When and where did humans develop language? To find out, look deep inside caves, suggests an MIT professor.

Stock image of a cave painting in South Africa [Credit: MIT]

More precisely, some specific features of cave art may provide clues about how our symbolic, multifaceted language capabilities evolved, according to a new paper co-authored by MIT linguist Shigeru Miyagawa.

A key to this idea is that cave art is often located in acoustic “hot spots,” where sound echoes strongly, as some scholars have observed. Those drawings are located in deeper, harder-to-access parts of caves, indicating that acoustics was a principal reason for the placement of drawings within caves. The drawings, in turn, may represent the sounds that early humans generated in those spots.

In the new paper, this convergence of sound and drawing is what the authors call a “cross-modality information transfer,” a convergence of auditory information and visual art that, the authors write, “allowed early humans to enhance their ability to convey symbolic thinking.” The combination of sounds and images is one of the things that characterizes human language today, along with its symbolic aspect and its ability to generate infinite new sentences.

“Cave art was part of the package deal in terms of how homo sapiens came to have this very high-level cognitive processing,” says Miyagawa, a professor of linguistics and the Kochi-Manjiro Professor of Japanese Language and Culture at MIT. “You have this very concrete cognitive process that converts an acoustic signal into some mental representation and externalizes it as a visual.”

Cave artists were thus not just early-day Monets, drawing impressions of the outdoors at their leisure. Rather, they may have been engaged in a process of communication.

“I think it’s very clear that these artists were talking to one another,” Miyagawa says. “It’s a communal effort.”

The paper, “Cross-modality information transfer: A hypothesis about the relationship among prehistoric cave paintings, symbolic thinking, and the emergence of language,” is published in the journal Frontiers in Psychology. The authors are Miyagawa; Cora Lesure, a PhD student in MIT’s Department of Linguistics; and Vitor A. Nobrega, a PhD student in linguistics at the University of Sao Paulo, in Brazil.

Re-enactments and rituals?

The advent of language in human history is unclear. Our species is estimated to be about 200,000 years old. Human language is often considered to be at least 100,000 years old.

“It’s very difficult to try to understand how human language itself appeared in evolution,” Miyagawa says, noting that “we don’t know 99.9999 percent of what was going on back then.” However, he adds, “There’s this idea that language doesn’t fossilize, and it’s true, but maybe in these artifacts [cave drawings], we can see some of the beginnings of homo sapiens as symbolic beings.”

While the world’s best-known cave art exists in France and Spain, examples of it abound throughout the world. One form of cave art suggestive of symbolic thinking — geometric engravings on pieces of ochre, from the Blombos Cave in southern Africa — has been estimated to be at least 70,000 years old. Such symbolic art indicates a cognitive capacity that humans took with them to the rest of the world.

“Cave art is everywhere,” Miyagawa says. “Every major continent inhabited by homo sapiens has cave art. … You find it in Europe, in the Middle East, in Asia, everywhere, just like human language.” In recent years, for instance, scholars have catalogued Indonesian cave art they believe to be roughly 40,000 years old, older than the best-known examples of European cave art.

But what exactly was going on in caves where people made noise and rendered things on walls? Some scholars have suggested that acoustic “hot spots” in caves were used to make noises that replicate hoofbeats, for instance; some 90 percent of cave drawings involve hoofed animals. These drawings could represent stories or the accumulation of knowledge, or they could have been part of rituals.

In any of these scenarios, Miyagawa suggests, cave art displays properties of language in that “you have action, objects, and modification.” This parallels some of the universal features of human language — verbs, nouns, and adjectives — and Miyagawa suggests that “acoustically based cave art must have had a hand in forming our cognitive symbolic mind.”

Future research: More decoding needed

To be sure, the ideas proposed by Miyagawa, Lesure, and Nobrega merely outline a working hypothesis, which is intended to spur additional thinking about language’s origins and point toward new research questions.

Regarding the cave art itself, that could mean further scrutiny of the syntax of the visual representations, as it were. “We’ve got to look at the content” more thoroughly, says Miyagawa. In his view, as a linguist who has looked at images of the famous Lascaux cave art from France, “you see a lot of language in it.” But it remains an open question how much a re-interpretation of cave art images would yield in linguistics terms.

The long-term timeline of cave art is also subject to re-evaluation on the basis of any future discoveries. If cave art is implicated in the development of human language, finding and properly dating the oldest known such drawings would help us place the orgins of language in human history — which may have happened fairly early on in our development.

“What we need is for someone to go and find in Africa cave art that is 120,000 years old,” Miyagawa quips.

At a minimum, a further consideration of cave art as part of our cognitive development may reduce our tendency to regard art in terms of our own experience, in which it probably plays a more strictly decorative role for more people.

“If this is on the right track, it’s quite possible that … cross-modality transfer helped develop a symbolic mind,” Miyagawa says. In that case, he adds, “art is not just something that is marginal to our culture, but central to the formation of our cognitive abilities.”

Author: Peter Dizikes | Source: Massachusetts Institute of Technology [February 21, 2018]

Modern humans have brains that are more than three times larger than our closest living relatives, chimpanzees and bonobos. Scientists don't agree on when and how this dramatic increase took place, but new analysis of 94 hominin fossils shows that average brain size increased gradually and consistently over the past three million years.

Models of human ancestors brain size compared to modern day humans [Credit: Matt Wood, UChicago]

The research, published this week in the Proceedings of the Royal Society B, shows that the trend was caused primarily by evolution of larger brains within populations of individual species, but the introduction of new, larger-brained species and extinction of smaller-brained ones also played a part.

"Brain size is one of the most obvious traits that makes us human. It's related to cultural complexity, language, tool making and all these other things that make us unique," said Andrew Du, PhD, a postdoctoral scholar at the University of Chicago and first author of the study. "The earliest hominins had brain sizes like chimpanzees, and they have increased dramatically since then. So, it's important to understand how we got here."

Du began the work as a graduate student at the George Washington University (GW). His advisor, Bernard Wood, GW's University Professor of Human Origins and senior author of the study, gave his students an open-ended assignment to understand how brain size evolved through time. Du and his fellow students, who are also co-authors on the paper, continued working on this question during his time at George Washington, forming the basis of the new study.

"Think about the entrance to a building. You can reach the front door by walking up a ramp, or you can take the steps," Wood said. "The conventional wisdom was that our large brains had evolved because of a series of step-like increases each one making our ancestors smarter. Not surprisingly the reality is more complex, with no clear link between brain size and behavior."

Modern human brains (left) are more than three times larger than our closest relatives, chimpanzees (right) [Credit: Andrew Du, UChicago]

"The moral is this: When you don't understand something ask a bunch of bright and motivated students to figure it out," he said.

Du and his colleagues compared published research data on the skull volumes of 94 fossil specimens from 13 different species, beginning with the earliest unambiguous human ancestors, Australopithecus, from 3.2 million years ago to pre-modern species, including Homo erectus, from 500,000 years ago when brain size began to overlap with that of modern-day humans.

