Friday, December 14, 2012

The Other Hobbit

The first installment of The Hobbit has hit theaters today, but scientists continue studying the real-life ancient "hobbit," homo floresiensis of Indonesia, to find out more about the individual.  Susan Hayes, an anthropologist from Australia, has used her background in forensic science to produce a facial approximation of the h.floresiensis specimen, who lived around 18,000 years ago, and was about three feet tall, 70 pounds, and female:

This reconstruction was created by making a 3D image of the skull, then constructing a face over this image.  The key was determining to use the features of modern humans, rather than monkey-like features, as artists had perviously done.  This decision seems reasonable, since the hobbit is more closely related to humans than chimpanzees, for example - modern humans provide the best model for facial reconstruction.   Some of the most notable features of this female are her small eyes and small forehead.  This work is exciting in that it quite literally puts a face on a fairly recent relative of ours, but should be taken with a grain of salt at this point; it has been released without first being published in a peer-reviewed journal, and it remains quite approximate in nature.

Romani people come from India

Scientists collaborating from many European universities have completed a genome-wide study to trace the history of the European Romani population, commonly referred to as "gypsies."  Previous computational modeling of the Indo-European language family suggested that the Romani people's language originated somewhere in India (though the methodology of the study in question remains questionable from a historical linguistic standpoint).  This genome study was able to corroborate an Indian origin, particularly a northwestern one, and to pinpoint their departure from India to about 1500 years ago.

Based on 800,000 SNPs from a sample of 152 Romani people, as well as pre-existing SNP data for Europeans, Indians, Central Asians, and inhabitants of the Middle East, the researchers were able to study the Romani migration path in detail.  They found that the Romani generally stayed together on their journey toward Europe, mating only moderately with the local populations and suffering from two population bottlenecks before beginning to disperse once they reached the Balkans.

Once the Romani dispersed throughout Europe, different pockets mixed with the local European populations to varying degrees.  The Welsh Romani have mixed to a great degree; the easter European Romani mostly kept to themselves until recently; and the Portugues, Spanish, and Lithuanian Romani seem to have mixed with the non-Romani Europeans in the past but then started isolating themselves again more recently. 

This analysis was a great first step in beginning to understand the history of a marginalized group and will hopefully help in giving the Romani a sense of identity as they continue to overcome their status as social outcasts.

When being short is adaptive

As a tall person, I've always been told that I had an advantage in life - indeed, height correlates with some metrics of success.  However, researchers at the University College London that there are actually cases where it is evolutionarily advantageous for individuals to be shorter.

The researchers examined 89 small populations from various environments across the world who employed various subsistence strategies, then performed statistical analyses to determine what factors proved predictive of height.  While there was some effect of environment and a very minor role of diet, the strongest correlates were measures of life expectancy.  The shorter the projected lifespan of a population, the shorter the people would physically be.  This makes intuitive evolutionary sense -- if you're likely to die young, you should stop devoting energy to development earlier on in life so that you can start devoting energy to producing offspring.  This shorter development window (which also correlates with earlier onset of menstruation) means that individuals have less  time to grow.   On the other hand, if you're going to live longer, the increased energy associated with being larger would ultimately permit you to later devote more energy to reproduction.

While these findings were for modern human populations, they actually are informative for further back in our evolutionary history; as we evolved from australopthecus ancestors into the homo genus, increased intelligence might have brought about increased lifespan, allowing the more recent ancestors of humans to grow taller than their more apelike ancestors.

14 new genes linked with arthritis

Rheumatoid arthritis is a chronic disorder that primarily affects our flexible joints. It causes inflammation in the joints, resulting in swelling, stiffness, pain and reduced joint function.  Women are 3 times more likely to develop this disorder than men are.

A recent study (reported Nov 26 2012) conducted by researchers from the University of Manchester has identified 14 genes in both genders that are associated with the disorder. These 14 join another 32 genes that have already been identified in a previous study. Out of those 14, some of them were X-chromosome genes. This newly- established association between the X chromosome and the disorder could possibly help explain the significantly higher incidence of it in women, who have 2 X chromosomes, than in men, who have only 1.

