You may have missed… curly hair kept humans cool, new species of frog, the ideal surgical knot, and octopus brains

Your hit of the best of last week’s science.

Curly hair kept early humans cool

While all hair reduces solar radiation to the scalp, tightly curled hair provides the best protection from the sun’s radiative heat while minimising the need to sweat to stay cool – according a new study in Proceedings of the National Academy of Sciences.

“Humans evolved in equatorial Africa, where the sun is overhead for much of the day. Here the scalp and top of the head receive far more constant levels of intense solar radiation as heat. We wanted to understand how that affected the evolution of our hair,” says co-author Nina Jablonski, Professor of Anthropology at Penn State University in the US.

“We found that tightly curled hair allowed humans to stay cool and actually conserve water.”

To examine how hair textures affect heat gain from solar radiation the researchers used human wigs and thermal manikins – a human-shaped model that uses electric power to simulate body heat and allows scientists to study heat transfer between human skin and the environment.

A graphic showing how scientists used a thermal manikin and human hair wigs to measure heat transfer from the scalp.
A graphic showing how scientists used a thermal manikin and human hair wigs to measure heat transfer from the scalp. Credit: Melisa Morales Garcia

New species of frog found in NSW

A newly discovered species of frog – Mixophyes australis – with a mating call likened to a stutter has been discovered in New South Wales, Australia.

It resembles its cousin the stuttering frog (Mixophyes balbus), and was originally thought to be a single species. But according to a new study in the journal Zootaxia, genomic testing of the population has revealed that the frogs are two distinct species.

M. balbus is found in Northern NSW, while the southern stuttering frog inhabits Central NSW to East Gippsland in Victoria. A large, ground-dwelling frog, it grows up to 7.5 centimetres long.

The mechanics of the ideal surgical knot

Researchers studying the mechanics of surgical knots have published the results of a new study that could be used to train surgeons to tie stronger, safer sutures.

They investigated which properties influence the strength of surgical knots by analysing knots tied by an experienced surgeon and found that the strength of sutures (made from polypropylene filaments) depend on the tension applied during the tying of the knot.

This pretension permanently deforms, or stretches, the filament which creates a holding force. Too little pretension causes the knot to come undone, but too much snaps the filament – so there’s a sweet spot.

“Our data gives us a recipe for determining the ideal pretension and number of throws, for example, depending on the type of filament used,” says Professor Pedro Reis, head of the Flexible Structures Lab at École polytechnique fédérale de Lausanne (EPFL), Switzerland.

“Quantifiable data on knot mechanics could be integrated into training programs to assess the tensile strength of each knot, ensuring trainees acquire necessary skills for successful surgeries. The data could also facilitate development of robotic surgery via the programming of robotic systems.”

The paper is in Science Advances.

Octopuses change the proteins to prevent brain freeze

Octopuses can’t thermoregulate like we can, so their brains are exposed to and potentially threatened by changes in temperature. Researchers studying California two-spot octopuses (Octopus bimaculoides) have now found that instead they adapt to seasonal temperature shifts by producing different neural proteins.

Described in a study in the journal Cell, the octopuses were able to do this by editing their RNA, the intermediate messenger molecule which acts to translate instructions from DNA to produce proteins.

RNA editing offers a temporary and flexible way for individuals to adapt to environmental changes. It occurs across the tree of life, but RNA recoding – when the editing changes the subsequent protein structure – is much rarer, except in soft-bodied cephalopods like octopuses and squid.

Certain types of neural proteins were more likely to be sensitive to temperature, for example, proteins associated with cell membranes (which are themselves very temperature-sensitive).

Next, the researchers want to explore whether octopuses and other cephalopods use RNA recoding to adapt to other environmental variables, such as low oxygen availability or varied social environments.

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