The researchers saw that when the species were counted at the clade level, or groups descending from a common ancestor, the average brain size increased gradually over three million years. Looking more closely, the increase was driven by three different factors, primarily evolution of larger brain sizes within individual species populations, but also by the addition of new, larger-brained species and extinction of smaller-brained ones. The team also found that the rate of brain size evolution within hominin lineages was much slower than how it operates today, although why this discrepancy exists is still an open question.

The study quantifies for the first time when and by how much each of these factors contributes to the clade-level pattern. Du said he likens it to how a football coach might build a roster of bigger, strong players. One way would be to make all the players hit the weight room to bulk up. But the coach could also recruit new, larger players and cut the smallest ones.

"That's exactly what we see going on in brain size," he said. "The dominant process is like the players hitting the gym. They're evolving larger brains within a population. But we also see speciation events adding larger-brained daughter species, or recruiting bigger players, and we see extinction, or cutting the smallest players too."

Source: University of Chicago Medical Center [February 20, 2018]

Human 'self-domestication' is a hypothesis that states that among the driving forces of human evolution, humans selected their companions depending on who had a more pro-social behavior. Researchers from a team of the UB led by Cedric Boeckx, ICREA professor at the Department of Catalan Philology and General Linguistics and member of the Institute of Complex Systems of the University of Barcelona (UBICS), found out new genetic evidence for this evolutionary process.

Craniofacial differences between modern humans and Neanderthals (top) and between dogs and wolves (bottom) [Credit: PLOS ONE]

The study, published in the science journal PLOS ONE, compared the genomes of modern humans to those of several domesticated species and their wild animal type, in order to look for overlapping genes that were associated with domestication traits, such as docility or a gracile physiognomy. The results showed a statistically significant number of genes associated with domestication which overlapped between domestic animals and modern humans, but not with their wild equals, like Neanderthals.

According to the researchers, these results reinforce the human self-domestication hypothesis and "help to shed light on one aspect that makes us human, our social instinct."

A new type of evidence: the genomes of extinct human relatives

Self-domestication would occur in species that display anatomical and behavioural features which are typical of domestic animals in comparison to their wild types. However, in these cases, domestication would have taken place without any other species domesticating the others. Several studies proposed the hypothesis stating that humans -and other species such as bonobos- domesticated themselves. The aim of this study was to find out biological evidence of the self-domestication by looking at a new type of data that has become available: the genomes of our extinct relatives, such as Neanderthals or Denisovans.

"One reason that made scientists claim that humans are self-domesticated lied within our behavior: modern humans are docile and tolerant, like domesticated species, our cooperative abilities and pro-social behaviour are key features of our modern cognition," says Cedric Boeckx. "The second reason is that modern humans, when compared to Neanderthals, present a more gracile phenotype that resembles the one seen in domesticates when compared to their wild-type cousins," added the expert.

To identify signs of a self-domestication process in humans, researchers made a list of genes associated with domestication features in humans, out of the comparison with the genome in Neanderthals and Denisovans, extinct human species. Then, they compared this list to the genome from some domesticated animals and their wild relatives, for instance, dogs compared to wolves, and cattle compared to wisents.

Results showed that this overlap was only relevant between domesticated species and humans. "Those modern humans' selected genes under selection may prove central to a relevant process of domestication, given that these interactions may provide significant data on relevant phenotypic traits," said Boeckx.

Intersection between modern humans and domesticated species

Researchers also employed other statistical measures, including control species, to certify these results. Their aim was to rule out the fact that these genes could be randomly overlapped between humans and domesticated animals when compared, so they compared the genomes among other great apes. "We found that chimpanzees, orangutans and gorillas do not show a significant overlap of genes under positive selection with domesticates. Therefore, it seems there is a 'special' intersection between humans and domesticated species, and we take this to be evidence for self-domestication," Boeckx said.

Researchers note that there is still more experimental work to do in order to find out the anatomical, cognitive and behavioural characteristics that are associated with these genes. "We suspect it will cover the anatomical, cognitive, and behavioral characteristics that researchers used to motivate the idea of self-domestication. We think that the overlap we found could help us explain our special mode of cognition and why we are strikingly cooperative, but this remains to be put to the test. In a sense, what we did is narrow down the set of genes to examine experimentally," concluded Cedric Boeckx.

Source: Universidad de Barcelona [February 15, 2018]

The evolution of human biology should be considered part and parcel with the evolution of humanity itself, proposes Nicole Creanza, assistant professor of biological sciences. She is the guest editor of a new themed issue of the Philosophical Transactions of the Royal Society B, the oldest scientific journal in the world, that focuses on an interdisciplinary approach to human evolution.

Credit: iStock

Stanford professor Marc Feldman and Stanford postdoc Oren Kolodny collaborated with Creanza on the special issue.

"Within the blink of an eye on a geological timescale, humans advanced from using basic stone tools to examining the rocks on Mars; however, our exact evolutionary path and the relative importance of genetic and cultural evolution remain a mystery," said Creanza, who specializes in the application of computational and theoretical approaches to human and cultural evolution, particularly language development. "Our cultural capacities-to create new ideas, to communicate and learn from one another, and to form vast social networks-together make us uniquely human, but the origins, the mechanisms, and the evolutionary impact of these capacities remain unknown."

The special issue brings together researchers in biology, anthropology, archaeology, economics, psychology, computer science and more to explore the cultural forces affecting human evolution from a wider perspective than is usually taken.

"Researchers have begun to recognize that understanding non-genetic inheritance, including culture, ecology, the microbiome, and regulation of gene expression, is fundamental to fully comprehending evolution," said Creanza. "It is essential to understand the dynamics of cultural inheritance at different temporal and spatial scales, to uncover the underlying mechanisms that drive these dynamics, and to shed light on their implications for our current theory of evolution as well as for our interpretation and predictions regarding human behavior."

In addition to an essay discussing the need for an interdisciplinary approach to human evolution, Creanza included an interdisciplinary study of her own, examining the origins of English's contribution to Sranan, a creole that emerged in Suriname following an influx of indentured servants from England in the 17th century.

Creanza, along with linguists Andre Sherriah and Hubert Devonish of the University of the West Indes and psychologist Ewart Thomas from Stanford, sought to determine the geographic origins of the English speakers whose regional dialects formed the backbone of Sranan. Their work combined linguistic, historical and genetic approaches to determine that the English speakers who influenced Sranan the most originated largely from two counties on opposite sides of southern England: Bristol, in the west, and Essex, in the east.

"Thus, analyzing the features of modern-day languages might give us new information about events in human history that left few other traces," Creanza said.

Author: Liz Entman | Source: Vanderbilt University [February 13, 2018]

Neanderthals had large brains and made complex tools but never demonstrated the ability to draw recognizable images, unlike early modern humans who created vivid renderings of animals and other figures on rocks and cave walls. That artistic gap may be due to differences in the way they hunted, suggests a University of California, Davis, expert on predator-prey relations and their impacts on the evolution of behaviour.

