Cupid’s Arrow: Light Shed On Laws of Attraction

Feb. 8, 2013 — We’ve heard the clichés: “It was love at first sight,” “It’s inner beauty that truly matters,” and “Opposites attract.” But what’s really at work in selecting a romantic or sexual partner?

University of Notre Dame Sociologist Elizabeth McClintock studies the impacts of physical attractiveness and age on mate selection and the effects of gender and income on relationships. Her research offers new insights into why and when Cupid’s arrow strikes.

In one of her studies, “Handsome Wants as Handsome Does,” published in Biodemography and Social Biology, McClintock examines the effects of physical attractiveness on young adults’ sexual and romantic outcomes (number of partners, relationship status, timing of sexual intercourse), revealing the gender differences in preferences.

“Couple formation is often conceptualized as a competitive, two-sided matching process in which individuals implicitly trade their assets for those of a mate, trying to find the most desirable partner and most rewarding relationship that they can get given their own assets,” McClintock says. “This market metaphor has primarily been applied to marriage markets and focused on the exchange of income or status for other desired resources such as physical attractiveness, but it is easily extended to explain partner selection in the young adult premarital dating market as well.”

McClintock’s study shows that just as good looks may be exchanged for status and financial resources, attractiveness may also be traded for control over the degree of commitment and progression of sexual activity.

Among her findings:

  • Very physically attractive women are more likely to form exclusive relationships than to form purely sexual relationships; they are also less likely to have sexual intercourse within the first week of meeting a partner. Presumably, this difference arises because more physically attractive women use their greater power in the partner market to control outcomes within their relationships.
  • For women, the number of sexual partners decreases with increasing physical attractiveness, whereas for men, the number of sexual partners increases with increasing physical attractiveness.
  • For women, the number of reported sexual partners is tied to weight: Thinner women report fewer partners. Thinness is a dimension of attractiveness for women, so is consistent with the finding that more attractive women report fewer sexual partners.

Another of McClintock’s recent studies (not yet published), titled “Desirability, Matching, and the Illusion of Exchange in Partner Selection,” tests and rejects the “trophy wife” stereotype that women trade beauty for men’s status.

“Obviously, this happens sometimes,” she says, pointing to Donald Trump and Melania Knauss-Trump as an example.

“But prior research has suggested that it often occurs in everyday partner selection among ‘normal’ people … noting that the woman’s beauty and the man’s status (education, income) are positively correlated, that is, they tend to increase and decrease together.”

According to McClintock, prior research in this area has ignored two important factors:

“First, people with higher status are, on average, rated more physically attractive — perhaps because they are less likely to be overweight and more likely to afford braces and nice clothes and trips to the dermatologist, etc.,” she says.

“Secondly, the strongest force by far in partner selection is similarity — in education, race, religion and physical attractiveness.”

After taking these two factors into account, McClintock’s research shows that there is not, in fact, a general tendency for women to trade beauty for money.

“Indeed, I find little evidence of exchange, but I find very strong evidence of matching,” she says. “With some exceptions, the vast majority of couples select partners who are similar to themselves in both status and in attractiveness.”

Story Source:

The above story is reprinted from materials provided byUniversity of Notre Dame. The original article was written by Susan Guibert.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

  1. Elizabeth Aura McClintock. Handsome Wants as Handsome Does: Physical Attractiveness and Gender Differences in Revealed Sexual Preferences.Biodemography and Social Biology, 2011; 57 (2): 221 DOI: 10.1080/19485565.2011.615172
University of Notre Dame (2013, February 8). Cupid’s arrow: Light shed on laws of attraction.ScienceDaily. Retrieved February 10, 2013, from

Histone Modification Controls Development: Chemical Tags On Histones Regulate Gene Activity

Feb. 8, 2013 — Every gene in the nucleus of an animal or plant cell is packaged into a beads-on-a-string like structure called nucleosomes: the DNA of the gene forms the string and a complex of proteins called histones forms the beads around which the DNA is wrapped. Scientists of the Max Planck Institute of Biochemistry in Martinsried near Munich, Germany, have now established that adding chemical tags on histones is critical for regulating gene activity during animal development.

