Nine human species walked the Earth 300,000 years ago. Now there is just one. The Neanderthals, Homo neanderthalensis, were stocky hunters adapted to Europe’s cold steppes.

The related Denisovans inhabited Asia, while the more primitive Homo erectus lived in Indonesia, and Homo rhodesiensis in central Africa.

Several short, small-brained species survived alongside them: Homo naledi in South Africa, Homo luzonensis in the Philippines, Homo floresiensis ("hobbits") in Indonesia, and the mysterious Red Deer Cave People in China.

Given how quickly we’re discovering new species, more are likely waiting to be found.

By 10,000 years ago, they were all gone. The disappearance of these other species resembles a mass extinction. But there’s no obvious environmental catastrophe – volcanic eruptions, climate change, asteroid impact – driving it.

Instead, the extinctions’ timing suggests they were caused by the spread of a new species, evolving 260,000-350,000 years ago in Southern Africa: Homo sapiens.

The spread of modern humans out of Africa has caused a sixth mass extinction, a greater than 40,000-year event extending from the disappearance of Ice Age mammals to the destruction of rainforests by civilisation today. But were other humans the first casualties?

Human evolution. (Nick Longrich)

We are a uniquely dangerous species. We hunted wooly mammoths, ground sloths and moas to extinction. We destroyed plains and forests for farming, modifying over half the planet’s land area. We altered the planet’s climate.

But we are most dangerous to other human populations, because we compete for resources and land.

History is full of examples of people warring, displacing and wiping out other groups over territory, from Rome’s destruction of Carthage, to the American conquest of the West and the British colonisation of Australia. There have also been recent genocides and ethnic cleansing in Bosnia, Rwanda, Iraq, Darfur and Myanmar.

Like language or tool use, a capacity for and tendency to engage in genocide is arguably an intrinsic, instinctive part of human nature. There’s little reason to think that early Homo sapiens were less territorial, less violent, less intolerant – less human.

Optimists have painted early hunter-gatherers as peaceful, noble savages, and have argued that our culture, not our nature, creates violence. But field studies, historical accounts, and archaeology all show that war in primitive cultures was intense, pervasive and lethal.

Neolithic weapons such as clubs, spears, axes and bows, combined with guerrilla tactics like raids and ambushes, were devastatingly effective. Violence was the leading cause of death among men in these societies, and wars saw higher casualty levels per person than World Wars I and II.

Old bones and artefacts show this violence is ancient. The 9,000-year-old Kennewick Man, from North America, has a spear point embedded in his pelvis. The 10,000-year-old Nataruk site in Kenya documents the brutal massacre of at least 27 men, women, and children.

It’s unlikely that the other human species were much more peaceful. The existence of cooperative violence in male chimps suggests that war predates the evolution of humans.

Neanderthal skeletons show patterns of trauma consistent with warfare. But sophisticated weapons likely gave Homo sapiens a military advantage. The arsenal of early Homo sapiens probably included projectile weapons like javelins and spear-throwers, throwing sticks and clubs.

Complex tools and culture would also have helped us efficiently harvest a wider range of animals and plants, feeding larger tribes, and giving our species a strategic advantage in numbers.

The ultimate weapon

But cave paintings, carvings, and musical instruments hint at something far more dangerous: a sophisticated capacity for abstract thought and communication. The ability to cooperate, plan, strategise, manipulate and deceive may have been our ultimate weapon.

The incompleteness of the fossil record makes it hard to test these ideas. But in Europe, the only place with a relatively complete archaeological record, fossils show that within a few thousand years of our arrival, Neanderthals vanished.

Traces of Neanderthal DNA in some Eurasian people prove we didn’t just replace them after they went extinct. We met, and we mated.

Elsewhere, DNA tells of other encounters with archaic humans. East Asian, Polynesian and Australian groups have DNA from Denisovans. DNA from another species, possibly Homo erectus, occurs in many Asian people. African genomes show traces of DNA from yet another archaic species. The fact that we interbred with these other species proves that they disappeared only after encountering us.

But why would our ancestors wipe out their relatives, causing a mass extinction – or, perhaps more accurately, a mass genocide?

