The question, 'Where do domestic dogs come from?', has vexed scholars for a very long time. Some argue that humans first domesticated wolves in Europe, while others claim this happened in Central Asia or China. A new paper, published in Science, suggests that all these claims may be right. Supported by funding from the European Research Council and the Natural Environment Research Council, a large international team of scientists compared genetic data with existing archaeological evidence and show that man's best friend may have emerged independently from two separate (possibly now extinct) wolf populations that lived on opposite sides of the Eurasian continent. This means that dogs may have been domesticated not once, as widely believed, but twice.
A major international research project on dog domestication, led by the University of Oxford, has reconstructed the evolutionary history of dogs by first sequencing the genome (at Trinity College Dublin) of a 4,800-year old medium-sized dog from bone excavated at the Neolithic Passage Tomb of Newgrange, Ireland. The team (including French researchers based in Lyon and at the National Museum of Natural History in Paris*) also obtained mitochondrial DNA from 59 ancient dogs living between 14,000 to 3,000 years ago and then compared them with the genetic signatures of more than 2,500 previously studied modern dogs.
The results of their analyses demonstrate a genetic separation between modern dog populations currently living in East Asia and Europe. Curiously, this population split seems to have taken place after the earliest archaeological evidence for dogs in Europe. The new genetic evidence also shows a population turnover in Europe that appears to have mostly replaced the earliest domestic dog population there, which supports the evidence that there was a later arrival of dogs from elsewhere. Lastly, a review of the archaeological record shows that early dogs appear in both the East and West more than 12,000 years ago, but in Central Asia no earlier than 8,000 years ago.
Combined, these new findings suggest that dogs were first domesticated from geographically separated wolf populations on opposite sides of the Eurasian continent. At some point after their domestication, the eastern dogs dispersed with migrating humans into Europe where they mixed with and mostly replaced the earliest European dogs. Most dogs today are a mixture of both Eastern and Western dogs -- one reason why previous genetic studies have been difficult to interpret.
Burger and her team succeeded in answering this question. The group of researchers analysed up to 7,000-year-old DNA from bones of wild and early-domesticated dromedaries and compared the samples with the genetic profiles of modern dromedary populations from around the world. For the first time, it was possible to identify the Southeast Arabian Peninsula as the region of first domestication. "Our results appear to confirm that the first domestication of wild dromedaries occurred on the southeast coast. This was followed by repeated breeding of wild dromedaries with the early-domesticated populations," Burger explains. The wild ancestor of today's dromedary had a geographically limited range and went extinct around 2,000 years after the first domestication.
If Pleistocene megafauna -- mastodons, mammoths, giant sloths and others -- had not become extinct, humans might not be eating pumpkin pie and squash for the holidays, according to an international team of anthropologists.
"It's been suggested before and I think it's a very reasonable hypothesis, that wild species of pumpkin and squash weren't used for food early in the domestication process," said Logan Kistler, NERC Independent Research Fellow, University of Warwick, U.K. and recent Penn State postdoctoral fellow. "Rather, they might have been useful for a variety of other purposes like the bottle gourd, as containers, tools, fishnet floats, etc. At some point, as a symbiotic relationship developed, palatability evolved, but the details of that process aren't known at the present."
Researchers believe that initially humans did not eat wild pumpkin and squash -- members of the cucurbita family -- because the wild fruit is not only bitter but also toxic to humans and smaller animals. However, clear evidence exists that very large animals -- megafauna -- that lived 12,000 years ago did eat these fruit.
"Lee Newsom (associate professor of anthropology, Penn State and study co-author) has recovered many wild gourd/squash seeds from ancient Mastodon dung, suggesting that large herbivores may have been an important feature in the natural history of these wild plants," said Kistler.
The researchers looked at varieties of modern domestic cucurbits, modern wild cucurbits and archaeological specimens. They believe that changes in distribution of the wild plants are directly related to the disappearance of the large animals.
The ancestry of domesticated cattle proves more complex than previously thought, reports a paper published today in the open access journal Genome Biology. The first nuclear genome sequence from an ancient wild ox reveals that some modern domestic cow breeds, including the Scottish Highland and Irish Kerry, had wild ancestors that were British, as well as Asian.
The aurochs, Bos primigenius, is an extinct wild ox species that ranged across the grasslands of Eurasia and North Africa 11,000 years ago. Domestication of aurochs gave rise to two major groups of cattle; Bos taurus and Bos indicus.
Previous studies have shown that European B. taurus are descended from western Asian populations of aurochs. However, little was known about the relationship between domesticated cattle and wild aurochs in Europe, and how wild populations contributed to the evolutionary history of the cows that graze our fields today.
