medicine,” Jianhai Xiang, a researcher with the Institute of Oceanology at the Chinese Academy of Sciences, said in a news release. “Our findings should also facilitate the understanding of the requirements for sustainable utilization and effective breeding of echinoderms, in support of the high-value sea cucumber industry.”

Scientists are hopeful that their insights into echinoderm regrowth will eventually translate to human therapies.

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Astronomers find sun-like star that ate its own planets

Oct. 12 (UPI) — Astronomers have discovered a faraway star with an unrelenting hunger for rocky planets. According the analysis of the star’s chemical commotion, the sun-like stellar system has swallowed enough rocky planets to equal 15 Earths.

“Even if our sun ate the entire inner solar system, it wouldn’t come close to the anomaly we see in this star,” David Hogg, head of astronomical data at the Flatiron Institute’s Center for Computational Astrophysics, said in a news release.

Scientists named the planet-eating star Kronos, a nod to the Greek Titan who ate all of his children after they were born.

Lead researcher Semyeong Oh, an astrophysicist at Princeton University, didn’t set out to find a planet-eating star. She was using observations by the European Space Agency’s Gaia spacecraft to study stellar duos traveling along similar trajectories and at similar speeds — stars likely to originate from a common star-forming regions be forged of the same material.

But Oh’s chemical analysis of the two stars’ innards revealed a significant dichotomy. The chemistry of the two members of the binary star system proved to be quite different.

“We started discussing what could make two stars that must have been born together have such different chemistry now,” Oh said.

Kronos, unlike its stellar sibling Krios, featured high concentrations of iron, silicon, magnesium and lithium, all elements that makeup rocky planets.

Because the heavy metals are found in Kronos’ outer layers, astronomers surmise the star consumed the rock planets more than a billion years after the star was born.

The findings could help astronomers better understand how stellar systems evolve over time.

“We assume that once stars are born, their chemistries are fixed,” said researcher Adrian Price-Whelan. “This is yet more evidence of stars changing.”

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Different types of learning happen at unique brainwave frequencies

Oct. 11 (UPI) — When neurons fire in the brain, they release a unique electrical signal that reverberates at distinctive frequencies. New research suggests different types of learning correspond with different brainwave frequencies.

The revelation — detailed in a new paper published this week in the journal Neuron — could help doctors diagnose and treat learning disabilities and cognitive diseases.

Since the 1950s, neuroscientists have understood that there are two kinds of learning and memory — explicit and implicit.

According to Earl K. Miller, a professor of neuroscience at MIT, explicit learning is the type that a person is cognizant of and can describe. Examples of explicit learning would be memorizing a poem or studying for a geography test.

“Implicit learning is the opposite. You might call it motor skill learning or muscle memory, the kind of learning that you don’t have conscious access to, like learning to ride a bike or to juggle,” Miller told MIT News. “By doing it you get better and better at it, but you can’t really articulate what you’re learning.”

Often, complex tasks, such as learning to play a song on the piano, require both kinds of learning.

When Miller and his colleagues studied animal learning, they found different tasks required one type of learning or the other, and each type corresponded to different signals.

When required to compare and match two things, animals used explicit learning, recalling both correct and incorrect answers to improve their performance. But when trained to move their eyes in one direction or the other in response to a visual stimuli, the animals’ only improved their correct responses, suggesting the use of implicit learning.

During explicit learning, researchers found alpha2-beta brain waves corresponded with correct responses while delta-theta wakes increased only after an incorrect response. Alpha2-beta frequencies also spiked when animals first learned a task. As animals repeated the task, alpha2-beta waves tapered off.

Researchers surmised that the initial spike in alpha2-beta brain waves represents the formation of a cognitive model needed to learn and absorb the task.

“And then after the animal learns the task, the alpha-beta rhythms then drop off, because the model is already built,” Miller said.

During implicit learning, correct answers corresponded with spikes in delta-theta waves. These waves also tapered off as the motor skill became engrained.

The realization that different types of learning work in unique ways could help scientists and educators improve the kinds of help offered to people as they learn new tasks — whether they have a learning disability or not.

Another recent study found a region of the brain — called the brain’s dendrites — are excited by unique brainwaves called spindles during sleep. Spindles trigger dendrites to help incorporate new memories and information into the neural infrastructure. Scientists hypothesized that the frequency of spindles could be mimicked to trigger dendrite activity in patients with memory loss.