Top image, No PRC2. Bottom image, altered histone. (Credit: Image courtesy of Max Planck Institute of Biochemistry)

Studies over the past two decades revealed that many proteins that control the activity of genes are enzymes that add small chemical tags on histone proteins but also on a variety of other proteins. With their studies the researchers have now shown that it is the tags on the histones that control if genes are active or inactive.

Their results were published in the journal Science.

Histone proteins can be modified by a number of different chemical tags at very specific sites. The researchers in the Research Group ‘Chromatin Biology’ of Jürg Müller focused on the histone tag that is added by an enzyme called Polycomb Repressive Complex 2 (PRC2). PRC2 is essential for a variety of different cell fate decisions in animals and plants. PRC2 functions to keep genes inactive in cells and at times where they should remain inactive.

Using the model organismDrosophila — the fruit fly — the scientists now generated animals with cells expressing an altered histone protein to which PRC2 can no longer add the tag. These cells cannot keep genes inactive anymore and many cell fate decisions go awry, exactly like in cells that lack the PRC2 enzyme.

“This observation demonstrates that the business end is the tag on the histone and not on some other protein” says Ana Pengelly, the PhD student who conducted the experiments. Her colleague Omer Copur adds: “The approach we used permits us to now also investigate the function of other tags on histone proteins that have a different chemical nature.” The insight gained from the work on PRC2 provides a strong impetus to figure how this tag alters the beads-on-a-string structure of genes and thereby controls gene activity.

Story Source:

The above story is reprinted from materials provided byMax Planck Institute of Biochemistry.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

  1. A. R. Pengelly, O. Copur, H. Jackle, A. Herzig, J. Muller. A Histone Mutant Reproduces the Phenotype Caused by Loss of Histone-Modifying Factor PolycombScience, 2013; 339 (6120): 698 DOI: 10.1126/science.1231382
Max Planck Institute of Biochemistry (2013, February 8). Histone modification controls development: Chemical tags on histones regulate gene activity. ScienceDaily. Retrieved February 10, 2013, from

Gene Silencing Spurs Fountain of Youth in Mouse Brain

Feb. 7, 2013 — Cognitive decline in old age is linked to decreasing production of new neurons. Scientists from the German Cancer Research Center have discovered in mice that significantly more neurons are generated in the brains of older animals if a signaling molecule called Dickkopf-1 is turned off. In tests for spatial orientation and memory, mice in advanced adult age whose Dickkopf gene had been silenced reached an equal mental performance as young animals.

Newborn neurons (in green) in the brain of a 3 month old mouse. (Credit: German Cancer Research Center)

The hippocampus — a structure of the brain whose shape resembles that of a seahorse — is also called the “gateway” to memory. This is where information is stored and retrieved. Its performance relies on new neurons being continually formed in the hippocampus over the entire lifetime. “However, in old age, production of new neurons dramatically decreases. This is considered to be among the causes of declining memory and learning ability,” Prof. Dr. Ana Martin-Villalba, a neuroscientist, explains.

Martin-Villalba, who heads a research department at the German Cancer Research Center (DKFZ), and her team are trying to find the molecular causes for this decrease in new neuron production (neurogenesis). Neural stem cells in the hippocampus are responsible for continuous supply of new neurons. Specific molecules in the immediate environment of these stem cells determine their fate: They may remain dormant, renew themselves, or differentiate into one of two types of specialized brain cells, astrocytes or neurons. One of these factors is the Wnt signaling molecule, which promotes the formation of young neurons. However, its molecular counterpart, called Dickkopf-1, can prevent this.

“We find considerably more Dickkopf-1 protein in the brains of older mice than in those of young animals. We therefore suspected this signaling molecule to be responsible for the fact that hardly any young neurons are generated any more in old age.” The scientists tested their assumption in mice whose Dickkopf-1 gene is permanently silenced. Professor Christof Niehrs had developed these animals at DKFZ. The term “Dickkopf” (from German “dick” = thick, “Kopf” = head) also goes back to Niehrs, who had found in 1998 that this signaling molecule regulates head development during embryogenesis.