To build a clearer picture of the ancestry of European cattle breeds, scientists from University College Dublin extracted genetic material from a bone of a 6,750 year old wild British aurochs discovered in a cave in Derbyshire, England. They then sequenced its complete genome - its genetic blueprint - and compared it with the genomes of 81 domesticated B. taurus and B. indicus animals, and DNA marker information from more than 1,200 modern cows.
Genetic structure in village dogs reveals a Central Asian domestication origin
Authors:
Shannon et al
Abstract:
Dogs were the first domesticated species, originating at least 15,000 y ago from Eurasian gray wolves. Dogs today consist primarily of two specialized groups—a diverse set of nearly 400 pure breeds and a far more populous group of free-ranging animals adapted to a human commensal lifestyle (village dogs). Village dogs are more genetically diverse and geographically widespread than purebred dogs making them vital for unraveling dog population history. Using a semicustom 185,805-marker genotyping array, we conducted a large-scale survey of autosomal, mitochondrial, and Y chromosome diversity in 4,676 purebred dogs from 161 breeds and 549 village dogs from 38 countries. Geographic structure shows both isolation and gene flow have shaped genetic diversity in village dog populations. Some populations (notably those in the Neotropics and the South Pacific) are almost completely derived from European stock, whereas others are clearly admixed between indigenous and European dogs. Importantly, many populations—including those of Vietnam, India, and Egypt—show minimal evidence of European admixture. These populations exhibit a clear gradient of short-range linkage disequilibrium consistent with a Central Asian domestication origin.
Toward a theory of punctuated subsistence change
Authors:
Ullah et al
Abstract:
Discourse on the origins and spread of domesticated species focuses on universal causal explanations or unique regional or temporal trajectories. Despite new data as to the context and physical processes of early domestication, researchers still do not understand the types of system-level reorganizations required to transition from foraging to farming. Drawing upon dynamical systems theory and the concepts of attractors and repellors, we develop an understanding of subsistence transition and a description of variation in, and emergence of, human subsistence systems. The overlooked role of attractors and repellors in these systems helps explain why the origins of agriculture occurred quickly in some times and places, but slowly in others. A deeper understanding of the interactions of a limited set of variables that control the size of attractors (a proxy for resilience), such as population size, number of dry months, net primary productivity, and settlement fixity, provides new insights into the origin and spread of domesticated species in human economies.
Using new morphological criteria to identify domesticated emmer wheat at the aceramic Neolithic site of Chogha Golan (Iran)
Authors:
Weide et al
Abstract:
Reconstructing the domestication process of cereals is a basic requirement for the understanding of the Early Neolithic in the Near East and how agriculture emerged. Although there is general agreement on the criteria of differentiating wild from domesticated cereals, their application to material from aceramic Neolithic sites is problematic for reasons of preservation and diversity of early transitional chaff remains. In the present study we established an identification key for the distinction of wild and domestic emmer wheat (Triticum turgidum subsp. dicoccoides/dicoccum). General morphological analyses as well as experimental charring and measurements on wild and domestic emmer from the Fertile Crescent were conducted to track the main features that distinguish the two forms. Wild emmer can be differentiated from domestic emmer using longitudinal sections through rachises. The scar morphology of wild emmer specimens with a rough upper abscission scar is distinct from domestic emmer. In addition, two of the measuring tracks distinguish between domestic emmer and its progenitor. These results were applied to archaeological specimens from the aceramic Neolithic site of Chogha Golan (Ilam Province, Iran), which was excavated in 2009 and 2010 by a team of the Tübingen Iranian Stone Age Research Project. The carbonized emmer remains dating to about 9,800 BP comprise domestic-type and wild-type rachises, which is typical for cereal assemblages from aceramic Neolithic deposits.
A new study suggests that dogs may have first successfully migrated to the Americas only about 10,000 years ago, thousands of years after the first human migrants crossed a land bridge from Siberia to North America.
The study looked at the genetic characteristics of 84 individual dogs from more than a dozen sites in North and South America, and is the largest analysis so far of ancient dogs in the Americas. The findings appear in the Journal of Human Evolution.
Unlike their wild wolf predecessors, ancient dogs learned to tolerate human company and generally benefited from the association: They gained access to new food sources, enjoyed the safety of human encampments and, eventually, traveled the world with their two-legged masters. Dogs also were pressed into service as beasts of burden, and sometimes were served as food, particularly on special occasions.
Their 11,000- to 16,000-year association with humans makes dogs a promising subject for the study of ancient human behavior, including migratory behavior, said University of Illinois graduate student Kelsey Witt, who led the new analysis with anthropology professor Ripan Malhi.
"Dogs are one of the earliest organisms to have migrated with humans to every continent, and I think that says a lot about the relationship dogs have had with humans," Witt said. "They can be a powerful tool when you're looking at how human populations have moved around over time."