Presently, about 1/3 of arthritis patients do not respond well to the medicine available on the market.  The results of this study will greatly improve clinical treatment of arthritis. Out of the 14 genes newly identified, 3 are currently "targets for drugs" - as in that we presently have drugs that are able to target those specific genes. The remaining 43 genes can & should be studied in terms of pharmacology to further develop our clinical treatment ability. 

Epigenetics underlie intergenerational transmission of homosexuality?

From a purely evolutionary standpoint, homosexuality may be seen to be a puzzling trait. As it doesn't increase -and in fact, can decrease- a person's reproductive success means that, according to the rules of natural selection, it should not be so common a trait as it is today, all over the world. Researchers have been trying to identify a genetic basis for homosexuality, seeing as how they seem to "run in families".

A new study has suggested that looking at the epigenome will be more fruitful than studying the genome. According to the article, some epi-marks (i.e. temporary switches that regulate gene expression) "affect sexual partner preference". Usually, epi-marks are "erased" between generations and are not passed on from parent to offspring. However, they can "escape erasure", and the sexual orientation of the parent can end up influencing the orientation of their offspring.

See here for a very unscientific response to the study:

Viruses can work together

Newsflash: viruses still smarter than we are

New research done at two English universities found that viruses can easily and transiently develop the ability to adjust their behavior based on how many other viruses there currently are in their host. This means that viruses don't infect a host on its own; it can work in conjunction with other viruses to maximize its spread (and its damage on the host population).

Furthermore, researchers found that the virus would only cooperate with similar viruses, i.e. viruses it was related to. When it infected alone, it would clone itself and then work with the newly cloned viruses to. When this was the case, all clones worked together to kill the host as slowly as possible to enable maximum replication of the virus. But when other viruses, to which it was not related, were present in the cell, it deliberately worked against them to kill the host cell faster so it could dominate the other viruses.

The study looked at a relatively simple virus, and thus the astonishing speed at which it can adapt its behavior is especially discouraging. Humans have been on a never-ending quest to evade/better the viruses like influenza that infect us, but this news tells us that we have a long way to go. The evolutionary arms race rages on.


Cocktail Chatter: Matt Killian (Anthropologist Finds Evidence of Hominin Meat Eating 1.5 Million Years Ago: Eating Meat May Have 'Made Us Human’)

Anthropologist Finds Evidence of Hominin Meat Eating 1.5 Million Years Ago: Eating Meat May Have 'Made Us Human’
via Science Daily

Anthropologists recently discovered a skull fragment in Tanzania that reveals that our ancient ancestors were eating meat more than 1.5 million years ago. This provides a new point of view of human psychology and brain development in ancient times. Other evidence includes stone butcher like tool engravings on ungulate fossils. "Meat eating has always been considered one of the things that made us human, with the protein contributing to the growth of our brains,” said Charles Musiba, Ph.D.,  a professor at the University of Denver who helped make the discovery. "Our work shows that 1.5 million years ago we were not opportunistic meat eaters, we were actively hunting and eating meat,” he also said. A common thought among scientists is that we truly became humans when we began eating meat and becoming ‘carnivorous-omnivorous creatures.’ Before this, developing hominins were omnivores leaning more toward herbivores. The two-inch skull fragment was dug up in northern Tanzania, specifically Olduvai Gorge, at a site that is considered ‘the cradle of mankind,’ because it has been a constant ground where anthropologists have found many clues of evolution. The fragment was said to belong to a two year old child, and it showed signs of a disease associated with anemia, porotic hyperostosis. Scientists concluded that the child’s diet was insufficient in certain nutrients that are linked to meat eating. This lack of meat may also have altered the mother’s breast milk, which would also cause nutrient deficiencies. "The presence of anemia-induced porotic hyperostosis…indicates indirectly that by at least the early Pleistocene meat had become so essential to proper hominin functioning that its paucity or lack led to deleterious pathological conditions," the study said. "Because fossils of very young hominin children are so rare in the early Pleistocene fossil record of East Africa, the occurrence of porotic hyperostosis in one…suggests we have only scratched the surface in our understanding of nutrition and health in ancestral populations of the deep past.” Scientists believe that the lack of meat eating may not have been by choice, but due to a scarcity in animal foods. The child had been lacking in specific vitamins B12 and B9, which leads researchers to believe meat eating dwindled. This research also leads anthropologists more in depth to the coming about of homo sapiens. Musiba said that the transition from herbivores and scavengers to omnivores and carnivores gave the hominins the protein that is need to give them an “evolutionary boost.” "Meat eating is associated with brain development,” Musiba said. "The brain is a large organ and requires a lot of energy. We are beginning to think more about the relationship between brain expansion and a high protein diet.”