Martin-Villalba’s team discovered that stem cells in the hippocampus of Dickkopf knockout mice renew themselves more often and generate significantly more young neurons. The difference was particularly obvious in two-year old mice: In the knockout mice of this age, the researchers counted 80 percent more young neurons than in control animals of the same age. Moreover, the newly formed cells in the adult Dickkopf-1 mutant mice matured into potent neurons with multiple branches. In contrast, neurons in control animals of the same age were found to be more rudimentary already.

Blocking Dickkopf improves spatial orientation and memory

Several years ago, Ana Martin-Villalba had shown that mice lose their spatial orientation when neurogenesis in the hippocampus is blocked. Now, is it possible that the young neurons in Dickkopf-deficient mice improve the animals’ cognitive performance? The DKFZ researchers used standardized tests to study how the mice orient themselves in a maze. While in the control animals, the younger ones (3 months) performed much better in orienting themselves than the older ones (18 months), the Dickkopf-1-deficient mice showed no age-related decline in spatial orientation capabilities. Older Dickkopf-1 mutant mice also outperformed normal animals in tests determining spatial memory.

“Our result proves that Dickkopf-1 promotes age-related decline of specific cognitive abilities,” says Ana Martin-Villalba. “Although we had expected silencing of Dickkopf-1 to improve spatial orientation and memory of adult mice, we were surprised and impressed that animals in advanced adult age actually reach the performance levels of young animals.”

These results give rise to the question whether the function of Dickkopf-1 may be turned off using drugs. Antibodies blocking the Dickkopf protein are already being tested in clinical trials for treating a completely different condition. “It is fascinating to speculate that such a substance may also slow down age-related cognitive decline. But this is still a dream of the future, since we have only just started first experiments in mice to explore this question.”

Story Source:

The above story is reprinted from materials provided byHelmholtz Association of German Research Centres, via EurekAlert!, a service of AAAS.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

  1. Désirée R.M. Seib, Nina S. Corsini, Kristina Ellwanger, Christian Plaas, Alvaro Mateos, Claudia Pitzer, Christof Niehrs, Tansu Celikel, Ana Martin-Villalba. Loss of Dickkopf-1 Restores Neurogenesis in Old Age and Counteracts Cognitive DeclineCell Stem Cell, 2013; 12 (2): 204 DOI: 10.1016/j.stem.2012.11.010
Helmholtz Association of German Research Centres (2013, February 7). Gene silencing spurs fountain of youth in mouse brain.ScienceDaily. Retrieved February 10, 2013, from

Most Comprehensive Tree of Life Shows Placental Mammal Diversity Exploded After Age of Dinosaurs

Feb. 7, 2013 — An international team of scientists including University of Florida researchers has generated the most comprehensive tree of life to date on placental mammals, which are those bearing live young, including bats, rodents, whales and humans.


Appearing  February 7 in the journalScience, the study details how researchers used both genetic and physical traits to reconstruct the common ancestor of placental mammals, the creature that gave rise to many mammals alive today. The data show that contrary to a commonly held theory, the group diversified after the extinction of dinosaurs 65 million years ago. The research may help scientists better understand how mammals survived past climate change and how they may be impacted by future environmental conditions.

UF researchers led the team that analyzed the anatomy of living and fossil primates, including lemurs, monkeys and humans, as well as their closest living relatives, flying lemurs and tree shrews. The multi-year collaborative project was funded by the National Science Foundation Assembling the Tree of Life Program.

“With regards to evolution, it’s critical to understand the relationships of living and fossil mammals before asking questions about ‘how’ and ‘why,’ ” said co-author Jonathan Bloch, associate curator of vertebrate paleontology at the Florida Museum of Natural History on the UF campus. “This gives us a new perspective of how major change can influence the history of life, like the extinction of the dinosaurs — this was a major event in Earth’s history that potentially then results in setting the framework for the entire ordinal diversification of mammals, including our own very distant ancestors.”

