the-BA : Science News Digest

Sheep (Image copyright: istockphoto.com)

In the news this week: ocean ice warnings, shrinking sheep and a potential cause of teenage mood swings. Plus, rats experience doubt and uncertainty...

Scientists whose work was published in the journal Science this week, expressed concerns that thinning Arctic ocean ice may have reached a tipping point which could impact on global weather patterns.

'When the ice thins to a vulnerable state, the bottom will drop out and we may quickly move into a new, seasonally ice-free state of the Arctic,' said study leader, Dr Mark Serreze. 'There is some evidence that we may have reached that tipping point, and the impacts will not be confined to the Arctic region.'

An estimated 38,000 square miles of sea ice is being lost every year. The reduced ice cover leaves more open water to absorb heat from the sun, leading to further increases in sea temperature in the Arctic and melting of ice. As early as 2040 could see the end of ice cover, according to computer models. As well as having an impact on species that hunt among the ice floes, the loss of ice could disrupt world climate – reducing snow across the western United States and causing bigger winter storms across parts of Europe.

The same Guardian article reported that British scientists who reviewed five years of Antarctic glacier observations warn that four of the largest glaciers may represent a disproportionate threat to sea level rises. They are flowing into the ocean 20 to 100 per cent faster than in previous decades and account for approximately 12 per cent of global sea level rises. A big worry is the volume of ice that the glaciers hold and that the cause of the accelerated movement is not understood. Geological records indicate that previous ice sheet collapses have caused sea levels to surge by up to 20 metres in less than 500 years.

Meanwhile, reported the Guardian, government ministers revealed a draft climate change bill that would make Britain the first country in the world to set legally binding limits on its carbon emissions. Failure to reduce them by 60 per cent by 2050 could, according to the proposed legislation, result in legal action against the government. Five-year carbon budgets would be set out to ensure the target is met, and the government also wishes to assess progress using an independent monitoring committee.

Environment Minister, David Miliband said: 'This ties the hands of future governments. It is the framework that will drive this government and future governments to do better.'

Three months of public and parliamentary consultation will now take place regarding the draft bill.

Emphasizing the need for dramatic action against climate change, the Times reported the first study to indicate that mankind is leaving an evolutionary legacy due to climate change, as well as an ecological one, by affecting natural selection. Using population data and field observations, researchers tracked the size and survival rates of Soay sheep on Hirta island, in the Outer Hebrides. They observed that when winters were harsh more of the larger sheep survived but in milder years more of the smaller sheep did.

‘As the climate changes and the Soay sheep are not subject to such tough winters, there will be reduced natural selection for larger animals,’ said Tim Coulson, one of the scientists involved in the study. ‘Winters have been getting better on this island. This could mean that if the climate in this region of Scotland continues to change, there will be changes in the size of sheep due to natural selection, which could have a significant impact on the population dynamics of the Soay sheep overall.’

The proliferation of wind turbines as a renewable energy source could have serious implications for bats. Their deaths at wind farms are thought to exceed those of birds. However, a new study suggests that radar could be used to prevent bats from approaching turbines and coming into danger, reported BBC News. The elecromagnetic radiation emitted at radar installations appears to deter bats from foraging nearby.

American scientists, led by the genome pioneer Craig Venter, have discovered more than six million new genes as part of a global ocean sampling exhibition to read the genetic codes of marine microbes. The vast majority of marine microbes are unknown but it is believed they could be important tools to deal with pollution. Their biological processes could help clear greenhouse gases such as carbon dioxide and methane from the atmosphere and even offer new ideas for alternative energy production.

The studies published this week, and reported in the Daily Telegraph, used new methods to read the DNA of microbes present in multiple samples of seawater collected during a two-year circumnavigation of Halifax, Nova Scotia to the Eastern Tropical Pacific.

In other news, figures released this week show that in the past 20 years there has been a dramatic increase in the number of young children with type 1 diabetes. Cases among children under five increased fivefold between 1985 and 2004, with a twofold increase in children under fifteen. But the cause of the rise in diabetes cases is as yet unknown.

‘It's too fast to be genetic,’ said diabetes specialist Polly Bingley, in the Guardian. ‘It's got to be some sort of environmental influence, something these children are being exposed to, or something they're no longer exposed to that had a protective effect in the past.’

She believes we should first look at the changes in babies’ diets that have occurred in the past 20 years for a potential cause. Other researchers are investigating whether changes in children’s immune systems, caused by either too sterile an environment or exposure to childhood infections, could be responsible.

According to researchers who conducted an analysis of fruit juice antioxidant content, some juices offer substantially greater health benefits than others. Scientists measured the number and overall levels of polyphenols – antioxidants that protect against harmful free radicals – in 13 different brands of fruit juices from a local supermarket. They found purple grape contained the highest levels. Cloudy apple, pomegranate and cranberry were also good sources.
(Daily Telegraph)

The Times speculated that scientists may have found the potential cause of teenage mood swings: a brain signalling chemical released in response to stress that reverses its effect at puberty. In adult mice, stress-induced release of the hormone THP, tetrahydropregnanalone, acts to calm nerve activity and reduce anxiety. However, in puberty this stress-fighting hormone actually leads to increased anxiety since it acts on a different receptor – produced in high numbers in response to sex hormones – that causes excitability. Whether this also occurs in human teenagers has yet to be determined, but the Daily Telegraph reported that the hormone has a similar effect on the human version of the receptor.

In other news, a scientist announced that the oldest human to have a modern childhood was an eight year old child who died in Morocco 160,000 years ago. A prolonged childhood is unique to humans and is related to the time we need to learn, as well as the time required for our larger brains to grow. Early fossil humans Homo habilis and Homo erectus were more similar to chimpanzees than modern humans in their growth periods. The latest study used teeth to analyse the maturation rate.
(Daily Telegraph)

Also in the Daily Telegraph: a new study suggests that attractiveness is more than a simple matter of hip-to-waist ratio. In ladies, it’s not just curves that count, but the way that they flaunt them. And for men, a swagger can increase how attractive others find them.

Researchers asked 370 individuals to rate the attractiveness of people as they walked, using videos of shadow figures and animations so that the sex of the walker had to be assumed. They discovered that in addition to their hip-to-waist ratio, the way a person moved affected their rating: a person perceived as female was rated more attractive if moving in a feminine manner such as a swaying their hips, and perceived males were rated as more attractive if moving in a masculine way.

And finally...

The evil rat geniuses of many children’s cartoons may be taking it a bit far, but it seems there’s more to the inner workings of rats than meets the eye.

Researchers have provided the first ever evidence to suggest that non-primates are capable of “metacognition” – the ability to reflect on or assess one’s own thinking processes – something previously only attributed to humans, monkeys and apes.

Rats were set tests in which they had to determine whether a signal was short or long. Giving the “right” answer led to a large food reward and no reward was given for the “wrong” answer. The rats were also given the option of declining to answer, a choice which always yielded a small reward. The decisions were sometimes obvious, sometimes difficult. The behaviour of the rats suggested that they know when they don’t know the answer.

‘This is a fascinating study, which suggests that rats, like monkeys, but unlike pigeons, may be aware of what they do and do not know or remember,’ commented Professor Nicky Clayton, a University of Cambridge expert on animal cognition, in the Daily Telegraph. ‘Of course it's not clear if we'll ever know if rats have an inner life, and if they do, what it is like. But their performance on these uncertainty monitoring paradigms certainly suggests rats are sensitive to "doubt and uncertainty".’