Diet plays key role in ADHD symptoms in children

 Here's a good reason for children with attention deficit hyperactivity disorder (ADHD) to eat their fruits and vegetables: It may help reduce inattention issues, a new study suggests.

As part of a larger study, researchers asked parents of 134 kids with ADHD symptoms to complete a detailed questionnaire about the typical foods the children ate, including portion sizes, over a 90-day period.

Another questionnaire asked parents to rate symptoms of inattention -- a hallmark of ADHD -- in their kids, such as having trouble staying focused, not following instructions, difficulty remembering things, and difficulty regulating emotions.

Results showed that kids who consumed more fruits and vegetables showed less severe symptoms of inattention, said Irene Hatsu, co-author of the study and associate professor of human nutrition at The Ohio State University.

"Eating a healthy diet, including fruits and vegetables, may be one way to reduce some of the symptoms of ADHD," Hatsu said.

The study was published online recently in the journal Nutritional Neuroscience.

The data for this research was collected as part of the Micronutrients for ADHD in Youth (MADDY) Study, which examined the efficacy of a 36-ingredient vitamin and mineral supplement to treat symptoms of ADHD and poor emotional control in the 134 kids aged 6 to 12.

The study that evaluated the effectiveness of the supplement showed that children who took the micronutrients were three times as likely to show significant improvement in their ADHD and emotional dysregulation symptoms than those who took a placebo. That study was published last year in the Journal of the American Academy of Child and Adolescent Psychiatry.

Another study involving the same children, published earlier this year in the journal Nutrients, showed that kids whose families had higher levels of food insecurity were more likely than others to show more severe symptoms of emotional dysregulation, such as chronic irritability, angry moods and outbursts of anger.

The three studies all paint a similar picture, Hatsu said: A healthy diet that provides all the nutrients that children require can help reduce the symptoms of ADHD in children.

"What clinicians usually do when kids with ADHD start having more severe symptoms is increase the dose of their treatment medication, if they are on one, or put them on medication," Hatsu said.

"Our studies suggest that it is worthwhile to check the children's access to food as well as the quality of their diet to see if it may be contributing to their symptom severity."

Children in the MADDY study, all of whom met the criteria for ADHD, were recruited from three sites: Columbus, Ohio; Portland, Oregon; and Lethbridge, Alberta, Canada. The study took place between 2018 and 2020. Participants were either not taking medication or stopped using it two weeks before the study began.

The studies on fruit and vegetable intake and the role of food insecurity were based on data collected when the children were first enrolled in the study, before they began taking the micronutrient supplement or placebo.

Why may diet be so important in ADHD?

Researchers believe that ADHD is related to low levels of some neurotransmitters in the brain -- and vitamins and minerals play a key role as cofactors in helping the body make those important neurochemicals and in overall brain function, Hatsu said.

Food insecurity may play an additional role.

"Everyone tends to get irritated when they're hungry and kids with ADHD are no exception. If they're not getting enough food, it could make their symptoms worse," she said.

Also, the stress of parents who are upset about not being able to provide enough food for their children can create family tension that could lead to more symptoms for children with ADHD.

The MADDY study is one of the first to look at the relationship between ADHD symptoms and diet quality among children in the United States and Canada, Hatsu said.

That's important because Western diets are more likely than many others, such as the Mediterranean diet, to fall short on fruit and vegetable intake, she said.

"We believe clinicians should assess the food security status of children with ADHD before creating or changing a treatment program," Hatsu said.

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Ghostly 'mirror world' might be cause of cosmic controversy

New research suggests an unseen 'mirror world' of particles that interacts with our world only via gravity that might be the key to solving a major puzzle in cosmology today -- the Hubble constant problem.

The Hubble constant is the rate of expansion of the universe today. Predictions for this rate -- from cosmology's standard model -- are significantly slower than the rate found by our most precise local measurements. This discrepancy is one that many cosmologists have been trying to solve by changing our current cosmological model. The challenge is to do so without ruining the agreement between standard model predictions and many other cosmological phenomena, such as the cosmic microwave background. Determining whether such a cosmological scenario exists is the question that researchers, including Francis-Yan Cyr-Racine, assistant professor in the Department of Physics and Astronomy at The University of New Mexico, Fei Ge and Lloyd Knox at the University of California, Davis have been trying to answer.

