A genetic mutation in extinct European apes that enabled them to convert fruit sugar into fat could be a cause of the modern obesity epidemic and diabetes, according to scientists. Fossil evidence reveals that apes living around 16 million years ago, in what was then subtropical Europe, began to suffer as global cooling subsequently changed the forest, making the fruit they ate scarce.
Extinct European apes evolved into today's great apes and the earliest hominids [Credit: Nathan Thompson, Lucille Betti-Nash, and Deming Yang]
Experts suggest that a mutation in the uricase gene which helps to convert fruit sugar (fructose) occurred around 15 million years ago. This aided apes in adding on fat layers so they could survive famines and harsh winters.
Persistence of the same mutation in all modern great apes and all modern humans, along with the fossil evidence, suggests that the now extinct European apes evolved into today's great apes and the earliest hominids.
Scientists have spent decades researching the genetic causes of obesity which is rarely found in other animals – apart from domesticated pets. The latest research focuses on fructose: a sugar which breaks down to form uric acid in the blood, according to a Sunday Times report.
The Western diet contains so much uric acid that it cannot be removed quickly enough, but triggers liver cells to turn fructose into fat, with the effect of humans adding on extra weight. The uricase mutation predisposes humans to obesity and diabetes in modern times. The results suggest a need to eat and drink much less fructose to fight obesity and prevent its dangerous complications.
"The gene enables uric acid levels to spike in response to two types of food," wrote Peter Andrews, professor of anthropology at University College London in Scientific American, co-authored with Richard Johnson, a professor of medicine in the US. "Those like beer that produce a lot of uric acid [directly] and those that contain a lot of fructose. These include honey and processed food that are high in table sugar or high-fructose corn syrup. When uric acid spikes we become susceptible to obesity and diabetes."
Obesity is considered as one of the biggest public health challenges of the century. Statistics show that it is affecting more than 500 million people worldwide. In the US alone, obesity costs at least $200 billion each year.
This medical condition also contributes to potentially fatal disorders such as cancer, type 2 diabetes and cardiovascular disease.
Author: Fiona Keating | Source: International Business Times [November 20, 2015]
Genes that drive the shape of human noses have been identified by a UCL-led study. The four genes mainly affect the width and 'pointiness' of noses which vary greatly between different populations. The new information adds to our understanding of how the human face evolved and may help contribute to forensic DNA technologies that build visual profiles based on an individual's genetic makeup.
Variation between nose shape and the specific genes responsible [Credit: Dr Kaustubh Adhikari, UCL]
The study, published today in >Nature Communications, analysed a population of over 6,000 people with varied ancestry across Latin America to study the differences in normal facial features and identify the genes which control the shape of the nose and chin.
The researchers identified five genes which play a role in controlling the shape of specific facial features. DCHS2, RUNX2, GLI3 and PAX1 affect the width and pointiness of the nose and another gene -- EDAR -- affects chin protrusion.
"Few studies have looked at how normal facial features develop and those that have only looked at European populations, which show less diversity than the group we studied. What we've found are specific genes which influence the shape and size of individual features, which hasn't been seen before.
"Finding out the role each gene plays helps us to piece together the evolutionary path from Neanderthal to modern humans. It brings us closer to understanding how genes influence the way we look, which is important for forensics applications," said the first author of the report, Dr Kaustubh Adhikari, UCL Cell & Developmental Biology.
People have different shaped facial features based on their genetic heritage and this is partly due to how the environment influenced the evolution of the human genome. The nose, for example, is important for regulating the temperature and humidity of the air we breathe in so developed different shapes in warmer and cooler climates.
"It has long been speculated that the shape of the nose reflects the environment in which humans evolved. For example, the comparatively narrower nose of Europeans has been proposed to represent an adaptation to a cold, dry climate. Identifying genes affecting nose shape provides us with new tools to examine this question, as well as the evolution of the face in other species. It may also help us understand what goes wrong in genetic disorders involving facial abnormalities," explained Professor Andrés Ruiz-Linares UCL Biosciences, who led the study.
The team collected and analysed DNA samples from 6,630 volunteers from the CANDELA cohort recruited in Brazil, Colombia, Chile, Mexico and Peru. After an initial screen, a sample size of 5,958 was used. This group included individuals of mixed European (50%), Native American (45%) and African (5%) ancestry, resulting in a large variation in facial features.
Both men and women were assessed for 14 different facial features and whole genome analysis identified the genes driving differences in appearance.
A subgroup of 3,000 individuals had their features assessed using a 3D reconstruction of the face in order to obtain exact measurements of facial features and the results identified the same genes.
