Several items from my reading pile have piqued my interest this week. Here are a few quick paragraphs for each:
Shades of Beige: the formal debut of a new type of fat cell in mammals
Biologists have long known of two types of fat cells in mammalian tissues: food-storing white fat, and food-burning brown fat. As obesity rates across the developed world continue to skyrocket, more and more physiologists are turning their attention to fat cells, how they develop, and where they come from. It was long assumed that brown fat (which generates heat by burning food) develops from white fat. However, several years ago, scientists discovered that brown fat cells are closely related to muscle cells, not white fat cells, dousing hopes that white fat could be easily converted into brown fat to trim excess pounds.
Now those hopes have been resurrected with the definitive description and isolation of a new type of fat cell in mice. As reported in the journal Cell, so-called “beige” or “brite” (brown-in-white) fat cells are brown-like cells found within white fat deposits. They share some physiological characteristics of both brown fat cells and white fat cells, though are distinct from both. Strikingly, beige fat cells (my preferred term) show evidence of the food-burning qualities found in brown fat cells. Thus, beige fat cells may be the great fat-burning hope: convert white fat cells into beige fat cells and you might switch a population of fat cells from energy-storage mode to energy-burning mode.
Before the champagne corks start popping, we must address many complex questions. How widespread is beige fat? Is it truly possible to convert white fat cells to beige fat cells? If so, do beige fat cells have the same energy-burning capacity as muscle-related brown fat cells? How widespread are beige fat cells? The authors present evidence that previously-identified brown fat cells in humans may actually be beige fat. How can well distinguish between these two types of cells, which share some superficial qualities?
Thus, we’re still far from a magical cure for obesity, though this new study does at least demonstrate that we are learning more about how fat is stored and distributed throughout our bodies. For now, keep up (or perhaps start) the proven regimen to avoid and combat obesity: regular exercise, coupled with a moderate diet of minimally-processed foods.
- Wu J, et al. 2012. “Beige Adipocytes Are a Distinct Type of Thermogenic Fat Cell in Mouse and Human.” Cell. Volume 150: 366-376. [Subscription required to view the full text, but abstract is available for free.]
- Cannon B, Nedergaard J. 2012. “Neither brown nor white.” Nature. Volume 488: 286-287. [A good overview of the primary article. Subscription required.]
Anatolian Birth: the ancestral language of English, Hindi, and everything in between may have originated over 8 millennia ago in central Turkey
Linguists have long noted that some languages are related to one another, sharing characteristics such as syntax, structure, and core vocabulary. One of the largest groups of related languages today is the Indo-European family. Descendant from a single ancestral language, today the Indo-European family includes well over 400 modern languages (including English, Spanish, Irish, Latin, Greek, Urdu, Persian, and Hindi) with over 3 billion speakers. Even discounting the influences of colonialism in the spread of this family, today Indo-European languages are spoken from Iceland to Sri Lanka. This geographic diversity begs the question: when and where did this language arise?
Archaeologists and linguists have proposed two hypotheses to explain the origins and spread of the Indo-European family. One theory posits that the family arose in Anatolia, within modern Turkey, with the practice of agriculture, before spreading west (to Europe) and east (to central and southern Asia) some 8,000-9,000 years ago. The alternative hypothesis states that this language family first appeared in the steppes of eastern Europe and central Asia, north of the Black and Caspian Seas, and spread from there via nomadic tribes approximately 5,000-6,000 years ago. Linguists have tried to map the evolution of Indo-European languages by charting similarities and differences among languages within the family, and correlating these findings with archaeological evidence of human activity across Eurasia. While these findings tended to support the “steppe hypothesis,” they were also far from conclusive.
New results published this week in the journal Science took a novel approach to investigating the origin of Indo-European languages. Rather than relying solely on linguistic similarities or archaeological findings, the authors theorized that languages can spread much like viruses or pathogens among humans, and similarly “modeled” the spread of a theoretical language among ancient human populations. They incorporated data of linguistic similarities from over 100 Indo-European languages into this “virus” model, and their results definitively pointed toward an Anatolian origin for this large language family.
Given the unorthodox approach and definitive results of this “virus” model, the article is certainly attracting attention. Both supporters and detractors have commented, alternatively praising or criticizing the approach and languages chosen for the analysis. Thus, we still do not definitively know when and where the Indo-European language family arose. But, this model may, in time, prove useful in the study of language evolution, for the Indo-European family and other language groups.
- Bouckaert R, Lemey P, Dunn M, Greenhill SJ, Alekseyenko AV, Drummond AJ, Gray RD, Suchard MA, Atkinson QD. 2012. “Mapping the Origins and Expansion of the Indo-European Language Family.” Science. Volume 337: 957-960. [Subscription required to view the full text, but abstract is available for free.]
- Pringle H. 2012. “New Method Puts Elusive Indo-European Homeland in Anatolia.” Science. Volume 337: 902. [Good overview of the above article. Subscription required to view the full text, though a summary is available for free.]
The New World: migration of First Peoples to the Americas likely occurred in waves
Humans first arrived in the Americas from northeast Asia via the Bering Strait approximately 15,000 years ago. Back then, the Strait was a land bridge (named “Beringia,” if you’re curious), which was gradually submerged as sea levels rose after the last ice age. As uncontroversial as that picture appears, the details of this migration and the ancestry of the First Peoples of the Americas (or Native Americans, if you prefer) are a matter of contentious debate among archaeologists and evolutionary biologists. Are all First Peoples descended from a single migration event? Or did the first Americans arrive in several waves of migration, from different ancestral Asian populations? If the latter case is true, then are modern First Peoples descendent from different groups of migrants, or did these different migratory groups eventually settle down and interbreed with one another?
