Tag: evolution

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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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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Fossil Holds New Insights Into How Fish Evolved Onto Land

The fossil of an early snake-like animal – called Lethiscus stocki – has kept its evolutionary secrets for the last 340-million years.

Now, an international team of researchers, led by the University of Calgary, has revealed new insights into the ancient Scottish fossil that dramatically challenge our understanding of the early evolution of tetrapods, or four-limbed animals with backbones.

Their findings have just been published in the research journal Nature.




It forces a radical rethink of what evolution was capable of among the first tetrapods,” said project lead Jason Anderson, a paleontologist and Professor at the University of Calgary Faculty of Veterinary Medicine (UCVM).

Before this study, ancient tetrapods – the ancestors of humans and other modern-day vertebrates – were thought to have evolved very slowly from fish to animals with limbs.

We used to think that the fin-to-limb transition was a slow evolution to becoming gradually less fish like,” he said.

But Lethiscus shows immediate, and dramatic, evolutionary experimentation. The lineage shrunk in size, and lost limbs almost immediately after they first evolved. It’s like a snake on the outside but a fish on the inside.

Using micro-computer tomography (CT) scanners and advanced computing software, Anderson and study lead author Jason Pardo, a doctoral student supervised by Anderson, got a close look at the internal anatomy of the fossilized Lethiscus.

After reconstructing CT scans its entire skull was revealed, with extraordinary results.

The anatomy didn’t fit with our expectations,” explains Pardo.

Many body structures didn’t make sense in the context of amphibian or reptile anatomy.” But the anatomy did make sense when it was compared to early fish.

We could see the entirety of the skull. We could see where the brain was, the inner ear cavities. It was all extremely fish-like,” explains Pardo, outlining anatomy that’s common in fish but unknown in tetrapods except in the very first.

The anatomy of the paddlefish, a modern fish with many primitive features, became a model for certain aspects of Lethiscus’ anatomy.

When they included this new anatomical information into an analysis of its relationship to other animals, Lethiscus moved its position on the ‘family tree’, dropping into the earliest stages of the fin-to-limb transition.

It’s a very satisfying result, having them among other animals that lived at the same time,” says Anderson.

The results match better with the sequence of evolution implied by the geologic record.

Lethiscus also has broad impacts on evolutionary biology and people doing molecular clock reproductions of modern animals,” says Anderson.

They use fossils to calibrate the molecular clock. By removing Lethiscus from the immediate ancestry of modern tetrapods, it changes the calibration date used in those analyses.

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