The study identified genes that are involved in bone and cartilage growth and the development of the face. GLI3, DCHS2 and PAX1 are all genes known to drive cartilage growth -- GLI3 gave the strongest signal for controlling the breadth of nostrils, DCHS2 was found to control nose 'pointiness' and PAX1 also influences nostril breadth. RUNX2 which drives bone growth was seen to control nose bridge width.
The genes GLI3, DCHS2 and RUNX2 are known to show strong signals of recent selection in modern humans compared to archaic humans such as Neanderthals and Denisovans; GLI3 in particular undergoing rapid evolution.
Consider the engineering marvel that is your foot. Be it hairy or homely, without its solid support you'd be hard-pressed to walk or jump normally.
Researchers have identified a change in gene expression between humans and primates that may have helped give us this edge when it comes to walking upright. And they did it by studying a tiny fish called the threespine stickleback that has evolved radically different skeletal structures to match environments around the world [Credit: Flickr/Emilian Robert Vicol]
Now, researchers at the Stanford University School of Medicine and the HudsonAlpha Institute for Biotechnology in Huntsville, Alabama, have identified a change in gene expression between humans and primates that may have helped give us this edge when it comes to walking upright. And they did it by studying a tiny fish called the threespine stickleback that has evolved radically different skeletal structures to match environments around the world.
"It's somewhat unusual to have a research project that spans from fish all the way to humans, but it's clear that tweaking the expression levels of molecules called bone morphogenetic proteins can result in significant changes not just in the skeletal armor of the stickleback, but also in the hind-limb development of humans and primates," said David Kingsley, PhD, professor of developmental biology at Stanford. "This change is likely part of the reason why we've evolved from having a grasping hind foot like a chimp to a weight-bearing structure that allows us to walk on two legs."
Kingsley, who is also a Howard Hughes Medical Institute investigator, is the senior author of a paper describing the work that will be >published in Cell. The lead author is former Stanford postdoctoral scholar Vahan Indjeian, PhD, now head of a research group at Imperial College London.
Adapting to different environments
The threespine stickleback is remarkable in that it has evolved to have many different body structures to equip it for life in different parts of the world. It sports an exterior of bony plates and spines that act as armor to protect it from predators. In marine environments, the plates are large and thick; in freshwater, the fish have evolved to have smaller, lighter-weight plates, perhaps to enhance buoyancy, increase body flexibility and better slip out of the grasp of large, hungry insects. Kingsley and his colleagues wanted to identify the regions of the fish's genome responsible for the skeletal differences that have evolved in natural populations.
The researchers identified the area of the genome responsible for controlling armor plate size, and then looked for differences there in 11 pairs of marine and freshwater fish with varying armor-plate sizes. They homed in on a region that includes the gene for a bone morphogenetic protein family member called GDF6. Due to changes in the regulatory DNA sequence near this gene, freshwater sticklebacks express higher levels of GDF6, while their saltwater cousins express less. Strikingly, marine fish genetically engineered to contain the regulatory sequence of freshwater fish expressed higher levels of GDF6 and developed smaller armor plates, the researchers found.
Regulatory regions in humans vs. chimps
Kingsley and his colleagues wondered whether changes in GDF6 expression levels might also have contributed to critical skeletal modifications during human evolution. The possibility was not as far-fetched as it might seem. Other studies by evolutionary biologists, including Kingsley, have shown that small changes in the regulatory regions of key developmental genes can have profound effects in many vertebrates.
They began by working with colleagues in the laboratory of Gill Bejerano, PhD, Stanford associate professor of developmental biology, of computer science and of pediatrics, to compare differences in the genomes of chimps and humans. In previous surveys, they found over 500 places in which humans have lost regulatory regions that are conserved from chimps and many other mammals. Two of these occur near the GDF6 gene. They homed in on one in particular.
"This regulatory information was shared through about 100 million years of evolution," said Kingsley. "And yet, surprisingly, this region is missing in humans."
To learn more about what the GDF6 regulatory region might be controlling, the researchers used the chimp regulatory DNA to control the production of a protein that is easy to visualize in mice. Laboratory mice with the chimp regulatory DNA coupled to the reporter protein strongly and specifically expressed the protein in their hind limbs, but not their forelimbs, and in their lateral toes, but not the big toes of the hind limbs. Mice genetically engineered to lack the ability to produce GDF6 in any part of their bodies had skull bones that were smaller than normal and their toes were shorter than those of their peers. Together, these findings gave the researchers a clue that GDF6 might play a critical role in limb development and evolution.
