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The Evolutionary Perspective
Category Archives: Evolution
Posted: August 25, 2017 at 4:10 am
Controversies like this one underscore the possibility that the bad reputation of naturally occurring hybrids is not entirely justified. Historically, hybrids have often been associated with the sterile or unfit offspring of maladaptive crossings (such as the mule, born of a female horse and a male donkey). Naturalists have traditionally viewed hybridization in the wild as a kind of irrelevant, mostly rare, dead-end fluke. If hybrids arent viable or fertile or common, how could they have much influence on evolution? But as genomic studies provide new insights into how species evolve, biologists are now seeing that, surprisingly often, hybrids play a vital role in fortifying species and helping them take on useful genes from close relatives.
In short, maladaptive pairings dont tell the full story of interbreeding. The genetic transfer that takes place between organisms while their lineages are diverging has a hand in the emergence of adaptive traits and in the creation of new species altogether. According to Arnold, not only is it common for newly emerging species to reacquire genes through hybrid populations, but its probably the most common way evolution proceeds, whether youre talking about viruses, plants, bacteria or animals.
Most recently, signatures of hybridization have turned up in studies on the evolution of the jaguar. In a paper published last month in Science Advances, a team of researchers from institutions spanning seven countries examined the genomes of the five members of the Panthera genus, often called the big cats: lions, leopards, tigers, jaguars and snow leopards. The scientists sequenced the genomes of the jaguar and leopard for the first time and compared them with the already existing genomes for the other three species, finding more than 13,000 genes that were shared across all five. This information helped them construct a phylogenetic tree (in essence, a family tree for species) to describe how the different animals diverged from a common ancestor approximately 4.6 million years ago.
Some of these adaptations, however, may not have originated in the jaguar lineage at all. Eiziriks team found evidence of many crossings between the different Panthera species. In one case, two genes found in the jaguar pointed to a past hybridization with the lion, which would have occurred after their phylogenetic paths had forked. Both genes turned out to be involved in optic nerve formation; Eizirik speculated that the genes encoded an improvement in vision the jaguars needed or could exploit. For whatever reasons, natural selection favored the lions genes, which took the place of those the jaguar originally had for that trait.
Such hybridization illustrates why the Eizirik groups delineation of the Panthera evolutionary tree is so noteworthy. The bottom line is that this has all become more complex, Eizirik said. Species eventually do become separated, but its not as immediate as people would frequently say. He added, The genomes we studied reflected this mosaic of histories.
Although supporting data as detailed and as thoroughly analyzed as Eiziriks is rare, the underlying idea that hybridization contributes to species development is by no means new. Biologists have known since the 1930s that hybridization occurs frequently in plants (its documented in about 25 percent of flowering plant species in the U.K. alone) and plays an important role in their evolution. In fact, it was a pair of botanists who, in 1938, coined the phrase introgressive hybridization, or introgression, to describe the pattern of hybridization and gene flow they saw in their studies. Imagine members of two species lets call them A and B that cross to produce 50-50 hybrid offspring with equal shares of genes from each parent. Then picture those hybrids crossing back to breed with members of species A, and assume that their offspring do the same. Many generations later, nature is left with organisms from species A whose genomes have retained a few genes from species B. Studies have demonstrated that this process could yield entirely new plant species as well.
But animal species seemed more discrete, at least for a while. Most zoologists supported the biological species concept proposed in 1942 by the legendary biologist Ernst Mayr, who was one of the architects of the modern synthesis, the version of evolution theory that combined Darwins natural selection with the science of genetics. Mayrs biological species concept was based on reproductive isolation: A species was defined as a population that could not or did not breed with other populations. Even when exceptions to that rule started to emerge in the 1970s, many biologists considered hybridization to be too rare to be important in animals. We had a blinkered attitude, said James Mallet, an evolutionary biologist at Harvard University. Today, he added, saying that such hybridizations dont affect reconstructions of evolutionary history or that this wasnt useful in adaptive evolution thats no longer tenable.
This is especially true now that computational and genomic tools prove just how prolific introgression is even in our own species. Since 2009, studies have revealed that approximately 50,000 to 60,000 years ago, some modern humans spreading out of Africa interbred with Neanderthals; they later did so with another ancestral human group, the Denisovans, as well. The children in both cases went on to mate with other modern humans, passing the genes they acquired down to us. At present, researchers estimate that some populations have inherited 1 to 2 percent of their DNA from Neanderthals, and up to 6 percent of it from Denisovans fractions that amount to hundreds of genes.
In 2012, Mallet and his colleagues showed a large amount of gene flow between two hybridizing species of Heliconius butterfly. The following year, they determined that approximately 40 percent of the genes in one species had come from the other. Mallets team is now working with another pair of butterfly species that exchange even more of their genes: something like 98 percent, he said. Only the remaining 2 percent of the genome carries the information that separates the species and reflects their true evolutionary trajectory. A similar blurring of species lines has already been found in malaria-carrying mosquitoes of the Anopheles genus.
