Elephant ancestors´ teeth evolved in response to long term changes in diet and climate in Africa

A new study shows that the cheek teeth of proboscideans (elephants and their ancient relatives) evolved in response to dietary changes due to vegetation changes and climate change in East Africa during the last 26 million years.

The latest study about of proboscideans (elephants and their ancient relatives) from the University of Helsinki provides proof that some proboscideans started to adapt to locally grass-rich environments in East Africa first by changing their behavior and starting to feed more on grasses. This happened in some lineages of proboscideans, such as choerolophodonts, much earlier than has been thought until now, about 23 to 11 million years ago in parts of East Africa

Also, around 7 million years ago in the lake Turkana region, increasingly grass-rich diets of the earliest true elephants were associated with dryer and more grass-rich savanna environments than elsewhere in East Africa.

"This supports the hypothesis of such regions as "species-factories" where evolutionary adaptation to changing environmental conditions first centered around," says Juha Saarinen from the University of Helsinki, who led the research.

Feeding on grasses is more demanding on teeth than feeding on most other kinds of plants due to a high content of mineral grains called phytoliths in their leaves, causing heavy abrasion on teeth.

Nonetheless, during the Early and Middle Miocene the choerolophodont lineage of proboscideans were able to shift to more grass-rich diets with relatively modest changes in the morphology of their teeth.

Since about 10 million years ago, major changes in climate had a more profound effect on the evolution of proboscidean teeth in East Africa, especially the evolution of true elephants (Elephantidae) with highly specialized high-crowned, multi-ridged molar teeth.

"We were able to show that the strongest peaks of drying of the East African climate during the last 7 million years (for example about 4 and 2 million years ago) correspond with evolutionary bursts in the increase of tooth crown height and the number of ridges on the molar teeth, while these evolutionary changes did not reverse during periods of less harsh climatic conditions" says Saarinen.

"This supports earlier suggestions that adaptive traits in organisms are adaptations to extreme rather than average environmental conditions."

Comparing evidence of past vegetation and the diet of elephants during the last 7 million years also showed an increase of grasslands and increasing dominance of grass-feeding elephants with highly specialized teeth throughout that period in most parts of East Africa. However, during the last 100,000 years this situation changed probably because of drastic fluctuations in global climate and eventually only the dietarily more generalist modern African savanna elephant (Loxodonta africana) with less specialized teeth survived in East Africa. Ecological generalism might similarly explain the survival of Asian elephant (Elephas maximus) in Asia, while the African forest elephant (L. cyclotis) was able to find refuge in more forested parts of Central and Western Africa.

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Family trees from the European Neolithic

The Neolithic burial site of Gurgy 'les Noisats' in France revealed two unprecedentedly large family trees which allowed a Franco-German team to explore the social organization of the 6,700-year-old community. Based on multiple lines of evidence, the team describes a close kin group which practiced monogamy and female exogamy, and experienced generally stable times.

The Neolithic lifestyle, based on farming instead of hunting and gathering, emerged in the Near East around 12,000 years ago and contributed profoundly to the modern way of life. The ability to produce and store extra food led Neolithic people to develop new social customs built on wealth, and therefore form social hierarchies. After an early phase of diffusion and having reached regions in western Europe, settled societies became more complex, which is sometimes reflected in the funerary world as well. The Paris Basin region in northern modern-day France is known for its monumental funerary sites, understood as being built for the society's "elite." In this context, the site of Gurgy 'Les Noisats', one of the biggest Neolithic funerary sites without monument in the region, begs the question who these people buried with different practices were.

Using new methods for obtaining and analysing ancient DNA data, and by sampling nearly every individual from the flat cemetery, researchers from the PACEA laboratory in Bordeaux, France, and from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, reveal two massive family trees which open a window into the lives of the people of this prehistoric community.

