evolution

‘Retenez ceci : il n’y a de bon, de vrai, de gai, de triste, d’aimable, de variable, de désirable, de potable, de chantable, de célébrable, d’idolâtrable, que le delta qui existe depuis la ceinture d’une femme jusqu’à ses jarretières.’ –George Sand & Alfred de Musset

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Pham and Schackelford (2013) argued that men with more attractive partners are at a greater recurrent risk of sperm competition because other men are more likely to woo them into having affairs. Therefore, men with more attractive partners have more reason to be concerned about and more likely to engage in behaviour aimed to detect infidelity. The idea that cunnilingus, oral sex performed on a woman, could function to detect infidelity was proposed in a 2006 book, but this study is the first to test this empirically. The idea is that oral sex may allow a man to detect the presence of another man’s semen through smell or taste. […]

As side-note I’d like to point out that there is a common misconception often advanced by its critics that evolutionary psychology assumes that everything that people do is somehow an evolutionary adaptation and that evolutionary psychologists cannot or will not acknowledge that some behaviours are simply by-products of other adaptations with no special function of their own. This is a gross misrepresentation of what evolutionary psychology is about and in fairness to the authors of the study they were attempting to actually test whether or not their hypothesis about the adaptive function of oral sex is valid, rather than just assuming it is. It is quite possible that oral sex has no evolutionary function in itself. Humans are a highly sexed species compared to most mammals and engage in many non-procreative sexual acts, perhaps for pleasure alone. Oral sex might simply be a by-product of this interest in sex that humans have. However, if it can be shown that this particular behaviour appears to serve a definite purpose that has an evolutionary history, a reasonable case can be made that it has an adaptive function. […]

They found that “recurrent risk of sperm competition” (attractiveness) predicted interest in performing oral sex independently of relationship length, relationship satisfaction, and duration of intercourse.

{ Psychology Today | Continue reading }

‘love these endocrine supplements i got at the natural foods store. they give you extra endocrine’ –@Mobute

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In response to a threat, the brain triggers the release of epinephrine and cortisol from your adrenal glands into the blood. As a result, your heart beats faster and stronger, your blood vessels dilate to move more blood, and your lung vessels dilate to exchange more oxygen for carbon dioxide. Equally as important, your liver breaks down glycogen (a sugar storage molecule) to glucose and dumps it into your bloodstream.

All these processes work together to increase your alertness and increase the power of your muscles for a short time — like when mothers who lift cars off their small children. You are now ready to respond to the threat; however, there is an exception — you may do nothing at all.

One of the major control mechanisms of the fight or flight response is the autonomic nervous system. This is part of the peripheral nervous system (PNS, outside the brain and spinal cord) and transmits information from the central nervous system to the rest of the body. The autonomic system controls involuntary movements and some of the functions of organs and organ systems.

Parts of the autonomic system acts like a teeter-totter, it’s their relative balance that controls the outcomes. In the fight or flight response, the sympathetic system predominates and your heart rate increases and your blood vessels dilate.

But what if the parasympathetic system gained an upper hand for a short time? […] The heart slows, the blood vessels constrict in the muscles, blood moves from muscles to the gut, and glycogen is produced from glucose. […] Many people have had the experience of parasympathetic domination coincident to a threat, for some folks it proceeds long enough to have an observable result – they faint. […] when your brain is starved of oxygen and glucose, you pass out. […]

Lower animals will faint as well, but they have additional defenses along these lines. Mammals, amphibians, insects and even fish can be scared enough to fake death. […] There are overlapping mechanisms for feigned death, from tonic immobility (not moving) to thanatosis (thanat = death, and osis = condition of, playing dead). […] One study in crickets showed that those who feigned death the longest were more likely to avoid being attacked, so this is definitely a survival adaptation.

{ biological exceptions | Continue reading }

photo { Steven Brahms }

‘I stick my finger in existence — it smells of nothing.’ –Kierkegaard

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We Westerners have a boring pointing repertoire. Most of the time, we just jut out our arm and index finger. If our hands are occupied — carrying a heavy load, say — then we might resort to a jerk of the head or elbow. But if the pointer finger’s free, we’ll point it.

Not so for the Yupno. Within a few days of their arrival in the valley, Núñez and Cooperrider noticed that the Yupno often point with a sharp, coordinated gesture of the nose and head that precedes them looking toward the point of interest. […]

Pointing, he answered, seems to be a fundamental building block of human communication. Great apes are never seen pointing in the wild. And in human babies, pointing develops even before the first word […]

The Yupno aren’t the only ones who point with their face. Lip pointing — in which protruding lips precede an eye gaze toward the area of interest — has been observed in people from Panama, Laos, and other groups in Australia, Africa, and South America. Head pointing, according to one study, happens frequently among people speaking Arabic, Bulgarian, Korean, and African-American Vernacular English.

{ Phenomena | Continue reading }

Don’t let go of me (Grip my hips and move me)

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Why do fingers get wrinkly in the water? […]

A hypothesis has been proposed which suggests that the wrinkling might be an evolutionary adaptation to make the handling of objects underwater easier. Wrinkling creates a kind of drainage path for water and so enhances the grip on an object (this is called a ‘rain tread’ hypothesis). In order to test if this hypothesis is true Kareklas et al. have recruited volunteers and tested their ability to transfer wet objects when the fingers are wrinkled and not. […]

20 participants had to transfer glass marbles from one container to another in two different conditions (1) take the marble from a container with water pass it through a small hole and put into an empty container and (2) take the marble from a container without water pass it through a small hole and put into an empty container. […]

When the marble ball was dry there was no difference between the transfer time with wrinkly and smooth fingers. However, when the marble was wet then on average it took 12% less time to transfer the object with wrinkly fingers. Therefore, the study concluded that the wrinkling of fingers improves the handling of wet objects (which supports the rain tread hypothesis). Why are our fingers not always wrinkled then? In paper’s discussion Kareklas et al. suggest that there potentially are some fitness trade-offs to the wrinkly fingers. Maybe wrinkled fingers are less sensitive to pain, pressure, heat etc. and are therefore damaged easier, which would explain why it is not good to always have those wrinkles.

{ The Question Gene | Continue reading }

The work done in this room lies at the heart of a department that handles some of the UK’s most cutting-edge research on forensics and anatomy. […]

The hand is Meadows’ area of focus. Variations in scars, skin pigmentation, the smallest nooks and crannies of the fingernail and, most importantly, superficial vein patterns: all of these can build a body of evidence and allow the police to identify an offender in an incriminating photograph. “The back of the hand is part of the anatomy that an offender is quite happy to have in an image, whereas they wouldn’t necessarily want their face captured,” Meadows says. In 2009, Cahid’s work was instrumental in the Neil Strachan case, part of Scotland’s biggest paedophile ring. His unusually distorted lunula (the white half moon at the bottom of a nail) helped identify and convict him.

Meadows and her colleagues have built up the UK’s only database of the hand’s vein patterns, with around 800 samples. Of the 40 or so cases they have worked on, their data have resulted in over 80 per cent of suspects changing their plea.

{ FT | Continue reading }