Visual reconstruction of the placental ancestor — a small, insect-eating animal — was made possible with the help of a powerful cloud-based and publicly accessible database called MorphoBank. Unlike other reconstructions, the new study creates a clearer picture of the tree of life by combining two data types: Phenomic data includes observational traits such as anatomy and behavior, while genomic data is encoded by DNA.

“Discovering the tree of life is like piecing together a crime scene — it is a story that happened in the past that you can’t repeat,” said lead author Maureen O’Leary, an associate professor in the department of anatomical sciences in the School of Medicine at Stony Brook University and research associate at the American Museum of Natural History. “Just like with a crime scene, the new tools of DNA add important information, but so do other physical clues like a body or, in the scientific realm, fossils and anatomy. Combining all the evidence produces the most informed reconstruction of a past event.”

Researchers recorded observational traits for 86 placental mammal species, including 40 fossil species. The resulting database contains more than 12,000 images that correspond to more than 4,500 traits detailing characteristics like the presence or absence of wings, teeth and certain bones, type of hair cover and brain structures. The dataset is about 10 times larger than information used in previous studies of mammal relationships.

“It was a great way to learn anatomy, in a nutshell,” said co-author Zachary Randall, a UF biology graduate student and research associate at the Florida Museum. “While coding for humans, I could clearly see which anatomical features are unique, shared or not shared with other groups of mammals. This study is a great backbone for future work.”

Bloch and Randall collaborated with study co-authors Mary Silcox of the University of Toronto Scarborough and Eric Sargis of Yale University to characterize humans, plus seven other living and one fossil species from the clade Euarchonta, which includes primates, tree shrews and flying lemurs.

“I think this database is amazing because it’s being presented in such a way that it will be reproducible for the future generations,” Bloch said. “It illustrates exactly what we did and leaves nothing to the imagination — you can actually go to the pictures and see it.”

The evolutionary history of placental mammals has been interpreted in very different ways depending on the data analyzed. One leading analysis based on genomic data alone predicted that a number of placental mammal lineages existed in the Late Cretaceous and survived the Cretaceous-Paleogene extinction.

“It has been suggested that primates diverged from other mammals well before the extinction of the dinosaurs, but our work using direct evidence from the fossil record tells a different story,” Bloch said.

The team reconstructed the anatomy of the placental common ancestor by mapping traits most strongly supported by the data to determine it had a two-horned uterus, a brain with a convoluted cerebral cortex, and a placenta in which maternal blood came in close contact with membranes surrounding the fetus, as in humans.

Story Source:

The above story is reprinted from materials provided byUniversity of Florida.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

  1. M. A. O’Leary, J. I. Bloch, J. J. Flynn, T. J. Gaudin, A. Giallombardo, N. P. Giannini, S. L. Goldberg, B. P. Kraatz, Z.-X. Luo, J. Meng, X. Ni, M. J. Novacek, F. A. Perini, Z. S. Randall, G. W. Rougier, E. J. Sargis, M. T. Silcox, N. B. Simmons, M. Spaulding, P. M. Velazco, M. Weksler, J. R. Wible, A. L. Cirranello. The Placental Mammal Ancestor and the Post-K-Pg Radiation of PlacentalsScience, 2013; 339 (6120): 662 DOI: 10.1126/science.1229237
University of Florida (2013, February 7). Most comprehensive tree of life shows placental mammal diversity exploded after age of dinosaurs. ScienceDaily. Retrieved February 10, 2013, from

Animal Magnetism: First Evidence That Magnetism Helps Salmon Find Home

Feb. 7, 2013 — When migrating, sockeye salmon typically swim up to 4,000 miles into the ocean and then, years later, navigate back to the upstream reaches of the rivers in which they were born to spawn their young. Scientists, the fishing community and lay people have long wondered how salmon find their way to their home rivers over such epic distances.

How do they do that?

A new study, published in this week’s issue of Current Biology and partly funded by the National Science Foundation, suggests that salmon find their home rivers by sensing the rivers’ unique magnetic signature.

