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Mysterious 'ghost population' of ancient humans discovered in African DNA – Daily Sabah

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Scientists examining the genomes of West Africans have detected signs that a mysterious extinct human species interbred with our own species tens of thousands of years ago in Africa, the latest evidence of humankind’s complicated genetic ancestry.

The study indicated that present-day West Africans trace a substantial proportion, some 2% to 19%, of their genetic ancestry to an extinct human species – what the researchers called a “ghost population.”

“We estimate interbreeding occurred approximately 43,000 years ago, with large intervals of uncertainty,” said University of California, Los Angeles (UCLA) human genetics and computer science professor Sriram Sankararaman, who led the study published this week in the journal Science Advances.

Homo sapiens first appeared a bit more than 300,000 years ago in Africa and later spread worldwide, encountering other human species in Eurasia that have since gone extinct including the Neanderthals and the lesser-known Denisovans.

Previous genetic research showed that our species interbred with both the Neanderthals and Denisovans, with modern human populations outside of Africa still carrying DNA from both. But while there is an ample fossil record of the Neanderthals and a few fossils of Denisovans, the newly identified “ghost population” is more enigmatic.

Asked what details are known about this population, Sankararaman said, “Not much at this stage.”

“We don’t know where this population might have lived, whether it corresponds to known fossils, and what its ultimate fate was,” Sankararaman added.

Sankararaman said this extinct species seems to have diverged roughly 650,000 years ago from the evolutionary line that led to Homo sapiens, before the evolutionary split between the lineages that led to our species and to the Neanderthals.

The researchers examined genomic data from hundreds of West Africans including the Yoruba people of Nigeria and Benin and the Mende people of Sierra Leone, and then compared that with Neanderthal and Denisovan genomes. They found DNA segments in the West Africans that could best be explained by ancestral interbreeding with an unknown member of the human family tree that led to what is called genetic “introgression.”

It is unclear if West Africans derived any genetic benefits from this long-ago gene flow.

“We are beginning to learn more about the impact of DNA from archaic hominins on human biology,” Sankararaman said, using a term referring to extinct human species. “We now know that both Neanderthal and Denisovan DNA was deleterious in general but there were some genes where this DNA had an adaptive impact. For example, altitude adaptation in Tibetans was likely facilitated by a Denisovan introgressed gene.”

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NASA probe leaking asteroid samples due to jammed door – Al Jazeera English

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Images beamed back to ground control revealed it caught more material than scientists anticipated and was spewing excess of flaky asteroid rocks into space.

A US probe that collected a sample from an asteroid earlier this week retrieved so much material that a rock is wedged in the container door, allowing rocks to spill back out into space.

On Tuesday, the robotic arm of the probe, OSIRIS-REx, kicked up a debris cloud of rocks on Bennu, a skyscraper-sized asteroid some 320 million kilometres (200 million miles) from Earth and trapped the material in a collection device for the return to Earth.

But images of the spacecraft’s collection head beamed back to ground control revealed it had caught more material than scientists anticipated and was spewing an excess of flaky asteroid rocks into space.

The leakage had the OSIRIS-REx mission team scrambling to stow the collection device to prevent additional spillage.

“Time is of the essence,” Thomas Zurbuchen, NASA’s associate administrator for science, told reporters on Friday.

Zurbuchen said mission teams will skip their chance to measure how much material they collected as originally planned and proceed to the stow phase, a fragile process of tucking the sample collection container in a safe position within the spacecraft without jostling out more valuable material.

NASA will not know how much material it collected until the sample capsule returns in 2023.

The troubleshooting also led mission leaders to forgo any more chances of redoing a collection attempt and instead commit to begin next March the spacecraft’s return to Earth.

“Quite honestly, we could not have performed a better collection experiment,” OSIRIS-REx’s principal investigator Dante Lauretta said.

But with the door lodged open by a rock and the “concerning” images of sample spillage, “we’re almost the victim of our own success here”, he added.

The roughly $800m, minivan-sized OSIRIS-REx spacecraft, built by Lockheed Martin, launched in 2016 to grab and return the first US sample of pristine asteroid materials.

Asteroids are among the leftover debris from the solar system’s formation some 4.5 billion years ago.

A sample could hold clues to the origins of life on Earth, scientists say.

