16 | NewScientist | 28 May 2011

IF YOU’VE ever dropped your cellphone in water, you can now claim you were testing that water for bacterial contamination. It seems liquid crystals, ubiquitous in electronic displays, could be a great way to detect water-borne toxins.

When suspended in water, the molecules in a liquid crystal form droplets in which the molecular chains line up like the lines of

longitude on a globe. But in the presence of endotoxins – disease-causing molecules produced by E. coli bacteria – they rearrange to form a pattern that radiates from the drop’s centre.

Previously, it was thought necessary to coat a droplet’s entire surface with toxins to produce the change. Now Nicholas Abbott at the University of Wisconsin-Madison and colleagues have

Mammals began brainy and nosy

THE mammal-like animals living alongside Jurassic dinosaurs had acute senses of smell and touch, which may have helped them survive their fearsome neighbours.

Timothy Rowe and colleagues at the University of Texas at Austin used high-resolution X-ray CT scans to create 3D maps of the skulls of two ancient shrew-like beasts, revealing the shapes of their brains. Both had a big neocortex, like modern mammals, but they also had large olfactory bulbs: two prominent bumps on the front of the brain that process smell. Rowe also found evidence of a strong sense of touch and motor coordination (Science, DOI: 10.1126/science.1203117).

Rowe says early mammals relied heavily on smell, as bears and bloodhounds do today. It would have helped them navigate dark burrows and hunt insects in leaf litter.

Muck-and-maize revolution powered Inca success

THE Inca civilisation was built on llama muck, an analysis of lake mud suggests.

The dung allowed prehistoric South Americans to cultivate maize, stop hunter-gathering and settle as farmers. Good yields gave them time for mining metals, developing a civilisation – and building an empire.

Analysis of pollen in mud cores from the bed of a lake near the Andean fortress city of Ollantaytambo, Peru, reveals that, there at least, the agricultural revolution happened very quickly, some 2700 years ago. Previously, people seem to have dined mostly on wild foods such as

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Liquid crystals could test water’s safety shown that only the “poles” of the droplet, where the longitudinal chains of its molecules meet up, need to touch the toxins to produce the realignment (Science, DOI: 10.1126/science.1195639).

That suggests liquid crystals can detect endotoxins at concentrations at just 1/10th of the concentration currently thought necessary, Abbott says. They could one day help ensure the safety of saline and other injectable medical fluids.

quinoa, but around that time the pollen record shows a sudden shift to maize, says Alex Chepstow-Lusty of the French Institute of Andean Studies in Lima, Peru.

A temporarily warmer climate probably helped the first maize farmers, but so did llama dung. Orbatid mites eat the dung, and Chepstow-Lusty’s mud cores revealed a spike in the number of mite remains around the time that maize pollen became dominant. Llamas had been domesticated by around 3500 years ago, but the mite boom at 2700 years ago suggests that llamas were suddenly everywhere. Their excrement would have proved as useful to farmers as to the mites, says Chepstow-Lusty (Antiquity, DOI: 10.1016/j.jas.2006.12.023). “The shift to agriculture was possible only with this extra ingredient – organic fertilisers on a vast scale.”

TURTLE embryos without limbs have biologists stumped. The legless embryos are able to move to the warmest parts of their eggs.

The behaviour of Chinese soft-shelled turtle embryos (Pelodiscus sinensis) mimics that of adult reptiles basking in the sun to warm their blood. Rick Shine of the University of Sydney, Australia, observed 800 embryos moving towards a heat source placed outside their eggs, and following the source if it moved (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1102965108).

Shine says the extra warmth may help them hatch earlier or have positive benefits for their health, but he has no idea how they manage to move.

Who needs legs to find hotspot in egg?