Evolutie in het Nieuws #4

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Revolutie in archeologie: eerste mens zou al 130.000 jaar geleden in Amerika zijn aangekomen

do 27/04/2017 - 12:23 Alexander Verstraete

In Californië hebben archeologen sporen gevonden van menselijke activiteit van 130.000 jaar oud. Dat staat te lezen in Nature. De ontdekking is spectaculair omdat lang is gedacht dat de mens ten vroegste 25.000 jaar geleden op het Amerikaanse continent is aangekomen. Andere archeologen trekken de conclusies dan ook in twijfel.
Wanneer heeft de eerste mens(achtige) voet aan de grond gezet op wat vandaag de Amerika's zijn? Over die vraag debatteren archeologen sinds jaar en dag. Algemeen heerst wel een consensus dat dit pas ten vroegste 25.000 jaar geleden gebeurde en velen zien pas 15.000 jaar geleden echte bewijzen van menselijke activiteit.

Onderzoekers verbonden aan het San Diego Natural History Museum in de VS gooien nu de knuppel in het hoenderhok met een nieuwe en spectaculaire analyse van een site die in 1992 in de buurt van San Diego is ontdekt tijdens graafwerken voor een nieuwe snelweg. Zij stellen dat ze bewijzen hebben gevonden van menselijke activiteit van liefst 130.000 jaar oud.

Uranium-thoriumdatering

Concreet hebben de archeologen de botten onderzocht van een mastodont, een uitgestorven prehistorisch slurfdier. Op basis van een uranium-thoriumdatering hebben ze vastgesteld dat de botten 130.000 jaar oud zijn. Tegelijk menen ze verschillende kenmerken te ontwaren die moeten bewijzen dat mensachtigen de botten destijds hebben bewerkt.

Zo vertonen de grootste en stevigste botten van de mastodont breukpatronen die enkel mensenhanden kunnen hebben aangebracht, een stelling die de archeologen bewijzen met experimenten met botten van olifanten.

Bovendien zijn alle botten in een patroon aangetroffen dat niet overeenkomt met een natuurlijke spreiding. Daarnaast zijn in de bewuste aardlaag grote keien en stenen fragmenten gevonden die daar geologisch niet thuishoren.

Op basis van al deze aanwijzingen concluderen de archeologen dat de site niet door natuurlijke processen tot stand is gekomen, maar door mensen is vorm gegeven.

Als die bevindingen kloppen, dan zijn ze niks minder dan een ware revolutie in de archeologie. Het zou betekenen dat mensachtigen 115.000 jaar eerder dan aangenomen op het Amerikaanse continent rondwandelden.

De grote vraag is dan om wat voor mensachtige het ging. Naast de homo sapiens bevolkte ook de neanderthaler en de denisovamens op dat moment de aarde, twee mensachtigen die inmiddels zijn uitgestorven. Om die vraag te beantwoorden, moeten archeologen resten van de mensachtige in kwestie kunnen onderzoeken. Zulke fossielen zijn echter (nog) niet gevonden.

"Natuur is ondeugend en kan op allerlei manieren botten en stenen breken"

Hoewel het onderzoek van de Amerikaanse archeologen in het prestigieuze wetenschappelijke tijdschrift Nature is verschenen, zijn niet alle archeologen even overtuigd. "Om een dergelijke vroege menselijke bewoning van de Amerika's te bewijzen, zijn ondubbelzinnige stenen artefacten nodig", vertelt professor Michael Water van de Texas A&M University aan de BBC. "Bij deze botten zijn geen ondubbelzinnige stenen werktuigen gevonden. Dit is waarschijnlijk gewoon een interessante paleontologische site."

Professor David Meltzer van de Southern Methodist University in Texas betwijfelt dan weer dat de breukpatronen in de botten enkel door mensen kunnen zijn veroorzaakt. "De natuur is ondeugend en kan op allerlei manieren botten en stenen breken." Volgens hem moeten de archeologen eerst bewijzen dat de breuken niet het gevolg van natuurlijke processen kunnen zijn.