Other types of organisms, from fish and birds to wolves and sheep, experience their share of introgression, too. The boundaries between species are now known to be less rigid than previously thought, said Peter Grant, an evolutionary biologist at Princeton University who, along with his fellow Princeton biologist (and wife) Rosemary Grant, has been studying the evolution of Galpagos finches for decades. Phylogenetic reconstructions depict treelike patterns as if there is a clear barrier between species that arises instantaneously and is never breached. This may be misleading.
Arnold concurred. Its a web of life, he said, rather than a simple bifurcating tree of life. That also means its more necessary than ever before to examine the entire genome, and not just selected genes, to understand a species evolutionary relationships and generate the correct phylogeny. And even that might not be enough. It may well be, Mallet said, that some actual evolutionary patterns are still completely irrecoverable.
Genomic studies cant create a complete picture of the introgressive movements of genes. Whenever one species inherits genes from another, the outcome can be either deleterious, neutral or adaptive. Natural selection tends to weed out the first, although some of the genes we have inherited from Neanderthals, for example, may be involved in disorders such as diabetes, obesity or depression. Neutral introgressed regions drift, so its possible for them to remain in the genome for very long periods of time without having an observable effect.
But its the beneficial introgressions that particularly fascinate researchers. Take the Neanderthal and Denisovan DNA again: Those genes have allowed people to adapt to the harsh environs of places like the Tibetan plateau, protecting them against the harmful effects of high altitudes and low oxygen saturation, which in nonlocals can cause stroke, miscarriage and other health risks. Variants from interbreeding with archaic humans have also conferred immunity to certain infections and made skin and hair pigmentation more suitable for Eurasian climes.
Mallets butterflies, too, reflect evidence of adaptive hybridization, particularly with traits involved in mimicry and predator avoidance. Researchers had observed that although most Heliconius species had highly divergent wing coloration and patterning, some bore a striking resemblance to one another. The researchers believed that these species had independently converged on these traits, but it turns out thats only partially correct. Mallet and others have found that introgression was also responsible. The same goes for Galpagos finches: Pieces of their genomes that control for features including beak size and shape were shared through hybridization. Once again, parallel evolution cant explain everything.
For these effects to occur, the rate of hybridization can be and most likely is very small. For Mallets almost entirely hybridized butterflies, the occasional trickle of one hybrid mating every 1,000 normal matings is sufficient to completely homogenize genes between the species, he said. Thats pretty exciting.
As these patterns of introgression have become more and more predominant in the scientific literature, researchers have set out to uncover their evolutionary consequences. These go beyond the fact that speciation tends to be a much more gradual process than its often made out to be. Diversification, adaptation and adaptive evolution really do seem to be driven quite often by genes moving around, Arnold said.
The research done by Eizirik and his team makes a compelling case for this. Around the time when the gene introgressions they analyzed occurred, the populations of all five Panthera species are estimated to have declined, likely due to climate changes. The smaller a population is, the greater the probability that a harmful mutation will get affixed to its genome. Perhaps the gene flow found between the different species, then, rescued them from extinction, providing adaptive mutations and patching deleterious ones. This kind of infusion of genetic mutations is so large that it can cause really rapid evolution, Arnold said.
And the process doesnt end with speeding up evolution in a single species. Adaptive introgression can in turn contribute significantly to adaptive radiation, a process by which one species rapidly diversifies into a large variety of types, which then form new lineages that continue to adapt independently. The textbook case can be found in the great lakes of East Africa, which are home to hundreds upon hundreds of cichlid species, a type of fish that diversified in explosive bursts (on the evolutionary timescale) from common ancestors, largely in response to climatic and tectonic shifts in their environment. Today, cichlids vary widely in form, behavior and ecology thanks in large part to introgressive hybridization.
Biologists will need many more years to understand the full importance of hybridization to evolution. For example, Arnold wants to see further investigations like the ones that have been done on the finches in the Galpagos and the wolves of Yellowstone National Park: behavioral, metabolic and other analyses that will reveal how much of introgression is adaptive and how much is deleterious or neutral as well as whether adaptive introgression affects only particular kinds of genes, or if it acts in a more widespread manner.
Unfortunately, for conservationists and others challenged with managing the diversity of imperiled species, the absence of satisfactory answers poses more immediate problems. They must often weigh the value of protecting wild hybrid populations against the harm hybrids can do to established species, including the ones from which they emerged.
A case in point: In the 1950s, a pair of California bait dealers from the Salinas Valley, seeking to expand their business, hopped into a pickup truck and took off to central Texas and New Mexico. They brought back barred tiger salamanders, which could grow to more than double the size of Californias native tiger salamander. The new species quickly proved to be good for the local fishermen but bad for the local ecosystem: The introduced salamanders mated with the natives, creating a hybrid breed that could outcompete its parent species. Soon the California tiger salamander found itself in danger of being wiped out entirely, and it remains a threatened species today.
See original here:
Posted: at 4:10 am
With its exceedingly deadly venom unchanged over the past 10 million years, the Australian tiger snake has essentially defeated evolution. Researcher Bryan Fry says in a press release it's "really unusual" for venom to remain unchanged over such a long period of time.