For most of us, the word "chicken" spells a cold, clammy slab of plastic-wrapped white meat plucked out of the refrigerated section of our local supermarket. But in the ancient world, and in many cultures today, chickens had deep religious and social significance.
Speaking from his home in Nashville, Tennessee, Andrew Lawler, author of Why Did the Chicken Cross the World: The Epic Saga of the Bird That Powers Civilization describes how fried chicken has its origins in West Africa, why the Puritans tried to ban the word "cock," and how the backyard chicken movement is bringing roosters to towns and cities all over America.
Prehistoric genomes reveal the genetic foundation and cost of horse domestication
Authors:
Schubert et al
Abstract:
The domestication of the horse ∼5.5 kya and the emergence of mounted riding, chariotry, and cavalry dramatically transformed human civilization. However, the genetics underlying horse domestication are difficult to reconstruct, given the near extinction of wild horses. We therefore sequenced two ancient horse genomes from Taymyr, Russia (at 7.4- and 24.3-fold coverage), both predating the earliest archeological evidence of domestication. We compared these genomes with genomes of domesticated horses and the wild Przewalski’s horse and found genetic structure within Eurasia in the Late Pleistocene, with the ancient population contributing significantly to the genetic variation of domesticated breeds. We furthermore identified a conservative set of 125 potential domestication targets using four complementary scans for genes that have undergone positive selection. One group of genes is involved in muscular and limb development, articular junctions, and the cardiac system, and may represent physiological adaptations to human utilization. A second group consists of genes with cognitive functions, including social behavior, learning capabilities, fear response, and agreeableness, which may have been key for taming horses. We also found that domestication is associated with inbreeding and an excess of deleterious mutations. This genetic load is in line with the “cost of domestication” hypothesis also reported for rice, tomatoes, and dogs, and it is generally attributed to the relaxation of purifying selection resulting from the strong demographic bottlenecks accompanying domestication. Our work demonstrates the power of ancient genomes to reconstruct the complex genetic changes that transformed wild animals into their domesticated forms, and the population context in which this process took place.
Early Holocene chicken domestication in northern China
Authors:
Xiang et al
Abstract:
Chickens represent by far the most important poultry species, yet the number, locations, and timings of their domestication have remained controversial for more than a century. Here we report ancient mitochondrial DNA sequences from the earliest archaeological chicken bones from China, dating back to ∼10,000 B.P. The results clearly show that all investigated bones, including the oldest from the Nanzhuangtou site, are derived from the genus Gallus, rather than any other related genus, such as Phasianus. Our analyses also suggest that northern China represents one region of the earliest chicken domestication, possibly dating as early as 10,000 y B.P. Similar to the evidence from pig domestication, our results suggest that these early domesticated chickens contributed to the gene pool of modern chicken populations. Moreover, our results support the idea that multiple members of the genus Gallus, specifically Gallus gallus and Gallus sonneratii contributed to the gene pool of the modern domestic chicken. Our results provide further support for the growing evidence of an early mixed agricultural complex in northern China.
In search of Paleolithic dogs: a quest with mixed results
Author:
Morey
Abstract:
Archaeological evidence has long placed the origins of the domestic dog (Canis lupus familiaris) just prior to the beginning of the Holocene Epoch, some 12,000–15,000 years ago. Some studies of genetic profiles of modern canids have, however, suggested a much earlier origin, dating to Paleolithic times and perhaps exceeding 100,000 years. With such studies as a backdrop, cases have been made recently on archaeological grounds for Paleolithic dogs that in certain cases exceed 30,000 years old. When examined systematically, however, some such studies exhibit conceptual and methodological flaws, calling into serious question the accuracy of the cases advanced. At least one recent study highlights that difficulty. When a series of cases for putative Paleolithic dogs is assessed, convincing cases for such dogs are confined to about the past 15,000 years, or latest Paleolithic times. Further developments on certain specific fronts may change that, but for the time being the longstanding archaeological understanding of the dog domestication time frame continues to be reasonably accurate. Recent molecular genetic studies are converging on that temporal framework as well. Archaeologists need not be automatically swayed by ongoing changes in molecular genetic profiles.
Modern humans appear in the fossil record about 200,000 years ago, but it was only about 50,000 years ago that making art and advanced tools became widespread.
A new study appearing Aug. 1 in the journal Current Anthropology finds that human skulls changed in ways that indicate a lowering of testosterone levels at around the same time that culture was blossoming.
"The modern human behaviors of technological innovation, making art and rapid cultural exchange probably came at the same time that we developed a more cooperative temperament," said lead author Robert Cieri, a biology graduate student at the University of Utah who began this work as a senior at Duke University.
The study, which is based on measurements of more than 1,400 ancient and modern skulls, makes the argument that human society advanced when people started being nicer to each other, which entails having a little less testosterone in action.
