Venus passed in front of the Sun this week for the last time until 2117. IN this NASA HD video, Venus transit as seen in the 171 wavelength. This channel is especially good at showing coronal loops - the arcs extending off of the Sun where plasma moves along magnetic field lines. The brightest spots seen here are locations where the magnetic field near the surface is exceptionally strong. The transit took almost seven hours but this video shows it in under a minute. Credit: NASA SDO
FEATURED IMAGE: Enterprise is towed by barge up the Hudson River with the World Trade Center's Freedom Tower in the background. The retired space shuttle moved to its new home, the flight deck of repurposed WWII aircraft carrier, now known as the Intrepid Sea, Air & Space Museum.
Is human activity pushing our planet to a tipping point? A multidisciplinary group of 21 scientists have published an important article in Nature this week, based on 100 scientific papers on environmental tipping points or shifts. Physicist Kenneth Wilson was awarded a Nobel Prize in 1982 for the mathematics describing tipping points. Possible environmental tipping points have been described for small systems like ponds, to huge systems like the Sahara or the Amazon forest. Scientists suspect that a tipping point, a sudden reconfiguration of environmental systems resulted in the Cambrian explosion, 540 million years ago, when the diversity of life exploded into myriad new life forms. While tipping points can occur, like in the Cambrian, due to natural factors, now we have a new force to contend with: 7 billion of us influencing basically every corner of our planet. Human activity covers 43% of the surface of the Earth but affects twice that area, so basically the whole globe. Twenty % of the life produced on land is for human consumption; and >30% of the entire planet's fresh water is used by humans. Scientists say that at this point, we are a force to contend with, and our activity can radically change ecological systems and regional climates, to a tipping point. A critical transition may well happen during the next century. The science is solid but it is still suggestive and not conclusive, like most models. But even though time will tell, this is a question of risk-benefit ratio, like so many human activities (including preventive medicine). The current information should be a cry for innovations, such as changes in food production, alternative fuel sources, reduce the population, and manage the ecosystems better, to achieve sustainability. Original report by Brandom Keim at Wired Science.
And while we are on the subject of humans (our favorite subject!), let’s consider why so many people, at least in the US, fail to consider any evidence that humans are indeed influencing our planet in very significant ways: ecology, climate, diversity, etc.
Why we don’t believe in science: our intuition interferes with the facts. Gallup announced this week that 46% of Americans are creationists. With overwhelming scientific evidence in support of evolution, why do so many people reject it in favor of an explanation for which there is exactly zero evidence? We are equipped with naïve intuitions about how the world works, and when science contradicts these naïve intuitions, many people choose to stick to their intuitions, because reasoning is actually hard work. Andrew Shtulman at Occidental College, devised an experiment to test this notion; he tested 150 college students who had taken various science courses on “easy” statements that all the students knew from their classes, and he included statements that were both intuitive and factually correct, such as “The moon revolves around the Earth” and statements that are factually correct but counter-intuitive, like “The Earth revolves around the sun” (remember Galileo? He had a hard time with that statement). The students were instructed to label these facts as true or false as quickly as they could. The students paused before answering “true” for statements that contradict our intuitions, such as “the Earth revolves around the Sun”, or “Air is composed of matter”. This shows that even though the students knew the right answer, their previous intuition interfered with the judgment. The conclusion is that we do not “unlearn” our naïve intuitions: we simply push them aside. This of course cannot be the only reason that Americans are so anti-science. If it were just a common cognitive issue, all humans everywhere would have the same beliefs. In America, it’s a combination of our human cognitive biases and outright manipulation of public opinion by corporate interests or religious interests who benefit from keeping the populace at a maximum level of scientific ignorance. Original post at The New Yorker by Jonah Lehrer.
Since we are talking about non-conscious cognitive processes that influence our beliefs and behaviors, and given the time all of us spend online, I think the following experiment on online behavior, specifically generosity, will interest you all.
Online flowers better than a pair of online watching eyes at making.... Remember the dictator game? In this experimental economics classical test, one person in a pair of players is given some money to do with it what they want; they can keep it all or give some to the other person. The second person has no say on the first person’s decision. Most people give some money to the passive partner, supposedly going against their own interest. This is supposedly because we humans do not like to be judge negatively by other people. In agreement with this hypothesis, people who believe are being watched, even unconsciously, are more generous: a picture of a pair of watchful eyes in a coffee break room to see how they affected donations to a “pay as you like” box, induced coffee drinkers to add 3 times the money they would add if no eye picture was present over the box. Under the eyes, drinkers paid three times more than usual. In a more subtle experiment, social scientists found that in a restaurant, wall portraits of eyes, as opposed to portraits of flowers, induced diners to clean up their mess. In this new experiment, Nichola Raihani of University College London, tested the effect of watchful eyes vs flowers in an online setting, because of its anonymity. He expected the results to be the same as the restaurant, but setting up a dictator game online, with several hundreds of participants from all over the world, revealed a surprising result. Dictators shown flowers, not eyes, gave significantly more money to their anonymous partners! Dictators shown a pair of watchful eyes on the decision screen gave away $0.16 of $0.50 cents on average, which was the same amount as dictators shown a featureless rectangle. It seems that online, we are really conscious of being totally anonymous, and social influence was reduced. Online anonymity weakens the effect of social cues. Dictators shown flowers on the decision screen gave away $0.19. Is it because images of nature put us in a good mood, and therefore, we are more relaxed or generous? It’s possible. More experiments will be needed with different images. Should we start posting beautiful pictures of nature on our background at Atheist Universe?