Typically, predators and prey evolve as they find solutions to each other's evolutionary changes, Gizmodo reports. Not so with the tiger snake, which Fry says represents "a novel twist to the chemical arms race which most snake venoms evolve under" and "a new addition to the theory of venom evolution." A study published in the current edition of Comparative Biochemistry and Physiology Part C explains why.
Tiger snake venom targets a protein called prothrombin, which handles heavy blood clotting. The venom's effect on prothrombin is what makes it so deadly, which means animals should be under a lot of evolutionary pressure to adjust.
However, prothrombin is so important in its current form that any possible mutations to it are just as deadly. As Fry explains, animals with a prothrombin mutation "would not be able to stop bleeding." All of which is a long way of saying tiger snakes "hit the jackpot" with their venom.
Surprisingly, tiger snake venom does possess one benefit to humans: Antivenom developed to combat it is effective against an unusually wide range of venomous snake bites.
(Scientists found a potential new use for spider venom.)
This article originally appeared on Newser: How the Tiger Snake's Venom Beat Evolution
Posted: at 4:10 am
Thank a cranky reptile for helping set a St. Louis boy on the road to Harvard.
Jonathan B. Losos went from carrying plastic dinosaurs to school to begging his parents for a pet caiman, those cousins of alligators that in the early 1970s could be bought in a neighborhood pet store.
"I had to wear ski gloves so I wouldn't get bit," he says.
Undeterred, Losos kept two caimans in a horse trough in the backyard of his family's Ladue, Mo., home. During the winter, the scaly chompers were moved to the basement, outfitted with a plastic swimming pool and sun lamp.
In his new book, Losos writes that he got the idea from an episode of "Leave It to Beaver," when Wally and the Beave hid a baby alligator in the bathroom.
At least the pre-adolescent Losos asked his parents. And because they were friends with Charles Hoessle, then deputy director of the St. Louis Zoo, they queried the professional herpetologist about what he thought. He thought it a superb idea.
"My mother was stuck, and soon our basement was full of all manner of reptile," Losos writes. "I was on my way to my own career in the field."
In fact his mother, Carolyn Losos, felt sorry for the single caiman and got a second one so it had company. But she drew the line at snakes.
Now a professor, researcher and curator of herpetology at Harvard's Museum of Comparative Zoology, Losos, 55, tells a few stories about himself in "Improbable Destinies: Fate, Chance, and the Future of Evolution."
An expert in evolutionary biology, he writes accessibly about the field today.
In short, Darwin notwithstanding, scientists can observe evolution as it happens. And it can happen quickly. It doesn't take millennia as the great Victorian believed.
"You can see evolution with bacteria in a matter of days," Losos says.
With guppies, a couple of years are enough to see them evolve: Research has shown that male guppies not threatened by predators soon develop more color, such as blue and iridescent spots.
Fish exposed to polluted rivers have evolved so they can live there. And wild elephants may even be changing to favor smaller tusks a possible result of hunters' poaching the magnificent beasts for ivory.
Most of these cases and more are described in "Improbable Destinies," an interesting title because some of the examples seem quite probable. Others, however, are curious and perhaps unknowable for instance, would humans have evolved if an asteroid hadn't wiped out dinosaurs millions of years ago?
Evolutionary biology is like a detective story, with researchers looking at historic clues, Losos writes.
But today's scientists also use lab experiments, DNA sequencing and fieldwork to learn about evolution: "Indeed, with the flood of genetic data now available for so many different species, our understanding of evolutionary relationships is advancing by leaps and bounds, producing a much firmer grasp on the evolutionary tree of life."
It was only 1980 when a study of guppies was published that helped show scientists that evolutionary biology could be an experimental science in natural settings.
Guppies in Trinidad have inspired several scientists, and Losos writes about the studies in detail. Most of his book is about a variety of researchers, but the chapter about lizards, particularly brown anoles, is much his own and is a great example of speedy evolution and what biologists call "convergence." That means that similar species in different places (without interbreeding) evolve some of the same traits.
For the lay reader, one of the most amusing parts of his story is how Losos catches lizards to measure their legs and look at other attributes such as the large, sticky toe pads that allow some to run up slick, vertical slopes like green or brown Spider-Men.
The scientist uses a fishing rod with a loop at the end made out of dental floss (preferably waxed). He approaches the anoles in the wild slowly, then with a quick flick snares the subject around the neck with the dental floss noose. It tightens but doesn't hurt the lizards, which have strong necks, he says.
What Losos found was that on various Caribbean islands, separate communities of lizards evolved in similar ways without any contact. Some that lived closer to the ground had longer legs to run quickly over wide surfaces. Others, which lived up higher on narrow twigs, had shorter legs to grasp small branches more easily.
Losos and colleagues X-rayed lizard legs to get precise measurements, then returned them to the exact place where they were caught. Much work was done on the islands, but some lizard Olympics were also held in labs to study how quickly the mini-athletes moved on various surfaces.