Replica of drawing of lions painted in the Chauvet Cave. Art in the cave has been identified as created by early modern humans [Credit: UC Davis]

Neanderthals used thrusting spears to bring down tamer prey in Eurasia, while Homo sapiens, or modern humans, spent hundreds of thousands of years spear-hunting wary and dangerous game on the open grasslands of Africa.

Richard Coss, a professor emeritus of psychology, says the hand-eye coordination involved in both hunting with throwing spears and drawing representational art could be one factor explaining why modern humans became smarter than Neanderthals.

In an article recently published in the journal Evolutionary Studies in Imaginative Culture, Coss examines archaeological evidence, genomics, neuroscience studies, animal behavior and prehistoric cave art.

New theory of evolution

From this, he proposes a new theory for the evolution of the human brain: Homo sapiens developed rounder skulls and grew bigger parietal cortexes -- the region of the brain that integrates visual imagery and motor coordination -- because of an evolutionary arms race with increasingly wary prey.

Early humans hunted with throwing spears in sub-Saharan Africa for more than 500,000 years -- leading their increasingly watchful prey to develop better flight or fight survival strategies, Coss said.

Some anthropologists have suggested that throwing spears from a safe distance made hunting large game less dangerous, he said. But until now, "No explanation has been given for why large animals, such as hippos and Cape buffalo, are so dangerous to humans," he said. "Other nonthreatening species foraging near these animals do not trigger alert or aggressive behavior like humans do."

Drawn from earlier research on zebras

Coss' paper grew out of a 2015 study in which he and a former graduate student reported that zebras living near human settlements could not be approached as closely before fleeing as wild horses when they saw a human approaching on foot -- staying just outside the effective range of poisoned arrows used by African hunters for at least 24,000 years.

Neanderthals, whose ancestors left Africa for Eurasia before modern human ancestors, used thrusting spears at close range to kill horses, reindeer, bison, and other large game that had not developed an innate wariness of humans, he said.

Hunting relates to drawing

"Neanderthals could mentally visualize previously seen animals from working memory, but they were unable to translate those mental images effectively into the coordinated hand-movement patterns required for drawing," Coss writes.

Coss, who taught drawing classes early in his academic career and whose previous research focused on art and human evolution, used photos and film to study the strokes of charcoal drawings and engravings of animals made by human artists 28,000 to 32,000 years ago in the Chauvet-Pont-d'Arc Cave in southern France.

The visual imagery employed in drawing regulates arm movements in a manner similar to how hunters visualize the arc their spears must make to hit their animal targets, he concludes.

These drawings could have acted as teaching tools. "Since the act of drawing enhances observational skills, perhaps these drawings were useful for conceptualizing hunts, evaluating game attentiveness, selecting vulnerable body areas as targets, and fostering group cohesiveness via spiritual ceremonies," he writes.

As a result, the advent of drawing may have set the stage for cultural changes, Coss said. "There are enormous social implications in this ability to share mental images with group members."

Author: Kathleen Holder | Source: UC Davis [February 08, 2018]

Today, biologists add an important discovery to a growing body of data explaining why we're different from chimps and other primate relatives, despite the remarkable similarity of our genes. The new evidence has to do with the way genes are regulated. It's the result of a comprehensive genome-wide computational analysis of multiple individuals across three primate species - human, chimpanzee and rhesus macaque.

Humans and chimps have strikingly similar genomes. This data helps us understand differences across these primate  species. It displays information about DNA segments that regulate genes in one small part of the human and chimp  genomes, aligned for comparative purposes. There are 3 "lines" of data for each species, with the top line in each  (red for human, green for chimp) reflecting the conclusion that in this genomic space, gene enhancer activity in unactivated T-cells is very similar, with one exception: the yellow "peak" (arrows) indicates a likely gene enhancer that's active in human but inactive in chimp [Credit: Siepel Lab, CSHL]

The researchers focused on regulatory DNA elements are called gene enhancers and promoters. Promoters sit immediately "upstream" of genes and must be activated for the genes they regulate to be switched on. Less is known about enhancers, which can be located varying distances up- and downstream of the genes they regulate. Enhancers can be much farther away from the "gene body" than promoters, but can come close to the gene because of the looping structure of chromatin, the structure that packages the genome. Often, multiple enhancers are involved in a given gene's activation, in combinations that differ under differing circumstances.

Professor Adam Siepel's team at Cold Spring Harbor Laboratory (CSHL) with colleagues at Cornell University led by Dr. Charles Danko, used a technology called PRO-Seq to measure nascent transcription - the generation of RNA copies of genomic DNA up- and downstream of genes. It enables researchers to detect which promoters and enhancers are actively regulating a gene. They studied a single cell type, CD4+ T cells of the immune system, comparing levels of RNA copying when the cells were in quiescent and activated states in the three primate species.

The experiments revealed that while the activity of genes across the three species was quite similar in the CD4+ T cells, there were intriguing differences in the way genes were regulated. The team paid particular attention to collections of enhancers that jointly influence the expression of a target gene, as an ensemble. "These ensembles come in various sizes," Siepel explains, "and we found that when they are large, the expression levels of the target genes tend to be stable over evolutionary time. When they are small, the expression levels are less stable." Stability in gene expression is evidence of what scientists call evolutionary conservation - the preservation of a feature across species because of the advantage it confers.

Through careful analysis, the team identified various features that distinguish fast-evolving enhancers from slower ones. "Particularly interesting to us were cases in which large numbers of enhancers together determine the expression of a target gene," says Siepel, who is Director of the Simons Center for Quantitative Biology at CSHL. "In these cases, the genes tend to be more stable, but we found each individual enhancer is more likely to change." What's under evolutionary selection is the target expression level of a given gene, which in these situations is jointly determined by the whole ensemble.

The research reveals how programs for gene expression change during evolution, leading to the differences in behavior and morphology we observe between humans and other primates. These evolutionary mysteries also offer clues about mutations that cause diseases by altering gene regulation, Siepel notes.

The findings are published in Nature Ecology & Evolution.

Source: Cold Spring Harbor Laboratory [January 29, 2018]

Homo sapiens are considered to be the only species with a predominance of a preferred use of the right hand, with a ratio of 9 right-handed to 1 left-handed people. However, when did the human handedness appeared in human evolution remains unknown. An international research recently published and led by Marina Lozano, researcher at IPHES (Institut Català de Paleoecologia Humana i Evolució Social), shows that this behaviour is more ancient than it was thought. At population level, Neanderthal as far as 130,000 years ago, showed a well-stablished hand preference as our species. Nevertheless, this practice goes back to Homo habilis showing that handedness is an ancestral characteristic of our genus.

A. An incisor of Homo antecessor (Gran Dolina, Atapuerca, Spain) and B. an incisor of pre-Neanderthal (Sima de los Huesos, Atapuerca, Spain) [Credit: Marina Lozano/IPHES]

The scientific community has developed a huge amount of studies focused on handedness and brain laterality in hominins. However, in this work, a large sample has been analyzed, for the first time, following the same methodology. That is 120 individuals of five different human species (Homo habilis, Homo antecessor, preneanderthals, European Neanderthals and Homo sapiens), spanning almost 2 million years.