And while we are on the subject of human cognition, here’s an interesting new fact from the world of smell perception:
The scent of old age and wisdom? Do you think elderly people give off a distinctive scent? And I'm not talking about incontinent elderly folks, I'm talking about the smell of old healthy folks with good hygiene habits. I always thought my grandmother smelled in a peculiar way when I was a teenager. Later in life, I thought my mother, who was in her 80s by then, also had developed a sweetish, not unpleasant smell at all, but very distinctively an old person's smell. Well, science has now proven that younger folks can tell distinguish the scent of older people from that of younger people, in a statistically significant way, in a blind test involving pads worn under the armpits during sleep, for 5 consecutive nights. The test subjects however, did not describe the smell as unpleasant but rather when compared with the "musk" of younger people, especially men, they found the old person's smell to be the least unpleasant. We associate the goodness or badness of smells with different contexts, so perhaps this is why young people describe old people's smell as unpleasant when asked (perhaps they associate it with nursing homes, or declining strength, etc.), but out of context, without knowing who the smell came from, they did not find it unpleasant. Is there an evolutionary reason for the ability to discern the age of a person by smell? It's not clear but some speculate that in ancient times, those who got to be old were the strongest and healthiest, and perhaps that increased their desirability as males. That seems a long stretch to me. It could simply be that old people sweat less and produce less testosterone, therefore the "musky" smell diminishes. Original story at ScienceNOW, here.
We are not always conscious of how developed our sense of smell is, but what about taste? Are we really aware of why we prefer certain tastes?
Evolution gave us a sweet tooth. An opinion piece written by an evolutionary biologist in the New York Times is not a common occurrence. Daniel Lieberman, professor of evolutionary biology at Harvard, wrote this very good opinion piece in defense of a controversial new rule that the NYC mayor, Mike Bloomberg, wants to impose on New Yorkers in an attempt to curtail the rising obesity rate of the city's population, especially among children. Mayor Bloomberg wants to prohibit the sale of sugary soft drinks (soda, juices with other sugar, etc.) in sizes greater than 16 oz, in all restaurants, cafeterias, food carts, food courts, etc., in other words, anywhere that is not a grocery story or a supermarket. We can of course, discuss whether that is fair or not, a good idea or not, etc. But first I want to summarize the core of Dr. Lieberman's argument: evolution selected for a sweet tooth in conditions under which it was adaptive, because humans did not have a superabundance of cheap, easily available sugary stuff, and because we got rid of any sugar stored as fat by constantly burning it through normal activities, mainly walking and running around a lot, as hunter-gatherers. Because evolution gave us a sweet tooth, it is not an impulse easy to control, and in fact, educational strategies have not worked very well so far, especially among children who by nature have a harder time at impulse control. We humans also evolved to eat whatever is in front of us, so big portions of food or drink tend to be finished no matter what the size. So it makes sense to impose regulations. Lieberman argued that although we did not evolve to watch what we eat and go to the gym, we evolved as a social species in which we care for one another's well being, and that includes cooperating with one another to help us survive and thrive. The circumstances have now changed. In ancient times we needed to help one another obtain sufficient calories to feed our expensive fuel-guzzling big brains, and our costly reproductive strategy. Now we must help each other to control our appetite and develop healthy habits, especially children who will otherwise face a lifetime of obesity-related illnesses, and impose a heavy cost of health care to the whole of society. Dr. Lieberman argues that if this involves a bit of government regulation, so be it. We already regulate and heavily tax the sale of tobacco, for example, so why would unhealthy super-sugary junk soft drinks be the exception? The only ones who benefit from lack of regulation are the big corporations that make tons of money by exploiting our biologically ingrained cravings without any regards for our health.
Let’s leave adults, and even children aside, and go to the very, very young, actually let’s go all the way back to fetuses.