Massive family trees

In their study, the scientists analysed genome-wide ancient DNA data from 94 individuals buried at Gurgy, combined with strontium isotope ratio values, mitochondrial DNA (maternal lineages) and Y-chromosome (paternal lineages) data, age-at-death, and genetic sex. Two family trees could be reconstructed, the first connecting 64 individuals over seven generations is the largest pedigree reconstructed from ancient DNA to date, while the second connects twelve individuals over five generations.

"Since the beginning of the excavation, we found evidence of a complete control of the funerary space and only very few overlapping burials, which felt like the site was managed by a group of closely related individuals, or at least by people who knew who was buried where," says Stéphane Rottier from the University of Bordeaux, the archaeo-anthropologist who excavated the site between 2004 and 2007. Indeed, a positive correlation between spatial and genetic distances showed that the deceased were likely to be buried close to a relative.

Insights into the social structure of Gurgy

Exploring the pedigrees revealed a strong patrilineal pattern, where each generation is almost exclusively linked to the previous generation through the biological father, which connects the entire group of Gurgy through the paternal line. At the same time, combined evidence from mitochondrial lineages and strontium stable isotope revealing a non-local origin of most women suggested the practice of patrilocality, meaning that the sons stayed where they were born, and had children with females from outside of Gurgy. Settling in with the male partner's home community is known as virilocality. By contrast, most of the lineage adult daughters are missing, in line with female exogamy, potentially indicating a reciprocal exchange system. Interestingly, these "new incoming" female individuals were only very distantly related to each other, meaning that they must have come from a network of nearby communities, instead of just one nearby group. This lends support to the existence of a relatively wide and potentially fluid exchange network comprising many (including smaller) groups.

Looking at the family trees, Maïté Rivollat, first author of the study, is amazed: "We observe a large number of full siblings who have reached reproductive age. Combined with the expected equal number of females and significant number of deceased infants, this indicates large family sizes, a high fertility rate and generally stable conditions of health and nutrition, which is quite striking for such ancient times." Another notably unique feature at Gurgy is a lack of half-siblings, suggesting neither polygamous nor serial monogamous reproductive partnerships (or the exclusion of offspring from these unions from the main cemetery), when compared to the so far only other example of union practices from Neolithic megaliths.

A founding ancestor

In the frame of this patrilocal system, one male individual from which everyone in the largest family tree was descended could be identified as the "founding father" of the cemetery. His burial is unique at the site, as his skeletal remains were buried as a secondary deposit inside the grave pit of a woman, for whom, unfortunately, no genomic data could be obtained. Therefore, his bones must have been brought from wherever he had originally died to be reburied at Gurgy. "He must have represented a person of great significance for the founders of the Gurgy site to be brought there after a primary burial somewhere else," explains Marie-France Deguilloux from the University of Bordeaux, co-senior author of the study.

Although the main pedigree spans seven generations, the demographic profile suggests that a large family group spanning several generations arrived at the site. With almost no subadults buried at the site during the first few generations, and by contrast no adult burials in the last generations, only a short use of the site is expected. The group must have left a previous site, leaving behind any previously deceased children but still brought the lineage father. Only a few generations later the same happened: the adult of the last generations left Gurgy for another place, leaving behind their own children. Hence, Gurgy was probably only used for three to four generations, or approximately one century.

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Lingering effects of Neanderthal DNA found in modern humans

Recent scientific discoveries have shown that Neanderthal genes comprise some 1 to 4% of the genome of present-day humans whose ancestors migrated out of Africa, but the question remained open on how much those genes are still actively influencing human traits -- until now.

A multi-institution research team including Cornell University has developed a new suite of computational genetic tools to address the genetic effects of interbreeding between humans of non-African ancestry and Neanderthals that took place some 50,000 years ago. (The study applies only to descendants of those who migrated from Africa before Neanderthals died out, and in particular, those of European ancestry.)

In a study published in eLife, the researchers reported that some Neanderthal genes are responsible for certain traits in modern humans, including several with a significant influence on the immune system. Overall, however, the study shows that modern human genes are winning out over successive generations.