The answer lies in population growth. Humans reproduce exponentially, like all species. Unchecked, we historically doubled our numbers every 25 years. And once humans became cooperative hunters, we had no predators.

Without predation controlling our numbers, and little family planning beyond delayed marriage and infanticide, populations grew to exploit the available resources.

Further growth, or food shortages caused by drought, harsh winters or overharvesting resources would inevitably lead tribes into conflict over food and foraging territory. Warfare became a check on population growth, perhaps the most important one.

Our elimination of other species probably wasn’t a planned, coordinated effort of the sort practised by civilisations, but a war of attrition. The end result, however, was just as final. Raid by raid, ambush by ambush, valley by valley, modern humans would have worn down their enemies and taken their land.

Yet the extinction of Neanderthals, at least, took a long time – thousands of years. This was partly because early Homo sapiens lacked the advantages of later conquering civilisations: large numbers, supported by farming, and epidemic diseases like smallpox, flu, and measles that devastated their opponents.

But while Neanderthals lost the war, to hold on so long they must have fought and won many battles against us, suggesting a level of intelligence close to our own.

Today we look up at the stars and wonder if we’re alone in the universe. In fantasy and science fiction, we wonder what it might be like to meet other intelligent species, like us, but not us. It’s profoundly sad to think that we once did, and now, because of it, they’re gone.

Nick Longrich, Senior Lecturer, Paleontology and Evolutionary Biology, University of Bath.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Source: https://www.sciencealert.com/did-homo-sapiens-kill-off-all-the-other-humans

Homo sapiens today look very different from our evolutionary origins, the microbes wriggling about in the primordial mud. But our emergence as a distinct species cannot, based on the current evidence, be conclusively traced to a single location at any single point in time.

In fact, according to a team of scientists, who have conducted a thorough review of our current understanding of human ancestry, there may never even have been such a time. Instead, the earliest known appearances of Homo sapiens traits and behaviours are consistent with a range of evolutionary histories.

We simply don’t have a large enough fossil record to definitively rule on a specific time and place in which modern humans emerged.

"Some of our ancestors will have lived in groups or populations that can be identified in the fossil record, whereas very little will be known about others," said anthropologist Chris Stringer of the Natural History Museum in London in the UK.

"Over the next decade, growing recognition of our complex origins should expand the geographic focus of paleoanthropological fieldwork to regions previously considered peripheral to our evolution, such as Central and West Africa, the Indian subcontinent and Southeast Asia."

We do have some general ideas about our history. Homo sapiens diverged from archaic ancestors sometime between a million and 300,000 years ago (by which time nine distinct human species populated the planet).

Then, we know that modern human ancestries diversified in Africa between 300,000 and 60,000 years ago.

Finally, between 60,000 and 40,000 years ago, those modern humans migrated out of Africa and across the globe, interbreeding with Neanderthals and Denisovans before those two species ultimately died out.

Based on current evidence, including genomic data and the fossil record, the researchers assert, a more precise location and time in Africa for modern human diversification cannot be identified.

"Contrary to what many believe, neither the genetic or fossil record have so far revealed a defined time and place for the origin of our species," explained geneticist Pontus Skoglund of The Francis Crick Institute in the UK.

"Such a point in time, when the majority of our ancestry was found in a small geographic region and the traits we associate with our species appeared, may not have existed. For now, it would be useful to move away from the idea of a single time and place of origin."

Instead, the researchers stress the importance of trying to separate the emergence of anatomy, physiology, traits and behaviours associated with Homo sapiens from genetic ancestry. This would help separate the question of when human ancestry emerged from when human behaviour emerged.

Conflating the two, they note, risks oversimplifying what was likely a long, continuous and complex process.

"Following from this, major emerging questions concern which mechanisms drove and sustained this human patchwork, with all its diverse ancestral threads, over time and space," said archaeologist Eleanor Scerri of the Max Planck Institute for the Science of Human History in Germany.

"Understanding the relationship between fractured habitats and shifting human niches will undoubtedly play a key role in unravelling these questions, clarifying which demographic patterns provide a best fit with the genetic and palaeoanthropological record."

The research has been published in Nature.