Sequencing the DNA of an unborn fetus from the mom’s blood. In an impressive feat of technological innovation, a group of Hong Kong researchers have succeeded in predicting the whole genome DNA sequence of two unborn fetuses (one at 18.5 weeks of gestation, the other at 8.5 weeks of gestation) in a completely non-invasive manner, using fetal DNA isolated from the mom’s blood, and DNA from the dad’s saliva. (As an aside, dad gets to spit in a tube while mom gets a needle in her arm for this test: who said biology was fair?). The reason why new advance is important is that right now, prenatal diagnosis of known genetic conditions require either amniocentesis or a little bit of placental tissue, both invasive procedures that have a 1% miscarriage rate. Back in the 90s, Dennis Lo, the head of the Hong Kong team, discovered that ~10% of the free floating DNA in a pregnant woman’s blood comes from the fetus. The trick is to distinguish fetal DNA in the blood from the mom's DNA. Since or each gene, the fetus will have only one of mom’s variants (the other will come from dad), a statistical analysis allowed the researchers to deduce which of mom’s copies the baby will have. And by sequencing the dad’s DNA, they could predict the genotype of the baby by computationally assembling the pieces. They compared this sequence to the DNA of the baby once it was born and it was found to be 98% accurate. They found 44 new mutations in the newborn baby that the parents didn’t have, and 39 of these were detected in the fetal DNA as well. None of these were disease causing (don’t forget all of us, in fact, all organisms are born with some de novo mutations, since mutations are the raw material of evolution, and this is completely normal). The big problem with this new technique is the huge number of false positives identified in the fetal DNA that ended up being errors in the prediction and not actual mutations that the newborn baby ended up having. This information needs to be filtered or the method vastly improved in order not to worry the future parents unnecessarily. This will probably be the future of prenatal testing but there is a long way to go until it becomes applicable; in addition the current cost would be $50,000.
But I think I posted too much about humans in this blog. Who do we think we are? Let’s not forget that we share this Earth with endless forms, most beautiful and most wonderful. For example, arthropods.
Ever wondered why insects are not bigger than they are? The largest living flying insects have a wingspan of ~10-12 inches, which is very impressive for an insect. But have you ever wondered why insects cannot be as big as birds? Insects do not have lungs, they "breathe" (meaning they exchange gases) through a tracheal system, which is a series of tubes of decreasing diameters that start off at the surface of the animal, as openings called spiracles. The tubes go everywhere in the insect's body and gas exchange takes place directly at the cell walls. So to be really big and fly, they need a lot of oxygen. In fact, in the Carboniferous, 300 million years ago, there were dragonflies that reached over 2 feet in wingspan! The oxygen content of the atmosphere was 35% back then, compared to 21% now. In fact, fossil insect wingspan correlates very well with the % of oxygen in the atmosphere, until the Jurassic, when oxygen started climbing up from an all-time low of 15%, but winged insects became smaller, not bigger. This is because there was a new type of flying predator in town: birds. If insects were too big, they would have lost the maneuverability contest with fast birds that had by then started to evolve an alula, a small front wing projection that allows birds to maneuver at low flying speeds without crashing. The double whammy of lower oxygen and fast aerial predators kept flying insects at more or less the current size. Original story at Ed Yong's blog, Not Exactly Rocket Science, here.
And while we are on the subject of monstrous insects, let’s discuss about some Frankenstein mosquitos that were built to study jumping spider predation:
Vampire spiders’ method of prey selection is visual and very accurate. The East African jumping spider Evarcha culicivora is a very picky eaters. This tiny predator eats blood, but since it cannot procure it itself, it captures female mosquitoes with a belly full of blood from a recent meal. Male mosquitoes, as you know, do not eat blood so they are useless to the spider. But how do they distinguish male from female mosquitoes? The males could have a full belly too, except it’ll contain nectar and not mammalian blood. In addition to providing food, blood makes the spiders more attractive to potential mates, so it is doubly important that the tiny jumping arthropod, itself no bigger than a mosquito, choose its prey judiciously. To figure out how spiders decide which mosquito to jump on, New Zealand biologist Ximena Nelson built Frankenstein mosquitoes made from the parts of different individual dead mosquitoes. That was a labor of precision and patience, of course. E. culicivora has great vision and eyes pointing in all directions, and it was previously known that it uses visual signals to hunt. The question is, will it attack any mosquito with a full belly? What are the minimal visual clues the spiders need to decide to go for it? Nelson’s team used males, females fed only on sugar water, and females who had recently fed on mammal blood. They cut the insects in half, and swapped parts: the results were female heads with male abdomens, etc. They used “uncut” insects as controls. The Frankenstein mosquitoes were mounted in a lifelike posture on a piece of corks, and then presented to the spiders. The spiders preferred the blood-filled abdomens with the right heads: female mosquitoes have very simple antennas while male mosquitoes have ornate, feathery ones. If only the mosquito's head was visible (they hid the abdomen part behind a wall, the spiders went for the heads with the simple antennas. So the spiders don’t only look for blood-engorged bellies, they also look at the antennas as part of their decision to pounce. This ensures that a male mosquito that ate a lot of nectar and has a distended belly too will not become a useless prey for the spiders. It’s astonishing to see how such a tiny arachnid uses so many complex visual clues to pick the right victim. In the wild, they are slow, stealthy, but sure hunters and they are capable of waiting until the right head with the right antennas and the right belly stop by.