"Interestingly, we found that several of the identified genes involved in modern human immune, metabolic and developmental systems might have influenced human evolution after the ancestors' migration out of Africa," said study co-lead author April (Xinzhu) Wei, an assistant professor of computational biology in the College of Arts and Sciences. "We have made our custom software available for free download and use by anyone interested in further research."

Using a vast dataset from the UK Biobank consisting of genetic and trait information of nearly 300,000 Brits of non-African ancestry, the researchers analyzed more than 235,000 genetic variants likely to have originated from Neanderthals. They found that 4,303 of those differences in DNA are playing a substantial role in modern humans and influencing 47 distinct genetic traits, such as how fast someone can burn calories or a person's natural immune resistance to certain diseases.

Unlike previous studies that could not fully exclude genes from modern human variants, the new study leveraged more precise statistical methods to focus on the variants attributable to Neanderthal genes.

While the study used a dataset of almost exclusively white individuals living in the United Kingdom, the new computational methods developed by the team could offer a path forward in gleaning evolutionary insights from other large databases to delve deeper into archaic humans' genetic influences on modern humans.

"For scientists studying human evolution interested in understanding how interbreeding with archaic humans tens of thousands of years ago still shapes the biology of many present-day humans, this study can fill in some of those blanks," said senior investigator Sriram Sankararaman, an associate professor at the University of California, Los Angeles. "More broadly, our findings can also provide new insights for evolutionary biologists looking at how the echoes of these types of events may have both beneficial and detrimental consequences."

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Scientists develop new index based on functional morphology to understand how ancestors of modern birds used their wings

Scientists at Nagoya University in Japan have developed an index to estimate how a bird uses its wings for flight or other locomotion by measuring the strength of the coracoid bone and the animal's body mass. It should improve our understanding of how extinct animals used their wings and the different patterns of wing-propelled locomotion that emerged as birds evolved. Their findings were published in the Journal of Anatomy.

The presence of a wing alone does not tell us whether an animal can fly. For example, penguins evolved wings to propel them through water whereas feathered dinosaurs may have used their wings for other purposes, such as thermoregulation and intraspecific display. Therefore, to better understand how animals evolved the ability to fly, an index must take into account both the presence of wings and the ability to perform powerful wing-beats.

"We wanted to create a new index because people think that if an animal has wings, then it can fly," said the study's second author, Assistant Professor Shin-ichi Fujiwara. "But this is not always true. An animal can also use its wings for other purposes, such as thermal insulation in flightless animals. Our research team focused on how changes in skeletal morphology can lead to changes in locomotion. Subsequently, these changes can lead to major ecological transitions such as a shift in lifestyle from a terrestrial environment to an aerial, aquatic, arboreal, or subterranean environment. The origin of flight in birds has been an important topic in this field. We, therefore, needed to develop an alternative index, based on biomechanics, to determine the flapping ability of birds and which we could also use to measure skeletal remains."

To create this index, the researchers used the avian coracoid bone. The coracoid bone acts as a strut to prevent the thoracic skeleton from deforming when an animal's powerful flight muscles, which connect the wings to the sternum, contract. Doctoral student Takumi Akeda of the Department of Earth and Planetary Sciences, Graduate School of Environmental Studies, at Nagoya University, and Fujiwara of the Nagoya University Museum, measured the size of a cross section of the coracoid bone in relation to the body mass of 220 bird specimens. Their sample of 209 species included extinct birds such as the dodo and the great auk.

The researchers then divided the birds into four groups based on how they used their wings. These groups were those that used flapping flight (e.g., pigeons); those that used wing-propelled diving (e.g., penguins); those that were flightless with no flapping ability (e.g., ostriches); and those that used thermal and dynamic soaring (e.g., albatrosses and vultures). Based on the strength of the coracoid bone and flapping ability, the researchers could create a new index to analyze flight patterns.

