Tiny molecules drove the evolution of the vertebrates

Blogging on Peer-Reviewed ResearchThe spinal column that runs down your back is an identity badge that signifies your membership among the vertebrates – animals with backbones. Vertebrates have arguably the most complex bodies and genomes of any animal group and certainly, our lineage has come a long way from its last common ancestor.

TigerThe closest evolutionary cousins of the vertebrates are simple aquatic creatures such as the jawless lancelets and the sac-like, immobile sea squirts. How did these simple body plans diversify into the vast array of sophisticated forms wielded by today’s fish, amphibians, reptiles and mammals?

Gene number

Many scientists have suggested that the answer lies in the number of our genes. At three different points, the vertebrate genome (its full suite of genes) experienced a massive jump in size as huge chunks of genes – possibly the entire lot – were duplicated. The first of these coincided with the origins of the group itself and the second happened alongside the rise of the first jawed fish, setting them and their descendants aside from more ancient jawless forms like the lampreys.

So far, there seems to be a tidy connection between gene number and complexity, but the third round of duplication is a bit of a stumbling block. It happened at some point during the evolution of the bony fishes and while this group proceeded to radiate into a multitude of different shapes, their basic body plan stayed essentially the same. No big jump in complexity there.

Indeed, as the full genome sequences of more and more species are revealed, it’s becoming clear that the basic genetic toolkit that controls the development of animal bodies is remarkably consistent across the kingdom. Even the genome of a sea anemone, one of the simplest and most ancient animals on Earth, is strikingly similar to that of vertebrates.

In this light, it’s looking increasingly unlikely that the advent of new genes can account for the large rise in vertebrate complexity. Now, Alysha Heimberg and colleagues from Dartmouth College have proposed a new theory, centred around tiny molecules called microRNAs.

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Testing, not studying, makes for strong long-term memories

Blogging on Peer-Reviewed ResearchIt’s a familiar scene – the wee hours of the morning are ticking away and your head is bent over a stack of notes, desperately trying to cram as much knowledge into your head before the test in the morning.

Exam roomBecause of the way our education system works, this process of hard studying has become almost synonymous with the act of learning, and the inevitable tests and exams that bookend this ordeal merely assess how much information has stuck.

But a new study reveals that the tests themselves do more good for our ability to learn that the many hours before them spent relentlessly poring over notes and textbook. The act of repeatedly retrieving and using learned information drives memories into long-term storage, while repetitive revision produced almost no benefits.

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Earliest bat shows flight developed before echolocation

Blogging on Peer-Reviewed ResearchTheir heads and bodies of bats have amassed an extraordinary array of adaptations that have make them lords of the night sky. Today, the thousand-plus types of bats make up a fifth of living mammal species. Richard Dawkins once described the evolution of bats as “one of the most enthralling stories in all natural history” and as of this week, the story has a clearer beginning.

OnychonycterisThe success of bats hinges on two key abilities: their mastery of flight, a feat matched only by birds and insects; and echolocation, the ability to navigate their way through pitch-blackness by timing the reflections of high-pitched squeaks. For evolutionary scientists, the big question has always been: which came first?

The ‘clawed bat’

Until now, fossil bats haven’t provided any clues for all of them show signs of both echolocation and flight. But a stunning new fossil, discovered by Nancy Simmons from the American Museum of Natural History is an exception and it provides a categorical answer to the long-running debate – the earliest bats could fly but could not echolocate.

The new creature hails from the Green River in Wyoming and is known as Onychonycteris, meaning “clawed bat”. Its fossils date back to about 52.5 million years ago and by comparing it to other prehistoric bats, Simmons found that it is the most ancient member of this lineage so far discovered. It acts as a ‘missing link’ in bat evolution, much like the famous Archaeopteryx hinted that birds may have evolved from dinosaurs.

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Third cousin couples have the most children and grandchildren

Blogging on Peer-Reviewed ResearchMarriage between closely related cousins is a heavy taboo in many cultures and its critics often cite the higher risk of genetic diseases associated with inbreeding. That risk is certainly apparent for very close relatives, but a new study from Iceland shows that very distant relatives don’t have it easy either. In the long run, they have just as few children and grandchildren as closely related ones.

Shuffling the genetic deck

Indian marriageSex chromosomes aside, every person has two copies of each gene, one inherited from their father and one by their mother. Not every gene will be in correct working order, but there’s a good chance that a faulty copy will be offset by a functional one from the other parent.