Source: https://www.sciencealert.com/the-origin-of-modern-humans-cannot-be-traced-to-any-one-single-point

Some scientists believe life came from Mars.

If life spread from somewhere else in our galaxy, it’s likely to have gotten to Mars first.

Scientists hope to find DNA scraps on samples of material from Mars.

Could life as we know it have begun on Mars instead of Earth? A handful of scientists believe so, and even more think we should at least consider the possibility.

This special case of the overall theory of panspermia, where life on Earth began somewhere else and traveled or was planted here, has some prominent supporters. In a new Salon article, these proponents say the theory makes intuitive sense based on what the two planets are like.

Let’s review the facts. First, no one knows for certain where and how life began. We can backform theories based on what we know now, and what life is like throughout the fossil and carbon record on Earth.

Researchers also study unique qualities that Mars and Earth share compared with the other planets in our solar system, and Mars is, in many ways, a smaller, older Earth that “burned out” its natural resources and electromagnetic core sooner. (This, too, makes intuitive sense. A smaller ice cube melts faster, and a smaller piece of hot food cools more quickly.)

Scientists study genomics as a way to extrapolate the origins of life. The order in which building blocks like RNA and DNA emerged can be cross-referenced with, for example, the many dozens of Mars-based meteorites that are known to have hit the Earth over time.

This idea coalesces around the last universal common ancestor (LUCA), meaning the single cell from which all the rest of the cells on Earth descended. All living things have some most recent common ancestor—think about humans and, say, horses, whose most recent common ancestor might be some extinct third mammal species.

LUCA is different, requiring a lot more backtracking to a much further past. Could the last universal common ancestor be from genetic material that came from Mars?

Scientists believe the first life on Earth came just 200 million years after the first liquid water—and Mars panspermists point out that Mars likely had surface water before Earth based on the two planets’ makeups.

“Let’s say you expect life to be flourishing whenever a planet cools down to the point where it can start to have liquid water,” Erik Asphaug, a professor of planetary science at the University of Arizona, told Salon. “But just looking at our own solar system, what planet was likely to be habitable first? Almost certainly Mars.”

He continued:
“If life was going to start anywhere it might start first on Mars. We don’t know what the requirement is—you know, if it required something super special like the existence of a moon or some factors that are unique to the Earth—but just in terms of what place had liquid water first, that would have been Mars.”

If pieces from Mars were knocked off via “ballistic” panspermia, where an impact breaks off pieces that fly and strike another planet, they could have landed and flourished in the right puddle on Earth.

Astronomers say the likelihood is greater for life to have traveled to Mars before it traveled to Earth, for very prosaic reasons. Earth is closer to the sun, and anything trying to reach us would have to avoid the sun’s enormous gravity, for example. Something traveling from outside our solar system could also be slingshotted by Jupiter’s gravity directly into Mars, for example.

Intelligent Life Can’t Exist Anywhere Else
One way to test this theory is to study every sample from Mars for the presence of DNA. This is the latest installment in a long, twisting narrative arc for the idea of life on Mars, from astronomer Percival Lowell’s insistence that Mars was covered in engineered canals, to the present, where we know there’s some frozen water on the Red Planet after all.

Either way, Mars’s once-molten core slowed and solidified, reducing the planet’s gravity and atmosphere to nearly nothing and removing essential protections for any life form of which we know. But cellular matter could still exist, dormant in the cold yet there to find.

Source: https://www.popularmechanics.com/space/moon-mars/a35450915/did-life-start-on-mars/?source=nl&utm_source=nl_pop&utm_medium=email&date=021021&utm_campaign=nl22896716&utm_content=A&utm_term=AAA%20–%20High%20Minus%20Dormant%20and%2090%20Day%20Non%20Openers

In the world of astronomy, the great spotlight sometimes falls on the famous planets of our solar system. What we quickly forget, however, in view of the numerous reports about Mars, Saturn and Co., is the fact that the natural satellites of those celestial bodies also exert a great fascination. It is not without reason that the first manned moon landing in 1969 is still considered one of the greatest milestones in the history of space exploration. Today we would like to take you on a journey to another, no less impressive moon. Our contribution today is dedicated to one of the most famous natural satellites in our planetary network: Jupiter’s moon Europa. We will explain to you what characterizes the celestial body, which missions have been carried out to study the moon, and we will go into some breathtaking real images of Europa.