They found that the strength of the coracoid in relation to body mass may reflect the force exerted by the flight muscles, which counteract the lifting force on the wings. This helps to estimate how a bird uses propulsion. Soaring birds had increased coracoid strength, probably to enable them to withstand the greater bending forces caused by the contraction of the flapping muscles. In contrast, non-flapping birds had lower coracoid strength. These findings show that coracoid strength in relation to body mass reflects the lifting force on the wings, therefore, it is a useful tool for reconstructing the type of propulsion used by the animal.

Akeda and Fujiwara's index should allow future researchers to assess the flight styles and flapping abilities of not only extinct birds but also other flying animals, including the Pteranodon and Quetzalcoatlus of "Jurassic World" fame. The index could also allow them to estimate the origin of flight in winged theropods, the ancestors of birds.

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New ancient 'marine crocodile' discovered on UK's Jurassic Coast -- and it's one of the oldest specimens of its type ever found

A new study has uncovered a new thalattosuchian -- an ancient 'sister' of modern-day crocodiles' ancestors.

The discovery of Turnersuchus hingleyae follows an impressive unearthing of fossils on the Jurassic Coast, in Dorset, UK, including part of the head, backbone, and limbs. In fact, the find at the Charmouth Mudstone Formation was so successful, Turnersuchus is the only complete enough thalattosuchian of its age -- dating back to the Early Jurassic, Pliensbachian period, around 185 million years ago -- to be named to date.

Published in the peer-reviewed Journal of Vertebrate Paleontology, experts state the discovery of this new predator helps fill a gap in the fossil record and suggests that thalattosuchians, with other crocodyliforms, should have originated around the end of the Triassic period -- around 15 million years further back in time than when Turnersuchus lived.

"We should now expect to find more thalattosuchians of the same age as Turnersuchus as well as older," states co-author Dr. Eric Wilberg, Assistant Professor at the Department of Anatomical Sciences, at Stony Brook University.

"In fact, during the publication of our paper, another paper was published describing a thalattosuchian skull discovered in the roof of a cave in Morocco from the Hettangian/Sinemurian (the time periods preceding the Pliensbachian where Turnersuchus was found), which corroborates this idea. I expect we will continue to find more older thalattosuchians and their relatives. Our analyses suggest that thalattosuchians likely first appeared in the Triassic and survived the end-Triassic mass extinction."

However, no digs have found thalattosuchians in Triassic rocks yet, which means there is a ghost lineage (a period during which we know a group must have existed, but we haven't yet recovered fossil evidence). Until the discovery of Turnersuchus, this ghost lineage extended from the end of the Triassic until the Toarcian, in the Jurassic, "but now we can reduce the ghost lineage by a few million years" the expert team states.

Thalattosuchians are referred to colloquially as 'marine crocodiles' or 'sea crocodiles', despite the fact they are not members of Crocodylia, but are more distantly related. Some thalattosuchians became very well adapted to life in the oceans, with short limbs modified into flippers, a shark-like tail fin, salt glands, and potentially the ability to give live birth (rather than lay eggs).

Turnersuchus is interesting as much of these recognized thalattosuchian features had yet to fully evolve. It lived in the Jurassic Ocean and preyed on marine wildlife. And, due to its relatively long, slender snout, would have looked similar in appearance to the currently living gharial crocodiles, which are found in all the major river systems of the northern Indian subcontinent.

"However," co-author Dr. Pedro Godoy, from the University of São Paulo in Brazil says, "unlike crocodiles, this approximately 2-meter-long predator lived purely in coastal marine habitats. And though their skulls look superficially similar to modern gharials, they were constructed quite differently."

Thalattosuchians had particularly large supratemporal fenestrae -- a region of the skull housing jaw muscles. This suggests that Turnersuchus and other thalattosuchians possessed enlarged jaw muscles that likely enabled fast bites; most of their likely prey were fast-moving fish or cephalopods. It's possible too, just as in modern-day crocodiles, that the supratemporal region of Turnersuchus had a thermoregulatory function -- to help buffer brain temperature.

