Tag: evolution

Oldest Fossils Of Homo Sapiens Found in Morocco

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Fossils discovered in Morocco are the oldest known remains of Homo sapiens, scientists reported, a finding that rewrites the story of mankind’s origins and suggests that our species evolved in multiple locations across the African continent.

Until now, the oldest known fossils of our species dated back just 195,000 years. The Moroccan fossils, by contrast, are roughly 300,000 years old.




Remarkably, they indicate that early Homo sapiens had faces much like our own, although their brains differed in fundamental ways.

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.

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Chimpanzees Aren’t Super Strong But Their Muscles Are More Powerful Than A Human’s

Since the 1920’s, some researchers and studies have suggested that chimps are ‘super strong’ compared to humans. These past studies implied that chimps’ muscle fibers, the cells that make up muscles are superior to humans’.

But a new study has found that contrary to this belief, a chimp muscles’ power output is just about 1.35 times higher than human muscle of similar size.

A difference the researchers call ‘modest‘ compared with historical, popular accounts of chimp ‘super strength’ being many times stronger than humans.




chimp

If the long-standing, assumption about chimpanzee’s exceptional strength was true, it ‘would indicate a significant and previously unappreciated evolutionary shift in the force and/or power-producing capabilities of skeletal muscle’ in either chimps or humans, whose lines diverged about 7 or 8 million years ago.

The authors of the study concluded that, contrary to some long-standing hypotheses, evolution has not altered the basic force, velocity or power-producing capabilities of skeletal muscle cells to induce the marked differences between chimpanzees and humans in walking, running, climbing and throwing capabilities.

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How Birds Survived The Dinosaur Apocalypse

When nearly every dinosaur went extinct 66 million years ago, the only ones that survived were those that had shrunk—that is, the birds.

Today, there are 10,000 species of these feathered fliers, making them the most diverse of all the four-limbed animals.

A new study reveals why this lineage has been so successful: Birds started downsizing well before the rest of the dinosaurs disappeared.

This is a very impressive piece of work and by far the most comprehensive analysis of dinosaur body size that has been conducted,” says Stephen Brusatte, a paleontologist at the University of Edinburgh in the United Kingdom, who was not involved in the research.

The study shows that birds didn’t just become small suddenly, but were the end product of a long-term trend of body size decline that took many tens of millions of years.

Dinosaurs were small in the beginning. About 230 million years ago, most weighed between 10 and 35 kilograms and were as big as a medium-sized dog.




But many species soon soared to tractor-trailer proportions, reaching 10,000 kilograms within 30 million years.

Later on, dinosaurs like the mighty Argentinosaurus, which stretched some 35 meters from nose to tail, weighed in at a staggering 90,000 kilograms.

Although many dinosaurs were getting bigger and bulkier over millions of years, one group seems to have hedged its bets on body size: the maniraptorans, feathered dinos that include Velociraptor of Jurassic Park fame and that eventually gave rise to the birds.

To pin down how dinosaur size changed over time, a team led by Roger Benson, a paleontologist at the University of Oxford in the United Kingdom, estimated the body size of 426 different species, using the thickness of their fossilized hind leg bones as a proxy for their overall weight.

The team found that although all dinosaur groups rapidly changed size at the beginning of dinosaur evolution—primarily by getting bigger—that trend slowed down fairly quickly in almost all groups.

For the most part, the dinos that got big stayed that way.

The exception was the maniraptorans, which continued to evolve bigger and smaller species as they expanded into an ever wider variety of ecological niches over a period of 170 million years.

When an asteroid hit Earth 66 million years ago, only those feathered maniraptorans that had downsized to about 1 kilogram or so—the birds—were able to survive, probably because their small size allowed them to adapt more easily to changing conditions, the team concludes online today in PLOS Biology.

The researchers argue that being small made it easier for maniraptorans to adapt to a wider variety of habitats, whereas the rest of the dinosaurs, encumbered by their huge bodies and enormous food requirements, simply didn’t make it.

This size reduction was essential for the evolution of flight, says Luis Chiappe, a paleontologist at the Natural History Museum of Los Angeles County in California, who was not involved in the study.

Flight is easier for smaller animals” because it is “a lot less energetically demanding,” he says.

And during all those millions of years when maniraptorans were changing body size more quickly than other dinos, Chiappe says, “they were experimenting with various degrees of birdness.

The really interesting story,” Brusatte adds, “isn’t so much to do with how some dinosaurs got so huge, but rather how birds and their close relatives got so small.