The main research teams focused on the study of handedness in fossil hominins are involved in this work. So, this is the result of an international collaboration between researchers of Spain, USA and Italy. Thanks to this work “we can affirm that the trend to have a preferred hand is an intrinsic characteristic of our genus. The handedness was established slowly in each of the species who precede us. From this research, we can do some inferences because handedness implies brain laterality that is closely related to language”, mentions the researcher Marina Lozano.

This international team studied the cultural dental wear, specifically the striations (cut marks) that result from the use of the mouth as a third hand, when some material is held between the anterior teeth and cut with a lithic tool. These marks are analyzed with environmental scanning electron microscopy.

The study is published in Evolutionary Anthropology.

Source: IPHES [January 28, 2018]

Researchers from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, reveal how and when the typical globular brain shape of modern humans evolved. Their analyses based on changes in endocranial size and shape in Homo sapiens fossils show that brain organization, and possibly brain function, evolved gradually within our species and unexpectedly reached modern conditions only recently.

Brain shape evolution in Homo sapiens: brain shape of one of the earliest known members of our species, the 300,000 year-old cranium Jebel Irhoud 1 (left). Brain shape, and possibly brain function, evolved gradually. Brain morphology has reached the globularity typical for present day humans suprisingly recently (right) [Credit: MPI EVA/ S. Neubauer, Ph. Gunz]

The evolutionary history of our own species can be traced back to fossils from Jebel Irhoud (Morocco) dated to about 300,000 years ago. Last year's analysis of these fossils by researchers from the Department of Human Evolution at the Max Planck Institute for Evolutionary Anthropology in Leipzig was highlighted as one of the top science stories of 2017 by a diverse range of print and online media. Together with crania from Florisbad (South Africa, 260,000 years old), and Omo Kibish (Ethiopia) dated to 195,000 years ago, the Jebel Irhoud fossils document an early evolutionary phase of Homo sapiens on the African continent. Their face and teeth look modern, however their elongated braincase appears more archaic as in older human species and in Neanderthals. In contrast, it is a globular braincase, which characterizes the skull of present-day modern humans together with small and gracile faces.

In a new paper published in Science Advances, members of the same research team now reveal additional surprising findings about brain evolution in Homo sapiens. The paleoanthropologists Simon Neubauer, Jean-Jacques Hublin and Philipp Gunz used micro computed tomography scans to create virtual imprints of the internal bony braincase, so called endocasts that approximate brain size and shape. They used state-of-art statistics to analyze endocasts of various fossils and present-day humans.

Evolution of the parietal lobe and the cerebellum

Neubauer and colleagues document a gradual change within Homo sapiens, from an elongated endocranial shape towards a more globular one. Two features of this process stand out: parietal and cerebellar bulging. Parietal brain areas are involved in orientation, attention, perception of stimuli, sensorimotor transformations underlying planning, visuospatial integration, imagery, self-awareness, working and long-term memory, numerical processing, and tool use. The cerebellum is not only associated with motor-related functions like the coordination of movements and balance, but also with spatial processing, working memory, language, social cognition, and affective processing.

The Homo sapiens fossils were found to have increasingly more modern endocranial shapes in accordance with their geological age. Only fossils younger than 35,000 years show the same globular shape as present-day humans, suggesting that modern brain organization evolved some time between 100,000 and 35,000 years ago. Importantly, these shape changes evolved independently of brain size -- with endocranial volumes of around 1,400 milliliters, even the oldest Homo sapiens fossils from Jebel Irhoud fell within present-day variation of brain size. "The brain is arguably the most important organ for the abilities that make us human," says Neubauer. But modern human brain shape was not established at the origin of our species together with other key features of craniodental morphology. Neubauer adds: "We already knew that brain shape must have evolved within our own species, but we were surprised to discover just how recent these changes to brain organization were."

Evolutionary changes in early brain development

In present-day humans, the characteristic globular shape of the braincase develops within a few months around the time of birth. Philipp Gunz explains, "The evolution of endocranial shape within Homo sapiens suggests evolutionary changes of early brain development -- a critical period for neural wiring and cognitive development." The researchers therefore argue that evolutionary changes to early brain development were key to the evolution of human cognition. Jean-Jacques Hublin, co-author and director of the Department of Human Evolution at the Max Planck Institute in Leipzig, says: "The gradual evolution of modern human brain shape seems to parallel the gradual emergence of behavioral modernity as seen from the archeological record."

The new findings are in agreement with recent genetic studies that show changes in genes related to brain development in our lineage since the population split between Homo sapiens and Neanderthals. They add to the accumulating archeological and paleoanthropological evidence demonstrating that Homo sapiens is an evolving species with deep African roots and long-lasting gradual changes in behavioral modernity, brain organization, and potentially brain function.

Source: Max Planck Society [January 25, 2018]

In the peaceful grasslands of northern Tanzania, a frenzy of research is occurring. The Olduvai area (from the Maasai name "Oldupai," for a native succulent plant) came to fame through the findings of Kenyan archaeologists and paleoanthropologists, Louis and Mary Leakey. Their research, beginning in the 1950s, uncovered numerous fossil hominins (the tribe of great apes, including modern humans) and stone tools dating back as far as two million years and earned the area the nickname "cradle of humankind." Olduvai has since become a hub for those exploring the origins, and future, of humanity.

Local Maasai staff lay out the geophones, a crucial piece of equipment in seismic imaging  of the Olduvai Basin [Credit: 2017 Sherif Hanafy]

Paleoanthropologists, however, no longer have sole claim here. A full picture of human evolution cannot be gleaned from fossils alone, but relies on understanding their environmental context.

To this end, a team of KAUST's geophysicists are conducting crucial surveys of the site's geology. Using state-of-the-art techniques developed for oil exploration, Gerard Schuster, Sherif Hanafy and doctoral student Kai Lu, with scientists from Indiana University, USA, and Liverpool University, UK, are mapping the shape and structure of the Olduvai Basin's bedrock.

This is no mean feat because the basin is six kilometers wide and almost half a kilometer deep. It comprises a complex mixture of sedimentary and volcanic rocks, traversed by multiple geological faults. Lying at the heart of the East African Rift Zone, where the tectonic plates making up the Earth's crust are moving apart, Schuster explains that the basin, "evolved and deepened over time as the ancient lake above it expanded, contracted and shifted laterally in space, partly caused by a sequence of eruptions of neighboring volcanoes."

Rewriting history

Two complementary experimental approaches are used: boring wells to extract physical 'cores' of sediment laid down over millions of years and the KAUST team's seismic imaging studies. Together, they are rewriting the geological history of Olduvai.