The big toe: an explanation
The fact that humans are missing the hind-limb-regulatory region probably means that we express less of the gene in our legs and feet during development, but comparable amounts in our nascent arms, hands and skulls. Loss of this particular regulatory sequence would also shorten lateral toes but not the first toe of feet. This may help explain why the big toe is aligned with other short, lateral toes in humans. Such a modification would create a more sturdy foot with which to walk upright.
"These bone morphogenetic proteins are strong signals for bone and cartilage growth in all types of animals," said Kingsley.
"You can evolve new skeletal structures by changing where and when the signals are expressed, and it's very satisfying to see similar regulatory principles in action whether you are changing the armor of a stickleback, or changing specific hind-limb structures during human evolution."
Author: Krista Conger | Source: Stanford University Medical Center [January 07, 2016]
A research team led by scientists of the Max Planck Institute for Evolutionary Anthropology scanned the skulls of Neandertals and found the small middle ear ossicles, which are important for hearing, still preserved within the cavities of the ear. To their surprise, the Neandertal ossicles are morphologically distinct from the ossicles of modern humans. Despite the differences in morphology, the function of the middle ear is largely the same in the two human species.
The authors relate the morphological differences in the ossicles to different evolutionary trajectories in brain size increase and suggest that these findings might be indicative of consistent aspects of vocal communication in modern humans and Neandertals. These findings are also of importance for shedding light on the emergence of human spoken language, which can only be inferred indirectly from the archaeological and fossil record.
The three bones of the middle ear (hammer, anvil, stapes) make up the ossicular chain. This bony chain, which is found in all mammals is dedicated to the transmission of sound waves from the tympanic membrane to the inner ear and helps in amplifying the energy of airborne sound in order to allow the sound wave to travel within the fluid-filled inner ear.
Moreover, the ear ossicles are not only important for correct hearing but are also the smallest bones of our body. Thus, it does not surprise that the ossicles are among the most rarely found bones in the mammalian fossil record including the one of human ancestors. Given their important role in audition this lack of knowledge has ever been frustrating for researchers interested in studying hearing capacities of extinct species.
Tiny bones still present
This also applies to our closest extinct relatives - the Neandertals whose communicative capacities including existence of human spoken language is a major scientific debate ever since the first discovery of Neandertal remains. A research team led by Alexander Stoessel from the Max Planck Institute for Evolutionary Anthropology in Leipzig used high-resolution computer tomography scans of Neandertal skulls and systematically checked for ossicles that potentially became trapped within the cavity of the middle ear.
And indeed, the researchers found ear ossicles in 14 Neandertal individuals coming from sites in France, Germany, Croatia and Israel, resulting in the largest sample of ear ossicles of any fossil human species. “We were really astonished how often the ear ossicles are actually present in these fossil remains, particularly when the ear became filled with sediments” says lead researcher Alexander Stoessel.
After virtually reconstructing the bones, the team - which also included scientist from the Friedrich-Schiller University in Jena and the University College in London – compared them to ossicles of anatomically modern humans and also chimpanzees and gorillas which are our closest living relatives.
Since ossicles are not only small but also complex-shaped the researchers compared them by means of three-dimensional analysis that uses a much larger number of measuring points allowing for examination of the three-dimensional shape of a structure. “Despite the close relationship between anatomically modern humans and Neandertals to our surprise the ear ossicles are very differently shaped between the two human species” says Romain David who was involved in the study.
Based on the results of the morphological comparison the research team examined the potential reasons for these different morphologies. In order to see if these differences may affect hearing capacity of Neandertals and modern humans or reflects a tight relationship with the base of the skull they also analyzed the structures surrounding the ear ossicles. The outcome of this analysis was surprising, again since the functional parameters of the Neandertal and modern human middle ear are largely similar despite contrasting morphologies.
Similar communication skills in archaic humans
Instead, the team found the ear ossicles strongly related to the morphology of the surrounding cranial structures which also differ between the two human groups. The reseachers attribute these differences to different evolutionary trajectories that Neandertals and modern humans pursued in order to increase their brain volume which also impacted the structures of the cranial base which the middle ear is a part of.
“For us these results could be indicative for consistent aspects of vocal communication in anatomically modern humans and Neandertals that were already present in their common ancestor” says Jean-Jacques Hublin who is an author of this study and continues “these findings should be a basis for continuing research on the nature of the spoken language in archaic hominins”.
The findings are published in >Proceedings of the National Academy of Sciences.
Source: Max Planck Institute for Evolutionary Anthropology [September 27, 2016]
In a remarkable technical feat, researchers have sequenced DNA from fossils in Spain that are about 300,000 to 400,000 years old and have found an ancestor—or close relative—of Neanderthals. The nuclear DNA, which is the oldest ever sequenced from a member of the human family, may push back the date for the origins of the distinct ancestors of Neanderthals and modern humans, according to a presentation here yesterday at the fifth annual meeting of the European Society for the study of human evolution.