According to NASA, cosmology is the scientific study of the large-scale properties of the universe as a whole. Cosmologists study concepts such as dark matter, and dark energy and whether there is one universe or many, sometimes called a multiverse. Cosmology entails the entire universe from birth to death with mysteries and intrigue at every turn.

Now, Cyr-Racine, Ge, and Knox have discovered a previously unnoticed mathematical property of cosmological models which could, in principle, allow for a faster expansion rate while hardly changing the most precisely tested other predictions of the standard cosmological model. They found that a uniform scaling of the gravitational free-fall rates and photon-electron scattering rate leaves most dimensionless cosmological observables nearly invariant.

"Basically, we point out that a lot of the observations we do in cosmology have an inherent symmetry under rescaling the universe as a whole. This might provide a way to understand why there appears to be a discrepancy between different measurements of the Universe's expansion rate."

The research, titled "Symmetry of Cosmological Observables, a Mirror World Dark Sector, and the Hubble Constant" was published recently in Physical Review Letters.

This result opens a new approach to reconciling cosmic microwave background and large-scale structure observations with high values of the Hubble constant H0: Find a cosmological model in which the scaling transformation can be realized without violating any measurements of quantities not protected by the symmetry. This work has opened a new path toward resolving what has proved to be a challenging problem. Further model building might bring consistency with the two constraints not yet satisfied: the inferred primordial abundances of deuterium and helium.

If the universe is somehow exploiting this symmetry researchers are led to an extremely interesting conclusion: that there exists a mirror universe very similar to ours but invisible to us except through gravitational impact on our world. Such "mirror world" dark sector would allow for an effective scaling of the gravitational free-fall rates while respecting the precisely measured mean photon density today.

"In practice, this scaling symmetry could only be realized by including a mirror world in the model -- a parallel universe with new particles that are all copies of known particles," said Cyr-Racine. "The mirror world idea first arose in the 1990s but has not previously been recognized as a potential solution to the Hubble constant problem.

"This might seem crazy at face value, but such mirror worlds have a large physics literature in a completely different context since they can help solve important problem in particle physics," explains Cyr-Racine. "Our work allows us to link, for the first time, this large literature to an important problem in cosmology."

In addition to searching for missing ingredients in our current cosmological model, researchers are also wondering whether this Hubble constant discrepancy could be caused in part by measurement errors. While it remains a possibility, it is important to note that the discrepancy has become more and more significant as higher quality data have been included in the analyses, suggesting that the data might not be at fault.

"It went from two and a half Sigma, to three, and three and a half to four Sigma. By now, we are pretty much at the five-Sigma level," said Cyr-Racine. "That's the key number which makes this a real problem because you have two measurements of the same thing, which if you have a consistent picture of the universe should just be completely consistent with each other, but they differ by a very statistically significant amount."

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Research brings hope for spinal cord injury treatment

Scientists from the University of Birmingham have shown an existing drug may reduce damage after spinal cord injury, by blocking the inflammatory response in the spinal cord.

Their research, published today in Clinical and Translational Medicine, demonstrates that AZD1236, a drug developed by AstraZeneca, can significantly reduce 'secondary damage' caused by the body's response to spinal cord injury (SCI).

Researchers led by Professor Zubair Ahmed, Professor of Neuroscience and lead for the Neuroscience and Ophthalmology Section at The University's Institute of Inflammation and Ageing, used animal models to demonstrate that AZD1236 can promote significant nerve regeneration, with a dramatic 80% preservation in nerve function following spinal cord compression injury.

Crucially, this translated into an 85% improvement in movement and sensation. These dramatic effects were observed following only three days of treatment with AZD1236, starting within 24 hours post-injury. Within three weeks, the AZD1236 treated animals showed unprecedented recovery, while controls still showed significant deficits at six weeks post-injury.

One of the key drivers of SCI secondary damage is breakdown of the blood-spinal cord barrier (BSCB). This results in oedema (excess fluid build-up around the spinal cord) and triggers an inflammatory response that can ultimately hinder the healing process, and lead to nerve cell death.

AZD1236 is a potent and selective inhibitor of two enzymes, MMP-9 and MMP-12, which are implicated in the inflammatory process.

The researchers demonstrated that AZD1236 halts SCI-induced oedema, and reduces BSCB breakdown and scarring at the site of the injury. They also examined the effect of AZD1236 dosing on MMP-9 and MMP-12 activity in both the bloodstream and cerebrospinal fluid, which surrounds the spinal cord.