Cocktail Chatter - Matt Killian

Blog Posts to Make Up For Quiz

It Now Only Costs $100 To Know Everything About Your DNA

            Thanks to an investment from a high-ranking employee at Google, Sergey Brin, is now offering its genome sequencing for $100. They offer information about how susceptible you are to certain diseases. They hope the lower price would take price out of the decision and allow interest to be the driving factor in whether or not you want to get your genome sequence. However, the results just boil down to percentages, so you don’t receive any concrete answers.

Tracing Humanity's African Ancestry May Mean Rewriting 'out of Africa' Dates

            A University of Alberta archeologist’s research is leading anthropologists to rethink the ‘out of Africa’ theory. Evidence included artifacts that point to human occupation of Africa at least 200kya, which encompasses a late Ice Age time where a “genetic bottleneck” likely occurred. Methods used to date these findings include radiocarbon dating as well as spin resonance. The importance is that they may be able prove that people lived through the bottleneck period.

Africa's Homo Sapiens Were the First Techies

            A search for finding the beginning of modern human behavior and technological advancement has led anthropologists to South Africa. Wits University professor, Christopher Henshilwood, has written a paper about the Still Bay techno-traditions from 70-75kya and the Howiesons Poort from 60-65kya. He has found evidence of the first abstract art, jewelry, and bone tools that were used to make spears. Henshilwood said, "All of these innovations, plus many others we are just discovering, clearly show that Homo sapiens in southern Africa at that time were cognitively modern and behaving in many ways like ourselves. It is a good reason to be proud of our earliest, common ancestors who lived and evolved in South Africa and who later spread out into the rest of the world after about 60,000 years.” He also mentioned that climate change as well as the rising sea levels could have led to these innovations. His goal is to prove the “Neanthropic Man” originated in Africa and led to the modern behavior in Europe. 

Wednesday, December 12, 2012

The Interdependence Hypothesis: How Human Evolution Evolved

Previous hypotheses:

(1) Big Mistake Hypothesis  --   collaboration evolved when humans lived in small groups. It is possible that collaboration had an advantage because it benefited kin and increased chances of reciprocity in the community. Reciprocity is critical because it determines an individual's reputation.

(2) Cultural Group Selection Hypothesis -- collaboration evolved in larger social groups. The hypothesis states that culture breads and individual's sense of altruism. The more altruistic a population is, the more successful it will be. Since humans tend to mimic one another, altruism becomes valorized by the community.

The Interdependence hypothesis is a new hypothesis of human evolution stating that at some point humans began to collaborate to survive and procreate. Collaboration first began in small populations and then spread to be a large societal norm.

When thinking about collaboration and altruism, people tend to use the prisoners dilemma as an example. However, there is also the "Stag Hunt Game," which states that individuals must collaborate with others to benefit; the benefits of collaboration are greater than those of any solo alternatives; and all solo alternatives must be forsaken in order to collaborate. Basically, if an individual can hunt a rabbit, but the group can hunt a deer (at the cost of losing the rabbit), then the group will collectively hunt the deer and have more food for the group. This is exhibited in human populations. It is not, however, exhibited in chimpanzees.

Since small communities benefited from working together, the community exhibited behaviors of altruism and collaboration. Once human populations began to grow and encounter other populations, collaboration allowed human sub-populations to better survive against increasing competition. Thus, collaboration was exhibited not only in individuals and small populations, but also in large communities and societies.

It is important to note that this explanation is a hypothesis, not a theory.


Monday, December 10, 2012

Oxytocin Produces More Engaged Fathers and More Responsive Infants

A recent study shows that oxytocin administration to fathers increases their parental engagement, while their babies are more responsive. As we know, oxytocin is a neuropeptide that plays an important role in the formation of attachment bonds.The scientists in this study examined whether oxytocin administration in fathers had an effect on their engagement and connection with their child. However, the study also examined whether oxytocin effects on the parent's behavior would affect  physiological and behavioral processes in the infant.

