Science is ever moving and ever changing, and we’re always finding new things. In this article I’m revisiting some of my past topics with some recent research.
The structure of skin
One of my first articles on thatscienceguy discussed the structure of human skin and how the sun’s radiation affects it. Skin is the largest organ in the human body, and has a critical role in protecting our body from external threats and stopping excessive water loss. The outermost layer, called the stratum corneum, can actually act like a sponge and absorb quite large amounts of water depending on the humidity of the surrounding environment. This ability to absorb water means it needs to be quite flexible, however it needs to balance this flexibility with being robust enough to be able to protect the deeper layers of skin and organs underneath.
Researchers from the Australian National University examined the structure of the stratum corneum to try to understand how its structure allows these dual roles. They found that the keratin filaments which provide skin its structure have a remarkable three-dimensional weave which allows individual fibres to wind and unwind. While the fibres can individually wind and unwind, they do so cooperatively to allow the stratum corneum to breathe without losing structural strength.
Male motor skills
The study which I rated as the strangest of last year investigated the perfect male dance moves to attract women – they even produced videos which demonstrated these moves. Needless to say, it was quite a popular topic!
I explained the importance of that study by likening it to courtship displays by other animals – the males will put on a ‘show’ to demonstrate their prowess to the female, and in the case of humans, dancing may well be one of our courtship displays. But the question remained why exactly do animals (including humans) put on these courtship displays, what exactly are they exhibiting?
Studying the manakin bird, researchers from the University of California Los Angeles found that the female birds preferred to mate with males who performed the courtship display at greater speeds, and were able to tell differences measured in the milliseconds. The speed and energy exertion required by the male to do this courtship display means they have extremely fast heart rates. From this the authors suggested that the courtship display is actually a demonstration of the male’s motor skills, coordination and cardiovascular qualities, and so being able to do it faster shows that the male is stronger and has better quality genes.
And for those wondering what the manakin bird is, from QI:
Sexual attraction
Back at the start of April I blogged about the science of sexual attraction, and in the intervening two months new research has been released which is worth examining.
In the original articles I wrote about the effects testosterone has on males and their attraction to women, and attractiveness to women. Now, new research has shown that men who have higher testosterone are flirtier. Remembering back, testosterone is important for competition between males, so researchers increased men’s testosterone levels by making them compete in computer tasks. The men who showed the highest increases in testosterone as a result of the competition subsequently showed more interest in the woman, made more eye contact with her, smiled more and talked more about themselves. So the testosterone increases induced by competition makes men more attentive to women – maybe this means the best plan before a big date is to do something competitive.
Males have also been found to be able to distinguish whether a female is fertile just from looking at her face. Back in the original articles I wrote how oestrogen levels, which rise during ovulation, slightly change the shape of a woman’s face, making it more rounded and considered as slightly more attractive. Using macaques (a species of monkey), new research has shown that men can recognise these signs of a female’s fertility, but only in faces they are familiar with. Researchers showed male macaques images of females faces which had been classified as being pre-ovulation, during ovulation, or post-ovulation (they found these stages out from measuring the female’s hormones). The male macaques were able to tell the difference between the faces of during ovulation and pre-ovulation, however they could only tell the difference if they were familiar with the particular female. When showed images of an unfamiliar female, they couldn’t tell the difference.
Little is known about the molecular reasons for sexual preference, but research published recently in Nature has investigated how chemicals in the brain may affect who we find attractive. Serotonin, also known as 5-HT, is known to have a huge effect on mood – in fact the most common drug treatment for depression works by making serotonin last longer in the brain. The researchers found that male mice normally prefer female over males as mates. However, when the same breed of mice was modified to make them unable to produce 5-HT, the males lost their sexual preference. When these mice had their 5-HT production restored to normal levels they regained their preference of females over males. This research is the first to show that 5-HT may be involved in sexual preference, and raises the question of whether other brain chemicals are involved in sexual preference.
Lapping dogs
And finally, another update from the strangest research studies from last year, this time the study which examined how cats drank. They found then that cats used the back of their tongues, skim over the surface of the liquid, and then pull rapidly upwards into their mouth. The surface tension would lift the liquid with their tongue straight into their mouth. This seemed much more refined than the simple scooping method that dogs use.
But do dogs really just scoop liquid? It turns out that comment was premature, as new research has now found. Using high speed video it has now been found that dogs too use a very similar method as cats, picking up liquid with the back of their tongue and relying on surface tension and inertia to keep the liquid in place. The liquid travels with the tongue through the oral cavity into the oesophagus, with the tongue then pressing up against the roof of the mouth to prevent the liquid from falling out.
You can see it all in action in these videos:
This is a 300 fps video of a dog lapping. It seems to show spooning of liquid into the mouth but X-ray video tells a different story. From Crompton A.W. and Musinsky C. 2011
This video shows that, contrary to published accounts, dogs do not scoop liquids into their mouths with a spoon-shaped cavity that forms in the ventral surface of a backwardly directed tongue tip. As in cats, an aliquot of liquid adheres to the dorsal surface of the tongue tip and is transported into the oral cavity as the tongue is rapidly withdrawn. From Crompton A.W. and Musinsky C. 2011
Dr Ben Lewis 