When talking to scientists about the work, he writes, sometimes pesky botanists ask whether the leg changes actually showed genetic change, or could lizards born on islands with slim vegetation simply have grown shorter legs? (The question refers to "phenotypic plasticity," such as plant growth that responds strongly to different conditions.)
Losos and his colleagues studied the research. He writes about how human weightlifters have thicker arm bones, "a plastic trait" affected by behavior. Those musclebound subjects don't, however, have children who inherit thicker arm bones. And some of the lizards' bones were longer, a trait that studies on exercise usually didn't explain.
Still, Losos did more work in the lab with lizard leg growth and found that, indeed, a small amount of the growth could be attributed to phenotypic plasticity. But he concluded that evolved genetic change was "likely responsible" for most of it, and he believes that in the next few years researchers will identify the relevant genes involved.
In 1997, Losos' studies were reported in The New York Times, which wrote that "a remarkable experiment with lizards in the Bahamas has now shown that evolution moves in predictable ways and can occur so rapidly that changes emerge in as little as a decade or so."
Dr. Douglas J. Futuyma, an evolutionary biologist at the State University of New York at Stony Brook, was quoted saying the study was "distinctive and exciting and one that will be cited for many years to come."
NATURE AND NURTURE
Losos says work in the Bahamas isn't quite as paradisiacal as it sounds. For one thing, hurricanes occasionally wiped out his lizard subjects (some communities amazingly recovered, though, when their eggs survived hours underwater). When not traveling, during the school year, he lives in the Boston area near Harvard University. His wife, Melissa, and two cats remain in their Ladue home, where he spends summers.
One of his favorite places to visit is actually Australia, which has great biodiversity and his favorite animal, the duckbill platypus. At age 7, Losos was angry when his parents, Joseph and Carolyn Losos, went to Australia without him (they did bring him back a stuffed toy platypus).
In fact, here it might be pertinent to note that although Losos seemed to be born interested in reptiles, his environment nurtured his hobby: He grew up in a family that traveled extensively, and his science teachers at Ladue's high school gave him a great education, he says.
Joseph Losos, a graduate of Harvard University, is a retired investment adviser and a commissioner for the St. Louis Zoo; he has also written book reviews for the Post-Dispatch. Carolyn Losos, a longtime activist in many St. Louis organizations, such as Focus St. Louis, is on the executive committee of the Missouri Botanical Garden and is chairwoman of Arts & Faith St. Louis.
As much as environment plays a role in development, biologists can't always explain, though, whether it is the deciding factor in evolution.
That platypus, for example is a one-off animal an "evolutionary singleton" despite living in streams and environmental conditions that can be found in other countries. (It does, though, have attributes that other animals have, so Losos writes that it is both "a paragon and a repudiation of convergence, evolutionarily unique, but a composite of convergent traits.")
"Who would have predicted the duckbill platypus?" Losos says, alluding to the book's title, "Improbable Destinies."
Other evolutionary singletons include chameleons, kiwis and humans, all of which are unlikely to have evolved elsewhere (including other planets). Losos thinks, in fact, that if an asteroid had not eliminated dinosaurs, there would not be today's homo sapiens. Variations on a "dinosauroid" have been proposed, a creature that evolved with a big brain, feathers, a tail and hands.
Speculations may not make the case for today's study of evolution. But there are other examples of practical applications. In particular, the study of how microbes can so easily evolve to evade antibiotics and pesticides.
If scientists pinpoint important ways bacteria and viruses evolve, they may find techniques to keep microbes from foiling public health efforts. As Losos says:
"It turns out evolution is important in the world today."
Posted: at 4:10 am
When I write articles about buying shares of companies like Alibaba (BABA) and Tencent (OTCPK:TCEHY), yet call myself a dividend growth investor, Im sure that people begin to wonder what in the world is going on? I wouldnt blame them. Those singular pieces focused on high-growth stocks dont do my focus on income justice. Ive had several people reach out to me, asking about my current holdings. Its been awhile since Ive done a portfolio review piece, so I decided to spend some time putting this together so that followers, old and new, can stay up to date on my portfolios construction.
We live in a different world now than investors did in the middle of the last century. Many of the markets that have given tremendous returns throughout much of the 20th century are very mature at this point, and therefore, I dont expect a lot more growth coming out of them. Im not saying that a company like Coca-Cola (KO) is going away. I expect continued large cash flows and capital returns, but Im not satisfied with 100% exposure to slow-growth industries. I bet that KO will continue to post low-single-digit top line growth on average over the long-term as it adds brands and takes market share. This is all a very mature company needs to do: Single-digit sales growth combined with respectable margins and a sustainable share buyback with excess cash flows is all a mature company needs to produce respectable bottom line growth. Being that these companies are typically evaluated based upon a price to earnings ratio, this bodes well for their stock prices over the long-term. With that being said, I dont expect many of the current dividend aristocrats to generate wealth for their investors over the next 50 years as they did during the last 50 years, and Ive been willing to place riskier bets to attempt to capitalize on truly wealth-building opportunities elsewhere.