However, if two parents are closely related, there’s a higher-than-average chance that they will already share some of the same genes and a similarly increased chance that their child will receive two defective copies. That can be very bad news indeed and in cases where important genes are affected, the results can include miscarriage, birth defects or early death.

Sex, then, is a shuffling of their genetic deck and theoretically the more closely related the partners are, the greater the chance that their child will be dealt a dud hand. And yet, some studies have found that some closely related couples actually do better than distant relatives in terms of the number of children they manage to raise. This trend is certainly unexpected and the big question is whether it is the result of biology or money.

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Malawi cichlids – how aggressive males create diversity

Blogging on Peer-Reviewed ResearchCertain groups of animals show a remarkable capacity for quickly evolving into new species to seize control of unexploited niches in the environment. And among these ecological opportunists, there are few better examples than the cichlids, a group of freshwater fishes that are one of the most varied group of back-boned animals on the planet.

Malawi cichlidsIn the words of Edward O. Wilson, the entire lineage seems “poised to expand.” The Great Lakes of Africa – Tanganyika, Malawi and Victoria – swarm with a multitude of different species; Lake Malawi alone houses over 500 that live nowhere else in the world.

All of these forms arose from a common ancestor in a remarkably short span of time. Now, a new study suggests that this explosive burst of diversity has been partly fuelled by rivalry between hostile males.

Michael Pauers of the Medical College of Wisconsin found that male cichlids have no time for other males that look like them and will bite, butt and threaten those who bear the same colour scheme. In doing so, they encourage diversity in the lake since mutant males with different tints are less likely to be set upon by territorial defenders.

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Colour-changing chameleons evolved to stand out, not blend in

Blogging on Peer-Reviewed ResearchChameleons aren’t exactly known for being showy. Indeed, they are so synonymous with blending in that we use the term ‘social chameleon’ to refer to people who are at home in any social setting. But new research suggests that this reputation needs a rethink. The chameleon’s ability to change colour evolved not to blend in, but to stand out.

Chameleon headChameleons are a group of small lizards that are almost synonymous with camouflage. Common folklore has it that their vaunted ability to change their skin colour allows them to go undetected in a variety of environments.

Certainly, their default colours match their surroundings well. But Devi Stuart-Fox and Adnan Moussalli from South Africa have found that the changing hues they are best known for evolved for communication not disguise. They allow chameleons to make themselves incredibly but temporarily noticeable to mates and rivals, while remaining inconspicuous for the rest of the time.

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Averaging photos creates infallible face recognition tool

Blogging on Peer-Reviewed ResearchCompare a photo of yourself all cleaned up for a night out with another one first thing the next morning, and you’ll begin to appreciate the problems that people working on face recognition software encounter.

DiazWhile some unfeasibly lucky people look great from all angles, most of us have to contend with a lottery of lighting conditions, odd angles, stupid expressions, stupider poses and the ravages of age. Faced with this unavoidable variability, it’s no wonder that automatic software flounder when tasked with comparing images to stock photos, like those in passports.

Now, Rob Jenkins and Mike Burton from the University of Glasgow have beaten the problem by creating a face recognition system that, so far, has proved to be 100% accurate. This level of accuracy is unheard of in the technological world. It is matched only by that most sophisticated of computers – the human brain – and indeed, it’s the brain that provided Jenkins and Burton with the inspiration for their method.

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Editing Ebola – how to tame one of the world’s deadliest viruses

Blogging on Peer-Reviewed ResearchIn a list of the most dangerous jobs in the world, ‘Ebola researcher’ must surely rank near the top. But if new research is anything to go by, it may soon fall several places. An international team of scientists have recently found a way to neuter the virus, making it easy to study without risking your life. The altered virus looks like Ebola and behaves like Ebola, but it can’t kill like Ebola. It should make studying the virus easier and most importantly, safer.

Ebola virusThe Ebolaviruses and their cousins, the closely related Marburg family, have a chilling and deserved reputation. In some outbreaks, 90% of those infected die from massive blood loss. There is no approved antiviral treatment. There is no vaccine. And given that it’s almost a rite du passage for infectious disease scientists to contract the contagion they study, working with Ebola is a delicate affair.

Maximum protection

Ebola research requires the highest level of safety possible – the “Biosafety Level-4” laboratory. The stand-alone facilities are designed to be easily sealed and impervious to animals and insects. All routes in and out, including all pipes and ventilation, are peppered with multiple airlocks, showers and rooms designed to prevent any chance of escaping viruses.