Heavy brows were out, rounder heads were in, and those changes can be traced directly to testosterone levels acting on the skeleton, according to Duke anthropologist Steven Churchill, who supervised Cieri's work on a senior honors thesis that grew to become this 24-page journal article three years later.
What they can't tell from the bones is whether these humans had less testosterone in circulation, or fewer receptors for the hormone.
The research team also included Duke animal cognition researchers Brian Hare and Jingzhi Tan, who say this argument is in line with what has been established in non-human species.
A new analysis of European archaeological sites containing large numbers of dead mammoths and dwellings built with mammoth bones has led Penn State Professor Emerita Pat Shipman to formulate a new interpretation of how these sites were formed. She suggests that their abrupt appearance may have been due to early modern humans working with the earliest domestic dogs to kill the now-extinct mammoth -- a now-extinct animal distantly related to the modern-day elephant. Shipman's analysis also provides a way to test the predictions of her new hypothesis. Advance publication of her article "How do you kill 86 mammoths?" is available online through Quaternary International.
Spectacular archaeological sites yielding stone tools and extraordinary numbers of dead mammoths -- some containing the remains of hundreds of individuals -- suddenly became common in central and eastern Eurasia between about 45,000 and 15,000 years ago, although mammoths previously had been hunted by humans and their extinct relatives and ancestors for at least a million years. Some of these mysterious sites have huts built of mammoth bones in complex, geometric patterns as well as piles of butchered mammoth bones.
"One of the greatest puzzles about these sites is how such large numbers of mammoths could have been killed with the weapons available during that time," Shipman said. Many earlier studies of the age distribution of the mammoths at these sites found similarities with modern elephants killed by hunting or natural disasters, but Shipman's new analysis of the earlier studies found that they lacked the statistical evaluations necessary for concluding with any certainty how these animals were killed.
Surprisingly, Shipman said, she found that "few of the mortality patterns from these mammoth deaths matched either those from natural deaths among modern elephants killed by droughts or by culling operations with modern weapons that kill entire family herds of modern elephants at once." This discovery suggested to Shipman that a successful new technique for killing such large animals had been developed and its repeated use over time could explain the mysterious, massive collections of mammoth bones in Europe.
The key to Shipman's new hypothesis is recent work by a team led by Mietje Germonpré of the Royal Belgian Institute of Natural Sciences, which has uncovered evidence that some of the large carnivores at these sites were early domesticated dogs, not wolves as generally had been assumed. Then, with this evidence as a clue, Shipman used information about how humans hunt with dogs to formulate a series of testable predictions about these mammoth sites.
Storytelling and story testing in domestication
Authors:
Gerbault et al
Abstract:
The domestication of plants and animals marks one of the most significant transitions in human, and indeed global, history. Traditionally, study of the domestication process was the exclusive domain of archaeologists and agricultural scientists; today it is an increasingly multidisciplinary enterprise that has come to involve the skills of evolutionary biologists and geneticists. Although the application of new information sources and methodologies has dramatically transformed our ability to study and understand domestication, it has also generated increasingly large and complex datasets, the interpretation of which is not straightforward. In particular, challenges of equifinality, evolutionary variance, and emergence of unexpected or counter-intuitive patterns all face researchers attempting to infer past processes directly from patterns in data. We argue that explicit modeling approaches, drawing upon emerging methodologies in statistics and population genetics, provide a powerful means of addressing these limitations. Modeling also offers an approach to analyzing datasets that avoids conclusions steered by implicit biases, and makes possible the formal integration of different data types. Here we outline some of the modeling approaches most relevant to current problems in domestication research, and demonstrate the ways in which simulation modeling is beginning to reshape our understanding of the domestication process.
Wolves likely were domesticated by European hunter–gatherers more than 18,000 years ago and gradually evolved into dogs that became household pets, UCLA life scientists report.
"We found that instead of recent wolves being closest to domestic dogs, ancient European wolves were directly related to them," said Robert Wayne, a professor of ecology and evolutionary biology in UCLA's College of Letters and Science and senior author of the research. "This brings the genetic record into agreement with the archaeological record. Europe is where the oldest dogs are found."
[...]
For the current study in Science, the researchers studied 10 ancient "wolf-like" animals and eight "dog-like" animals, mostly from Europe. These animals were all more than 1,000 years old, most were thousands of years old, and two were more than 30,000 years old.
The biologists studied the mitochondrial DNA of the animals, which is abundant in ancient remains. (Mitochondria are tiny sub-cellular structures with their own small genome.) By comparing this ancient mitochondrial DNA with the modern mitochondrial genomes of 77 domestic dogs, 49 wolves and four coyotes, the researchers determined that the domestic dogs were genetically grouped with ancient wolves or dogs from Europe — not with wolves found anywhere else in the world or even with modern European wolves. Dogs, they concluded, derived from ancient wolves that inhabited Europe and are now extinct.
