walking-fish-reveal-how-our-ancestors-evolved-onto-land

Walking Fish Reveal How Our Ancestors Evolved Onto Land

Researchers at McGill University published in the journal Nature, turned to a living fish, called Polypterus, to help show what might have happened when fish first attempted to walk out of the water. Polypterus is an African fish that can breathe air, ‘walk’ on land, and looks much like those ancient fishes that evolved into tetrapods. The team of researchers raised juvenile Polypterus on land for nearly a year, with an aim to revealing how these ‘terrestrialized’ fish looked and moved differently. “Stressful environmental conditions can often reveal otherwise cryptic anatomical and behavioural variation, a form of developmental plasticity”, says Emily Standen, a former McGill post-doctoral student who led the project, now at the University of Ottawa. “We wanted to use this mechanism to see what new anatomies and behaviours we could trigger in these fish and see if they match what we know of the fossil record.”

The fish showed significant anatomical and behavioural changes. The terrestrialized fish walked more effectively by placing their fins closer to their bodies, lifted their heads higher, and kept their fins from slipping as much as fish that were raised in water. “Anatomically, their pectoral skeleton changed to become more elongate with stronger attachments across their chest, possibly to increase support during walking, and a reduced contact with the skull to potentially allow greater head/neck motion,” says Trina Du, a McGill Ph.D. student and study collaborator. “Because many of the anatomical changes mirror the fossil record, we can hypothesize that the behavioural changes we see also reflect what may have occurred when fossil fish first walked with their fins on land”, says Hans Larsson, Canada Research Chair in Macroevolution at McGill and an Associate Professor at the Redpath Museum.

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Human Altruism Traces Back To the Origins of Humanity

Humans are generally highly cooperative and often impressively altruistic, quicker than any other animal species to help out strangers in need. A new study suggests that our lineage got that way by adopting so-called cooperative breeding: the caring for infants not just by the mother, but also by other members of the family and sometimes even unrelated adults. In addition to helping us get along with others, the advance led to the development of language and complex civilizations, the authors say.

In the late 1990s, Sarah Blaffer Hrdy, now an anthropologist emeritus at the University of California, Davis, proposed the cooperative breeding hypothesis. According to her model, early in their evolution humans added cooperative breeding behaviors to their already existing advanced ape cognition, leading to a powerful combination of smarts and sociality that fueled even bigger brains, the evolution of language, and unprecedented levels of cooperation. Soon after Hrdy’s proposal, anthropologists Carel van Schaik and Judith Burkart of the University of Zurich in Switzerland began to test some of these ideas, demonstrating that cooperatively breeding primates like marmosets engaged in seemingly altruistic behavior by helping other marmosets get food with no immediate reward to themselves.

The researchers suggest that cooperative breeding might have developed when our earliest ancestors, who evolved in Africa, first moved from life in the trees to a more precarious existence in savanna and woodland environments, several million years ago. “From other species, such as birds, we know that [cooperative breeding] is typically associated with adverse environmental conditions where it is difficult to survive,” Burkart says. “Once they moved into those savannah habitats, it may simply have become impossible for mothers to rear and provision their offspring alone.” Among the advantages of cooperative breeding, Burkart adds, is that mothers can give birth to new offspring while the previous ones are still dependent on adult care, thus increasing their reproductive success.

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Why Do Humans Grow Up So Slowly? Blame the Brain.

Humans are late bloomers when compared with other primates—they spend almost twice as long in childhood and adolescence as chimps, gibbons, or macaques do. But why? One widely accepted but hard-to-test theory is that children’s brains consume so much energy that they divert glucose from the rest of the body, slowing growth. Now, a clever study of glucose uptake and body growth in children confirms this “expensive tissue” hypothesis.

Previous studies have shown that our brains guzzle between 44% and 87% of the total energy consumed by our resting bodies during infancy and childhood. Could that be why we take so long to grow up? One way to find out is with more precise studies of brain metabolism throughout childhood, but those studies don’t exist yet. However, a new study published online today in the Proceedings of the National Academy of Sciences (PNAS) spliced together three older data sets to provide a test of this hypothesis.

The researchers, led by Christopher Kuzawa, an anthropologist at Northwestern University in Evanston, Illinois, found that when the brain demands lots of energy, body growth slows. For example, the period of highest brain glucose uptake—between 4.5 and 5 years of age—coincides with the period of lowest weight gain. This strongly suggested that the brain’s high energy needs during childhood are compensated for by slower growth. “This is a very, very cool paper,” says Karin Isler, a biological anthropologist at the University of Zurich in Switzerland. “It very convincingly shows that the conflicting demands of the brain’s and the body’s energy requirements for growth are met, in humans, by a temporal sequence of delayed growth.”

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When Cooperation Counts

Everybody knows the shortest distance between two points is a straight line, and now Harvard researchers have evidence that sperm have been taking the familiar axiom to heart.   Though competition among individual sperm is usually thought to be intense, with each racing for the chance to fertilize the egg, Harvard scientists say that in some species, sperm form cooperative groups that allow them to take a straighter path to potential fertilization.