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New analysis relocates the “hobbit” on the human family tree

The story of how modern humans got to be where we are is constantly changing as new evidence is found. This often forces us to confront the idea that we aren’t as unique as we thought, as we find evidence of behaviors like tool use further and further back in our family tree. New evidence hints that our ancestors may have left Africa—and gone farther from it—than we had thought previously.

A paper currently in press at the Journal of Human Evolution takes a look at how Homo floresiensis, the diminutive “hobbit” species, fits into this picture. Its findings suggest that the hobbit lies further down on the family tree than previously thought, something that would only be possible if our ancestors had migrated out of Africa much earlier than any other data suggested.

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When a tiny embryonic dinosaur that died some 90 million years ago was featured on the front of a National Geographic magazine in 1996, it suddenly became known the world over. It now turns out that the embryo, dubbed “Baby Louie”, belongs to an entirely new species of giant bird-like dinosaur.

The fossil was identified as being that of a type of oviraptorosaur, a theropod dinosaur that would have been coated in feathers and sported an impressive beak. Although no fossil bones of the adults have been found, the researchers have been able to estimate that they weighed up to a staggering 2.7 tonnes (3 tons), which would make them the largest species of dinosaur known to incubate eggs and care for its young.

“Thanks to this fossil, we now know that these eggs were laid by a gigantic oviraptorosaur, a dinosaur that would have looked a lot like an overgrown cassowary,” explains Dr. Darla Zelenitsky, who helped describe the new species in Nature Communications, in a statement. “It would have been a sight to behold with a three ton animal like this sitting on its nest of eggs.”

During the 1980s and 1990s, thousands of dinosaur eggs dating to the Cretaceous were discovered by local farmers in China, with many of them exported for international sales, until the country clamped down on the practice. Baby Louie was among these that were sold, and it would be two decades before the tiny embryo and half a dozen associated eggs made their way back to their country of origin.

Now that the eggs – and the tiny embryos associated with them – have been returned to China, researchers have finally been able to properly analyze them. It turns out that they may once have belonged to an entirely new species, called Beibeilong sinensis, which translates to “Chinese baby dragon”.

The eggs, measuring 45 centimeters (17.7 inches) long and weighing at the time around 5 kilograms (11 pounds), are some of the largest dinosaur eggs ever discovered. This gave the researchers a hint that they were the young of a big beast, and comparisons with other eggs from known species meant they could describe the famous fossil as being a new species of giant oviraptor.

Fossil eggs similar to that of Baby Louie's, which are collectively known as Macroelongatoolithus, dating to the Late Cretaceous have been found throughout much of China, Korea, Mongolia, and North America. The researchers therefore suspect that the giant oviraptors were quite common during this period, despite the fact that very few fossil bones from adults have been discovered.

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Oldest evidence of life on land found in 3.48-billion-year-old Australian rocks

Fossil evidence of early life has been discovered by UNSW scientists in 3.48 billion year old hot spring deposits in the Pilbara of Western Australia - pushing back by 3 billion years the earliest known existence of inhabited terrestrial hot springs on Earth.

Previously, the world's oldest evidence for microbial life on land came from 2.7- 2.9 billion year old deposits in South Africa containing organic matter-rich ancient soils.

"Our exciting findings don't just extend back the record of life living in hot springs by 3 billion years, they indicate that life was inhabiting the land much earlier than previously thought, by up to about 580 million years," says study first author, UNSW PhD candidate, Tara Djokic.

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Op woensdag 10 mei 2017 14:11 schreef Perrin het volgende:
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Op woensdag 10 mei 2017 15:23 schreef Pietverdriet het volgende:

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Begreep uit een boek van Bill Bryson over Australie dat daar, in Australie, ook nog kolonien van de oudste levensvormen op aarde zijn.