View the video here: https://www.youtube.com/watch?v=wOG2iLYd4a4

It may sound like something out of a futuristic science fiction film, but scientists have managed to engineer spinach plants which are capable of sending emails.

Through nanotechnology, engineers at MIT in the US have transformed spinach into sensors capable of detecting explosive materials. These plants are then able to wirelessly relay this information back to the scientists.

When the spinach roots detect the presence of nitroaromatics in groundwater, a compound often found in explosives like landmines, the carbon nanotubes within the plant leaves emit a signal. This signal is then read by an infrared camera, sending an email alert to the scientists.

This experiment is part of a wider field of research which involves engineering electronic components and systems into plants. The technology is known as “plant nanobionics”, and is effectively the process of giving plants new abilities.

“Plants are very good analytical chemists,” explains Professor Michael Strano who led the research. “They have an extensive root network in the soil, are constantly sampling groundwater, and have a way to self-power the transport of that water up into the leaves.”

“This is a novel demonstration of how we have overcome the plant/human communication barrier,” he adds.

ENVIRONMENTAL POTENTIAL

While the purpose of this experiment was to detect explosives, Strano and other scientists believe it could be used to help warn researchers about pollution and other environmental conditions.

Because of the vast amount of data plants absorb from their surroundings, they are ideally situated to monitor ecological changes.

In the early phases of plant nanobionic research, Strano used nanoparticles to make plants into sensors for pollutants. By altering how the plants photosynthesized, he was able to have them detect nitric oxide, a pollutant caused by combustion.

“Plants are very environmentally responsive,” Strano says. “They know that there is going to be a drought long before we do. They can detect small changes in the properties of soil and water potential. If we tap into those chemical signalling pathways, there is a wealth of information to access.”

When it’s not busy emailing researchers, spinach seems to also hold the key to efficiently powering fuel cells too.

Scientists from the American University have found that when spinach is converted into carbon nanosheets, it can function as a catalyst to help make metal-air batteries and fuel cells more efficient.

“This work suggests that sustainable catalysts can be made for an oxygen reduction reaction from natural resources,” explains Professor Shouzhong Zou, who led the paper.

Metal-air batteries are a more energy efficient alternative to lithium-ion batteries, which are commonly found in commercial products like smartphones.

Spinach was specifically chosen because of its abundance of iron and nitrogen, which are important elements in compounds that act as catalysts. The researchers had to wash, juice and grind the spinach into a powder, turning it from its edible form into nanosheets suitable for the process.

“The method we tested can produce highly active, carbon-based catalysts from spinach, which is a renewable biomass," adds Zou. "In fact, we believe it outperforms commercial platinum catalysts in both activity and stability.”

Source: https://www.euronews.com/living/2021/02/01/scientists-have-taught-spinach-to-send-emails-and-it-could-warn-us-about-climate-change

Some interesting science as our technology races forward:

https://www.youtube.com/watch?v=ZA-U7_zuV1w

The past is fascinating!

https://www.youtube.com/watch?v=u8HKr9sG5kQ

Hunting in Deep water:
https://www.youtube.com/watch?v=54acHHUqObM

The surface of Venus can’t be seen because of the dense, cloudy atmosphere.

Here’s the video of what we know:

https://www.youtube.com/watch?v=Fbdojp9LTLc

Named "Sasha," the remains were first found in 2015, but only recently brought back to life.

IT’S NAMED SASHA after the hunter who found it.

Russian scientists aren’t quite sure if their 10,000-year-old Sasha was male or female, but the name, they say, universally applies.

That any of Sasha, the Ice Age woolly rhino, is intact at all has been a surprising find for the researchers who study this bygone period.

Unlike woolly mammoths, which also lived during the Ice Age, woolly rhino remains are rare to find. Their place on the evolutionary timeline is less clear. And their lifestyles—what they ate and how long they lived—is hazy.

Rebuilding Sasha

Last December, after months of work, a taxidermist from the Yakutian Academy of Sciences took the small, slumped remains of Sasha and brought them back to life. A team of scientists from the Paleontological Institute at the Russian Academy of Sciences and the Sakha Academy of Sciences in northeastern Russia has also been studying Sasha for years.