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Revealing the genome of the common ancestor of all mammals

An international team has reconstructed the genome organization of the earliest common ancestor of all mammals. The reconstructed ancestral genome could help in understanding the evolution of mammals and in conservation of modern animals. The earliest mammal ancestor likely looked like the fossil animal "Morganucodon" which lived about 200 million years ago. The work is published the scientific journal Proceedings of the National Academy of Sciences.

Every modern mammal, from a platypus to a blue whale, is descended from a common ancestor that lived about 180 million years ago. We don't know a great deal about this animal, but the organization of its genome has now been computationally reconstructed by an international team of scientists.

"Our results have important implications for understanding the evolution of mammals and for conservation efforts," says Harris Lewin, distinguished professor of evolution and ecology at the University of California, Davis, and senior author on the paper.

The scientists drew on high-quality genome sequences from 32 living species representing 23 of the 26 known orders of mammals. They included humans and chimps, wombats and rabbits, manatees, domestic cattle, rhinos, bats and pangolins. The analysis also included the chicken and Chinese alligator genomes as comparison groups. Some of these genomes are being produced as part of the Earth BioGenome Project and other large-scale biodiversity genome sequencing efforts. Lewin chairs the Working Group for the Earth BioGenome Project.

The reconstruction shows that the mammal ancestor had 19 autosomal chromosomes, which control the inheritance of an organism's characteristics outside of those controlled by sex-linked chromosomes, (these are paired in most cells, making 38 in total) plus two sex chromosomes, said Joana Damas, first author on the study and a postdoctoral scientist at the UC Davis Genome Center. The team identified 1,215 blocks of genes that consistently occur on the same chromosome in the same order across all 32 genomes. These building blocks of all mammal genomes contain genes that are critical to developing a normal embryo.

Chromosomes stable over 300 million years

The scientists found nine whole chromosomes, or chromosome fragments in the mammal ancestor whose order of genes is the same in modern birds' chromosomes.

"This remarkable finding shows the evolutionary stability of the order and orientation of genes on chromosomes over an extended evolutionary timeframe of more than 320 million years," Lewin says. In contrast, regions between these conserved blocks contained more repetitive sequences and were more prone to breakages, rearrangements and sequence duplications, which are major drivers of genome evolution.

"Ancestral genome reconstructions are critical to interpreting where and why selective pressures vary across genomes. This study establishes a clear relationship between chromatin architecture, gene regulation and linkage conservation," says Professor William Murphy, Texas A&M University, who was not an author on the paper. "This provides the foundation for assessing the role of natural selection in chromosome evolution across the mammalian tree of life."

The scientists were able to follow the ancestral chromosomes forward in time from the common ancestor. They found that the rate of chromosome rearrangement differed between mammal lineages. For example, in the ruminant lineage (leading to modern cattle, sheep and deer) there was an acceleration in rearrangement 66 million years ago, when an asteroid impact killed off the dinosaurs and led to the rise of mammals.

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New species of extinct vampire-squid-like cephalopod is the first of its kind with 10 functional arms

New research led by scientists at the American Museum of Natural History and Yale shows that the oldest ancestors of the group of animals that includes octopuses and vampire squids had not eight but 10 arms. The study, which describes a new species of vampyropod based on a 328-million-year-old fossil that had not been previously described, pushes back the age of the group by nearly 82 million years. The details are published today in the journal Nature Communications.

"This is the first and only known vampyropod to possess 10 functional appendages," said lead author Christopher Whalen, a postdoctoral researcher in the Museum's Division of Paleontology and a National Science Foundation postdoctoral fellow in Yale's Department of Earth & Planetary Sciences.

Vampyropods are soft-bodied cephalopods typically characterized by eight arms and an internalized chitinous shell or fin supports. Because they lack hard structures, Vampyropoda are not well represented in the fossil record. The new study is based on an exceptionally well-preserved vampyropod fossil from the collections of the Royal Ontario Museum (ROM). Originally discovered in what is now Montana and donated to ROM in 1988.

