30 October 2010 | NewScientist | 19
Indias island past rewritten in amber
FIFTY-million-year-old insects preserved in amber are helping to rewrite the story of Indias almighty crash into the Eurasian continent, suggesting that for as long as a few million years before the collision, India was connected to Asia by archipelagos.
India spent tens of millions of years as an island before colliding with Asia. Yet the fossil record contains no evidence that unique species evolved on the subcontinent during this time, so India may not have been as isolated as it seemed to be.
To study this further, Jes Rust of the University of Bonn, Germany, and colleagues collected some 150 kilograms of amber from the Cambay region of Gujarat, India. The amber dates from just before the Indian-Asian collision and contains more than 700 arthropods, preserved with lifelike, microscopic fidelity (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1007407107).
Many of the insects are close relatives of species found in Eurasia at the time, indicating that there may have been island chains linking India and southern Asia by 50 million years ago.
Thank snowballs and spikes for complex lifeTHE rise of complex life on Earth may have been given a boost by a spike in the levels phosphate, best known now as a plant fertiliser.
Timothy Lyons at the University of California, Riverside, and colleagues have worked out how phosphate levels changed in Earths oceans over the last 3 billion years by measuring the relative amounts of phosphorus in 700 samples from various rock formations around the world. More phosphorus in the rocks means there was more of the mineral phosphate in the
sea when they were formed.The team found that between
750 and 620 million years ago, phosphate levels were much higher than they were either before or since.
That high level roughly corresponds to the period known as snowball Earth, when most or possibly all of the planet was iced over. Lyons says that shifting ice sheets would have ground away at the continents, releasing large amounts of rocks and sediment rich in phosphate. And when the ice retreated, the phosphate
WERE all happier on sunny days, but why? It seems that light taps directly into brain areas that process emotion good and bad.
Although light is used to treat mood disorders, we dont understand how this works. While rods and cones in the eye process visible light, a third type of photoreceptor, particularly sensitive to blue light, mediates non-visual responses such as sleep cycles and alertness. So light may make us feel better because it helps regulate circadian rhythms.
Gilles Vandewalle at the University of Lige, Belgium, and colleagues
wondered whether this pathway directly affects our emotional state too. To find out, they scanned the brains of volunteers exposed to green or blue light while a neutral or angry voice recited meaningless words. As expected, brain areas responsible for processing emotion responded more strongly to the angry voice, but this effect was amplified by blue light (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1010180107).
Vandewalle suggests blue light is likely to amplify emotions in both directions.
Moody blue light taps into emotions
would have been dumped into the oceans, creating a huge surplus.
Phosphate is a fertiliser, and the surplus would have driven the growth of many more plants, says Lyons. In turn, these would have released extra oxygen into the atmosphere, making it more hospitable for multicellular animals (Nature, DOI: 10.1038/nature09485).
The rise of complex animals has long been linked to a jump in atmospheric oxygen, and Lyons says that a phosphate spike could help explain why that happened.
How kids get grown-up vision
CHILDREN do not see objects in a fully grown-up way until the age of 13, a new study suggests.
When judging whether shaded images are convex or concave, adult brains assume that light comes from above unless there is reason to think otherwise. Young children have to learn this ability.
To investigate when this happens, Jim Stone at the University of Sheffield, UK, showed embossed shapes such as squares and shaded images such as footprints to 171 children aged from 4 to 10. Each child was shown 10 images and asked whether they were convex or concave. The correct answer assumed an object was lit from above.
The children got better with age, with the average score out of 10 improving by 0.43 each year (Perception, DOI: 10.1068/p6725). If children of other ages develop at the same rate, Stone predicts that babies will learn to assume that light comes from above at about 21 months. But this aspect of their visual perception wont be fully grown until the age of 13 or so.
Children really do see the world differently to adults, inasmuch as their perceptions seem to be more variable, says Stone. No wonder they cant look at a cloud without seeing a dog or a bear.
For new stories every day, visit www.NewScientist.com/news
101030_N_InBrief.indd 19 25/10/10 18:07:44