Tag: evolution

Secret Life Of The Dodo Revealed

Scientists are piecing together clues about the life of the dodo, hundreds of years after the flightless bird was driven to extinction.

Few scientific facts are known about the hapless bird, which was last sighted in 1662.

A study of bone specimens shows the chicks hatched in August and grew rapidly to adult size.

The bird shed its feathers in March revealing fluffy grey plumage recorded in historical accounts by mariners.

Delphine Angst of the University of Cape Town, South Africa, was given access to some of the dodo bones that still exist in museums and collections, including specimens that were recently donated to a museum in France.




Her team analysed slices of bone from 22 dodos under the microscope to find out more about the bird’s growth and breeding patterns.

Before our study we knew very very little about these birds,” said Dr Angst.

Using the bone histology for the first time we managed to describe that this bird was actually breeding at a certain time of the year and was moulting just after that.

The scientists can tell from growth patterns in the bones that the chicks grew to adult size very rapidly after hatching from eggs around August.

This would have given them a survival advantage when cyclones hit the island between November and March, leading to a scarcity of food.

However, the birds probably took several years to reach sexual maturity, possibly because the adult birds lacked any natural predators.

The bones of adult birds also show signs of mineral loss, which suggests that they lost old damaged feathers after the breeding season.

Ancient mariners gave conflicting accounts of the dodo, describing them as having “black down” or “curled plumes of a greyish colour”.

The research could also shed light on the dodo’s extinction about 350 years ago, less than 100 years after humans arrived on the island.

Hunting was a factor in the dodo’s demise, but monkeys, deer, pigs and rats released on the island from ships probably sealed their fate.

Dodos laid their eggs in nests on the ground, meaning they were vulnerable to attack by feral mammals.

Dr Angst said the dodo is considered “a very big icon of animal-human induced extinction“, although the full facts are unknown.

It’s difficult to know what was the real impact of humans if we don’t know the ecology of this bird and the ecology of the Mauritius island at this time,” she explained.

So that’s one step to understand the ecology of these birds and the global ecosystem of Mauritius and to say, ‘Okay, when the human arrived what exactly did they do wrong and why did these birds became extinct so quickly’.

Julian Hume of the Natural History Museum, London, a co-researcher on the study, said there are still many mysteries surrounding the dodo.

Our work is showing the seasons and what was actually affecting the growth of these birds because of the climate in Mauritius,” he said.

The cyclone season, when often the island is devastated with storms – all the fruits and all the leaves are blown off the trees – is quite a harsh period for the fauna – the reptiles and the birds on Mauritius.

The dodo, which is related to the pigeon, evolved on Mauritius.

However, bone samples are rare, making it difficult to trace the evolutionary process.

Although many specimens of the dodo ended up in European museums, most were lost or destroyed in the Victorian era.

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Scientists Reveal What The First Flower Looked Like

ancient-flower

Until 140 million years ago, there were no flowers anywhere on Earth. Then, primitive flowers burst onto the scene, and flowering plants took over the world.

All living flowers today came from a single ancestor that lived about that time, according to a new study published Tuesday in the peer-reviewed British journal Nature Communications.

Scientists also reconstructed what they believe that first flower looked like: Somewhat similar to a water lily, with circles of broad petals around a center of protruding pollen spikes.




However, lead author Hervé Sauquet, an evolutionary biologist from Paris-Sud University, said it’s difficult to make a direct comparison with flowers of today: “All flowering plants have evolved and changed since that ancestor, that’s how evolution works,” he said.

So there is no single species or group of species that would have existed some long time ago and still exists today unchanged.

The origin and early evolution of flowering plants and especially their flowers have long been one of the biggest enigmas in biology, almost 140 years after Charles Darwin called their rapid rise in the Cretaceous “an abominable mystery.

The ancestral flower was bisexual, with both female (carpels) and male (stamens) parts, and with multiple whorls (concentric cycles) of petal-like organs, in sets of threes, according to the new study.

ancient-flower

About 20% of flowers today have such “trimerous” whorls, but typically fewer: lilies have two, magnolias have three.

These results call into question much of what has been thought and taught previously about floral evolution,” said study co-author Juerg Schoenenberger of the University of Vienna.

It has long been assumed that the ancestral flower had all organs arranged in a spiral.

Study co-author Maria von Balthazar, another University of Vienna scientist, said “the results are really exciting! This is the first time that we have a clear vision for the early evolution of flowers.

flower

No flower fossils exist from 140 million years ago, though, Sauquet said. The fossil record of flowering plants is still very incomplete, he said, and scientists have not yet found fossil flowers as old as the group itself. The earliest flower fossil is “only” 130 million years old.

As for where that original flower 140 million years ago came from, Sauquet said that “we’re not sure, and that remains one of the biggest mysteries in plant science. We know it came deep down from a common ancestor with all gymnosperms (conifers, cycads, ginkgo), maybe 310 million years ago.

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Did Humans And Neanderthals Interbreed?