The seismic experiments are based on a remarkably simple premise: a heavy weight is repeatedly slammed onto the ground, creating vibrations that travel through it until they are reflected or refracted (bent) as they move from one material to another (in the same way that light reflects off a mirror or bends as it enters water). A series of receivers (known as geophones) are placed just below the ground to monitor these reflected and refracted waves. By recording the time taken for the waves to reach each of the geophones, the team can calculate the speed at which they traveled. In a similar way to ultrasound scanning, these measurements are built into a picture of the subsurface geology, including the basin's shape and size, and the location of buried faultlines.

Complex and logistically challenging, the method is intriguing to local people, many of whom are employed on the project. As Hanafy explains, "they are used to working with paleoanthropologists and geologists, but this is the first time they have worked with geophysicists." The project has inspired some youngsters to develop a potentially life-changing interest in science-with one even traveling to KAUST to study.

The results of this research suggest that the Olduvai Basin, once considered shallow, is more than 400 meters deep, almost twice as deep as boreholes were able to penetrate. This indicates that the bedrock lining the basin may be around four million years old, and that environments suitable for hominins may be equally ancient: "much older," says Hanafy, "than previously extrapolated from exposed rocky outcrops." The base layers of the basin were probably derived from nearby volcanoes, which may have influenced the environment, including water availability, in the distant past. This in turn would have impacted upon early hominids, who needed "water, a favorable climate, trees for protection and open plains for foraging, all of which were provided at Olduvai," explains Hanafy.

A new documentary

In Lasting Marks, a celebrated documentary about this work, the University of Liverpool's Ian Stanistreet argues that seismic imaging helps us understand the entire makeup of Olduvai: geological, climatic and otherwise. The changing climate has proven a challenge to mankind throughout our history: if we can better appreciate this history, we may be moved to alter our trajectory. As the director of Lasting Marks, Sarah Schuster-Johnson, eloquently explains, "the dedicated and passionate Olduvai researchers carefully interpret marks from an undeciphered history, a history that paved the way for our existence and our future on this planet."

Source: King Abdullah University of Science and Technology [January 21, 2018]

Research shows a collection of small adaptations in stress activated proteins, accumulated over millennia of human history, could help to explain our increased natural defences and longer lifespan.

Credit: Newcastle University

Publishing in Nature Communications, the team of collaborators from the UK, France and Finland and lead by researchers at Newcastle University, UK explain the importance of a protein called p62.

Many cells in our body, such as those which make up our brain need to last us a lifetime. To do this our cells have developed ways of protecting themselves. One way is through a process called autophagy, which literally means self-eating, where damaged components are collected together and removed from the cell.

This is very important as accumulation of damage in cells has been linked to several diseases including dementia.

Lead author, Dr. Viktor Korolchuk from Newcastle University's Institute for Ageing explains: "As we age, we accumulate damage in our cells and so it is thought that activating autophagy could help us treat older people suffering from dementia. In order to be able to do this we need to understand how we can induce this cell cleaning."

The importance of protein, p62

In the study the authors were able to identify how a protein called p62 is activated to induce autophagy. They found that p62 can be activated by reactive oxygen species (ROS). ROS are by-products of our metabolism that can cause damage in the cell. This ability of p62 to sense ROS allows the cell to remove the damage and to survive this stress. In lower organisms, such as fruit flies, p62 is not able to do this.

The team identified the part of the human p62 protein which allows it to sense ROS and created genetically modified fruit flies with 'humanised' p62. These 'humanised' flies survived longer in conditions of stress. Dr. Korolchuk adds: "This tells us that abilities like sensing stress and activating protective processes like autophagy may have evolved to allow better stress resistance and a longer lifespan."

Indeed, in the study, the authors found that specific mutations in human p62, which cause a neurodegenerative disease called amyotrophic lateral sclerosis (ALS), can prevent activation of p62 by ROS. These cells are then unable to induce protective autophagy, and the authors explain that this could underlie the premature death of neurons in patients with this devastating age-related disease.

In contrast, 'humanised' p62 fruit flies did not live longer suggesting that other mechanisms may be required.

The research demonstrates that a collection of small adaptations like that of human p62 could have accumulated over time and these adaptations could underlie our increased natural defences and longer lifespans.

The discovery of these adaptations allows a better understanding of how we can protect against and treat age-related diseases.

Source: Newcastle University [January 18, 2018]

Organisms that aren't closely related may evolve similar traits as they adapt to similar challenges. It's called convergent evolution, and familiar examples include the wings of birds, bats, and insects, and echolocation in bats and dolphins. Now, molecular biologists have found evidence of convergent evolution in an important mechanism of gene regulation in humans and mice.

This evolutionary tree shows the split between primate and rodent lineages about 90 million years ago, before  the emergence of Alu elements in primates and B/ID elements in rodents. These short interspersed elements  evolved independently in the two lineages to play the same role in gene regulation  [Credit: Bronwyn Lucas]

The new study, published in Proceedings of the National Academy of Sciences, was led by researchers at UC Santa Cruz and the University of Rochester Medical Center. They described a complex system that regulates the same genes in the same way in both species, yet evolved independently in the two lineages.

In both cases, the regulatory system involves noncoding RNA (sequences not translated into protein molecules) with origins in DNA segments randomly inserted into the genome by "jumping genes" (retrotransposons).

"This study highlights the importance of noncoding RNA and transposable elements in the regulation of gene expression and in the evolution of gene expression networks in mammalian genomes," said coauthor Manuel Ares, professor of molecular, cell, and developmental biology at UC Santa Cruz.

Only about 2 percent of the human genome is copied into messenger RNA molecules to code for the proteins that run the main processes in all cells. Most of the rest of the genome is transcribed into noncoding RNA whose function is largely unknown but which is suspected of playing a variety of roles in gene regulation and evolution.

Many of these noncoding RNAs are copied from repeated DNA sequences called short interspersed nuclear elements (SINEs). Once transcribed into RNA, they can be copied back into DNA and "pasted" into the genome at new locations in a process called retrotransposition. Sometimes these new copies land in or near genes and can damage them. Other times they can add new properties to the gene.

In the human genome, the major SINE family is made of so-called "Alu elements." There are more than 1 million copies of Alu, comprising more than 10 percent of human DNA, scattered throughout the genome, and some of them are likely still able to jump to new locations.

Alu elements, labelled with green fluorescence in these human chromosomes, make up more than  10 percent of the human genome [Credit: Bolzer et al., (2005)]

The mouse genome, however, doesn't have Alus; instead it has a distinct set of SINEs called B/ID elements. Different mammalian genomes have different SINEs because periodic bursts of retrotransposition by different SINEs continued to occur after the separation of different species from their last common ancestors. In the case of human and mouse, their lineages diverged about 90 million years ago.

"Surprisingly, when the mouse and human genomes were compared, the locations of SINEs were very similar, even though the SINEs themselves and the events that placed them at those locations were very different," Ares said. "We wondered what could explain this apparent convergence of SINE insertion in two independently evolving genomes."

