Did Neanderthals invent graffiti?

A new dating method has shown that cave painting started in Europe at least 40,800 years ago – several thousand years earlier than previously believed. A study carried out in 11 caves in northern Spain leads to two alternative conclusions, both controversial. Either our modern human ancestors started painting almost as soon as they arrived in western Europe between 42,000 and 41,000 years ago, or the art was done by Neanderthals who were already there. Scientific opinions about Neanderthals’ cognitive abilities differ markedly – and many experts will find it hard to believe that they created the world’s first cave art.

Ancient cave painting has been extremely hard to date, because traditional radiocarbon dating becomes very inaccurate beyond about 35,000 years and, more fundamentally, it is useless when the artworks use mineral pigments rather than carbon-containing organic compounds.

The new technique is different: rather than dating the painting directly, it dates the very thin layer of calcium carbonate (calcite) that forms with time on the surfaces of limestone caves, including any art on their walls. This gives a minimum age for the art, which must be older than the calcite on top of it. The technique is based on the radioactive decay of the tiny amount of natural uranium incorporated in the calcite when it was laid down. The concentration of thorium, a decay product of uranium, can give an accurate age from samples as small as a rice grain.

The oldest paintings discovered so far are stencils made by blowing red pigment over a hand or, in one case, a circular disc. The artistically more interesting – and much more sophisticated – painting of animals started several thousand years later.

“We see evidence for earlier human symbolism in the form of perforated beads, engraved eggshells and pigments in Africa 70,000 to 100,000 years ago, but it appears that the earliest cave paintings are in Europe,” says Alistair Pike of Bristol University, leader of the research team. Scientists from the UK, Spain and Portugal took part in the study, which is published in the journal Science.

“One argument for the development [of cave painting in Europe] is that competition for resources with Neanderthals provoked increased cultural innovation from the earliest groups of modern humans in order to survive,” he adds.

“Alternatively, cave painting started before the arrival of modern humans, and was done by Neanderthals. That would be a fantastic find as it would mean the hand stencils on the walls of the caves are the outlines of Neanderthals’ hands. But we will need to date more examples to see if this is the case.”

How to mend a broken heart

A new discovery in regenerative medicine could revolutionise the treatment of heart failure within five years.

After a heart attack, scar tissue renders the heart less able to pump effectively, causing breathlessness, anxiety and palpitations. More than 750,000 people in the UK suffer from this condition, and 80 per cent of deaths following heart attacks are due to heart failure.

Transplants may help a few patients, but they are far from providing a cure. A transplanted heart typically lasts 10 to 15 years, while the patient’s immune system is undermined by constantly taking immunosuppressants to prevent rejection, and each procedure costs around £30,000.

Research by Deepak Srivastava, at the Gladstone Institute of Cardiovascular Disease in California, aims to regenerate scar tissue in pig hearts, building upon a recent discovery in mice published in Nature. Scar tissue cells in the hearts of mice were transformed into myocytes – functioning heart cells with regenerative potential – using three transcription factors or proteins instructing the cell’s genes. Activating these factors effectively reprogrammed cells, transforming scar tissue back into muscle.

“Once heart cells are dead, they are dead for life,” says Srivastava. “The only way to address this is to create new muscle.

“The step in mice was important, as it was the first time the tissue reprogramming worked in vivo,” he adds. “We are hoping for a similar outcome in pigs, which could lead to clinical trials in as little as two years’ time.”

The research is part of a global effort to find treatments for heart failure. In the UK, scientists are working to regenerate heart muscle and blood vessels by restoring the potential of embryonic development in adult cells, while scientists in Switzerland are looking at how zebra fish naturally repair heart damage. Pippa Stephens

Where you live can alter what you become

Blue indicates environmental influence, red genetic

The nature-nurture balance – the extent to which human development is affected by our genes or our environment – has a strong geographical component, a large study of twins at King’s College London has shown. For example, children who grow up in London and south-east England are more susceptible to environmental influences than their counterparts elsewhere in Britain when it comes to classroom behaviour problems.

The study, published in the journal Molecular Psychiatry, used data from 13,000 pairs of twins born between 1994 and 1996, both identical and non-identical, relating to 45 characteristics that range from IQ and hyperactivity to height and weight. The geographical variations that the researchers found were presented as a series of “nature-nurture maps”.

“These days we’re used to the idea that it’s not a question of nature or nurture; everything, including our behaviour, is a little of both,” says Oliver Davis of the Institute of Psychiatry at King’s. “But when we saw the maps, the first thing that struck us was how much the balance of genes and environment can vary from region to region.”

When it comes to classroom behaviour, around 60 per cent of the difference between children is explained by genes in most of the UK. In the south-east, however, genes explain less than half of the variation. For classroom behaviour, London is an “environmental hotspot” – perhaps because income inequalities are greater there.

Our new and slightly worrying neighbour

Astronomers occasionally spark alarm when they spot an asteroid on a path that might conceivably lead to a cataclysmic collision with Earth.

The latest cause for concern is asteroid 2011 AG5, a rock 140m across, discovered last year and tracked by several observatories over nine months.

Now that AG5 has temporarily moved too far away to observe, the US space agency Nasa has convened an international panel of experts to assess the risk. The conclusion is that there is a remote chance of the asteroid hitting Earth in 2040.

“While there is general consensus there is only a very small chance that we could be dealing with a real impact scenario for this object, we will still be watchful and ready to take further action if additional observations indicate it is warranted,” says Lindley Johnson, who runs Nasa’s Near-Earth Object Observation Programme.

Astronomers will be able to observe AG5 again from late 2013 until 2016 – and refine their risk calculations.

Things will become clearer in February 2023 when AG5 will be 1.8 million km away. If it then passes through an area of space just 365km wide, called a keyhole, Earth’s gravity might pull the asteroid on to a trajectory leading to impact on February 5 2040.

But Nasa says reassuringly that there would still be time to plan and execute a mission to nudge AG5 on to another course that would miss Earth.

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