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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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Is there really life on Venus? How do we find out? – News 1130

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In today’s Big Story podcast, last week, an unlikely research project made a startling discovery: Phosphine gas in the atmosphere of Venus. That’s something that, as far as we know, is created by living organisms. Our efforts to find signs of life on other worlds, and a lot of our space dreaming in general, tend to focus on Mars. But all of a sudden we need to take a closer look at our other planetary neighbour.

So how can we find out if there’s really life right next door? What do we know about Venus and why has it been so hard to figure out so far? What else could possibly cause the presence of Phosphine and what would it mean, to space exploration and everything else, if this is really true?

GUEST: Neel Patel, space reporter, MIT Technology Review

You can subscribe to The Big Story podcast on Apple Podcasts, Google and Spotify

You can also find it at thebigstorypodcast.ca.

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Is there really life on Venus? How do we find out? – HalifaxToday.ca

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Last week, an unlikely research project made a startling discovery: Phosphine gas in the atmosphere of Venus. That’s something that, as far as we know, is created by living organisms. Our efforts to find signs of life on other worlds, and a lot of our space dreaming in general, tend to focus on Mars. But all of a sudden we need to take a closer look at our other planetary neighbour.

So how can we find out if there’s really life right next door? What do we know about Venus and why has it been so hard to figure out so far? What else could possibly cause the presence of Phosphine and what would it mean, to space exploration and everything else, if this is really true?

GUEST: Neel Patel, space reporter, MIT Technology Review

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The 'Red Planet' approaches – Coast Reporter

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This summer has been pretty interesting with Comet NEOWISE, the Perseids and some close lunar/planetary appulses in September. (Yes, it’s my new vocabulary word of the month.) October, however, is all about Mars – but the COVID-19 threat we’re facing limits our options somewhat. 

Opposition occurs when Earth passes between the sun and a celestial object – they’re opposite to each other in the sky. Because of our orbital periods – 365 days for Earth and 780 earth days for Mars – a Mars opposition happens about every 26 months. However, the accompanying composite of Hubble images from previous oppositions illustrates that there’s more to it than just that. For example, although opposition is Oct. 13, we’re actually slightly closer on Oct. 6. 

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First, neither planet has a circular orbit; Earth’s is slightly elliptical and Mars’ is much more so. Hence, the close approach distance varies according to how close or far from the Sun each planet is. Second, Earth and Mars orbit in slightly different planes; Mars can be above or below the plane of Earth’s orbit and therefore a bit further away. As well, Mercury and Venus slightly affect Earth’s orbit and Jupiter affects everything, so all the orbits change slowly over time. Finally, we’re in the northern hemisphere; a near-winter opposition puts Mars much higher in the sky at night and we look through much less atmosphere. Although Mars isn’t quite as close as it was in July 2018, it will be about 30 degrees higher – better seeing. 

The Astronomy Picture of the Day site (APOD) at https://apod.nasa.gov/apod/ for Sept. 11 has a striking photo of Mars emerging from behind the Moon taken on Sept. 6 from Brazil, one of five occultations this year. The photo, lovely as it is, illustrates the problem of viewing Mars for most of us: you need a telescope. While you can see Jupiter as a small disc and four moons with good binoculars and a tripod, Mars at its best is only a third that size. Without the current pandemic, I’m sure the Sechelt observatory would be open to the public for this opposition and people could stare to their hearts’ content, but at this point it doesn’t look good. Any changes will be posted on the club website. 

As in September, Jupiter and Saturn are low in the south after sunset, after their opposition in late July. The New Moon on the 16th coincides with its perigee (large tides) and it will pass Jupiter and Saturn a week later on the 22nd and 23rd. Interestingly, it will be a Full Moon on the 1st AND the 31st. 

Remember, all of the movements of moon and planets described can be checked out on the web at: www.heavens-above.com. The next regular meeting of the Astronomy Club should be Oct. 9 at 7 p.m. using Zoom. Information on the speaker and topic and how to register for the meeting will be on the club website at https://sunshinecoastastronomy.wordpress.com/ the week of the meeting.

– Richard Corbet

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