In 1856, laborers working in a limestone quarry near Düsseldorf, Germany, unearthed bones that scientists initially thought belonged to a deformed human.

The skull was oval shaped, with a low, receding forehead, distinct brow ridges, and bones that were unusually thick.

Subsequent study revealed that the remains belonged to a previously unknown species of hominid, or early human ancestor, that was similar to our own species, Homo sapiens.

In 1864, the specimen was dubbed Homo neanderthalensis, after the Neander Valley where the skull was discovered.

Neanderthals were our closest evolutionary relatives. Their ancestors left Africa before modern humans, venturing into Europe as far back as 500,000 years ago, and were still there when our ancestors embarked on the same journey about 70,000 years ago.

Neanderthals and modern humans actually lived alongside each other in Europe for several thousand years before Neanderthals vanished some 30,000 years ago.




Their disappearance is one of the most enduring mysteries in all of human evolution.

But perhaps the most controversial theory for why there are no more Neanderthals is that they interbred with modern humans and the two lineages merged into one.

According to this idea, most of modern humanity—with the possible exception of some Africans who are descended from humans who never left Africa—is part Neanderthal.

Evidence for interbreeding comes largely from the study of fossils that, according to some scientists, show hybrid traits from both species.

For example, anthropologist Erik Trinkhaus believes that a 29,000-year-old skull discovered in Romania belonging to a modern human has an unusually long and flat forehead and unusually large molars.

There is some genetic evidence to support the interbreeding theory as well. In 2010, a team of scientists comparing a rough draft of the Neanderthal genome with that of modern humans concluded that most humans have 1 to 3 percent Neanderthal DNA.

The team suggested that the first opportunity for Neanderthal-human interbreeding probably occurred about 60,000 years ago, after modern humans had left Africa but before they had made significant inroads into Europe.

However, recent computer models suggest the genetic similarities shared between Neanderthals and modern humans could also be due to the two species sharing a recent common ancestor rather than hybridization.

Investigating The 580-Million-Year-Old Fossil With CT Scan

ediacaran

The Ediacaran biota (flourished 579-541 Mya) forms an important and unresolved episode in the history of life. These organisms arose soon after the end of the major glaciations of the Cryogenian, and persisted until the beginning of the Cambrian.

They are thought to include some of the earliest animals. Understanding the nature and lifestyle of the Ediacaran organisms is therefore important in tracing the potentially long fuse of the Cambrian explosion.

Yet they remain puzzling. This project will use micro-CT to investigate two particularly contentious structures found in rocks of this age, and assess how they fit into the larger picture of the origin of multicellular animals in this age.

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3 Animals That Mate For Life

Did you know there are members of the animal kingdom (other than humans) that mate for life?

In some cases of monogamous mates – for example, beavers – both parents care for their offspring.

When one partner in a monogamous pair dies, most surviving partners go on to find a new mate before the next breeding season.




Beavers

Adult beavers can weigh 40 pounds or more, and they mate for life during their third year. Their babies are called kits, and typically 1 to 4 are born in the spring.

Both parents care for their kits, who stay with them for about two years. The yearlings typically help care for the next litter. A beaver colony can consist of six or more individuals, including parents, yearlings, and kits.

Gibbons

Gibbons are the nearest relatives to humans that mate for life. They live in small, stable family groups with a monogamous mated pair and offspring under the age of 7.

Gibbon families are territorial and defend their territory with morning songs sung by the breeding pair.

Gibbons reach sexual maturity between 6 and 8 years of age. Females give birth to one baby at a time, and mating pairs produce an average of 5 to 6 offspring over their reproductive lifetimes.

Wolves

Wolves live in packs that are typically family groups including a male and female breeding pair and their offspring of varying ages. Only the breeding pair mates, and has one litter a year.

Wolves reach sexual maturity between 2 and 3 years of age, and once the youngsters are ready to mate, most leave their birth pack to start their own pack or join an existing pack.

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How Do Jumping Genes Cause Disease, Drive Evolution?

To address this problem, a team of Carnegie researchers developed new techniques to track the mobilization of jumping genes.

They found that during a particular period of egg development, a group of jumping-genes called retrotransposons hijacks special cells called nurse cells that nurture the developing eggs.

These jumping genes use nurse cells to produce invasive material that move into a nearby egg and then mobilize into the egg’s DNA. The research is published in the July 26 on-line issue of Cell.

Animals have unwittingly developed a powerful system to suppress jumping gene activity that uses small, non-coding RNAs called piRNAs, which recognize jumping genes and suppress their activity.

Occasionally, jumping genes still manage to move, suggesting that they employ some special tactics to escape piRNA control.

However, tracking the mobilization of jumping genes to understand their tactics has been a daunting task.




The Carnegie team developed approaches to track the movements of jumping genes using the fruit fly Drosophila melanogaster.

To facilitate their investigation, they disrupted piRNA suppression to increase the activity of these jumping genes and then monitored the movement of them during the egg-development process.

This led to their discovery on the tactic that allows jumping genes to move.