A new study, conducted by Heidi Fisher, a postdoctoral student working in the lab of Hopi Hoekstra, the Alexander Agassiz Professor of Zoology in the Museum of Comparative Zoology, and postdoctoral student Luca Giomi, who works with L. Mahadevan, the Lola England de Valpine Professor of Applied Mathematics, professor of organismic and evolutionary biology, and of physics, shows that in Peromyscus maniculatus, a species of deer mouse known to be promiscuous, sperm clump together to swim in a more linear fashion. The study is described in a July paper in Proceedings of the Royal Society B.  “We generally think that each individual sperm cell swims its little heart out to get to the egg. But it had been discovered that, in at least a handful of organisms, sperm will cooperate and swim as a group,” said Hoekstra, who is also a professor of organismic and evolutionary biology.

The new paper builds on a 2010 study conducted in Hoekstra’s lab, which found that sperm cells preferentially clump with those produced by the same male. Spurred by that earlier paper, Mahadevan approached Hoekstra with the idea of creating a mathematical model to understand whether and how sperm received an advantage by forming groups.

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Now Your Food Has Fake DNA In It

Like many novel technologies in this age of TED Talks and Silicon Valley triumphalism, synthetic biology—synbio for short—floats on a sea of hype. One of its founding scientists, Boston University biomedical engineer James Collins, has called it “genetic engineering on steroids.” Whereas garden-variety genetic engineers busy themselves moving genes from one organism into another—to create tomatoes that don’t bruise easily, for example—synthetic biologists generate new DNA sequences the way programmers write code, creating new life-forms.

It may sound like science fiction, but synbio companies have already performed modest miracles. The California-based firm Amyris, for example, has harnessed the technology to make a malaria drug that now comes from a tropical plant. In order to do this, company scientists leveraged the well-known transformative powers of yeast, which humans have used for millennia to turn, say, the sugar in grape juice into alcohol: They figured out how the wormwood tree generates artemisinic acid—the compound that makes up the globe’s last consistently effective anti-malarial treatment—and programmed a yeast strain to do the same thing.  And there could be more innovations on the horizon. In 2011, Craig Venter, the scientist/entrepreneur who spearheaded the mapping of the human genome, vowed to synthesize an algae that would use sunlight to unlock the energy in carbon dioxide. If successful, this attempt to replicate photosynthesis could transform CO2 from climate-heating scourge into a limitless source of energy. Synthetic biologists also aim to conjure up self-growing buildings, streetlight-replacing glowing trees, and medicines tailored to your body’s needs. No wonder the market for synbio is expected to reach $13.4 billion by 2019.

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Antibacterial Soap Exposes Health Workers to High Triclosan Levels

Handwashing with antibacterial soap exposes hospital workers to significant and potentially unsafe levels of triclosan, a widely-used chemical currently under review by the U.S. Food and Drug Administration, according to a study led by researchers from UC San Francisco.

Triclosan, a synthetic antibacterial agent, is found in thousands of consumer products, including soaps, cosmetics, acne creams and some brands of toothpaste. The FDA is reviewing its safety based on a growing body of research indicating that it can interfere with the action of hormones, potentially causing developmental problems in fetuses and newborns, among other health concerns.  “Antimicrobial soaps can carry unknown risks, and triclosan is of particular concern,” said co-investigator Paul Blanc, MD, a professor of medicine at UCSF who holds the Endowed Chair in Occupational and Environmental Medicine. “Our study shows that people absorb this chemical at work and at home, depending on the products that they use.”

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Strongest Evidence Yet That Pygmies’ Short Stature Is Genetic

It’s not another tall tale: Evolutionary biologists have developed a new understanding of the genetic basis of short stature in humans. Also known as the pygmy phenotype, a study published Monday in the Proceedings of the National Academy of Sciences shows that this trait has evolved several times over the course of human history.

“We have found the strongest evidence yet that the pygmy phenotype is controlled by genetics,” said Luis Barreiro of the University of Montreal and the senior author of this recent study. Although height is a tremendously variable trait among humans, several rain forest-dwelling populations in Asia and Africa have been noted for their unusually short stature. The average height among Batwa men (60.1 inches, 152.9 centimeters) and women (57.4 inches, 145.7 centimeters) is significantly lower than in neighboring Bakiga men (65.1 inches, 165.4 centimeters) and women (61.0 inches, 155.1 centimeters).

Barreiro and colleagues gathered genetic data from the Batwa and Baka peoples, as well as from three neighboring agricultural groups of average height. When they scanned different regions of the genome, they found significant genetic differences among the Batwa and Baka in an area of the genome that is known to code for the receptors for human growth hormones. When the researchers looked more closely, they found that these genetic differences weren’t just random chance and that the first Batwa and Baka people just happened to be short. Instead, these genetic differences were somehow benefiting the individuals living in these rain forest environments. It’s an example of convergent evolution, Barreiro says, in that the same trait (short stature) evolved independently in several different populations.

The results will help provide an understanding not just of the pygmy phenotype, but also of the evolution of the tremendous amount of diversity in our species.

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A Record Number of Out-of-State Students Brings Windfall for UC System

Human Biology and Society student featured in a recent LA Times article