Whalen and coauthor Neil Landman, a curator emeritus in the Museum's Division of Paleontology, identified the fossil specimen as a completely new genus and species that dates to about 328 million years old, making it the oldest known vampyropod and extending the fossil record of the group by about 82 million years. In the new study, they also describe its 10 arms -- all with preserved suckers -- corroborating previous scientific arguments that the common ancestor of vampyropods had 10 arms as well.

"The arm count is one of the defining characteristics separating the 10-armed squid and cuttlefish line (Decabrachia) from the eight armed octopus and vampire squid line (Vampyropoda). We have long understood that octopuses achieve the eight arm count through elimination of the two filaments of vampire squid, and that these filaments are vestigial arms," said Whalen. "However, all previously reported fossil vampyropods preserving the appendages only have 8 arms, so this fossil is arguably the first confirmation of the idea that all cephalopods ancestrally possessed ten arms."

Two of the cephalopod's arms appear to have been elongated relative to the other eight arms, and its torpedo-shaped body is reminiscent of today's squids. The fossil was given the name Syllipsimopodi bideni. The genus name is derived from the Greek word "syllípsimos" for "prehensile" and "pódi" for "foot" -- because this is the oldest known cephalopod to develop suckers, allowing the arms, which are modifications of the molluscan foot, to better grasp prey and other objects. The species name is to honor the recently inaugurated (at the time of paper submission) 46th President of the United States, Joseph R. Biden.

"Syllipsimopodi may have filled a niche more similar to extant squids, a midlevel aquatic predator," said Landman. "It is not inconceivable that it might have used its sucker-laden arms to pry small ammonoids out of their shells or ventured more inshore to prey on brachiopods, bivalves, or other shelled marine animals."

Based on the age, characters, and phylogenetic position, the fossil challenges the predominant arguments for vampyropod origins, and the authors propose a new model for coleoid (internally shelled cephalopod) evolution.

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Tooth study prompts rethink of human evolution

A study into tooth wear in a group of wild Japanese macaques has significant implications for the study of human evolution, a University of Otago study has shown.

Lead author Dr Ian Towle and Dr Carolina Loch, of the Sir John Walsh Research Institute, in collaboration with colleagues from Japan, studied root grooves and large uniform scratches in the macaques' teeth, which had previously only been described in fossil humans.

"Unusual wear on our fossil ancestors' teeth is thought to be unique to humans and demonstrates specific types of tool use. These types of wear have also been considered some of the earliest evidence of cultural habits for our ancestors," Dr Towle says.

"However, our research suggests this idea may need reconsidering, since we describe identical tooth wear in a group of wild monkeys that do not use tools.

"This research raises questions for our understanding of cultural changes during human evolution and suggests we may need to reassess early evidence of cultural habits."

The study, published in the American Journal of Biological Anthropology, concluded the 'toothpick'-like grooves on back teeth and large uniform scratches on the macaques' front teeth were actually caused by something more mundane, yet still surprising -- eating shellfish from rocks and accidentally chewing grit and sand with their food.

This macaque group is well-known for undertaking remarkable behaviours, including washing foods in water, and consuming fish. They have been studied for more than 70 years and have not been seen using tools or other items that could cause the unusual tooth wear observed.

Dr Towle has been studying tooth wear and pathologies in a wide variety of primate species and was "extremely surprised" to find this type of tooth wear in a group of wild monkeys.

"Up until now, the large scratches in the front teeth of fossil humans have been considered to be caused by a behaviour called 'stuff and cut', in which an item such as an animal hide is held between the front teeth and a stone tool is used for slicing. Similarly, 'toothpick' grooves are thought to be caused by tools being placed between back teeth to remove food debris or relieve pain.

"Although this does not mean hominins were not placing tools in their mouths, our study suggests the accidental ingestion of grit and/or normal food processing behaviours could also be responsible for these atypical wear patterns."

Dr Towle believes the findings provide insight into how researchers interpret cultural changes through the course of human evolution.