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Proterozoïcum

De eerste organismen die een duidelijk spoor nalaten, zijn stromatolieten. Hoewel deze levensvormen zo'n drie miljard jaar geleden zijn ontstaan, bestaan ze nog steeds.

Aan de westkust van Australië in de getijdenzone zijn kleine bulten en zuilen te zien van ongeveer een halve meter hoogte. Ze groeien heel langzaam. Een speling van de natuur? Pas in de vorige eeuw wordt ontdekt, dat ze afstammen van de oudste herkenbare levensvormen uit de begintijd van de aarde.

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In 1871, Charles Darwin suggested that a female’s choice of mate could drive the evolution of mating signals in males. His idea stems from his observations of the iconic courtship displays of peacocks, the songs of crickets and his contemporary insights into the whimsical nature of human females. [...]

[...] “But Darwin also proposed that sexual selection can favour males who are better at detecting and responding to signals from females, including chemical signals like pheromones. So males with sensory structures that can better detect female signals may have the edge in finding them in order to mate and pass on their genes.”
But he says this idea has been largely overlooked until now.

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Fossils discovered in Morocco are the oldest known remains of Homo sapiens, scientists reported on Wednesday.

Dating back roughly 300,000 years, the bones indicate that mankind evolved earlier than had been known, experts say, and open a new window on our origins.

The fossils also show that early Homo sapiens had faces much like our own, although their brains differed in fundamental ways.

Until now, the oldest fossils of our species, found in Ethiopia, dated back just 195,000 years. The new fossils suggest our species evolved across Africa.

We did not evolve from a single cradle of mankind somewhere in East Africa, said Phillipp Gunz, a paleoanthropologist at the Max Planck Institute for Evolutionary Anthropology in Liepzig, Germany, and a co-author of two new studies on the fossils, published in the journal Nature.

Today, the closest living relatives to Homo sapiens are chimpanzees and bonobos, with whom we share a common ancestor that lived over six million years ago.

After the lineages split, our ancient relatives evolved into many different species, known as hominins. For millions of years, hominins remained very ape-like. They were short, had small brains, and could fashion only crude stone tools.

Until now, the oldest fossils that clearly belonged to Homo sapiens were discovered in Ethiopia. In 2003, researchers working at a site called Herto discovered a skull estimated to be between 160,000 and 154,000 years old.

A pair of partial skulls from another site, Omo-Kibish, dated to around 195,000 years of age, making these the oldest fossils of our species.

Findings such as these suggested that our species evolved in a small region perhaps in Ethiopia, or nearby in East Africa. After Homo sapiens arose, researchers believed, the species spread out across the continent.

Only much later roughly 70,000 years ago did a small group of Africans make their way to other continents.

Yet paleoanthropologists were aware of mysterious hominin fossils discovered in other parts of Africa that didnt seem to fit the narrative.

In 1961, miners in Morocco dug up a few pieces of a skull at a site called Jebel Irhoud. Later digs revealed a few more bones, along with flint blades.

Using crude techniques, researchers estimated the remains to be 40,000 years old. In the 1980s, however, a paleoanthropologist named Jean-Jacques Hublin took a closer look at one jawbone.

The teeth bore some resemblance to those of living humans, but the shape seemed strangely primitive. It did not make sense, Dr. Hublin, now at the Max Planck Institute, recalled in an interview.

Since 2004, Dr. Hublin and his colleagues have been working through layers of rocks on a desert hillside at Jebel Irhoud. Theyve found a wealth of fossils, including skull bones from five individuals who all died around the same time.

Just as important, the scientists discovered flint blades in the same layer as the skulls. The people of Jebel Irhoud most likely made them for many purposes, putting some on wooden handles to fashion spears.

Many of the flint blades showed signs of having been burned. The people at Jebel Irhoud probably lit fires to cook food, heating discarded blades buried in the ground below. This accident of history made it possible to use the flints as clocks.

Dr. Hublin and his colleagues used a method called thermoluminescence to calculate how much time had passed since the blades were burned. They estimated that the blades were roughly 300,000 years old. The skulls, which were discovered in the same rock layer, must have been the same age.