Here they demonstrated significant suppression of enzyme activity after both oral dosing, and intrathecal dosing (injection into the spinal canal). Oral dosing reduced enzyme activity by 90% in serum, and 69-74% in the cerebrospinal fluid. Unsurprisingly, intrathecal injection delivered higher levels (88-90%) of suppression in the cerebrospinal fluid.

Further studies showed the AZD1236 supressed the formation of pro-inflammatory cytokines (molecules that are known to contribute to the development of long-lasting neuropathic pain, which often follows SCI) by 85-95%. AZD1236 was also found to be 82% more effective at alleviating SCI-induced neuropathic pain sensitivity to cold, heat and touch when compared to currently used pain medications such as pregabalin (Lyrica) and gabapentin.

Professor Ahmed commented: "There is currently no reparative drug available for SCI patients, treatments only provide symptomatic relief and do not tackle the underlying molecular mechanisms that cause or contribute to oedema and blood-spinal cord barrier breakdown. This drug has the potential to be a first-in-class treatment against some of the key pathological drivers of SCI and could revolutionise the prospects for recovery of SCI patients."

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Lost or extinct? Study finds the existence of more than 500 animal species remains uncertain

An international study provides the first global evaluation of all terrestrial vertebrate species that have not been declared extinct and identifies more than 500 species considered to be 'lost' -- those that haven't been seen by anyone in more than 50 years.

Researchers reviewed information on 32,802 species from the International Union for Conservation of Nature Red List of Threatened Species (IUCN Red List) and identified 562 lost species. Their findings appear in the journal Animal Conservation.

The IUCN Red List defines extinct as 'when there is no reasonable doubt the last individual of a species has died,' which can be challenging to verify. According to Simon Fraser University biodiversity professor and study co-author Arne Mooers, the Red List categorizes 75 of these 562 lost species as 'possibly extinct.' The researchers note the existence of many species with an uncertain conservation status may become increasingly problematic as the extinction crisis worsens and more species go missing.

A total of 311 terrestrial vertebrate species have been declared extinct since 1500, meaning 80 per cent more species are considered lost than have been declared extinct.

Reptiles led the way with 257 species considered lost, followed by 137 species of amphibians, 130 species of mammals and 38 species of birds. Most of these lost animals were last seen in megadiverse countries such as Indonesia (69 species), Mexico (33 species) and Brazil (29 species).

While not surprising, this concentration is important, according to researchers. "The fact most of these lost species are found in megadiverse tropical countries is worrying, given such countries are expected to experience the highest numbers of extinctions in the coming decades," says study lead author Tom Martin from the UK's Paignton Zoo.

Mooers, who anchored the study, says: "While theoretical estimates of ongoing 'extinction rates' are fine and good, looking hard for actual species seems better."

Gareth Bennett, an SFU undergraduate student who did much of the data combing, adds: "We hope this simple study will help make these lost species a focus in future searches."

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Satellite monitoring of biodiversity moves within reach

Internationally comparable data on biodiversity is needed to protect threatened ecosystems, restore destroyed habitats and counteract the negative effects of global biodiversity loss. Current biodiversity monitoring, however, is labor-intensive and costly. In addition, many places around the world are difficult to access.

Biodiversity monitoring from space possible via satellite

Anna Schweiger from the Remote Sensing Laboratories at the Department of Geography, University of Zurich (UZH), and Etienne Laliberté from the University of Montréal, have now shown that plant biodiversity across ecosystems ranging from Arctic tundra to tropical forests can be reliably assessed using image spectrometry. "With our study, we hope to contribute to the future detection of changes in species composition of our Earth's ecosystems from space. The goal is to provide evidence-based guidance for policy measures to protect species and mitigate negative consequences of biodiversity loss," says first author Anna Schweiger.

Imaging spectrometers measure the reflectance of light from the visible to the shortwave infrared range of the electromagnetic spectrum. The reflectance of plants is determined by their chemical, anatomical and morphological characteristics, which are important for interactions among plants and with their environment. "Plants with similar traits, as well as closely related species, therefore tend to have similar reflectance spectra," explains Schweiger.

Using reflected light to assess the characteristics of individual plants and plant communities

The current study is a continuation of the researchers' work on spectral diversity metrics. Their indices calculate spectral variation among individual plants within communities, and among communities within a region. The diversity within communities is called alpha-diversity, while the diversity among communities is called beta-diversity.