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Largest ever human family tree: 27 million ancestors

Researchers from the University of Oxford's Big Data Institute have taken a major step towards mapping the entirety of genetic relationships among humans: a single genealogy that traces the ancestry of all of us. The study has been published today in Science.

The past two decades have seen extraordinary advancements in human genetic research, generating genomic data for hundreds of thousands of individuals, including from thousands of prehistoric people. This raises the exciting possibility of tracing the origins of human genetic diversity to produce a complete map of how individuals across the world are related to each other.

Until now, the main challenges to this vision were working out a way to combine genome sequences from many different databases and developing algorithms to handle data of this size. However, a new method published today by researchers from the University of Oxford's Big Data Institute can easily combine data from multiple sources and scale to accommodate millions of genome sequences.

Dr Yan Wong, an evolutionary geneticist at the Big Data Institute, and one of the principal authors, explained: "We have basically built a huge family tree, a genealogy for all of humanity that models as exactly as we can the history that generated all the genetic variation we find in humans today. This genealogy allows us to see how every person's genetic sequence relates to every other, along all the points of the genome."

Since individual genomic regions are only inherited from one parent, either the mother or the father, the ancestry of each point on the genome can be thought of as a tree. The set of trees, known as a "tree sequence" or "ancestral recombination graph," links genetic regions back through time to ancestors where the genetic variation first appeared.

Lead author Dr Anthony Wilder Wohns, who undertook the research as part of his PhD at the Big Data Institute and is now a postdoctoral researcher at the Broad Institute of MIT and Harvard, said: "Essentially, we are reconstructing the genomes of our ancestors and using them to form a vast network of relationships. We can then estimate when and where these ancestors lived. The power of our approach is that it makes very few assumptions about the underlying data and can also include both modern and ancient DNA samples."

The study integrated data on modern and ancient human genomes from eight different databases and included a total of 3,609 individual genome sequences from 215 populations. The ancient genomes included samples found across the world with ages ranging from 1,000s to over 100,000 years. The algorithms predicted where common ancestors must be present in the evolutionary trees to explain the patterns of genetic variation. The resulting network contained almost 27 million ancestors.

After adding location data on these sample genomes, the authors used the network to estimate where the predicted common ancestors had lived. The results successfully recaptured key events in human evolutionary history, including the migration out of Africa.

Although the genealogical map is already an extremely rich resource, the research team plans to make it even more comprehensive by continuing to incorporate genetic data as it becomes available. Because tree sequences store data in a highly efficient way, the dataset could easily accommodate millions of additional genomes.

Dr Wong said: "This study is laying the groundwork for the next generation of DNA sequencing. As the quality of genome sequences from modern and ancient DNA samples improves, the trees will become even more accurate and we will eventually be able to generate a single, unified map that explains the descent of all the human genetic variation we see today."

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The impacts from using genetic testing to track down relatives

Genetic genealogy has become a popular hobby over the past several years, thanks to direct-to-consumer (DTC) genetic testing and relative-finder services offered by some DTC genetic testing companies. In a paper published February 24 in the American Journal of Human Genetics, researchers report results from a survey that asked people who had participated in these services what effect the discovery of previously unknown relatives had on their lives.

Among the most important findings were that identifying a genetic relative appeared to be somewhat common. Additionally, those discoveries were generally experienced as neutral or positive and didn't appear to have a big impact on participants' lives. However, some participants learned things that could be considered significant and destabilizing -- such as that their biological parent wasn't who they thought. These participants were especially vulnerable to negative outcomes.

"Everyone on our team is involved in studying the ethical, legal, and social implications of DTC genetic testing, and we've been paying attention to stories in the media about individuals who've made surprising family discoveries from these tests and relative-matching services," says lead author Christi Guerrini of the Center for Medical Ethics and Health Policy at Baylor College of Medicine. "We wanted to understand if these and other kinds of discoveries are common, how they're experienced by those making the discoveries, and what people are doing as a result."

