Science at Atheist Universe
VIDEO THE WEEK: Here’s a great video explaining how many patterns in nature relate to the Fibonacci sequence. The Fibonacci sequence is a number series in which the numbers in the series are the sum of the previous 2 numbers. As a rule, it can written as xn = xn-1 + xn-2. The ratio of any two successive numbers in the series is very close to the Golden Ratio "φ" which is approximately 1.618034... Thanks to Doone for posting it in the Mathematics group!
HUMAN GENETICS: Genetic adaptation in early African-Americans? A Shanghai team of genome scientists has published a paper claiming that there are signs of genetic change in the genomes of African Americans that likely occurred as a consequence of having to adapt to the new harsh environment. While their results are interesting and important to advance the understanding of genetic variations in African Americans, which could be of medical importance, I think their conclusion is premature, because they have not really shown proof of selection. Basically the authors claim that the increased prevalence of genetic variants predisposing African-Americans to hypertension, prostate and bladder cancer, and others, may have resulted from an early adaptation, hypothesizing that the variants were beneficial for early adaptation. It is intriguing, but more data is needed. They have found that other variants, such as the allele for sickle cell anemia (inn the image), that confers resistance to malaria, have decreased in frequency, presumably due to the lower incidence of malaria in America. Dr. Alkes Price, a Harvard geneticist, however, rightly points out the decrease in sickle cell anemia gene frequency may be explained by the fact that resistance to malaria varies in strength in different regions of West Africa, and that the difference in malaria resistance between today’s African-Americans and their African ancestors, could simply reflect the difference between the Yoruba and other African populations.
HUMAN EVOLUTIONARY BIOLOGY: Why are deep male voices attractive?. As I suspect most female humans would agree, a lower pitched male voice is considered more attractive than a higher-pitched voice. Studies have shown that women prefer deep-voiced males as short-term sexual partners, that American men with deeper voices have more sexual partners, and that Hazda men with deeper voices have more surviving offspring. But to deflate the balloon of the sexual selection theory, a recent paper reported that deeper-voiced men have lower quality sperm than their shrill counterparts. So, is there an evolutionary reason for perceiving deep-voices as more attractive? Deep voices are associated with a heavier, taller man, presumably a better fighter or provider. But why would this undoubtedly very masculine quality result in lower sperm quality? The researchers speculate that the evolutionary model to be applied in this case is not based on phenotype-indicates-fecundity but rather on a trade off between sperm production and a heavy male investment in competition between males for female attention.
EVOLUTIONARY BIOLOGY: World-first hybrid shark found off Australia. I learned something really novel this week. Related species of sharks had never been reported to form hybrids, until now. Hybrids between the common black-tip shark, that lives in global waters, and an Australian black-tip shark species were found in Australian waters. Scientists think the hybrids occur in response to climate change, and that this could be an example of evolution in action. And this is not a rare occurrence for these shark populations: 57 specimens belonging to several generations were found, indicating that the hybrid species is stable. The hybrids were found by genetic testing. The Australian black-tip is slightly smaller than the global species and is adapted exclusively to tropical waters, while the hybrid sharks have been found in cooler seas, 2,000 kilometers farther south. The Australian species has effectively expanded its range of habitat by producing the hybrids. The hybrids appear to be stronger than the Australian species, and they are abundant, accounting for ~ 20 % of the black-tip shark populations in some areas.
GENETIC ENGINEERING/ZOOLOGY: Chimeric silkworms spin a spider silk mixture. Here's another cool thing one can do with genetic engineering: improve the strength of silk by expressing spider silk genes in the silk glands of silkworms. Why go through the trouble? Spider silk is remarkably strong, almost as strong as Kevlar, and flexible, and it could have many potential uses from natural sutures to body armor. Because spiders are territorial and feisty, growing spiders to collect their silk is impossible. Researchers have been trying to make artificial spider silk, and although all the genes that make silk proteins have been isolated, lab production remains very low in yield, thus extremely expensive. The next best thing is to get silkworms to spin spider silk, or at least composite silk, make of silkworm material but with spider fibers in it. The breakthrough that allowed this is called PiggyBac, a transposon (mobile genetic element) that can be used to transfer genes from a lab-made vector into the genome of an animal. The transposon was used to introduced the spider silk genes into the silk-making glands of the silkworm. The transposon also carries a gene that codes for a red fluorescent protein, so the silkworms that took up the spider genes could be easily identified by their glowing red eyes. The resulting transgenic silk is only 1-4 % spider silk, but even that small amount is sufficient to produce silk fibers that were twice as strong and more elastic than regular silkworm silk. The researchers are now trying to refine their technique to achieve an end result of a transgenic silkworm that weaves 100% spider silk.