Data for the study came from the National Ecological Observatory Network (NEON). The network uses standardized methods to collect biodiversity and Earth observation data across the United States which are then made publicly available. NEON imaging spectrometer data collected from research flights have a pixel size of 1x1 meter.

Spectral diversity calculations showed that the detection of alpha-diversity depends on plant size. Spectral diversity calculated in forests with closed canopies and large individual trees matched plant diversity determined on the ground better than spectral diversity calculated in open landscapes dominated by small herbaceous plants and grasses. Spectral beta-diversity, however, captured differences in plant community composition across all ecosystems studied based on a spatial resolution of 20x20 meters. This pixel size corresponds to the size of NEON's vegetation inventory plots.

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Insomnia in midlife may manifest as cognitive problems in retirement age

The Helsinki Health Study at the University of Helsinki investigated the development of insomnia symptoms in midlife and their effects on memory, learning ability and concentration after retirement. The follow-up period was 15-17 years.

According to the study, long-term insomnia symptoms and later poorer cognitive functioning have a clear connection.

"The findings indicate that severe insomnia symptoms were associated with worse cognitive function among those who were on statutory pension," says Doctoral Researcher Antti Etholén, describing the results of the study.

The study also found that the memory problems, and problems in learning ability and concentration increased as the insomnia symptoms were prolonged.

Sleeping well already in middle age

Prior research has shown that there are a number of mechanisms that can explain how sleep can affect cognitive functioning. What makes the recently published study exceptional is the long follow-up period for insomnia symptoms.

Among other things, the study demonstrated that if insomnia symptoms eased over the years, cognitive functioning was also found to be better at retirement age compared to the problems persisting.

According to the researchers, long-lasting insomnia symptoms should be considered as risk factors for poor cognitive functioning.

"Based on our findings, early intervention tackling insomnia symptoms, or measures aimed at improving the quality of sleep would be justified," says Professor Tea Lallukka.

There are many ways to improve the quality of sleep, including the regularity of the sleep rhythm, the appropriate temperature and brightness of the sleeping environment, and the optimal timing of physical exercise, coffee consumption and eating.

However, Lallukka believes that intervention studies are still needed to ascertain the effects of measures in support of good sleep.

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Prehistoric feces reveal parasites from feasting at Stonehenge

A new analysis of ancient faeces found at the site of a prehistoric village near Stonehenge has uncovered evidence of the eggs of parasitic worms, suggesting the inhabitants feasted on the internal organs of cattle and fed leftovers to their dogs.

Durrington Walls was a Neolithic settlement situated just 2.8km from Stonehenge, and dating from around 2500 BC, when much of the famous stone monument was constructed. It is believed that the site housed the people who built Stonehenge.

A team of archaeologists led by the University of Cambridge investigated nineteen pieces of ancient faeces, or 'coprolite', found at Durrington Walls and preserved for over 4,500 years. Five of the coprolites (26%) -- one human and four dog -- were found to contain the eggs of parasitic worms.

Researchers say it is the earliest evidence for intestinal parasites in the UK where the host species that produced the faeces has also been identified. The findings are published today in the journal Parasitology.

"This is the first time intestinal parasites have been recovered from Neolithic Britain, and to find them in the environment of Stonehenge is really something," said study lead author Dr Piers Mitchell from Cambridge's Department of Archaeology.

"The type of parasites we find are compatible with previous evidence for winter feasting on animals during the building of Stonehenge," he said.

Four of the coprolites, including the human one, contained the eggs of capillariid worms, identified in part by their lemon shape.

While the many types of capillariid around the world infect a wide range of animals, on the rare occasion that a European species infects humans the eggs get lodged in the liver and don't appear in stool.

The evidence of capillariid eggs in human faeces indicates that the person had eaten the raw or undercooked lungs or liver from an already infected animal, resulting in the parasite's eggs passing straight through the body.

During excavations of the main 'midden' -- or dung and refuse heap -- at Durrington Walls, archaeologists uncovered pottery and stone tools along with over 38,000 animal bones. Some 90% of the bones were from pigs, with less than 10% from cows. This is also where the partially mineralised faeces used in the study were found.

"As capillariid worms can infect cattle and other ruminants, it seems that cows may have been the most likely source of the parasite eggs," said Mitchell.