The results showed that salivary oxytocin levels rose significantly in the fathers after oxytocin administration. Interestingly, infants showed similar increases in their oxytocin levels. Under the increased oxytocin condition, fathers showed increases in key parenting behaviors, such as touch and social reciprocity that fostered increases in infant social behavior, such as the social gaze and exploratory behavior.

These findings have important implications for the treatment of young children at risk for social difficulties. This insight may eliminate the need to administer drugs to young children in some cases.

New Study Sheds Light On How Salmonella Spreads in the Body

Salmonella enterica is a major threat to public health. The disease is known to cause systemic diseases, such as Typhoid Fever, and gastroenteritis in humans and other animal species. The disease is acquired through oral ingestion of contaminated water or food and through contact with a carrier. Scientists at Cambridge wanted to find out how diseases such as Salmonella grow at the single-cell level and spread throughout the body.

During the infection, salmoellae are found in cells in the immune system, where they thrive and continue to grow. The bacteria adapt to their surroundings and inhibit the immune system cell's natural antimicrobial activity. These scientists discovered that the bacteria must also leave already-infected cells to spread to distant sites in the body. This exodus is necessary to combat escalating efforts by the local immune system. Ultimately, these scientists discovered certain genes and gene regions that play pivotal roles in the bacteria's ability to spread throughout the body. Their findings provide valuable knowledge that could help change the way we treat diseases.

How Fins Became Limbs

Recent research suggests that hands and feet evolved from fins due to gains in DNA components that activate certain genes.

Researches added extra Hoxd13, a gene known to affect the forming of body parts, to the fin of a zebrafish embryo. The experimental embryo developed more cartilage and had reduced fin cartilage. This is consistent with the formation process of human limbs. As a result, the zebrafish developed one limb that appeared more like a leg than a fin.

After they confirmed that Hoxd13 is essential to limb development, the researches guessed that evolutions in control elements were responsible for increased expression of that gene. They introduced a Hoxd13 control element that is present in mice to the zebrafish. As they suspected, the control element had the ability to drive gene expression in mice.

Wednesday, December 5, 2012

The Evolutionary Crime of Holding Algae Captive

Protozoa, apparently, "captured" algae millions of years ago, and used their genes for energy production. The result was a more powerful organism, which actually serves as the "missing link" in the evolutionary chain we have constructed today.

The genes of algae allowed protozoa to perform photosynthesis, and thus produce easy energy using sunlight. This was evidenced by frozen protozoa's dual nuclei cell structure, manifesting both its own and algae's.

The relationship with mutual, known as endosymbiosis, in which algae was literally living in the protozoa, and the sugars protozoa created through respiration were shared with the algae living inside of it.

Over millions of years, the organism eventually became one - the missing link in evolution.

The most harmful mutations in humans arose recently

A new study shows that over 86% of the most harmful mutations to humans actually arose only 5,000-10,000 years ago. 

These mutations are single nucleotide polymorphisms (SNPs), and while some of these are, as we know, not dangerous or sometimes even beneficial, they are more harmful than not.

Its posited that the Out-of-Africa Bottleneck led to an inefficient elimination of the most harmful mutations, rather than ridding our old genetic makeups of the harmful mutations. Furthermore, while these mutations existed before the bottleneck, they were essentially unseen or ineffective because of the large population of humans. The bottleneck diminished the human population to the point where the mutations became more manifest and more effective at affecting a significant portion of the population.

The study also found that "the older the genetic variant, the less likely it was to be deleterious." Additionally, about 81% of SNPs in Europeans and about 58% of SNPs in Africans arose in the past 5000 years. Older variants, from over 50,000 years ago were more frequent in Africans. These statistics serve as a testament to the out of Africa Bottleneck, and show how these harmful mutations became, essentially, more popular in the past 5,000-10,000 years.

Social Cooperation and Punishment

A new study found how social cooperation may be linked to social exclusion through punishment.

Through punishment, cooperation may become more apparent and valued in society because organisms have an inherent proclivity against being excluded.

A present example of this is how drivers will have their licenses taken away if they drive under the influence, thus "excluding them from the driving community."

This model shows how, unlike past models, the punisher can be benefitted, which very easily links to the possibly transformation and relationship between punishment and social cooperation. Those who are not excluded feel more welcome, and also find more reason to remain within the group, because of the adverse effects of being excluded.