The investigators sent the survey to about one million DTC genetic testing customers and genetic genealogy database participants; more than 26,000 responded. The final sample for analysis consisted of 23,196 completed or substantially completed surveys. Among the reasons that respondents said they chose to participate in this type of testing were to learn more about their family or build their family trees; to search for a biological parent, child, or other relative; or to investigate a suspicion that they might not be genetically related to family members.

"It seems that many -- perhaps most -- are just curious about their families and interested in building out their family trees, but it's clear that quite a lot of participants are looking for someone or hoping to confirm something in particular," Guerrini says. "It might be that they're adopted and looking for a biological parent, or that they've always felt out of place in their family and want to see if there's something to that feeling. Or they might be looking for information about a branch of their family tree that's unknown to them, or to confirm a family story that's been passed down over the years."

Most respondents (82%) reported that they learned the identity of at least one genetic relative. Among this subpopulation, 10% identified a biological grandparent, 10% identified a full or half- sibling, and 7% identified a biological father. The survey asked whether the participant had chosen to contact any of their newly identified relatives and, if so, the reasons for doing so. It also asked whether their discoveries resulted in any life changes, including changes in health-related behaviors.

Guerrini says that the high number of people overall who identified an unknown genetic relative was not unexpected, because many of those relatives could be very distant ones. But she acknowledges that the high number of participants who found close relatives could be skewed by the type of people who choose to undergo relative matching in the first place. "Unfortunately, we can't answer that question with our data, but I'm very interested in trying to do so in future research," she says.

She adds that although these experiences appear to be interesting and enjoyable to a large number of people, it's clear that some who are participating in these services have experienced negative outcomes. "In future research, we'd like to better understand those outcomes and what resources could be helpful in managing them," she says.

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Ancestors of legionella bacteria infected cells two billion years ago

Researchers at Uppsala University have discovered that the ancestors of legionella bacteria infected eukaryotic cells as early as two billion years ago. It happened soon after eukaryotes began to feed on bacteria. These results, described in a new study published in Molecular Biology and Evolution, are also relevant in the chicken-or-egg debate about whether mitochondria or phagocytosis came first.

"Our study can help us understand how harmful bacteria arise and how complex cells evolved from simpler cells," says Lionel Guy, associate professor of evolutionary microbiology at the Department of Medical Biochemistry and Microbiology, who headed the study.

Two billion years ago, ancestors of legionella bacteria already had the ability to avoid being digested by eukaryotes. Instead, they began using eukaryotic cells -- complex cells with a nucleus that make up amoebas, fungi and human beings -- to multiply.

The legionella bacterium, which causes Legionnaires' disease, belongs to a large group of bacteria called Legionellales. All Legionellales bacteria can infect eukaryotic hosts: amoebas, insects or our own cells.

"We discovered that the ancestor of the whole group lived about two billion years ago, at a time when eukaryotes were still in the making, evolving from simpler cells to the complex cell structure they have now," says Andrei Guliaev, a researcher at the Department of Medical Biochemistry and Microbiology. "We believe Legionellales were among the first to infect eukaryotic cells."

The first step in an infection with legionella bacteria is for a eukaryotic host, such as an amoeba, to bring the bacterium into its cell through a process called phagocytosis. The next step for the amoeba would be to digest the bacterium and use its parts as an energy source. But legionella bacteria have molecular tools that keep them from being digested and allow them to instead use the amoeba as an energy source so they can multiply.

In the study, the researchers show that all Legionellales have the same kind of molecular tools as legionella. That suggests that the ability to infect eukaryotes already existed in the ancestor of all Legionellales. This means that phagocytosis is at least as old as Legionellales -- two billion years old -- when eukaryotes were in the early stages of their evolution.

Which has implications for a hot chicken-or-egg debate in evolutionary biology about how eukaryotes came into being. Which came first? Was it the mitochondria, which originated from another group of bacteria and became our cells' own energy factories? Or was it phagocytosis, which is considered necessary to absorb mitochondria but is very costly from an energy standpoint?

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