Tag: evolution

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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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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