Monday, December 3, 2012

SIlvery Fish Elude Predators with Light-Bending

It has been found in a new study that fish with a silvery coloring have developed a way to become basically invisible to predators. At practically every angle these colored fish are able to use the make up of their skin to camouflage themselves into their surrounding, protecting them from any near predators. Like the many adaptations we read about in The Making of the Fittest, silver fish like sardines and Atlantic herring have become the "masters of camouflage" with this new adaptation.

Dr. Nicholas Roberts, one of the authors of the study, believes these fish have the ability to work their way around a basic reflection law. This law states that whenever light is reflected off a surface, the resulting light that comes off of this surface becomes polarized. Silver fish have the ability to avoid such polarization with the different makeup of their skin. Their skin is composed of alternating layers of cytoplasm and two different types of guanine crystals. These guanine crystals refract light, which is key in their invisibility process. They contain different refractive indexes, allowing the fish to create a unique reflective property.

Dr. Roberts explains that "the polarization happens over a range of angles instead of one, and the end product of having all the layers together is that it creates a polarization-neutral reflector." This details how the fish are able to have such a capability and explains what seems to be an observation of invisibility as something more controllable. Silver fish have evolved over time to contain the exact ratios of the two types of guanine and have achieved near-constant reflectivity because of this. The invisibility mechanism is seen in all silvery fish.


Monday, November 26, 2012

Scientists find that different cells contain different genomes

Basic, high-school level biology currently teaches that every cell in the human body contains the entire human genome, and that this genome is identical. The difference between a kidney cell and a brain cell has so far been believed to be in the expression of genes, and not the amino acid code itself.

Some scientists, though, have questioned the current dogma by positing that the copying of DNA from mother cells to daughter cells during human development is not 100% faithful, and that deletions, duplications and sequence changes occur.

Recently, a study conducted by Yale and Stanford scientists has helped give this hypothesis strong support. Using stem cells, the researchers have shown that "humans are made up of a mosaic of cells with different genomes", thereby debasing the longstanding belief that every cell contains the same genome.

The scientists used whole-genome sequencing to study stem cells (called iPS cells) that they developed from mature differentiated skin cells (i.e. matured daughter skin cells) of the inner upper arm area of two human families.

They compared these cells to the skin cells from which they originated (i.e. mother skin cells), and found that the iPS cell genomes closely resembled their mother cell genomes. However, there were deletions or duplications involving fairly large chunks of DNA (up to a thousand base pairs). Upon further inspection of where these differences first occurred, it was found that up to half these differences "pre-existed", i.e. already found among the mother skin cells and were not a result of deletions/duplications/changes during the copying of mother cell genome to daughter cells.

As it turns out, "mosaicism is extensive" in the cells of the skin. 30% of skin cells contain copy number variations (CNVs), meaning segments of DNA that are deleted or duplicated (without a change in sequence). These CNVs were previously only thought to occur in association with diseases such as cancer. These findings have huge implications because up till now, genetic analyses have only use blood samples. Evidently, blood cell genomes might be different from those of the cells of other parts of the body, and all work that has involved DNA (e.g. developing vaccines/medicine) may be missing mutations that exist outside of blood cells.

See the Yale article here
See another article here

Saturday, November 17, 2012

Ancestry Solves Disease Riddles

Being able to find the genetic roots of idiopathic diseases (diseases that arise spontaneously) is a crucial part of finding the cures and treatments for those illnesses. However, when human genomes have literally millions of genetic variations that could effectively cause a disease, looking for a particular mutation is like looking for a needle in a haystack; the task is near impossible. But what if there was a way that the amount of variations a researcher or doctor was choosing from was significantly decreased?

A new study by scientists at The Scripps Research Institute, Scripps Health, and Scripps Translational Institute has proven that looking at the genomes of people with similar ancestries dramatically reduces the amount of variations produced when comparing genomes, making finding a specific genetic mutation much easier. The scientists examined the genomes of 52 individuals from 10 different populations and ancestry and compared the amount of variations between the populations and between each individual genome. The results were as expected: within a specific population and ancestry, the amount of mutations were decreased and between individual genomes of different ancestry, the amount of mutations was drastically increased.