Despite the age of the teeth and jaws, anatomical details showed they nevertheless belonged to Homo sapiens, not to another hominin lineage such as the Neanderthals.

Resetting the clock on mankinds debut would be achievement enough. But the new research is also notable for the discovery of several early humans rather than just one, as so often happens, said Marta Mirazon Lahr, a paleoanthropologist at the University of Cambridge who was not involved in the new study.

We have no other place like it, so its a fabulous finding, she said.

The people at Jebel Irhoud shared a general resemblance to one another and to living humans. Their brows were heavy, their chins small, their faces flat and wide. But all in all, they were not so different from people today.

The face is that of somebody you could come across in the Metro, Dr. Hublin said.

The flattened faces of early Homo sapiens may have something to do with the advent of speech, speculated Christopher Stringer, a paleoanthropologist at the National Museum in London.

We really are at very early stages of trying to explain these things, Dr. Stringer said.

The brains of the inhabitants of Jebel Irhoud, on the other hand, were less like our own.

Although they were as big as modern human brains, they did not yet have its distinctively round shape. They were long and low, like those of earlier hominins.

Dr. Gunz, of the Max Planck Institute, said that the human brain may have become rounder at a later phase of evolution. Two regions in the back of the brain, known as the parietal lobe and the cerebellum, appear to have become enlarged over thousands of years.

I think what we see reflect adaptive changes in the way the brain functions, he said. Still, he added, no one knows how a rounder brain changed how we think.

The people of Jebel Irhoud were certainly sophisticated. They could make fires and craft complex weapons, such as wooden handled spears, needed to kill gazelle and other animals that grazed the savanna that covered the Sahara 300,000 years ago.

The flint is interesting for another reason: Researchers traced its origin to another site about 20 miles south of Jebel Irhoud. Early Homo sapiens, then, knew how to search out and to use resources spread over long distances.

Similar flint blades of about the same age have been found at other sites across Africa, and scientists have long wondered who made them. The fossils at Jebel Irhoud raise the possibility that they were made by early Homo sapiens.

And if thats true, Dr. Gunz and his colleagues argue, then our species may have been evolving as a network of groups spread across the continent.

John Hawks, a paleoanthropologist at the University of Wisconsin who was not involved in the new study, said that it was a plausible idea, but that recent discoveries of fossils from the same era raise the possibility that they were used by other hominins. The only way to resolved the question will be to find more hominin fossils from the time when our species emerged.

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Op vrijdag 9 juni 2017 20:59 schreef Begripvol het volgende:
Laten wij bij het begin beginnen.
Wat was het eerst?

Geest of stof?

Is stof uit geest ontstaan of is geest uit stof ontstaan?

Uit geest (energie) zijn gassen, vloeistoffen en stof (materie) ontstaan.

En uit een combinatie hiervan is leven ontstaan.

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Helaas voor de wetenschap, het was geen genenkwestie, maar een kwestie van opvoeding: de volwassenen hadden niet geleerd om te lopen, en bleven daardoor in een kruipstadium hangen.

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Meet Rare Sea Wolves Who Live Off The Ocean And Can Swim For Hours

Along the wild Pacific coast of British Columbia, there lives a population of the sea wolves. “We know from exhaustive DNA studies that these wolves are genetically distinct from their continental kin,” says McAllister. “They are behaviourally distinct, swimming from island to island and preying on sea animals. They are also morphologically distinct — they are smaller in size and physically different from their mainland counterparts,” says Ian McAllister, an award-winning photographer who has been studying these animals for almost two decades.

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Ancient infant ape skull sheds light on the ancestor of all humans and living apes

Anthropologists have waited decades to find the complete cranium of a Miocene ape from Africa—one that lived in the hazy period before the human lineage split off from the common ancestors we share with chimpanzees some 7 million years ago. Now, scientists in Kenya have found their prize at last: an almost perfectly preserved skull roughly the size of a baseball.