DNA from these fossilized bones and teeth in a Spanish cave are providing clues about the origins of Neanderthals and modern humans [Credit: J.-J. Hublin; Royal Museum For Central Africa, Tervuren, Belgium]
Ever since researchers first discovered thousands of bones and teeth from 28 individuals in the mid-1990s from Sima de los Huesos (“pit of bones”), a cave in the Atapuerca Mountains of Spain, they had noted that the fossils looked a lot like primitive Neanderthals. The Sima people, who lived before Neanderthals, were thought to have emerged in Europe. Yet their teeth, jaws, and large nasal cavities were among the traits that closely resembled those of Neanderthals, according to a team led by paleontologist Juan-Luis Arsuaga of the Complutense University of Madrid. As a result, his team classified the fossils as members of Homo heidelbergensis, a species that lived about 600,000 to 250,000 years ago in Europe, Africa, and Asia. Many researchers have thought H. heidelbergensis gave rise to Neanderthals and perhaps also to our species, H. sapiens, in the past 400,000 years or so.
But in 2013, the Sima fossils’ identity suddenly became complicated when a study of the maternally inherited mitochondrial DNA (mtDNA) from one of the bones revealed that it did not resemble that of a Neanderthal. Instead, it more closely matched the mtDNA of a Denisovan, an elusive type of extinct human discovered when its DNA was sequenced from a finger bone from Denisova Cave in Siberia. That finding was puzzling, prompting researchers to speculate that perhaps the Sima fossils had interbred with very early Denisovans or that the “Denisovan” mtDNA was the signature of an even more ancient hominin lineage, such as H. erectus. At the time, researchers at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who had obtained the mtDNA announced that they would try to sequence the nuclear DNA of the fossils to solve the mystery.
After 2 years of intense effort, paleogeneticist Matthias Meyer of the Max Planck Institute for Evolutionary Anthropology has finally sequenced enough nuclear DNA from fossils of a tooth and a leg bone from the pit to solve the mystery. The task was especially challenging because the ancient DNA was degraded to short fragments, made up of as few as 25 to 40 single nucleotides. (Nucleotides—also known as base pairs—are the building blocks of DNA.) Although he and his colleagues did not sequence the entire genomes of the fossils, Meyer reported at the meeting that they did get 1 million to 2 million base pairs of ancient nuclear DNA.
Researchers have spent decades studying the remains found in the 'Pit of Bones', reconstructing the skull shown above, which revealed it had suffered a heavy blow to the head before death [Credit: msf]
They scanned this DNA for unique markers found only in Neanderthals or Denisovans or modern humans, and found that the two Sima fossils shared far more alleles—different nucleotides at the same address in the genome—with Neanderthals than Denisovans or modern humans. “Indeed, the Sima de los Huesos specimens are early Neanderthals or related to early Neanderthals,” suggesting that the split of Denisovans and Neanderthals should be moved back in time, Meyer reported at the meeting.
Researchers at the meeting were impressed by this new breakthrough in ancient DNA research. “This has been the next frontier with ancient DNA,” says evolutionary biologist Greger Larson of the University of Oxford in the United Kingdom.
The close affinity with Neanderthals, but not with Denisovans or modern humans, suggests that the lineage leading to Neanderthals was separate from other archaic humans earlier than most researchers have thought. That means that the ancestors of modern humans also had to split earlier than expected from the population that gave rise to Neanderthals and Denisovans, who were more closely related to each other than they were to modern humans. (Although all three groups interbred at low levels after their evolutionary paths diverged—and such interbreeding may have been the source of the Denisovan mtDNA in the first Sima fossil whose DNA was sequenced.) Indeed, Meyer suggested in his talk that the ancestors of H. sapiens may have diverged from the branch leading to Neanderthals and Denisovans as early as 550,000 to 765,000 years ago, although those results depend on different mutation rates in humans and are still unpublished.
That would mean that the ancestors of humans were already wandering down a solitary path apart from the other kinds of archaic humans on the planet 100,000 to 400,000 years earlier than expected. “It resolves one controversy—that they’re in the Neanderthal clade,” says paleoanthropologist Chris Stringer of the Natural History Museum in London. “But it’s not all good news: From my point of view, it pushes back the origin of H. sapiens from the Neanderthals and Denisovans.” The possibility that humans were a distinct group so early shakes up the human family tree, promising to lead to new debate about when and where the branches belong.
Author: Ann Gibbons | Source: ScienceMag/AAAS [September 11, 2015]