This find is important because it will encourage the sequencing of more human genomes for use in the medical world. The more genomes that are sequenced, the more genomes will be available to compare with when trying to find a genetic mutation that may be the cause of harmful diseases for which the cure was unknown. This will make finding the mutation easier diagnosing the disease quicker, and prescribing treatment or finding a cure more efficient and faster.


Thursday, November 15, 2012

Genetic Diversity in Cancer Cells

A recent study performed by Stefanie Jeffrey, MD (professor of surgery and chief of surgical oncology research at the Stanford University School of Medicine) and her research team has brought new insight into the heterogeneity of cancer cells and how we may be able to treat them. Through the use of two relatively new technologies (the Magsweeper and the PCR microfluidic chip) the researchers were able to isolate and sequence 95 genes from the circulating tumor cells of 50 patients with breast cancer. Circulating tumor cells, or CTCs, are a rare type of red blood cell believed to help disseminate cancer from organ to organ throughout the body. The results of the study reflected a surprising amount of genetic diversity in CTCs. “In the patients, we ended up with a subset of 31 genes that were most dominantly expressed,” said Jeffrey. “And by looking at levels of those genes, we could see at least two distinct groups of circulating tumors cells.” The researchers were able to divide the CTCs into as many as five groups, depending on which genes were used, each with different combinations of genes turned on and off. The diversity among these CTCs suggests that a single biopsy of a patient’s tumor does not necessarily indicate all of the molecular changes driving the cancer forward and helping it to spread. As we continue in our efforts to learn more about cancer and how to treat it, we must keep in mind that different cells may require different therapies.

According to an article published on the Stanford University School of Medicine website, this study is “the first time that scientists have used high-throughput gene analysis to study individual CTCs, and opens the door for future experiments that delve even more into the cell diversity. The Stanford team is now working on different methods of using CTCs for drug testing as well as studying the relationship between CTC genetic profiles and cancer treatment outcomes. They’ve also expanded their work to include primary lung and pancreatic cancers as well as breast tumors.”

1. “Not all tumor cells are equal: Stanford study reveals huge genetic diversity in cells shed by tumors” <>
2. “Not all tumor cells are equal: Study reveals genetic diversity in cells shed by tumors” <>
3. “Single Cell Profiling of Circulating Tumor Cells: Transcriptional Heterogeneity and Diversity from Breast Cancer Cell Lines” <>

Wednesday, November 7, 2012

Inflammation Marker Linked to Increase Risk for Death From Cancer in Korean Men

Inflammation marker linked to increased risk for death from cancer in Korean men

PHILADELPHIA — Measuring blood levels of high-sensitive C-reactive protein, an important marker of inflammation, in apparently cancer-free men could potentially help identify those at increased risk for death from cancer, in particular lung cancer, according to data published in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.
"Inflammation has been linked to the initiation and progression of several types of cancer, as well as to the progression of atherosclerosis and cardiovascular disease," said Minseon Park, M.D., Ph.D., M.P.H., assistant professor in the Department of Family Medicine at the Center for Health Promotion at Seoul National University Hospital in South Korea. "We wanted to determine whether there was a relationship between a well-established marker of inflammation, high-sensitive C-reactive protein (hs-CRP), and death from all causes, death from cancer or death from a site-specific cancer in Koreans."
Park and colleagues retrospectively analyzed data from 33,556 individuals who had completed medical checkups, answered questions on cancer-related behavioral factors (like smoking status and exercise habits) and had been screened for blood hs-CRP at the health-screening center at Seoul National University Hospital between May 1995 and December 2006. During an average follow-up of 9.4 years, 1,054 deaths from all causes and 506 deaths from cancer were recorded.
When the researchers adjusted for several variables, including age, diabetes, smoking status and exercise habits, men with the highest level of hs-CRP in their blood (3 mg per liter or more) were 38 percent more likely to have died from any cause compared with men with the lowest hs-CRP level (1 mg per liter or less). They were also 61 percent more likely to have died from cancer.
For women, after adjusting for a number of variables, no statistically significant association was observed for hs-CRP level and death from any cause or death from cancer.
Through analysis of associations between hs-CRP levels and site-specific cancers, the researchers found that a significant relationship existed only for lung cancer. After adjusting for multiple variables, individuals with the highest hs-CRP level were more than twice as likely to die from lung cancer compared with those with the lowest hs-CRP level.
The association between hs-CRP levels and all-cause mortality and cancer mortality was stronger in lean individuals compared with those who were overweight.
"This was surprising," said Park. "Because obesity is a major risk factor for chronic diseases like cancer, physicians and the mass media often recommend eating less and exercising more. While an important public health message, some people are too concerned with these recommendations and they eat fewer calories than their body actually needs. It is important that we eat enough to meet the metabolic demands of our body to make sure our organs function adequately for a healthy life."