Previous isotopic analyses of cow teeth from Durrington Walls suggest that some cattle were herded almost 100km from Devon or Wales to the site for large-scale feasting. Patterns of butchery previously identified on cattle bones from the site suggest beef was primarily chopped for stewing, and bone marrow was extracted.

"Finding the eggs of capillariid worms in both human and dog coprolites indicates that the people had been eating the internal organs of infected animals, and also fed the leftovers to their dogs," said co-author Evilena Anastasiou, who assisted with the research while at Cambridge.

To determine whether the coprolites excavated from the midden were from human or animal faeces, they were analysed for sterols and bile acids at the National Environment Isotope Facility at the University of Bristol.

One of the coprolites belonging to a dog contained the eggs of fish tapeworm, indicating it had previously eaten raw freshwater fish to become infected. However, no other evidence of fish consumption, such as bones, has been found at the site.

"Durrington Walls was occupied on a largely seasonal basis, mainly in winter periods. The dog probably arrived already infected with the parasite," said Dr Piers Mitchell.

"Isotopic studies of cow bones at the site suggests they came from regions across southern Britain, which was likely also true of the people who lived and worked there."

The dates for Durrington Walls match those for stage two of the construction of Stonehenge, when the world-famous 'trilithons' -- two massive vertical stones supporting a third horizontal stone -- were erected, most likely by the seasonal residents of this nearby settlement.

While Durrington Walls was a place of feasting and habitation, as evidenced by the pottery and vast number of animal bones, Stonehenge itself was not, with little found to suggest people lived or ate there en masse.

Prof Mike Parker Pearson from UCL's Institute of Archaeology, who excavated Durrington Walls between 2005 and 2007, added: "This new evidence tells us something new about the people who came here for winter feasts during the construction of Stonehenge."

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Astronauts may one day drink water from ancient moon volcanoes

Billions of years ago, a series of volcanic eruptions broke loose on the moon, blanketing hundreds of thousands of square miles of the orb's surface in hot lava. Over the eons, that lava created the dark blotches, or maria, that give the face of the moon its familiar appearance today.

Now, new research from CU Boulder suggests that volcanoes may have left another lasting impact on the lunar surface: sheets of ice that dot the moon's poles and, in some places, could measure dozens or even hundreds of feet thick.

"We envision it as a frost on the moon that built up over time," said Andrew Wilcoski, lead author of the new study and a graduate student in the Department of Astrophysical and Planetary Sciences (APS) and the Laboratory for Atmospheric and Space Physics (LASP) at CU Boulder.

He and his colleagues published their findings this month in The Planetary Science Journal.

The researchers drew on computer simulations, or models, to try to recreate conditions on the moon long before complex life arose on Earth. They discovered that ancient moon volcanoes spewed out huge amounts of water vapor, which then settled onto the surface -- forming stores of ice that may still be hiding in lunar craters. If any humans had been alive at the time, they may even have seen a sliver of that frost near the border between day and night on the moon's surface.

It's a potential bounty for future moon explorers who will need water to drink and process into rocket fuel, said study co-author Paul Hayne.

"It's possible that 5 or 10 meters below the surface, you have big sheets of ice," said Hayne, assistant professor in APS and LASP.

Temporary atmospheres

The new study adds to a growing body of evidence that suggests that the moon may be awash in a lot more water than scientists once believed. In a 2020 study, Hayne and his colleagues estimated that nearly 6,000 square miles of the lunar surface could be capable of trapping and hanging onto ice -- mostly near the moon's north and south poles. Where all that water came from in the first place is unclear.

"There are a lot of potential sources at the moment," Hayne said.

Volcanoes could be a big one. The planetary scientist explained that from 2 to 4 billion years ago, the moon was a chaotic place. Tens of thousands of volcanoes erupted across its surface during this period, generating huge rivers and lakes of lava, not unlike the features you might see in Hawaii today -- only much more immense.

"They dwarf almost all of the eruptions on Earth," Hayne said.

Recent research from scientists at the Lunar and Planetary Institute in Houston shows that these volcanoes likely also ejected towering clouds made up of mostly carbon monoxide and water vapor. These clouds then swirled around the moon, potentially creating thin and short-lived atmospheres.

That got Hayne and Wilcoski wondering: Could that same atmosphere have left ice on the lunar surface, a bit like frost forming on the ground after a chilly fall night?