The remains, gray when they were first found, were cleaned. Scientists were surprised to see the young rhino was originally a light strawberry blond color. An analysis of Sasha’s teeth revealed the animal was about seven months old when it died.

That it was so young was a surprise to scientists, reports the Siberian Times. Sasha is big for seven months old. It measures almost five feet long and stands about two and a half feet tall. Modern rhinos in Africa typically don’t reach that size until 18 months of age.

Left:

The remains were first found in 2015 by a hunter in Siberia.

Right:

Sasha is almost five feet long, much larger than modern rhinos at seven months old.

PHOTOGRAPH BY SAKHA ACADEMY OF SCIENCES, THE SIBERIAN TIMES (LEFT) AND PHOTOGRAPH BY SAKHA ACADEMY OF SCIENCES , THE SIBERIAN TIMES (RIGHT)

Olga Potapova is a scientist at The Mammoth Site of Hot Springs South Dakota, a preservation and research organization. Her work has focused on large extinct mammals of the Ice Age, and she’s currently conducting research on Sasha, though she says she can’t yet reveal too much.

Sasha is currently being studied by a team of international scientists led by the Russian Academy of Sciences.

What she can discuss is how important the find is for scientists’ understanding of this time period. Other bits and pieces of woolly rhinos like teeth bones have been found, but Sasha is the only intact baby rhino mummy of this species, Coelodonta antiquitatis.

"This find will allow scientists to shed light on different sides of the woolly rhino biology and morphology," she says. Meaning they’ll be able to learn how it developed, what it ate, and how it differed from modern rhinos.

How Sasha died, and was so well preserved, is also still a mystery.

"We [paleontology and geology scientists] think we know a lot about the last Ice Age in general and about animals inhabiting it, but in reality, we just scratched the surface of this past world," Potapova says.

Clues About the Last Ice Age

The remains were first found in 2015 in the permafrost lining a Siberian riverbank. Permafrost, as the name might indicate, refers to ground that’s permanently frozen for more than two consecutive years, but in Siberia, it often refers to ground that has been frozen for thousands.

Play Video

FARMER FINDS WOOLLY MAMMOTH BONES IN MICHIGAN

The region is the only known habitat of the woolly rhino. One of the greatest mysteries surrounding the species is why it didn’t cross the Bering Bridge, says Potapova. She’s referring to a land bridge that may have once connected northeastern Russia and Alaska.

Woolly mammoths, steppe bison, reindeer, and other species are thought to have crossed it during the Pleistocene. But what particular adaptations woolly rhinos had to survive in this climate are also unclear.

A Mysterious End

Scientist have a few theories as to why the woolly rhino went extinct but no solid explanation.

One study published in August of last year suggested they may have gone extinct from a genetic abnormality. A look at their fossilized remains found many contain a cervical neck rib, a condition associated with birth defects. The study suggested that inbreeding could have therefore factored into their decline.

For her part, Potapova referred to two theories as to why the species went extinct.

TODAY’SPOPULAR STORIES

SCIENCECORONAVIRUS COVERAGE
FDA confirms Moderna’s vaccine is 94.1-percent effective; emergency approval expected this week

ANIMALS
Meet Phelan the rescue pup—now America’s fastest dog

SCIENCE
Who is really ‘first in line’ for the vaccine? It depends on your state.

The first is that climactic changes impacted the feeding habitats of herbivores, which in turn led to the extinction of larger carnivores like cave lions and saber-tooth cats.

The second theory is that they were killed off by people.

"Recent research of the ancient DNA of many extinct herbivores showed that populations declined and their genetic pool degenerated well before human appearances on these two continents," she says, suggesting the former theory is more likely.

Sasha’s remains alone can’t tell scientists why the species went extinct, but Potapova says it’s an important piece to the larger puzzle of this species.

Source: https://www.nationalgeographic.com/news/2018/01/sasha-woolly-rhino-mummy-siberia-ice-age-spd/

A very interesting video about the dangers of Space Debris:

https://www.youtube.com/watch?v=itdYS9XF4a0