Science bits and news from other sites:
The New Year in Space: NASA’s Missions and Events in 2012. Wired science has a wonderful piece on NASA’ planned missions for next year, with details on every mission and beautiful photographs. The one illustrated here is the Lunar GRAIL. 2012 started off with the second of the twin GRAIL satellites successfully entering orbit around the moon January 1st. Starting in March, the two probes will collect data to be used for an accurate map of the moon’s gravitational field. This will give test the hypothesis that our planet once had two moons, and that one crushed into our current moon. If this is true, the GRAIL satellites will find that the far side of the moon has a thicker crust than the visible face.
The world’s first chimeric monkeys. Researchers at the Oregon National Primate Research Center at Oregon Health & Science University have produced the world's first chimeric monkeys. Unlike mice that can be made into chimeras by integrating genetically engineered embryonic stem cells into mouse embryos, embryonic stem cells from rhesus monkeys fail to be integrated into embryos. In order to produce the chimeric rhesus monkeys, the researchers had to combine several very early embryos together, at the stage where the cells are totipotent (i.e. capable of giving rise to a whole baby plus the placenta and other embryonic tissues). The resulting babies are all healthy and are the combination of up to 6 different embryos, meaning up to 6 different genomes! This is not simple genetic engineering playing, but has great potential. Transgenic mice (chimeric mice) have helped the field tremendously by allowing the study of gene function in mice lacking specific genes (“knock-out mice”) or containing novel genes, for example. In addition, the research suggests that the use of primate (including human) cultured embryonic stem cells is limited, because those maintained in tissue-culture dishes may lose its ability to generate different tissues, unlike those from living embryo. In order to move stem cell therapies from the lab to the clinics and from mouse models to humans, we may need to understand the behavior of embryonic stem cells from primates.
Dogs’ eyes on a screen. Those of you who are owned by dogs have noticed that dogs follow our gaze and also our pointing fingers. But can they watch TV? My dogs only look up at the TV screen if they hear barking or another animal noise; otherwise they ignore the TV, but I sit in front of the computer and video-chat with my sister via Skype, if she whistles to them, or baby-talks to them, using their names, they immediately respond and try to figure out where the voice is coming from. They even wag their tails. Now cognitive scientist Ernő Téglás (Central European University, Budapest , Hungary) has shown that dogs are engaged when a person on the TV screen talks to them, and in that case, when they are engaged, they actually look at the screen in detail enough to follow the gaze of the person on the screen. The person on the video was flanked by 2 pots, and looked at either pot alternatively. Téglás used a specially programmed camera below the television screen to follow and records, the dog's eye movements. Over 20 dog of different breeds where used for the study. Once engaged, the dogs looked at the same pot the person was looking at 69% of the time. When the person avoided eye contact and spoke in a low voice, the dog didn't look at one pot more often than the other. The results are similar to those obtained with 6 month old human children. Dogs have co-evolved with us, to be able to intimately communicate with us. It’s a wonderful adaptation.
Male spiders watch their rivals on TV and copy their courtship dances. And in case you are not amazed enough at dogs watching TV and following a human gaze on the screen, spiders can watch TV, too. And imitate what the spider on TV is doing too! As you probably know, male spiders dance with elaborate moves to court females. And they compete with other males for the females’ attention. Researchers put male wolf spiders (Schizocosa ocreata) in front of tiny television sets and made them watch videos of other males performing a courtship dance. These dances consist mostly of leg tapping and leg rising. The spiders copied the moves of their on-screen rivals, adjusting the rate of leg tapping to match and even outperform them. And these were wild-caught spiders, not lab spiders. Lab-raised spiders that had not been previously exposed to the mating dance of rival males did not understand what was happening on screen and did not copy the video spider’s dance moves. This type of “signal matching”, copying behavior had only been seen in vertebrate animals before. The more we study nature, the more we realize how animals considered to be “inferior”, such as invertebrates, are capable of very complex behavior.
Two centuries late, “male” explorer is revealed as a female. Two centuries ago, it wasn’t easy for a woman to be a scientist, let alone, to be allowed in the company of men to circumnavigate the globe. A French botanist and explorer, Jeanne Baret disguised herself as a man, and called herself Jean Baret. She was the first woman to circumnavigate the globe. She became a member of Louis Antoine de Bougainville’s expedition on the ships La Boudeuse and Étoile in the 1700s, as an assistant to the expedition’s naturalist. She collected thousands of plant specimens from exotic locales around the globe, even collected the first specimen of one of the world’s best known flowering plants, bougainvillea. The naturalist, Philibert Commerçon, was in on the trick; he and Baret were actually a couple though they never married; she later married someone else. And now biologist Eric Tepe, at the University of Utah and the University of Cincinnati, named one of the newfound species after Baret, when he became aware of her story after hearing an NPR program about Baret. The new plant name is Solanum baretiae. Dr. Tepe thinks it’s what Commerçon would have wanted since he had already intended to name a similar plant after her. She could not have had recognition in her lifetime, because women who were involved in science were thought of as eccentrics or even as an abomination, trying to take on roles assigned to men. I take my hat off to you, Madame Baret.