Lynne Maquat's lab at the University of Rochester found that SINEs that land in the part of the gene encoding the tails of the messenger RNA (called the 3-prime untranslated region or 3'-UTR) bring the mRNA under the control of a protein called Staufen, which down-regulates expression of the gene by a process called "Staufen-mediated decay" or SMD. Individual examples of SINE-mediated SMD were previously documented in both human and mouse cells, in each case with different SINEs.

Since the modern SINEs in the human and mouse genomes were not in the common ancestor, all of the changes in gene expression that depend on SINEs must have occurred after humans and mice separated, and not in their common ancestor.

"Normally we think of important gene expression control systems as having evolved long ago, but for regulation by SINE-mediated SMD, this cannot be the case," Ares explained. "The question we asked was: Are there any cases where the same gene in mouse and human have been brought under SINE-mediated SMD, albeit using different SINEs at some point during the separate evolutionary histories of mice and men? If so, how many? And how common is convergent evolution of gene regulatory networks? How often do SINEs play a role in critically altering gene expression control?"

These questions were explored in a collaboration between the Rochester and UCSC labs, in which muscle precursor cells (myoblasts) from both organisms were analyzed to identify gene pairs (the mouse and human gene coding for the same protein) that had a SINE inserted in the mRNA tail and were under control of Staufen. Examples of such gene pairs in numbers greater than expected by chance would signal the possibility of convergent evolution of the Staufen regulatory network in myoblasts, where SMD is known to be important for gene control.

In myoblasts, the researchers were able to detect 24 genes that are both regulated by Staufen and have species-specific SINEs. This is a minimum number of potentially convergent pairs because not all genes are expressed in myoblasts, Ares noted. Additional experiments in the paper confirm the role of the SINE (by removing it and showing the mRNA becomes stable and insensitive to the presence of Staufen) for two gene pairs.

Author: Tim Stephens | Source: University of California - Santa Cruz [January 18, 2018]

A team of scientists from the Centro Nacional de Investigacion sobre la Evolucion Humana (CENIEH), led by Jose Maria Bermudez de Castro, together with the French researcher Amelie Vialet, from the Natural History Museum in Paris, has just published a paper in the journal PLOS ONE on the Middle Pleistocene Montmaurin-La Niche mandible, which reveals the complexity of the origin of the Neanderthals.

Top view of the Montmaurin-La Niche mandible/Jose Maria Bermudez de Castro  [Credit: CENIEH]

This mandible was found by Raoul Cammas on 18 June 1949 in the karstic cavities of Montmaurin within the La Niche cave (France), where stone tools and fossil remains of different species of canids, equids and ursids also appeared, helping to place it in time.

The presumed age of this mandible, between 200,000 and 240,000 years, had led a close morphological similarity to the mandible of European Neanderthals to be presumed, particularly in the teeth, but the mathematical techniques applied to the study of a wide variety of mandibles, including those of a group of recent African ones, show that it is more in line with the most archaic specimens from Europe, including those from Dmanisi.

"We find here an archaic mandible, and dental pieces which taxonomically are indisputably Neanderthal, which helps to support the hypothesis that the Neanderthal lineage did not evolve linearly but in mosaic," explains Bermudez de Castro.

Comparative studies

Considered for two decades to be the oldest human fossil found in France, the mandible has formed part of different comparative studies, and the description published by G. Billy and Henri V. Vallois in 1977 stands out. That work was undertaken more than 40 years ago, in the context of what was then known and of the theories then current on the colonization of the European continent.

However, human evolution in Europe was undoubtedly more complex than was thought only a couple of decades ago, as is explained in this paper entitled A reassessment of the Montmaurin-La Niche mandible (Haute Garonne, France) in the context of European Pleistocene human evolution, in which Mario Modesto, Maria Martinon-Torres and Marina Martinez de Pinillos also participated.

The possibility that there could have coexisted at least two hominin lineages, and that interbreeding, prolonged periods of isolation, genetic drift and other processes were habitual in the Middle Pleistocene in Europe is gaining momentum, while at the same time linear hypotheses such as "accretion" are losing ground.

"The appearance of the classic Neanderthals in the Late Pleistocene is a question by no means finally settled. There remain many open questions, and the Montmaurin-La Niche mandible now joins the list of X-files," concludes Bermudez de Castro.

Source: CENIEH [January 16, 2018]

In a newly published study in the Journal of Paleolithic Archaeology, Senckenberg scientist Professor Dr. Ralf-Dietrich Kahlke, in conjunction with an international team of renowned Stone Age experts, refutes a recent publication regarding the dispersal of humans in Europe. This publication postulates that the first humans occurred in Northern and Central Europe as early as about one million years ago -- more than 200,000 years earlier than previously documented. Moreover, the team of scientists around the Ice Age researcher from Weimar was able to show that the specimens of the archaeological study were presumably stolen from the research excavation in Untermassfeld.

Untermassfeld research excavation: Top (a) – Exposed skeleton parts of various large mammal species, with a completely  preserved metacarpal bone (rectangle) of an early fallow deer (Dama nestii vallonnetensis) on the day prior to the theft.  Photo: T. Korn, Senckenberg Weimar. Bottom (b) – Vandalism caused by illegal excavation: The lower part of the rare  deer bone was broken off and stolen (rectangle) [Credit: J.-A. Keiler, R.-D. Kahlke, Senckenberg Weimar]

Saber- and dirk-toothed cats, giant hyenas, hippopotamuses and elephants -- the Untermassfeld fossil site in the Thuringian Werra Valley offers a unique representation of the time period around one million years ago. "Each recovered fossil helps us to understand the ecosystem at that time and offers a detailed view into the life history on earth," explains Professor Dr. Ralf-Dietrich Kahlke of the Senckenberg Research Station for Quaternary Paleontology in Weimar, and he continues, "The diversity of the more than 17,000 specimens retrieved to date ranges from a tiny frog skeleton to the largest known cheetahs in geological history."

A recently published study in the Journal of Human Evolution now announced a new "sensational discovery" from the Thuringian fossil site. The study's authors describe several bones that were "processed with tools by humans." This is taken as proof for the presence of early humans in Central Europe around one million years ago, according to the study's senior author and hobby collector from Hesse.

"We have been digging in Untermassfeld since the 1970s, with a cumulative total of 90 months of recovery activity. More than 30 researchers from 20 institutes in Germany and abroad are involved in the analysis of our discoveries and results. None of us has ever before encountered traces of fossil hominids," cautions Kahlke. For the Ice Age researcher from Weimar, this was sufficient reason to get to the bottom of this asserted claim, together with a German-Dutch team of archaeologists, including Professor Dr. Wil Roebroeks (University of Leiden), Professor Dr. Sabine Gaudzinski-Windheuser (University of Mainz) and Professor Dr. Michael Baales (University of Bochum).