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Asteroid samples escaping from jammed NASA spacecraft – Phys.org

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In this image taken from video released by NASA, the Osiris-Rex spacecraft touches the surface of asteroid Bennu on Tuesday, Oct. 20, 2020. (NASA via AP)

A NASA spacecraft is stuffed with so much asteroid rubble from this week’s grab that it’s jammed open and precious particles are drifting away in space, scientists said Friday.

Scientists announced the news three days after the named Osiris-Rex briefly touched asteroid Bennu, NASA’s first attempt at such a mission.

The mission’s lead scientist, Dante Lauretta of the University of Arizona, said Tuesday’s operation 200 million miles away collected far more material than expected for return to Earth—in the hundreds of grams. The sample container on the end of the robot arm penetrated so deeply into the asteroid and with such force, however, that rocks got sucked in and became wedged around the rim of the lid.

Scientists estimate the sampler pressed as much as 19 inches (48 centimeters) into the rough, crumbly, black terrain.

“We’re almost a victim of our own success here,” Lauretta said at a hastily arranged news conference.

Lauretta said there is nothing can do to clear the obstructions and prevent more bits of Bennu from escaping, other than to get the samples into their as soon as possible.

So, the flight team was scrambling to put the sample container into the capsule as early as Tuesday—much sooner than originally planned—for the long trip home.

“Time is of the essence,” said Thomas Zurbuchen, chief of NASA’s science missions.

This is NASA’s first asteroid sample-return mission. Bennu was chosen because its carbon-rich material is believed to hold the preserved building blocks of our solar system. Getting pieces from this cosmic time capsule could help scientists better understand how the planets formed billions of years ago and how life originated on Earth.

Scientists were stunned—and then dismayed—on Thursday when they saw the pictures coming from Osiris-Rex following its wildly successful touch-and-go at Bennu two days earlier.

A cloud of asteroid particles could be seen swirling around the spacecraft as it backed away from Bennu. The situation appeared to stabilize, according to Lauretta, once the robot arm was locked into place. But it was impossible to know exactly how much had already been lost.

The requirement for the $800 million-plus mission was to bring back a minimum 2 ounces (60 grams).

Regardless of what’s on board, Osiris-Rex will still leave the vicinity of the asteroid in March—that’s the earliest possible departure given the relative locations of Earth and Bennu. The samples won’t make it back until 2023, seven years after the spacecraft rocketed away from Cape Canaveral.

Osiris-Rex will keep drifting away from Bennu and will not orbit it again, as it waits for its scheduled departure.

Because of the sudden turn of events, scientists won’t know how much the sample capsule holds until it’s back on Earth. They initially planned to spin the spacecraft to measure the contents, but that maneuver was canceled since it could spill even more debris.

“I think we’re going to have to wait until we get home to know precisely how much we have,” Lauretta told reporters. “As you can imagine, that’s hard. … But the good news is we see a lot of material.”

Japan, meanwhile, is awaiting its second batch of samples taken from a different asteroid, due back in December.


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NASA spacecraft sent asteroid rubble flying in sample grab


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Two flights into Abbotsford have had recent COVID-19 exposures – Maple Ridge News

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Two flights to Abbotsford have each had a recent COVID-19 exposure, according to the B.C. Centre for Disease Control (CDC).

The agency indicates on its website that the flights involved were WestJet flight 637 from Calgary to Abbotsford on Wednesday, Oct. 14 (rows nine to 15) and Swoop flight 107 from Hamilton to Abbotsford on Monday, Oct. 19 (rows 20 to 26).

The CDC advises that anyone who was on these flights should self-monitor for symptoms for 14 days.

RELATED: Vancouver airport to pilot pre-flight COVID-19 tests for select WestJet passengers

Passengers on domestic flights are not required to self-isolate, but those who have travelled outside of Canada are required to self-isolate for 14 days upon their arrival.

Passengers seated on a plane with a case of COVID-19 that was later identified are no longer directly notified of their potential exposure. Instead, anyone who has travelled is asked to monitor the CDC website.

Passengers seated in the affected rows are considered to be at higher risk of exposure due to their proximity to the case.

RELATED: WestJet to offer full refunds for flights cancelled due to COVID-19 pandemic



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