Forever ice

To find out, the duo alongside Margaret Landis, a research associate at LASP, set out to try to put themselves onto the surface of the moon billions of years ago.

The team used estimates that, at its peak, the moon experienced one eruption every 22,000 years, on average. The researchers then tracked how volcanic gases may have swirled around the moon, escaping into space over time. And, they discovered, conditions may have gotten icy. According to the group's estimates, roughly 41% of the water from volcanoes may have condensed onto the moon as ice.

"The atmospheres escaped over about 1,000 years, so there was plenty of time for ice to form," Wilcoski said.

There may have been so much ice on the moon, in fact, that you could, conceivably, have spotted the sheen of frost and thick, polar ice caps from Earth. The group calculated that about 18 quadrillion pounds of volcanic water could have condensed as ice during that period. That's more water than currently sits in Lake Michigan. And the research hints that much of that lunar water may still be present today.

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Past events reveal how future warming could harm cold-water corals

How will future warming of the planet impact cold-water corals? A new analysis of ancient evidence from the last major global warming event identifies food and oxygen supply as key environmental factors that influence the vitality of cold-water corals in the North Atlantic Ocean and the Mediterranean Sea. Rodrigo da Costa Portilho-Ramos of the University of Bremen, Germany, and colleagues present these findings in the open-access journal PLOS Biology on May 19th.

Much like tropical corals in shallower waters, cold-water corals serve as crucial "engineers" of deep-sea reefs and mounds that are home to rich, unique ecosystems. As climate change progresses, researchers predict, cold-water corals are likely to face harm from such factors as rising ocean temperatures, decreased food supply, lower oxygen levels, and ocean acidification. However, no extinctions of cold-water coral ecosystems have been documented in real-time, so the precise factors that may determine their fate have been unclear.

To shed new light, Portilho-Ramos and colleagues turned to ancient evidence of past climate change as captured in seafloor sediments. They analyzed sediments collected at or near six sites of cold-water coral ecosystems in the North Atlantic Ocean and the Mediterranean Sea, applying standard techniques to reconstruct ocean conditions and the abundance of the common coral species Lophelia pertusa over the last 20,000 years. This period encompasses Earth's last major global warming event.

The analysis revealed that ancient L. pertusa abundance was most strongly influenced by changes in food supply, delivered either vertically from shallower depths or by lateral water flow along the seafloor. Low oxygen concentration also appeared to be a key stressor for L. pertusa. Meanwhile, changes in ocean temperature and salinity did not appear to be significantly associated with proliferation or disappearance of L. pertusa over time.

These findings suggest that climate change-driven alterations to ocean processes that affect food and oxygen supplies may play key roles in the future health of cold-water coral ecosystems. In some cases, the data suggest, high abundance of food may compensate for low oxygen levels.

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First animals developed complex ecosystems before the Cambrian explosion

Early animals formed complex ecological communities more than 550 million years ago, setting the evolutionary stage for the Cambrian explosion, according to a study by Rebecca Eden, Emily Mitchell, and colleagues at the University of Cambridge, UK, publishing May 17 in the open-access journal PLOS Biology.

The first animals evolved towards the end of the Ediacaran period, around 580 million years ago. However, the fossil record shows that after an initial boom, diversity declined in the run-up to the dramatic burgeoning of biodiversity in the so-called "Cambrian explosion" nearly 40 million years later. Scientists have suggested this drop in diversity is evidence of a mass extinction event roughly 550 million years ago -- possibly caused by an environmental catastrophe -- but previous research has not investigated the structure of these ancient ecological communities.

To evaluate the evidence for an Ediacaran mass extinction, researchers analyzed the metacommunity structure of three fossil assemblages that span the last 32 million years of this geological period (between 575 to 543 million years ago). They used published paleoenvironmental data, such as ocean depth and rock characteristics, to look for metacommunity structure indicative of environmental specialization and interactions between species. The analysis revealed increasingly complex community structure in the later fossil assemblages, suggesting that species were becoming more specialized and engaging in more inter-species interactions towards the end of the Ediacaran era, a trend often seen during ecological succession.

The results point to competitive exclusion, rather than mass extinction, as the cause of the diversity drop in the late Ediacaran period, the authors say. The analysis indicates that the features of ecological and evolutionary dynamics commonly associated with the Cambrian explosion -- such as specialization and niche contraction -- were established by the first animal communities in the late Ediacaran.

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