Reader’s Scigest 07-10-15

By Bruno Martin

Eyes peeled

ScigestThe shape of an animal’s pupil reveals its position in the food chain, Durham University researchers have found in collaboration with the University of California, Berkeley. They discovered that vertical elongated pupils on the front of the head, found in cats and foxes, are well suited to ambush prey, as they enable predators to accurately judge distances without moving their head while crouching. Animals with horizontal elongated pupils, however, are often grazers like goats, sheep and horses. This configuration enables more light to permeate from the front and back than the top and bottom of the eye, giving prey a panoramic vision of potential predators on the ground. These animals are also capable of rotating their eyes when lowering their head, maintaining the horizontal alignment even while grazing.

Sonic cell switch

Brain cells can be remotely activated with sound waves. At least this is the case for the neurons of a few nematode worms in the Salk Institute, California. Researchers genetically modified worms so they would grow neurons with a membrane channel (TRP-4) that responds to ultrasound waves. When the worms are grown in a medium filled with micro-bubbles of gas to amplify the sound waves, their neurons can be stimulated in response to sonic pulses. These low-frequency sound waves can travel through the body without any scattering, so the team is optimistic that this technique could be used for treating human diseases which currently require invasive therapy like deep-brain stimulation.

Updating the family tree

Excavations in the Rising Star cave system in South Africa over the past two years have culminated with the largest collection of hominin bones ever to be found together and the discovery of a previously unknown species: Homo naledi. From the fossils of 15 individuals, we can infer that H. naledi possessed a mismatch of features found in our other extinct relatives: small skull like Homo erectus, strong upper body of Australopithecus afarensis and remarkably human-like extremities. The fossils have not been dated, but are thought to be at least 2 million years old, which would place them at the base of the Homo genus ancestry. Most intriguingly, it is thought that the close proximity of the fossil remains is indicative of ritualistic burial, a trait up to now considered to be exclusively human.

Photograph: Pablo Dodda via Wikimedia Commons

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