I dont think that any of this could come across as a controversial or revolutionary statement. As markets mature, growth slows, and expectations of future returns should change. When seeking that same sort of generational growth that early investors in the dividend aristocrats of today experienced, Im looking at new growth frontiers. Im looking for developing markets in terms of both sectors/industries and economies. In other words, when it comes to growth, Im looking at things like software, and not soft drinks.
But before we get to the growth portion of my portfolio, lets take a look at the more conservative dividend growth portion, which makes up the vast majority of my holdings. I end up writing about my more speculative bets much more often than my conservative holdings, but thats sort of the point, isnt it? When I buy shares of a dividend aristocrat, I hope that I never have to write about them again. I dont want these companies in the news. Im quite happy to sit back and watch as they slowly and steadily grow. Im happy to watch their dividends compound via re-investment in an un-noteworthy fashion and track my monthly income, which is surely trending in the right direction. For the most part, I hope that my dividend growth holdings are boring. That would mean that theyre meeting my expectations and goals.
My dividend growth investments make up nearly 75% of my portfolio. When you consider the fact that ~8.5% of my portfolio is currently in cash, this majority appears even larger. My speculative bets basket amounts to 16.7% of my portfolio, though 5 of the 11 companies that currently comprise that basket pay a growing dividend and I imagine that in a decade or so, their yields will be high enough for me to move them up into the main dividend growth category. So without further ado, here are the graphs I put together to break down my holdings.
Speculative Growth Basket:
As you can see, I hold more holdings than many of the other DGI portfolios that are regularly tracked here on Seeking Alpha. I think only RoseNose owns more individual names. This highly diversified strategy may not be best for other investors; Im essentially a full-time investor at this point, and I have the time/energy available to track a portfolio with 75 holdings. I know Jim Cramer says that retail investors shouldnt hold more than a dozen or so stocks because of the time it takes to properly track them. I dont think there is any one magic number in terms of the right amount of holdings. I imagine it comes down to investable capital, risk tolerance, and the aforementioned time, energy, and passion for the markets. I look at a lot of professionally managed funds/sovereign wealth funds, and these portfolios are typically highly diversified. While I ultimately make investment decisions based upon my own personal goals, I like to see what the big boys and girls are doing as I strive to become a better investor. I imagine that my portfolio will continue to grow to the point where its 100 holdings or so and plateau there due to the fact that, for me at least, money doesnt grow on trees.
I understand that my industry/sector allocations are different than many of the other DGI portfolios that youll see here on Seeking Alpha. Technology, not consumer staples, utilities, or real estate, is my largest sector allocation at more than 26% of my overall portfolio. Up next is consumer cyclical and healthcare, coming in at ~16.5% and ~15%, respectively. The rest of my major sectors/industries are currently weighted fairly equally in the 7-10% range. None of these sector allocations are set in stone. Over time I buy value where I see it (healthcare throughout 2016, for example), and I imagine these weightings will change as market sentiment ebbs and flows. When I take a step back and look at my portfolio through a wider lens, Im happy with where they all currently sit.
Maybe the most glaring difference between my portfolio and others is the fact that I have basically zero exposure to energy and utilities. Ive been a bear with regard to the energy space for some time now, having divested all of my oil/gas-related names in 2015/early 2016. Id love to add exposure to the utilities back into my portfolio, but for the time being, I believe theyre irrationally overpriced in this low-rate environment. These high valuations combined with the fact that utilities typically dont offer the dividend growth that Id like to see have caused me to avoid the sector, in general.
77% of my holdings are of the large/mega cap variety. 6% are mid-caps and less than 1% are small caps. Generally, because of my focus on shareholder returns, reliable earnings, strong balance sheets and large cash reserves, Im attracted to large-cap companies. Even when I look at growth names I find myself attracted to large-/mega-cap names because of my focus on best in breed names. The cream typically rises to the top in the markets, and once a growth company becomes profitable (something that I usually wait for before investing), their market caps are relatively large. Im OK with this. Ive seen amazing stories of investors who created generational wealth with relatively small investments in early stage companies that turned into the industry leaders that we see today, but for every one of these home runs Im sure there were numerous strike outs, and sticking to the baseball metaphor, Im content to bat for average rather than power.
Nearly 92.5% of my overall portfolio is comprised of companies domiciled in North America. I dont mind being so overweight with North American (primarily American) companies because many of them are multinationals and Im getting exposure to foreign and emerging markets through their sales anyway. I have taken steps recently to reduce this vastly overweight exposure, hoping to become a bit more diversified internationally. European companies currently make up about ~5% of my portfolio and Id probably like to see that figure rise to the 10% range. Asia makes up the last ~2.5% of my portfolio; as time moves forward, Id like to see this figure rise as well, probably to the 5-10% range. Right now Im seeing better value in Europe and Asia than I am in the U.S. markets, generally. I hope to take advantage of these value gaps as the world plays catch up to the American markets.