As part of the study, the research team used data from more than 56 years of catches in salmon fisheries to identify the routes that salmon had taken from their most northerly destinations, which were probably near Alaska or the Aleutian Islands in the Pacific Ocean, to the mouth of their home river–the Fraser River in British Columbia, Canada. This data was compared to the intensity of Earth’s magnetic field at pivotal locations in the salmon’s migratory route.

Earth has a magnetic field that weakens with proximity to the equator and distance from the poles and gradually changes on a yearly basis. Therefore, the intensity of the magnetosphere in any particular location is unique and differs slightly from year to year.

Because Vancouver Island is located directly in front of the Fraser River’s mouth, it blocks direct access to the river’s mouth from the Pacific Ocean. However, salmon may slip behind Vancouver Island and reach the river’s mouth from the north via the Queen Charlotte Strait or from the south via the Juan De Fuca Strait.

Results from this study showed that the intensity of the magnetic field largely predicted which route the salmon used to detour around Vancouver Island; in any given year, the salmon were more likely to take whichever route had a magnetic signature that most closely matched that of the Fraser River years before, when the salmon initially swam from the river into the Pacific Ocean.

“These results are consistent with the idea that juvenile salmon imprint on (i.e. learn and remember) the magnetic signature of their home river, and then seek that same magnetic signature during their spawning migration,” said Nathan Putman, a post-doctoral researcher at Oregon State University and the lead author of the study.

Important results

It has long been known that some animals use Earth’s magnetic field to generally orient themselves and to follow a straight course. However, scientists have never before documented an animal’s ability to “learn” the magnetic field rather than to simply inherit information about it or to use the magnetic field to find a specific location.

This study provides the first empirical evidence of magnetic imprinting in animals and represents the discovery of a major new phenomenon in behavioral biology.

In addition, this study suggests that it would be possible to forecast salmon movements using geomagnetic models–a development that has important implications for fisheries management.

Get out the map

Putman says scientists don’t know exactly how early and how often salmon check Earth’s magnetic field in order to identify their geographic locations during their trip back home. “But,” he says, “for the salmon to be able to go from some location out in the middle of the Pacific 4,000 miles away, they need to make a correct migratory choice early–and they need to know which direction to start going in. For that, they would presumably use the magnetic field.”

Putman continues, “As the salmon travel that route, ocean currents and other forces might blow them off course. So they would probably need to check their magnetic position several times during this migration to stay on track. Once they get close to the coastline, they would need to hone in on their target, and so would presumably check in more continuously during this stage of their migration.”

Putman says that once the salmon reach their home river, they probably use their sense of smell to find the particular tributary in which they were born. However, over long distances, magnetism would be a more useful cue to salmon than odors because magnetism–unlike odors–can be detected across thousands of miles of open ocean.

A long, strange trip

Like other Pacific Salmon, sockeye salmon spawn in the gravel beds of rivers and streams. After the newly hatched salmon emerge from these beds, they spend one to three years in fresh water, and then they migrate downstream to the ocean.

Next, the salmon travel thousands of miles from their home river to forage in the North Pacific for about two more years, and then, as well-fed adults, they migrate back to the same gravel beds in which they were born.

When migrating, salmon must transition from fresh water to sea water, and then back again. During each transition, the salmon undergo a metamorphosis that Putman says is almost as dramatic as the metamorphosis of a caterpillar into a butterfly. Each such salmon metamorphosis involves a replacement of gill tissues that enables the fish to maintain the correct salt balance in its environment: the salmon retains salt when in fresh water and pumps out excess salt when in salt water.

Salmon usually undertake their taxing, round-trip migration, which may total up to 8,000 miles, only once in their lives; they typically die soon after spawning.

Story Source:

The above story is reprinted from materials provided byNational Science Foundation.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

  1. Nathan F. Putman, Kenneth J. Lohmann, Emily M. Putman, Thomas P. Quinn, A. Peter Klimley, David L.G. Noakes.Evidence for Geomagnetic Imprinting as a Homing Mechanism in Pacific SalmonCurrent Biology, 2013; DOI: 10.1016/j.cub.2012.12.041
National Science Foundation (2013, February 7). Animal magnetism: First evidence that magnetism helps salmon find home.ScienceDaily. Retrieved February 10, 2013, from