New results published in the journal Nature indicate that most modern First Peoples are descendant from a single population of ancestors that migrated over Beringia millennia ago. However, extensive genetic sampling of First People tribes did reveal at least two other migrations of Asian groups over the land bridge. These two groups interbred with some members of the first, larger migratory group from Asia. Among modern Inuit from northern Canada, Greenland, and Alaska, roughly 43% of their ancestry stem from one of these later groups of Asian migrants. Chipewyans from northern Canada inherited approximately one-tenth of their genes from another migratory group. Thus, Asians migrated to the Americas in at least three distinct waves, though two of these waves leave genetic footprints only among First Peoples from the northern reaches of North America. Further genetic sampling, coupled with archaeological surveys of First People settlement history, could determine if these two smaller waves of migration left descendants among other tribes, or if there are other waves of migration that this survey missed entirely.
- Reich D, et al. 2012. “Reconstructing Native American population history.” Nature. Volume 488: 370-374. [Subscription required to view the full text, but abstract is available for free.]
The Nose Knows: a useful primer on the fungal scourge of North American bats
Forget viruses and bacteria: the new pathogens are the fungus among us. “Fungi” are the general term for a large and complex chunk of the tree of life, encompassing species from mushrooms and bread molds to the single-celled yeast that make alcoholic beverages possible. Fungal diversity is also a vastly neglected area of study for biologists (we’ve tended to concentrate on yeast); worldwide, there are estimates that a mere 10% of all species of fungus have been identified and described.
Today, we’ve some new and unsettling reasons to pay attention to fungi: they are among the modern age’s most ferocious pathogens. In a recent edition of the journal PLoS Pathogens, Dr. David Blehert with the United States Geological Survey (yes, they hire biologists) pens a useful primer on a particularly nasty fungal pathogen that is decimating bat populations in the eastern United States and Canada. White-nose syndrome (WNS) first appeared in several bat species in North America in 2006. Since that time, it has decimated populations of some insect-eating bats across 19 states and 4 Canadian provinces. As the disease name suggests, the fungal agent responsible for this fatal infection (Geomyces destructans, until recently part of that 90% of fungal species we knew nothing about) colonizes the face, ears, and wings of hibernating bats, penetrating deep into the animal’s musculature. This fungus grows best at temperatures well below the typical mammalian body temperature, so they thrive in hibernating bats, where the core body temperature plummets during this long period of inactivity. Since the discovery of white-nose syndrome six years ago, scientists have shown that it is a recent arrival to this continent, likely originating in Europe (where native bat species do not seem to die from Geomyces destructans infection).
White-nose syndrome is one of several new fungal diseases found in animals. These deadly pathogens spread quickly, globally, and show little or no susceptibility to drug treatment (though there are precious few anti-fungal drugs available). Obviously, we have our work cut out for us.
- Blehert DS. 2012. “Fungal Disease and the Developing Story of Bat White-nose Syndrome.” PLoS Pathogens. Volume 8 (Number 7): e1002779. [Open access.]
- Image credit: National Institute for Mathematical and Biological Synthesis.
Welcome to the Neighborhood: modern humans arrived in Europe before our Neanderthal cousins died out
Neanderthals settled across Europe over 100,000 years before modern humans. The question is: why did they die out? Did the harsh climactic fluctuations in Europe during the last periods of glaciation weaken their populations beyond recovery? Did modern humans invade Europe and wipe out their Neanderthal cousins by direct competition? Scientists have proposed these and other theories (including disease, radiation exposure, and even cannibalism of Neanderthals by their modern cousins) to explain their extinction. However, these possibilities are difficult to investigate due to the difficulty of dating archeological sites with sufficient precision. The most popular dating method, using the decay rate of radioactive carbon isotopes (14C), cannot accurately resolve when the last Neanderthals disappeared relative to the appearance of modern humans on the continent.
A new report in The Proceedings of the National Academy of Sciences of the United States of America presents evidence that Neanderthals and modern humans overlapped significantly in ancient Europe before Neanderthal presence declined rapidly 30,000-40,000 years ago. The authors can make this claim because they “calibrated” the age of different Neanderthal and modern human archeological sites in eastern and southern Europe to an event of known age and scope: a cataclysmic volcanic eruption in southern Italy approximately 39,300 years ago. The eruption spread volcanic ash across southern and eastern Europe, and the report’s authors were able to detect the unique chemical signatures of this ash in archeological sites and sedimentary layers across the continent. Using the presence of volcanic ash as a point of reference, the authors showed that there is evidence of Neanderthal and modern human presence in Europe well before and after the volcanic disaster. Thus, modern humans and Neanderthals shared the European soil long before Neanderthals went extinct. In addition, the volcanic eruption and other climate-shifting events during the end of the last glaciation period did not drive Neanderthals to extinction. Both of these human species appear quite resilient to potentially catastrophic shifts in climate. So, what ultimately drove Neanderthals quietly into that good night? If it wasn’t the climate, it was probably us.
- Lowe J, et al. 2012. “Volcanic ash layers illuminate the resilience of Neanderthals and early modern humans to natural hazards.” The Proceedings of the National Academy of Sciences of the United States of America. Volume 109 (Number 34): 13532-13537. [Subscription required to view the full text, but abstract is available for free.]
- Hublin JJ. 2012. “The earliest modern human colonization of Europe.” The Proceedings of the National Academy of Sciences of the United States of America. Volume 109 (Number 34): 13471-13472. [A good overview of the above article. Subscription required to view the full text, but a partial text is available for free.]
- Image credit: The Daily Mail.