But heres the most important graph that Ill be including in this piece: my monthly dividend income totals. Im quite pleased with the progress that Ive made in this regard and I feel confident that Im well on my way to financial freedom because of this passive income. Every few months it seems that I cross a new monthly income threshold with potentially impactful meaning to my life. I remember a few years ago when I was excited to know that my dividends could cover my utility bills if I needed them to. Now my utilities and both of our car payments could fall under the dividend income umbrella if I decided to spend the cash rather than re-invest it. I havent had a month yet where my dividend income could have potentially covered my mortgage payment, but I expect to achieve that goal within the next year or so. Tracking dividend income, rather than the overall value of my portfolio, gives me an anchor to hold on to during market volatility. This is one of the reasons why Ive become so attracted to the DGI portfolio management strategy.
Sure, if I was to eliminate my speculative growth basket and put those funds into a handful of stocks yielding 3%, my monthly income would be even higher. But since Im still in the accumulation phase, I like having that growth exposure and the opportunity to generate outsized returns over the long-term. Although I like to focus on my income stream, I still track the major market indexes and attempt to beat them on an annual basis. The competition aspect of the stock market is a large part of what I love so much about it. Having exposure to companies like Facebook and Amazon and Alibaba and Tencent as a small piece of my portfolio gives me what I believe to be the best of both worlds: steady, reliable income and the potential to make large jumps up the social ladder due to the massive potential of a sub-set of my portfolio.
All of this just goes to show that there are many ways to skin the cat in terms of a dividend growth portfolio. I dont think it matters much what ones sector/industry allocation weights look like so long as they stay true to standard value investing principles with an extra focus on shareholder return related metrics. I look forward to hearing what everyone has to say about the portfolio that Ive constructed over the last 5 years or so. I look forward to the continued journey moving forward. Until next time, best wishes all!
Disclosure: I am/we are long AAPL, DIS, T, BA, AMGN, ABBV, BMY, MDT, MRK, PFE, NVO, JNJ, AMZN, FB, GOOGL, NVDA, MA, V, EXPE, REGN, CELG, BABA, TCEHY, KR, MKC, SJM, KO, PEP, MMM, MO, HASI, NNN, STOR, VER, VTR, SBRA, OHI, CMCSA, MSFT, DLR, AVGO, NKE, QCOM, CSCO, UPS, WHR, FDX, NSRGY, C, MS, GS, BAC, JPM, TRV, BRK.B, GILD, HON, UNP, BX, BLK, UL, XLF, XLK, EZU, IEUR, DEO, BUD, VZ, KMB, IBM.
I wrote this article myself, and it expresses my own opinions. I am not receiving compensation for it (other than from Seeking Alpha). I have no business relationship with any company whose stock is mentioned in this article.
Additional disclosure: Just incase I missed a long in the disclosure form, I am long every stock mentioned in the graphs posted in this article.
Editor's Note: This article discusses one or more securities that do not trade on a major U.S. exchange. Please be aware of the risks associated with these stocks.
Posted: at 4:10 am
Genome sequencing allows us to compare and contrast the DNA of different animals
DNA sequencing technology is helping scientists unravel questions that humans have been asking about animals for centuries. By mapping out animal genomes, we now have a better idea of how the giraffe got its huge neck and why snakes are so long.Genome sequencing allows us to compare and contrast the DNA of different animals and work out how they evolved in their own unique ways.
But in some cases were faced with a mystery. Some animal genomes seem to be missing certain genes, ones that appear in other similar species and must be present to keep the animals alive. These apparently missing genes have been dubbed dark DNA. And its existence could change the way we think about evolution.
My colleagues and I first encountered this phenomenon when sequencing the genome of the sand rat (Psammomys obesus), a species of gerbil that lives in deserts. In particular we wanted to study the gerbils genes related to the production of insulin, to understand why this animal is particularly susceptible to type 2 diabetes.
But when we looked for a gene called Pdx1 that controls the secretion of insulin, we found it was missing, as were 87 other genes surrounding it. Some of these missing genes, including Pdx1, are essential and without them an animal cannot survive. So where are they?
The first clue was that, in several of the sand rats body tissues, we found the chemical products that the instructions from the missing genes would create. This would only be possible if the genes were present somewhere in the genome, indicating that they werent really missing but just hidden.
The DNA sequences of these genes are very rich in G and C molecules, two of the four base molecules that make up DNA. We know GC-rich sequences cause problems for certain DNA-sequencing technologies. This makes it more likely that the genes we were looking for were hard to detect rather than missing. For this reason, we call the hidden sequence dark DNA as a reference to dark matter, the stuff that we think makes up about 25% of the universe but that we cant actually detect.
By studying the sand rat genome further, we found that one part of it in particular had many more mutations than are found in other rodent genomes. All the genes within this mutation hotspot now have very GC-rich DNA, and have mutated to such a degree that they are hard to detect using standard methods. Excessive mutation will often stop a gene from working, yet somehow the sand rats genes manage to still fulfil their roles despite radical change to the DNA sequence. This is a very difficult task for genes. Its like winning Countdown using only vowels.