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180 Million-Year-Old Crocodile Had Dolphin-Like Features, Tells Tale Of ‘Missing Link’

The discovery of an ancient type of crocodile that lived during the Jurassic Period, at the height of the age of dinosaurs, has shed new light on the species.

The 180 million-year-old fossil, named Magyarosuchus fitosi, shows that some ancient crocodiles evolved to have dolphin-like features.

The fossil was analyzed recently and found to have abnormal vertebra in its tail fin, effectively combining two different families of crocodiles – one that had limbs for walking on the surface and a bone-like protective armor on its back and one that had tail fins and flippers to aid with swimming in the ancient seas.




This fossil provides a unique insight into how crocodiles began evolving into dolphin and killer whale-like forms more than 180 million years ago,” Dr. Mark Young, of the University of Edinburgh’s School of GeoSciences, said in a statement.

The presence of both bony armour and a tail fin highlights the remarkable diversity of Jurassic-era crocodiles.

The new finding was made after the team of paleontologists analyzed the bones, which had been kept at a museum in Budapest. The fossil was originally discovered in Hungary in the Gerecse Mountains.

With an estimated body length of 4.67–4.83 m [15 feet – 16 feet] M. fitosi is the largest known non-metriorhynchid metriorhynchoid,” the study’s abstract reads.

The abstract continues: “The combination of retaining heavy dorsal and ventral armors and having a slight hypocercal tail is unique, further highlighting the mosaic manner of marine adaptations in Metriorhynchoidea.”

In addition, the newly-discovered species had large, pointed teeth, used to grasp prey, the statement added.

The study was published on May 10, in PeerJ, a peer-reviewed scientific journal.

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Blind Fish In Dark Caves Shed Light On The Evolution Of Sleep

Out of the approximately 3 billion letters of DNA that make up your genome, there are about a 100 letters that neither of your parents possess.

These are your own personal mutations. The machinery that copies DNA into new cells is very reliable, but it is not perfect. It makes errors at a rate equivalent to making a single typo for every 100 books filled with text.

The sperm and egg cells that fused to form you carried a few such mutations, and therefore so do you.

Changes to DNA are more likely to be disruptive than beneficial, simply because it is easier for changes to mess things up than to improve them.

This mutational burden is something that all life forms have to bear. In the long run, individuals that carry harmful mutations will, on average, produce fewer offspring than their peers.




Over many generations, this means that the mutation will dwindle in frequency. This is how natural selection is constantly ‘weeding out’ disruptive mutations from our genomes.

There is a flip side to this argument, and it is the story of the blind cave fish. If a mutation disrupts a gene that is not being used, natural selection will have no restoring effect.

This is why fish that adapt to a lifestyle of darkness in a cave tend to lose their eyes. There is no longer any advantage to having eyes, and so the deleterious mutations that creep in are no longer being weeded out.

Think of it as the ‘use it or lose it’ school of evolution.

A world without light is quite an alien place. There are many examples of fish that live in completely dark caves.

Remarkably, if you compare these fish to their relatives that live in rivers or in the ocean, you find that the cavefish often undergo a similar set of changes. Their eyes do not fully develop, rendering them essentially blind.

They lose pigmentation in their skin, and their jaws and teeth tend to develop in particular ways.

This is an example of what is known as convergent evolution, where different organisms faced with similar ecological challenges also stumble upon similar evolutionary solutions.

The changes mentioned above are all about appearance, but what about changes in behavior? In particular, when animals sleep, they generally line up with the day and night cycle.

In the absence of any daylight, how do their sleep patterns evolve?

A recent paper by Erik Duboué and colleagues addressed this question by comparing 4 groups of fish of the same species Astyanax mexicanus.

Three of the populations (the Pachón, Tinaja, and Molino) were blind cavefish that inhabited different dark caves, whereas the fourth was a surface-dwelling fish.

The authors defined sleep for their fish to be a period of a minute or more when the fish were not moving. They checked that this definition met the usual criteria.

Sleeping fish were harder to wake up, and fish that were deprived of sleep compensated by sleeping more over the next 12 hours (these are both situations that any college student is familiar with).

The researchers also tracked the speeds of all the fish, and found that, while they were awake, the cavefish moved faster or just as fast as the surface fish.

This means that it’s not that the cavefish are constantly sleep deprived and in a lethargic, sleepy state. They are just as wakeful as the surface fish (if not more so), and genuinely need less sleep.