Left and center: (a, b) – Lower part of the stolen bone specimen, recovered via an anonymous  package (rectangle, cf. image 1), and associated upper part, which was left behind by the robbers.  Front and back views. Right (c) – Stolen and retrieved parts of the find, combined with parts recovered by Senckenberg [Credit: S. Döring, R.-D. Kahlke, Senckenberg Weimar]

"The archaeological studies clearly show that the described bones and rocks neither constitute human tools, nor do the objects reveal signs of processing," explains Kahlke. Upon closer inspection, the marks on the fossil animal bones that were described as signs of cutting and hammering caused by humans turned out to be "the results of root etching, feeding traces by predators and rodents, as well as improper retrieval," according to Gaudzinski-Windheuser.

In addition, the team of scientists was able to prove that the 'archaeological specimens' were obtained by the senior author through questionable means. They also refuted the author's claim that the objects came from an "old GDR collection." "We diligently documented the excavation in Untermassfeld with daily photographs; therefore, we can state with certainty that the 'analyzed' fossils were only broken out of the excavation surface in the period between 2009 and 2012 and therefore cannot originate from an old collection," adds John-Albrecht Keiler, the Senckenberg excavation leader in Untermassfeld.

The team of scientists from Weimar links the described objects to a series of thefts between 2002 and 2012 at the fossil site -- this assumption is primarily based on a fossil fallow deer bone, which found its way into the Senckenberg Research Station's collection by way of an anonymous mailing via the Natural History Museum "Schloss Bertholdsburg Schleusingen." Kahlke comments as follows: "Among others, this bone fragment is presented as part of the archaeological study refuted by us -- and it was demonstrably stolen from our excavation in 2009." All in all, about 400 specimens with a potential six-figure total value were taken. With the support of the Free State of Thuringia, these specimens shall now be made available to science again. "Following the series of thefts, we have significantly expanded our safety concept, in cooperation with the police agencies. We hope that illegal excavations and the resulting faulty scientific 'findings' will now be a thing of the past," offers Kahlke in conclusion.

Source: Senckenberg Research Institute and Natural History Museum [January 15, 2018]

Women today tend to live longer than men almost everywhere worldwide -- in some countries by more than a decade.

Migrant mother and children during the Great Depression. Women survive better than men in times of adversity,  research shows [Credit: Dorothea Lange, 1936, Library of Congress]

Now, three centuries of historical records show that women don't just outlive men in normal times: They're more likely to survive even in the worst of circumstances, such as famines and epidemics, researchers report.

Most of the life expectancy gender gap was due to a female survival advantage in infancy rather than adulthood, the researchers found. In times of adversity, newborn girls are more likely to survive.

The fact that women have an edge in infancy, when behavioral differences between the sexes are minimal, supports the idea that explanation is at least partly biological, the researchers say.

Led by Virginia Zarulli, an assistant professor at the University of Southern Denmark, and James Vaupel, a research professor at Duke University, the team analyzed mortality data going back roughly 250 years for people whose lives were cut short by famine, disease or other misfortunes.

The data spanned seven populations in which the life expectancy for one or both sexes was a dismal 20 years or less. Among them were working and former slaves in Trinidad and the United States in the early 1800s, famine victims in Sweden, Ireland and the Ukraine in the 18th, 19th and 20th centuries, and Icelanders affected by the 1846 and 1882 measles epidemics.

In Liberia, for example, freed American slaves who relocated to the West African country in the 1800s experienced the highest mortality rates ever recorded. More than 40 percent died during their first year, presumably wiped out by tropical diseases they had little resistance to. Babies born during that time rarely made it past their second birthday.

Another group of people living in Ireland in the 1840s famously starved when a potato blight caused widespread crop failure. Life expectancy plummeted by more than 15 years.

Overall the researchers discovered that, even when mortality was very high for both sexes, women still lived longer than men by six months to almost four years on average.

Girls born during the famine that struck Ukraine in 1933, for example, lived to 10.85, and boys to 7.3 -- a 50 percent difference.

When the researchers broke the results down by age group, they found that most of the female survival advantage comes from differences in infant mortality. Newborn girls are hardier than newborn boys.

The results suggest that the life expectancy gender gap can't be fully explained by behavioral and social differences between the sexes, such as risk-taking or violence.

Instead, the female advantage in times of crisis may be largely due to biological factors such as genetics or hormones. Estrogens, for example, have been shown to enhance the body's immune defenses against infectious disease.

"Our results add another piece to the puzzle of gender differences in survival," the researchers said.

The findings were published in the early online edition of Proceedings of the National Academy of Sciences.

Author: Robin A. Smith | Source: Duke University [January 09, 2018]

The question of where we humans come from is one many people ask, and the answer is getting more complicated as new evidence is emerging all the time.

The story of where we come from evolves almost every year  [Credit: Shutterstock/Eugenio Marongiu]

For most of recorded history humankind has been placed on a metaphorical, and sometimes literal, pedestal. Sure, modern humans were flesh and blood like other animals.

But they were regarded as being so special that in the Linnaean taxonomy that prevailed well into the second half of the 20th century they were given their own family, the Hominidae.

This distinguished them from the Pongidae, the separate family used for the three African great apes – the common chimpanzee, bonobo and gorilla – plus the orangutan from Southeast Asia.

We now realise that modern humans are just one of the African great apes.

So when and how did this radically changed perception come about?

Early observations

In the 19th century the only evidence available for determining the closeness of the relationship between any two living animals was how similar they were in terms of what the naked eye could tell from their bones, teeth, muscles and organs.

The first person to undertake a systematic comparative review of these differences between modern humans and the apes was English biologist Thomas Henry Huxley.

In the central section of a small book he published in 1863, called Evidence as to Man’s Place in Nature, Huxley concluded that the differences between modern humans and African apes were less than those between African apes and orangutans.

This was the evidence the English naturalist Charles Darwin referred to in The Descent of Man in 1871.

He speculated that because African apes were morphologically closer to modern humans than the apes from Asia, then the ancestors of modern humans were more likely to be found in Africa than elsewhere.

A closer inspection

Developments in biochemistry and immunology during the first half of the 20th century enabled the search for evidence of the relationships between modern humans and the apes to shift from macroscopic morphology to the morphology of molecules.

The results of applying a new generation of analytical methods to proteins were reported by the Austrian-born French biologist Emile Zuckerkandl and American biologist Morris Goodman in the early 1960s.

Zuckerkandl used enzymes to break up the protein component of haemoglobin into its peptide components. He showed that the patterns of the peptides from modern humans, gorilla and chimpanzee were indistinguishable.

Goodman used a different method, immunodiffusion, to study albumin, a serum protein. He showed that the patterns produced by the albumins of modern humans and the chimpanzee were identical. He concluded that this was because the albumin molecules were, to all intents and purposes, identical.

Apes and humans: related

Proteins are made up of a string of amino acids and in many instances one amino acid can be substituted for another without changing the function of the protein.

In the late 1960s, the American anthropologist Vince Sarich and New Zealand biologist Allan Wilson exploited these minor differences in protein structure and concluded that modern humans and the African apes were very closely related.

They also provided the first molecular clock estimate of modern human-African ape divergence, dating the split to only around five million years ago. This date was less than half of contemporary estimates based on fossil evidence.