This kind of dark DNA has previously been found in birds. Scientists have found that 274 genes are missing from currently sequenced bird genomes. These include the gene for leptin (a hormone that regulates energy balance), which scientists have been unable to find for many years. Once again, these genes have a very high GC content and their products are found in the birds body tissues, even though the genes appear to be missing from the genome sequences.
Shedding light on dark DNA
Most textbook definitions of evolution state that it occurs in two stages: mutation followed by natural selection. DNA mutation is a common and continuous process, and occurs completely at random. Natural selection then acts to determine whether mutations are kept and passed on or not, usually depending on whether they result in higher reproductive success. In short, mutation creates the variation in an organisms DNA, natural selection decides whether it stays or if it goes, and so biases the direction of evolution.
But hotspots of high mutation within a genome mean genes in certain locations have a higher chance of mutating than others. This means that such hotspots could be an underappreciated mechanism that could also bias the direction of evolution, meaning natural selection may not be the sole driving force.
So far, dark DNA seems to be present in two very diverse and distinct types of animal. But its still not clear how widespread it could be. Could all animal genomes contain dark DNA and, if not, what makes gerbils and birds so unique? The most exciting puzzle to solve will be working out what effect dark DNA has had on animal evolution.
In the example of the sand rat, the mutation hotspot may have made the animals adaptation to desert life possible. But on the other hand, the mutation may have occurred so quickly that natural selection hasnt been able to act fast enough to remove anything detrimental in the DNA. If true, this would mean that the detrimental mutations could prevent the sand rat from surviving outside its current desert environment.
The discovery of such a weird phenomenon certainly raises questions about how genomes evolve, and what could have been missed from existing genome sequencing projects. Perhaps we need to go back and take a closer look.
Adam Hargreaves, Postdoctoral Research Fellow, University of Oxford
This article was originally published on The Conversation. Read the original article.
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Posted: at 4:10 am
It seems the political hyper-partisanship engulfing the United States has found yet another victim: science. New research shows that political and religious orientations are strongly associated with polarized views of scientific consensus.
Theres a twist, however: the more scientific education and literacy a person has, the more their views are likely to be polarized. These puzzling findings are outlined in a paper published in the Proceedings of the National Academy of Sciences authored by Caitlin Drummond and Baruch Fischoff of Carnegie Mellon University.
The pair studied data from the General Social Survey about Americans views on six controversial topics: human evolution, the Big Bang, stem cell research, anthropogenic climate change, genetically modified foods and nanotechnology. For the first four issues there was significant polarization among respondents, while the last two showed little evidence of it.
Respondents who identified themselves as politically and religiously conservative were far more likely to reject scientific consensus on the polarised issues, while those who identified as liberal were more likely to accept it.
Both for other subjects, such as genetically modified food, that are controversial but have not become part of these larger social conflicts in America, Drummond and Fischoff found no connection between education and polarisation.
So how to explain this? One model the authors suggest is known as motivated reasoning which suggests that more knowledgeable individuals are more adept at interpreting evidence in support of their preferred conclusions. The authors also speculate that better educated people are more likely to know when political and religious communities have chosen sides on an issue, and hence what they should think (or say) in keeping with their identity.
This, of course, will have a substantial effect on science communications efforts. Drummond suggests that science communication on polarized topics should take into account not just science itself, but also its context and its implications for things people care about, such as their political and religious identities. While pragmatic, this may be a bitter pill to swallow for those who think that science should stand or fall on its epistemic merits.
There was one positive finding: greater trust in the scientific community meant greater agreement with the scientific consensus. Perhaps, then, scientists and sciences advocates need to work on building such trust, on both sides of the aisle.
Posted: at 4:10 am
Are Turkey's schools dropping evolution and teaching jihad? - BBC ...
From next month Turkish schools have a new curriculum and it is dividing parents.
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Posted: at 4:10 am
Richard Prum has written a provocative book supporting the theory that beauty drives much of evolution. Most scientists have argued that natural selection (i. e. the survival of the fittest) is the only evolutionary apparatus at work in nature.
Prum, however, encourages readers to consider Darwins mostly ignored idea of aesthetic evolution as a new model for mate choice. He contends that beauty and desire are dynamic forces in natural selection. He purports that each species develops its own characteristic norms of beauty by which it chooses mates.
After a brief exposition on scientists historic resistance to Darwins aesthetic evolution theory, ornithologist Prum illustrates his point by citing the role of beauty in bird mating. He describes the courting rituals of the Great Argus Pheasant of Borneo, one of the most aesthetically extreme animals on the planet.
According to Darwins aesthetic theory, Prum says, male plumage evolves primarily not as a sexual signaling device but in order to meet a value for beauty determined solely by the females of a species.
He then transports the reader to Suriname to view Club-winged Manikins. Males sing with their wings as they seek to appear most beautiful to potential female mates. These sparrow- sized males perform mate-attracting gymnastics in the branches of trees in the understory of Central and South American forests.