These three cavefish populations all evolved independently, and yet they have converged on remarkably similar sleep patterns.

To study the genetics of this phenomenon, the researchers cross-bred the surface fish with the cavefish. The cave dwellers and surface fish all belong to the same species, which means that they can have viable offspring.

They found that the mixed offspring (Pachón x surface and Tinaja x surface) had a reduced need for sleep that was indistinguishable from that of their cave-dwelling parent.

Thus sleep reduction is clearly a genetic trait, and it is a dominant trait (Dominant traits are present in the offspring if they are inherited from just one parent. A recessive trait, on the other hand, will only be present if it is inherited from both parents.)

Unlocking the secrets of sleep is inherently cool science, and it also has the potential to help people suffering from sleep disorders.

Who knows, it may even lead to the superpower of doing away with sleep altogether.

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Giant Penguins, As Tall As People, Lived In New Zealand Millions Of Years Ago

Scientists have discovered the fossil remains of an ancient giant penguin with a body length of about 5.8 feet that roamed the waters off New Zealand soon after the dinosaurs’ demise.

Kumimanu biceae, newly described in the journal Nature Communications, is one of the oldest penguin species found yet – and it adds a surprising twist to what researchers thought they knew about penguin evolution.

The K. biceae bones were discovered on a beach in New Zealand many years ago, embedded in rock.

So obscured that at first the scientists thought they had belonged to a turtle, said lead author Gerald Mayr, an ornithologist at Senckenberg Research Institute and Natural History Museum Frankfurt in Germany.

They painstakingly cleared rock away from the bones, revealing that the fossil was actually of an enormous penguin — roughly 1½ times the size of the emperor penguin, the largest living species today.




At about 223 pounds and 5 feet, 9 inches in body length, K. biceae was the size of a human man.

I was amazed at how big it actually was,” said Mayr, whose co-authors in New Zealand brought him in to examine the fossil.

K. biceae was dated to 55.5 million to 59.5 million years ago, which puts it in the Paleocene epoch. Back then it was so warm that even Antarctica hosted subtropical waters

In New Zealand, the birds probably dined on fish as they do today, but may have speared them with long beaks.

The strangest thing about these penguins was not just their size, although that is pretty exceptional. What caught researchers’ eye was how old they were — how early they appeared in the penguin family tree.

There have been plenty of other oversized penguins in the fossil record, but those species came tens of millions of years later.

Leading many researchers to figure that it probably took time for penguins to evolve into megafaunal species.

The partly prepared skeleton of the giant penguin. The rectangles emphasize the humerus and a bone from the shoulder girdle, which are shown separated from the original bone cluster (G. Mayr/Senckenberg Research Institute)

This new fossil shows that penguins had grown to enormous proportions very quickly after the dinosaurs were killed off around 66 million years ago.

On top of that, K. biceae seems to have more primitive features than those later large penguins, and it appears to have developed into a large species independently of the others.

That time frame – penguins’ ancestors losing flight and gaining the ability to swim, and then getting very, very big, all in about 5 million years – seems really, really fast, the scientists said.

It could potentially mean that the flying ancestors of penguins coexisted with dinosaurs for a good long while before the asteroid wiped them out, though that’s just a hypothesis for now, Mayr said.

Aside from the speed with which it seems to have happened, this super-sizing is to be expected, the ornithologist said.

After all, once you don’t have to spend the energy to get airborne, you don’t have to watch your weight as closely.

And there are certain advantages to going up a few sizes: you can muscle out the competition for food or territory, and you might be much harder for predators to kill.

So what happened to these feathered heavyweights?

That disappearance may have something to do with the rise of marine mammals such as seals and toothed whales, Mayr said.

As they began to flourish in the fossil record, those big-boned ocean birds started fading out.

It’s unclear whether there’s a causal relationship there, and if so, what one would be, Mayr said. Perhaps marine mammals competed with large penguins for food, or for breeding grounds.

Perhaps they actually hunted the jumbo penguins.

For now, this is just one specimen. Scientists hope to find more of them, especially with their skulls and beaks intact.

There were also plenty of smaller penguins that appear to have coexisted with this giant penguin, and it’s unclear exactly what the relationships were between those species.

We hope there will be future finds,” Mayr said. “There are many questions.”

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Which Came First, The Lizard Or The Egg?

Evolution has been caught in the act, according to scientists who are decoding how a species of Australian lizard is abandoning egg-laying in favor of live birth.