There are very few people who are qualified to work in such a prohibitive environment and those that do have to wear a Hazmat suit at all times and breathe from a self-contained oxygen supply. No wonder then that the majority of Ebola research doesn’t actually use live, infectious viruses.

Scientists must instead settle with isolated proteins, proteins shoved into other, less harmful viruses or even “virus-like particles”. But these artificial systems are different to the virus proper, and using them is like staring at a complex machine through a cobweb-covered keyhole. Peter Halfmann from the University of Wisconsin has found a way around this, opening the door for scientists to get a proper look at the virus.

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Sex runs hot and cold – why does temperature control the gender of Jacky dragons?

Blogging on Peer-Reviewed ResearchAmong Jacky dragons, females are both hot and cool, while males are merely luke-warm. For this small Australian lizard, sex is a question of temperature. If its eggs are incubated at low temperatures (23-26ºC) or high ones (30-33ºC), they all hatch as females; anywhere in the idle, and both sexes are born.

Jacky dragonThis strategy – known as ‘temperature-dependent sex determination (TSD) – seems unusual to us, with our neat gender-assigning X and Y chromosomes, but it’s a fairly common one for reptiles. Crocodiles are all-male at high temperatures and all-female at low ones, while turtles flip the rules around and produce more males in cooler climes. Now, a thirty-year old idea to explain this puzzling system has finally been confirmed.

Assigning gender based on temperature is not uncommon but it is nonetheless puzzling. Gender seems like an incredibly fundamental physical trait to leave to something as variable as the temperature of your surroundings. How has such a system evolved? What possible benefits could a species receive by switching control of from chromosomes to the environment?

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Canny breeding creates vitamin A-rich maize without genetic modification

Blogging on Peer-Reviewed ResearchOn Thursday, I wrote about a way of genetically modifying carrots to turn them into rich sources of calcium. The method could be more widely used in vegetables to help reduce nutritional deficiencies, but it risks raising the ire of the anti-GM environmentalist camp. But there is another way of altering the genes of crop plants that avoids such controversy, and it’s a traditional one – selective breeding.

Types of maizeBy cross-breeding individuals with desirable qualities, farmers have been tinkering with the genes of both animals and plants for centuries. Traditionally, the process has been a bit messy. Genes don’t always easily translate into physical characteristics, so there is a certain amount of trial-and-error involved.

Now, Carlos Harjes from Cornell University had developed a way of using modern genetic techniques to make selective breeding even more selective. For his first trick, he has developed a variety of maize to combat vitamin A deficiencies. Best of all, no genes were added, tweaked or subtracted in the making of this vegetable – he only used the natural genetic variation within the world’s maize strains.

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Meet the genetically modified super-carrot, now fortified with calcium

Blogging on Peer-Reviewed ResearchFor centuries, mothers have wrongly told their children that eating carrots will improve their vision. The sight-enhancing properties of these iconic vegetables is be a myth (albeit a fascinating one involving Nazis and fighter pilots) but if Jay Morris has anything to say about it, they may soon be better known for building strong bones.

Types of carrotsMorris, together with Kendal Hirschi and other Texan colleagues, has found a way to double the calcium content of carrots through genetic modification, making them a rich source of the element that is so vital for bones

The team loaded their super-carrots with a protein called sCAX1, which pumps calcium into the plant’s cells. The protein originally hailed from the plant-of-choice for geneticists, Arabidopsis thaliana, where it exists in a larger version. Morris’s team lopped off a small piece from its tip that stops the protein from funnelling in more calcium once a certain amount has been reached.

In this shortened form, sCAX1 is relentless in its import of calcium and the researchers have found that it can greatly increase the calcium content of several vegetables including tomatoes, potatoes and carrots. These super-charged vegetables could help to reduce the risk of osteoporosis, one of the world’s leading nutritional disorders, where a lack of calcium leads to brittle bones.

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Dinosaurs grew fast, had teen pregnancies and died young

Blogging on Peer-Reviewed ResearchTyrannosaurusFor some dinosaurs, the best strategy was to grow fast and breed early. New fossil evidence suggests that at least three species, including celebrities like Tyrannosaurus and Allosaurus, were having sex in their teens. In this way, their pace of growth and maturity was closer to that of modern birds and mammals than it would be to a reptile scaled-up to the same size.

They also started to breed well before they had finished growing, which suggests that they lived relatively short and brutal lives and needed as much time as possible to reproduce before they met an untimely demise. Modern back-boned animals with high adult death rates use a similar strategy.

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