After years of watching the males carry on until they nearly collapse, Prum is convinced that much of the mate selection is linked to nothing except the female love of beauty itself. The male calisthenics have nothing to do with perceived physical usefulness: females choose a mate for purely aesthetic reasons. Prum offers this as evidence of Darwins assertion that beauty for the sake of beauty is an engine of evolutionary change.
The author not only tries to prove Darwins aesthetic theory with avian creatures. Later in the book he explores female mate choice based on the taste for the beautiful (as Darwin called it) in primates. Prum states that a proper reading of sexual selection indicates that it is a means for females to develop sexual autonomy. By controlling various aspects of male behavior through their choice of mates, females of many species have reduced the prevalence of rape and improved male social skills.
Prums thought-provoking first book traverses many boundaries. The author also proposes that aesthetic evolution theory accounts for the development of the female orgasm and homosexuality and places feminism firmly within a biological framework.
Doubleday is the publisher of this beautifully illustrated and well-researched 428-page book.
Posted: at 4:10 am
Justin Chon may have made it in Hollywood through a key role in the "Twilight" franchise, but he appreciates the "renegade" approach of YouTube. (Aug. 24)
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Gone Hunting: Shotgun shells have undergone an evolution for a resolution on lead shot issue – Greeley Tribune
Posted: at 4:10 am
I am a staunch believer in the Book of Genesis and what it teaches us about how we arrived at where we are today.
However, when it comes to shotgun ammunition, evolution is the key to successful hunting.
Thirty years ago, in 1987, the Federal government began phasing in its ban on toxic lead shot for waterfowl/migratory bird hunting. This ban spread nationwide in 1991.
The reasoning behind this ban was the thought that crippled birds that flew off, died and were then ingested by birds of prey such as our national symbol, the Bald Eagle. There was evidence to support this theory, with several instances of birds of prey found dead or dying from lead poisoning.
I know hunters that carry nothing but steel even when hunting upland/non-migratory birds just to avoid having to switch loads in the field.
Waterfowl hunters were sent scrambling for alternative ammunition. Even upland (pheasant/quail) hunters needed options if they were hunting on federal waterfowl production areas and national wildlife refuges.
The initial and often-used option to lead shot was steel shot. The results were not good. Unprepared for this new law, ammo manufacturers simply switched out steel for lead without changing much of anything else in the shell.
Steel shot is not nearly as heavy as lead shot and does not pack the wallop or shock when it contacts the target. Steel shot also patterns more tightly which reduces the "kill zone". Hunters crippled more birds but didn't kill them.
I can vividly remember hunting geese with my brother Jack in the cornfields north of Greeley back in the late 80s. The first morning flock of Canadian honkers were locked up, feet down and settling into our decoys. We emptied our shotguns on them.
It literally rained feathers on us as we watched that flock hurry into the sky and safety. Not one pellet penetrated enough to be lethal.
Ammo manufacturers tried alternative shot such as bismuth and tungsten, which were comparable to lead in weight and shocking power but not in price.
Manufacturers began to concentrate on making a better steel-shot shotgun shell. Evolution, trial and error, and test markets were used well, and finally, we have a better product.
It began with the guts of the shotshell. The wad that cradles the tiny pellets was re-tooled. It became a bit shorter to accommodate more pellets.
The primers that ignite the powder were redesigned to burn slower and reduce chamber pressure. The steel shot remained spherical but some manufacturers experimented with different shapes of the tiny BB's. I likened this to the dimples on a golf ball. Ball manufacturers claim their dimple pattern is the best for straight flight or longer flight. The same claims were made by the shotshell makers. The results of this evolutionary period are shotgun shells that contain steel pellets that perform virtually as well as lead ammo.
My favorite lead ammo continues to be a Federal shotshell that contains 1 oz. of no. 4 lead pellets pushed by 3 drams of gunpowder at 1330 feet per second. I prefer this load for upland hunting because it has been my most consistently lethal load at all ranges and in any wind and weather conditions.
Federal, Remington, Fiocchi all make loads similar to what I have just described.
I know hunters that carry nothing but steel even when hunting upland/non-migratory birds just to avoid having to switch loads in the field.
A good example of an effective modern steel load is Federal's Prairie Storm Steel. It comes in a 3-inch shell (requiring at least a 3-inch chamber in your shotgun) and launches number 3 or 4 steel shot at 1600 feet per second. Sixteen hundred feet per second is fast and should have enough wallop out at 40 yards or in the killing zone.
There are also two shapes of pellets or BB's in the Prairie Storm shell. About half of the 170 pellets are spherical while the remaining pellets are spherical with a band (called Flitestoppers). They resemble the planet Saturn and help deliver a lethal punch.
I don't hunt waterfowl much any more. I don't like to kill something that I don't like to eat. However, I do carry a box of steel shot along with me in my F-150 just in case I get the urge.
When you stop to think about it, steel shotgun shell evolution had to have a genesis, too.
Jim Vanek is a longtime hunter who lived in Greeley for many years. He can be reached at email@example.com.
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