Along the warm coastal lowlands of New South Wales, the yellow-bellied three-toed skink lays eggs to reproduce.

But individuals of the same species living in the state’s higher, colder mountains are almost all giving birth to live young.

Only two other modern reptiles—another skink species and a European lizard—use both types of reproduction.

Evolutionary records shows that nearly a hundred reptile lineages have independently made the transition from egg-laying to live birth in the past, and today about 20 percent of all living snakes and lizards give birth to live young only.

But modern reptiles that have live young provide only a single snapshot on a long evolutionary time line, said study co-author James Stewart, a biologist at East Tennessee State University.




The dual behavior of the yellow-bellied three-toed skink therefore offers scientists a rare opportunity.

One of the mysteries of how reptiles switch from eggs to live babies is how the young get their nourishment before birth.

In mammals a highly specialized placenta connects the fetus to the uterus wall, allowing the baby to take up oxygen and nutrients from the mother’s blood and pass back waste.

In egg-laying species, the embryo gets nourishment from the yolk, but calcium absorbed from the porous shell is also an important nutrient source.

Some fish and reptiles, meanwhile, use a mix of both birthing styles. The mother forms eggs, but then retains them inside her body until the very last stages of embryonic development.

The shells of these eggs thin dramatically so that the embryos can breathe, until live babies are born covered with only thin membranes—all that remains of the shells.

This adaptation presents a potential nourishment problem: A thinner shell has less calcium, which could cause deficiencies for the young reptiles.

Stewart and colleagues, who have studied skinks for years, decided to look for clues to the nutrient problem in the structure and chemistry of the yellow-bellied three-toed skink’s uterus.

Both birthing styles come with evolutionary tradeoffs: Eggs are more vulnerable to external threats, such as extreme weather and predators, but internal fetuses can be more taxing for the mother.

For the skinks, moms in balmier climates may opt to conserve their own bodies’ resources by depositing eggs on the ground for the final week or so of development.

Moms in harsh mountain climates, by contrast, might find that it’s more efficient to protect their young by keeping them longer inside their bodies.

In general, the results suggest the move from egg-laying to live birth in reptiles is fairly common—at least in historic terms—because it’s relatively easy to make the switch, Stewart said.

We tend to think of this as a very complex transition,” he said, “but it’s looking like it might be much simpler in some cases than we thought.

The skink-evolution research was published online August 16 by the Journal of Morphology.

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The Evolution Of Forests And Trees In Devonian Period

The vascular plant emerged around 400 million years ago and started Earth’s forest-building process during the Silurian geologic period.

Although not yet a “true” tree, this new member of the terrestrial plant kingdom became the perfect evolutionary link (and the largest plant species) with developing tree parts and considered the first proto-tree.

Vascular plants developed the ability to grow large and tall with massive weight needed for the support of a vascular internal plumbing system.




The First Trees

The earth’s first real tree continued to develop during the Devonian period and scientists think that tree was probably the extinct Archaeopteris.

These tree species followed later by other tree types became the definitive species comprising a forest during the late Devonian period.

As mentioned, they were the first plants to overcome the biomechanical problems of supporting additional weight while delivering water and nutrients to fronds (leaves) and roots.

Entering the Carboniferous period around 360 million years ago, trees were prolific and a major part of the plant life community, mostly located in coal-producing swamps.

Trees were developing the parts that we immediately recognize today. Of all the trees that existed during the Devonian and Carboniferous, only the tree fern can still be found, now living in Australasian tropical rainforests.

If you happen to see a fern with a trunk leading to a crown, you have seen a tree fern.

During that same geologic period, now extinct trees including clubmoss and giant horsetail were also growing.

Our Present Evolutionary Forest

Few dinosaurs ever made a meal on hardwood leaves because they were rapidly disappearing before and during the beginning of the new “age of hardwoods” (95 million years ago).

Magnolias, laurels, maples, sycamores and oaks were the first species to proliferate and dominate the world.

Hardwoods became the predominant tree species from mid-latitudes through the tropics while conifers were often isolated to the high-latitudes or the lower latitudes bordering the tropics.

Not a lot of change has happened to trees in terms of their evolutionary record since the palms made their first appearance 70 million years ago.

Fascinating are several tree species that simply defy the extinction process and show no indication that they will change in another dozen million years.

Ginkgo was mentioned earlier but there are others: dawn redwood, Wollemi pine, and monkey puzzle tree.