Similarly, Miller and his colleagues at MIT believe their work could lead to new treatments for Alzheimer’s.

“In Alzheimer’s, a kind of explicit fact learning disappears with dementia, and there can be a reversion to a different kind of implicit learning,” said Roman F. Loonis, a graduate student in the Miller Lab. “Because the one learning system is down, you have to rely on another one.”

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Reused SpaceX rocket carries satellite into orbit

Oct. 11 (UPI) — A used Falcon 9 rocket landed on a droneship in the Atlantic ocean Wednesday after launching a communications satellite into orbit.

It was the third time SpaceX depended on a used Falcon 9 rocket to carry out a launch mission.

The rocket blasted off at 6:53 p.m. from Kennedy Space Center in Florida.

The Falcon 9 rocket previously was used to deliver cargo to the International Space Station in February. This time, the rocket carried a high-powered, hybrid communications satellite shared by SES and EchoStar. The satellite is expected to support the delivery of high-definition television broadcasts to viewers across North America.

After carrying SpaceX’s Dragon capsule to the edge of space last winter, the rocket’s first stage detached and fell back to Earth before executing a controlled landing at SpaceX’s ground-based Landing Zone 1. This time, the rocket detached from the payload, fell back to Earth, then slowed its descent for a controlled landing.

“Falcon 9 first stage has landed on “Of Course I Still Love You” — third successful mission with a flight-proven orbital class rocket,” SpaceX said on Twitter.

“The satellite will be deployed approximately 36 minutes after liftoff,” SpaceX said.

The space company hopes to fly more used rockets in the coming months as it works to further reduce the cost of space travel. SpaceX successfully flew a mission with a used rocket for the first time in March. A second attempt in June also proved successful.

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Scientists discover remains of an ancient bobcat-sized predator in Tanzania

Oct. 12 (UPI) — Paleontologists have discovered a new species of extinct hyaenodont in Tanzania. The fossil offers new insights into the disappearance of hyaenodonts — once Africa’s top predator — during the Paleogene.

Hyaenodonts were cat-like in appearance, but walked on flat feet. After the dinosaurs bit the dust at then end of the Cretaceous period 66 million years ago, hyaenodonts became Africa’s most dominant carnivore.

Scientists named the newly discovered species Pakakali rukwaensis. “Pakakali” is a Swahili term meaning “fierce cat,” and “rukwaensis” is the Swahili name for the Rukwa Rift region in Tanzania’s Great Rift Valley, where the species’ remains were discovered.

Researchers described their discovery in a new paper, published on Wednesday, national “Fossil Day,” in the journal PLOS One.

The reign of the hyaenodonts was relatively short-lived. Around the time of Pakakali rukwaensis, between 23 and 25 million years ago, the earliest relatives of dogs, cats and hyenas emerged. These new carnivores eventually won the evolutionary race and hyaenodonts joined the dinosaurs in extinction.

“The shift from hyaenodonts to modern carnivores in Africa is like a controlled experiment,” Matthew Borths, a paleontologist at Ohio University, said in a news release. “We start with only hyaenodonts. Then the relatives of cats and dogs arrive. They coexist for a few million years, then the hyaenodonts are driven to extinction and we’re left with ‘The Lion King.'”

Because Pakakali rukwaensis arrived on the scene around the time the trajectory of the hyaenodonts began to take a turn southward, researchers believe the species could offer clues to the demise of its family.

“With Pakakali, we can start to unravel that extinction,” Borths said. “Were the lineages competing? Were they adapting differently to a drier, more open landscape?”

The new species’ fossilized skull was discovered among the same 25-million-year-old rock strata that revealed the split between Old World monkeys and apes. At the time, Africa was colliding with Eurasia, forming the East African Rift System. The tectonic shifts underpinned dramatic climate change.

At the time of Pakakali rukwaensis emergence, the bobcat-sized predators were struggling to adapt to a drier, more wide-open environment. As a result of increased competition, hyaenodonts were also forced to specialize in the consumption of meat. They weren’t able to adapt quick enough, and ultimately, they died out.

“The environment containing Pakakali reveals a fascinating window into extinction,” said Nancy Stevens, a paleontologist at Ohio University. “It highlights the vulnerability of carnivorous species to rapid environmental change, a topic we are grappling with on the African continent today.”

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