In 1975 the American human geneticist Mary-Claire King and Allan Wilson showed that 99% of the amino-acid sequences of chimpanzee and modern human blood proteins were identical.

Enter DNA

The discovery by James Watson and Francis Crick, with unwitting help from Rosalind Franklin, of the basic structure of DNA, and the subsequent discovery by Crick and others of the nature of the genetic code, meant that the relationships among organisms could be pursued at the level of the genome.

How close? A chimpanzee (top left), an orangutan (top right), a gorilla (bottom left) and a bonobo (bottom right)  [Credit: Shutterstock/Sergey Uryadnikov/Petr Masek/Sergey Uryadnikov/Eric Gevaert]

Nowadays technological advances mean that whole genomes can be sequenced. Over the past decade researchers have published good draft sequences of the nuclear genomes of the chimpanzee, orangutan, gorilla and the bonobo.

More and better data are steadily being accumulated, and in 2013 a review of ape DNA based on the genomes of 79 great apes was published.

These new ape genome sequences support the results of earlier analyses of both nuclear and mitochondrial DNA that suggested modern humans and chimpanzees are more closely related to each other than either is to the gorilla.

When DNA differences among modern humans and the great apes are calibrated using the best palaeontological evidence for the split between the apes and the old world monkeys, those differences predict that the hypothetical common ancestor of modern humans, chimpanzees and bonobos lived about 8 million years ago.

The rise of the hominins

Most researchers now recognise the modern human as hominins.

Still, the question “where do we come from” can from a scientific perspective be difficult for someone outside of the discipline to come to grips with. In part this is because the fossil record for human evolution seems to grow exponentially, with the author of each new discovery often claiming that the textbooks need to be rewritten.

The interdisciplinary nature of palaeoanthropology also means that new evidence that helps us make sense of our ancestry does not always come in the form of new fossils.

It comes from advances in a range of disciplines that include archaeology, comparative anatomy, earth sciences, evolutionary biology, genomics and primatology.

A further complicating factor is that the human fossil record does not just consist of the fossil evidence of our direct ancestors.

Many of the fossils belong to lineages that do not make it to the surface of the Tree of Life. They belong to extinct close relatives, and the task of sorting close relatives from ancestors is one with which we are only just now beginning to grapple.

There is a lineage that leads to today’s Homo sapiens, but there are also a host of side experiments that are equally important to understand. They represent some of the most interesting chapters in human evolution.

Origins of the genus Homo

Understanding the origins of our own genus Homo means establishing what fossils we recognise as being the first early humans.

Sometime before 4 million years ago we see the first evidence of the genus Australopithecus. These fossils sample the kind of creature that was most likely the ancestor to the genus Homo.

Around 2.5 million years ago we see the first fossil evidence of species in Africa that many argue belong to our own lineage. One of these, Homo habilis, almost certainly made stone tools, had a slightly larger brain than Australopithecus, stood upright and regularly walked on two legs.

Some recognise a second species, Homo rudolfensis, about which we know even less.

These possible human ancestors lived alongside close relatives that were almost certainly not our ancestors. These species are called Paranthropus or robust australopiths – they had small brains, big jaw bones, large flat faces, and huge chewing teeth.

They lasted for at least a million years, so whatever they were eating (which is still a mystery) they were successful in the sense that they lasted as long in the fossil record as the average mammal.

But some researchers think that Homo habilis and Homo rudolfensis are not different enough from the australopiths that preceded them to justify being included in the genus Homo.

They claim that the size and shape of their body and the size of their teeth and jaws was little different from that of the australopiths. This means that their locomotion and diet had not shifted far enough in the direction of pre-modern Homo species such as Homo erectus to justify inclusion in Homo.

Tool making is not enough

Also, because it is becoming evident that australopiths may have been making tools earlier than Homo habilis it means that tool-making can no longer be seen as the sole prerogative of Homo.

There is a developing consensus that the relaxation of the criteria more than 50 years ago that saw the inclusion of Homo habilis into the genus Homo needs to be reconsidered.

Species that emerge slightly later from Africa, such as Homo ergaster, fit much more clearly within what we understand by the genus Homo. That species probably left Africa around 2 million years ago and migrated ultimately as far east as China and Indonesia where it evolved, eventually, into Homo erectus.

A number of further migrations out of Africa probably occurred after the initial Homo ergaster migration, one of which, Homo heidelbergensis, is considered by many palaeoanthropologists to be the ancestor of both Neanderthals (Homo neanderthalensis) and modern humans (Homo sapiens).

As far as we know, Neanderthals evolved outside of Africa, perhaps in response to the ice ages of Europe. Our ancestors remained in Africa where perhaps as early as 300,000 years ago, as revealed from recent redating of the Moroccan site of Jebel Irhoud, were well along in the process of evolving into modern humans.

So the origins of ‘us’

Once we get to the origins of our own species Homo sapiens we have the added advantage that we are able to now use next generation sequencing methods to recover ancient DNA (aDNA).

As geneticists recover ancient genomes from different extinct hominin species, they are generating insights that are not possible from comparing the anatomy of the fossils alone.

There is now fossil evidence from teeth to suggest that Homo sapiens may have been in China by 120,000 years ago and in South East Asia by 67,000 years.

The discovery of some distinctive modern human DNA within the DNA recovered from a Neanderthal fossil suggests that modest interbreeding was occurring between Neanderthals and modern humans in Central Asia by 100,000 years ago.

Modern humans have not shared the planet with another hominin species for several tens of thousands of years. But before that, in the past 300,000 years or so, there is fossil and DNA evidence of several hominin species, including the recently reported archaic hominin Homo naledi

First and foremost there was Homo neanderthalensis, whose range overlapped with modern humans in the Near East. Neanderthals most likely became extinct as a result of direct competition with the more technologically sophisticated Homo sapiens.

The evidence from DNA shows that there was interbreeding between our species and pre-modern humans, including the Neanderthals and the other enigmatic hominin referred to as the Denisovans.

We do not yet know how and when Homo erectus became extinct. It would appear that another unexpected side experiment in hominin evolution, known from the island of Flores and called Homo floresiensis most likely became extinct sometime after 60,000 years ago.

Indeed this hominin may represent something far more significant than simply an interesting side experiment, with many leading palaeoanthropologists arguing that the Hobbit may represent a pre-ergaster migration out of Africa.

What next?

Even though thousands of hominin fossils have now been recovered and described there is still much work to be done.

Was there a hominin that successfully migrated out of Africa prior to Homo ergaster? Did most of human evolution occur in Africa? Did some important transitions occur outside of Africa?

When did Homo erectus become extinct, and was there genetic exchange between erectus, sapiens and perhaps other hominin species?

As is often the case in science, with the recovery of additional data, in this case fossils and DNA extracted from fossils, we generate more questions than answers.

But ultimately all of this new evidence will result in a far more sophisticated appreciation of not only our evolution, but also the evolution of our extinct fossil cousins.

Authors: Bernard Wood and Michael Westaway | Source: The Conversation [January 08, 2018]