Carnegie co-author Zhao Zhang explained: “We were very surprised that the these jumping genes barely moved in stem cells that produce developing egg cells, possibly because the stem cells would only have two copies of the genome for these jumping genes to use.

“Instead, these moving elements used the supporting nurse cells, which could provide up to thousands copies of the genome per cell, as factories to massively manufacture virus-like particles capable of integration.

“However, they didn’t integrate into nurse cells where they were produced. Rather, they waited while they were transported into an interconnected egg cell, and then added hundreds, if not thousands, of new copies of themselves into the egg DNA.

“Our research shows how parasitic genetic elements can time their activity and distinguish between different cell types to robustly propagate to drive evolutionary change and cause disease.

My group has found that egg development in mammals uses many of the same mechanisms as in the fruit fly, such as feeding the developing egg using nurse cells.

“So the Zhang group’s findings are likely to be important for understanding mammalian evolution and disease as well,” commented Allan Spradling, who is a pioneer researcher on studying the egg development in both fruit fly and mammals and a longtime scientist at Carnegie’s Department of Embryology.

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European Colonization Of Americas Wiped Out Native Dogs Alongside Indigenous People

European colonisers arriving in the Americas almost totally wiped out the dogs that had been kept by indigenous people across the region for thousands of years.

The original American dogs were brought across the land bridge that once connected North America and Siberia over 10,000 years ago, by their human owners.

These dogs subsequently spread throughout North and South America, but genetic analysis has revealed they were ultimately replaced by dogs imported from Europe.

This study demonstrates that the history of humans is mirrored in our domestic animals,” said Professor Greger Larson, director of the palaeogenomics and bio-archaeology research network at the University of Oxford and senior author of the research.

People in Europe and the Americas were genetically distinct, and so were their dogs. And just as indigenous people in the Americas were displaced by European colonists, the same is true of their dogs.




In their paper, published in the journal Science, the researchers compared genetic information from dozens of ancient North American and Siberian dogs spanning a period of 9,000 years.

Their analysis showed the dogs persisted for a long time but ultimately vanished, which to Dr Laurent Frantz from Queen Mary University of London said suggests “something catastrophic must have happened”.

It is fascinating that a population of dogs that inhabited many parts of the Americas for thousands of years, and that was an integral part of so many Native American cultures, could have disappeared so rapidly,” said Dr Frantz, who was also a senior author of the study.

Today, few modern dogs possess any genetic traces of the ancient breeds.

The researchers suggested the dogs’ near-total disappearance from the region was likely a result of both disease and cultural changes brought over by Europeans.

It is possible, for example, that European colonists discouraged the sale and breeding of the dogs kept by indigenous Americans.

It is known how indigenous peoples of the Americas suffered from the genocidal practices of European colonists after contact,” said Kelsey Witt, who led part of the genome work as a graduate student at the University of Illinois.

Bizarrely, one of the only traces of genetic information from “pre-contact” dogs can be found in a transmissible tumour that spreads between dogs known as CTVT.

It’s quite incredible to think that possibly the only survivor of a lost dog lineage is a tumour that can spread between dogs as an infection,” added Maire Ní Leathlobhair, co-first author, from the University of Cambridge.

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Neanderthals: We Were Not Alone

Neanderthal spear.

The three human subspecies known to have hybridised to produce the present human population of the planet, Neanderthals, Homo sapiens and Denisovans, last had a common ancestor more than half a million years ago.

Until now it has been assumed that the only branch of her descendants to think symbolically was us, Homo sapiens.

In fact, until the development of sequencing techniques sensitive enough to work on ancient DNA, it was thought that the other two species had died out entirely, rather than leaving portions of their genome in European and Melanesian populations respectively.

But the discovery, reported last week, of palaeolithic art at four sites in Spain that dates from the time when the peninsula was occupied only by Neanderthals, shows that they worked with symbols of stone and paint.




We have no idea what these markings mean. That is in the nature of symbolism, and indeed of language: the meaning of a sound, or a marking on the wall, is given by the community that uses it; it can’t be read by outsiders.

We already know that Neanderthals were anatomically equipped for speech; their use of painted symbols suggests that they could make audible symbols and not just visible ones.

One of the effects of the discovery reported last week has been to push one of the standard tropes of science fiction 40,000 years into our past.

That was when Homo sapiens met Homo neanderthalensis, another symbolically intelligent species, and our ancestors realised that they were not alone in the universe.

We can deduce that these encounters must have been reasonably peaceable, because Europeans and all other populations outside Africa carry some Neanderthal DNA.

Animal studies have shown that almost all of the capacities that we once considered uniquely human are shared with animals.

Some birds are capable of choosing and using wooden tools, chimpanzees use stone ones, and even sheep recognise one another as individuals.

Many creatures communicate with sounds, as well as with smells and expressions. But only humans have symbolic language, so far as we know.

Only humans form concepts and combine them as if they were physical tools before using them to shape the world. Now it seems that to be human in this sense is an older and stranger thing than anyone had earlier dared to dream.

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Oldest Fossils Of Homo Sapiens Found in Morocco

jaw

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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