Arboreal and Bipdeal Ancestors

Australopithecus afarensis, a hominid and closely related human ancestor, was an upright-walking species, or bipedal. However, it has long been debated whether or not this species were also climbers who spent much of their time in trees. This has question has remained a mystery due to the fact that a complete set of A. afarensis shoulder blades had never been available to study. However, for the first time ever, David Green and Zeresenay Alemseged were able to analyze a complete set of shoulder blades and conduct a study on their ability to climb.

The two scientists took 11 years to extract the shoulder blades from a skeleton embedded in sandstone. The skeleton, named Selam, lived 3.3 million years ago. The extraction took so long because shoulder blades are extremely thin and rarely fossilize. When they do fossilize, they often fragment.

The scientists digitized the shoulder blades and compared them to fossils of other human relatives as well as other old world apes. They discovered that these shoulder blades were quite apelike, suggesting that this species was adapted to climbing in trees, in addition to its bipedalism.

This study is significant because it moves us closer to answering the question: When did our ancestors stop climbing? This study shows that this happened much later than previously thought. In addition, this study answers this question of arboreal adaptation that had been debated about for several decades.


Monday, November 5, 2012

A Theory of Human Longevity

Humans have an incredibly maximum potential life expectancy especially in comparison with our primate ancestors and our hunter-gatherer counterparts. The decline in mortality rate can be attributed to improvements in technology. Currently, a 65 year-old Japanese man is 200 times less likely to die than his hunter-gatherer counterpart. The Japanese man has an expected annual probability of death of 0.8%, compared to the 65 year-old hunter-gatherer with an expected annual probability of death of 5.3%.

Technology does not explain why humans posses a much higher maximum potential human lifespan. Today, because of our long life expectancy we are able to postpone aging and its detriments. We are able to pass down our genes before the effects of old age set in. This is the result of oocyte depletion, but oocyte depletion happens before the other defects of age occur. The short-finned pilot whale and the Asian elephant are the only other known species that experience the same post-reproductive phenomenon; In fact the average American woman lives 79.2 years, 30 of which are post reproductive.

A recent study modeled the Grandmother Hypothesis and found that even a small contribution of gradmothering was attributed to longer potential lifespan. In the study I found they assumed that only women above the age of 45 could be grandmother. At age two the study assumed that children are able to leave mothers for their grandmothers because they have gone through the nursing period, and at 3 the mother is able to have a second child. Then at 8.2 children reach the age of independence. So the grandmother cares for the child for 6.2 years. Under the assumptions of this study, eligible grandmothers initially make up less than 1% of females, but that proportion steadily increases to 43%. Showing the dramatic effect grandmothering has on increasing longevity

The reasoning for this is that grandmothers are able to supply food that the child cannot get himself; they also allow the mother to reproduce before her first child’s age of independence. Grandmothers are investing in their grandchildren’s lives to ensure the success of their genes. This gives credence to why menopause may have been selected.

This study does not disprove other theories as to why humans have a longer lifespan, but it is a narrow study that shows the benefits that the role of a grandmother has in evolution. 

Works Cited:
Brooks, Rob. "Is Human Longevity Due to Grandmothers or Older Fathers?" The Huffington Post., 31 Oct. 2012. Web. 05 Nov. 2012. <>.
Burger, Oksar, Annette Baudisch, and James W. Vaupel. "Human Mortality Improvement in Evolutionary Context." Proceedings of the National Academy of Science of the United States of America 109.44 (2012): n. pag. Print.
Kim, Peter S., James E. Coxworth, and Kristen Hawkes. "Increased Longevity Evolves from Grandmothering." Proceedings of the Royal Society Biological Sciences (2012): n. pag. Increased Longevity Evolves from Grandmothering. Web. 05 Nov. 2012. <>.
Kuhle, B. "An Evolutionary Perspective on the Origin and Ontogeny of Menopause." Maturitas 57.4 (2007): 329-37. Print.