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More Than 90 Percent Of All Organisms That Have Ever Lived On Earth Are Extinct

As new species evolve to fit ever changing ecological niches, older species fade away. But the rate of extinction is far from constant.

At least a handful of times in the last 500 million years, 50 to more than 90 percent of all species on Earth have disappeared in a geological blink of the eye.

Though these mass extinctions are deadly events, they open up the planet for new life-forms to emerge.

Dinosaurs appeared after one of the biggest mass extinction events on Earth, the Permian-Triassic extinction about 250 million years ago.

The most studied mass extinction, between the Cretaceous and Paleogene periods about 65 million years ago, killed off the dinosaurs and made room for mammals to rapidly diversify and evolve.




Scientists have narrowed down several of the most likely causes of mass extinction. Flood basalt events (volcano eruptions), asteroid collisions, and sea level falls are the most likely causes of mass extinctions, though several other known events may also contribute.

These include global warming, global cooling, methane eruptions and anoxic events–when the earth’s oceans lose their oxygen.

Both volcano eruptions and asteroid collisions would eject tons of debris into the atmosphere, darkening the skies for at least months on end.

Starved of sunlight, plants and plant-eating creatures would quickly die.

Space rocks and volcanoes could also unleash toxic and heat-trapping gases that—once the dust settled—enable runaway global warming.

An extraterrestrial impact is most closely linked to the Cretaceous-Paleogene extinction event, one of the five largest in the history of the world, and the most recent.

A huge crater off Mexico’s Yucatán Peninsula is dated to about 65 million years ago, coinciding with the extinction.

Global warming fueled by volcanic eruptions at the Deccan Flats in India may also have aggravated the event. Dinosaurs, as well as about half of all species on the planet, went extinct.

Massive floods of lava erupting from the central Atlantic magmatic province about 200 million years ago may explain the Triassic-Jurassic extinction.

About 20 percent of all marine families went extinct, as well as most mammal-like creatures, many large amphibians, and all non-dinosaur archosaurs.

An asteroid impact is another possible cause of the extinction, though a telltale crater has yet to be found.

The Permian-Triassic extinction event was the deadliest: More than 90 percent of all species perished. Many scientists believe an asteroid or comet triggered the massive die-off, but, again, no crater has been found.

Another strong contender is flood volcanism from the Siberian Traps, a large igneous province in Russia. Impact-triggered volcanism is yet another possibility.

Starting about 360 million years ago, a drawn-out event eliminated about 70 percent of all marine species from Earth over a span of perhaps 20 million years.

Pulses, each lasting 100,000 to 300,000 years, are noted within the larger late Devonian extinction.

Insects, plants, and the first proto-amphibians were on land by then, though the extinctions dealt landlubbers a severe setback.

Today, many scientists think the evidence indicates a sixth mass extinction is under way. The blame for this one, perhaps the fastest in Earth’s history, falls firmly on the shoulders of humans.

By the year 2100, human activities such as pollution, land clearing, and overfishing may drive more than half of the world’s marine and land species to extinction.

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Life On Earth May Have Begun 300 Million Years Earlier Than Previously Thought

Living organisms may have existed on Earth as long as 4.1bn years ago – 300m years earlier than was previously thought, new research has shown.

If confirmed, the discovery means life emerged a remarkably short time after the Earth was formed from a primordial disc of dust and gas surrounding the sun 4.6bn years ago.

Researchers discovered the evidence in specks of graphite trapped within immensely old zircon crystals from Jack Hills, Western Australia.

Atoms in the graphite, a crystalline form of carbon, bore the hallmark of biological origin. They were enriched with 12C, a “light” carbon isotope, or atomic strain, normally associated with living things.




It suggests that a terrestrial biosphere had emerged on Earth as early as 4.1bn years ago, said the scientists writing in the journal Proceedings of the National Academy of Sciences.

The US scientists, led by Dr Mark Harrison, from the University of California at Los Angeles, said the graphite was completely encased in zircon that was crack-free and could not have been contaminated despite the passing of aeons.

They wrote: “This study extends the terrestrial carbon isotope record around 300m years beyond the previously oldest-measured samples from south-west Greenland.

Some non-biological processes could also produce the light form of carbon, notably meteorite impacts, said the researchers.

But the amount of extra-terrestrial carbon needed to account for the findings made meteorites an unlikely source.

A biogenic origin seems at least as plausible,” the scientists added.

Confirming the connection with early life would represent “a potentially transformational scientific advance” they said.

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