Friday, March 27, 2015

New light on the anatomy of Neanderthals

The Neanderthals (Homo neanderthalensis) inhabited Europe and parts of western Asia between 230,000 and 28,000 years ago; during the last few millennia they coincided with Homo Sapiens Sapiens, and became extinct for reasons that are still being challenged. The archaeological site at La Ferrassie, excavated throughout the 20th century, is a mythical enclave because it was where 7 Neanderthal skeletons, ranging from foetuses to almost complete skeletons of adults, were found.

Among the remains discovered at La Ferrassie is the skeleton of a 2-year-old Neanderthal child found between 1970 and 1973 and baptised La Ferrassie 8; over 40 years since its discovery it has turned out to be useful in shedding new light on the anatomy of this extinct species.

The study began by reviewing the collections at the Muséum National d'Histoire Naturelle in Paris and at the Museo d'Archéologie national de St. Germain-en-Laye linked to the excavations at La Ferrassie in 1970 and 1973; it was there that 47 new fossils belonging to La Ferrassie 8, which complete its skeleton further, were recovered. Remains of a skull, jaw, vertebrae, ribs and hand phalanges were found among the new fossils.

Featuring among the remains is a very complete left temporal bone and an auditory ossicle was found inside it: a complete stapes. Virtual 3D reconstruction techniques enabled this ossicle to be "extracted virtually" and studied.

This stapes is the most complete one in the Neanderthal record and certifies that there are morphological differences between our species and the Neanderthals even in the smallest ossicles in the human body. As Asier Gómez-Olivencia pointed out, "we do not yet know the relation between these morphological differences and hearing in the Neanderthals. This would constitute a new challenge for the future".

The study of these new remains has been published in the prestigious Journal of Human Evolution, and has also had the participation of researchers of the CNRS (French National Centre for Scientific Research) in Paris and Bordeaux. The fact that a discovery of such significance has been made thanks to reviewing the remains excavated in the 1970s provides the researcher with proof of "the importance and need to review old excavations. We're in no doubt about that".

Friday, March 20, 2015

Did a volcanic cataclysm 40,000 years ago trigger the final demise of the Neanderthals?

The Campanian Ignimbrite (CI) eruption in Italy 40,000 years ago was one of the largest volcanic cataclysms in Europe and injected a significant amount of sulfur-dioxide (SO2) into the stratosphere. Scientists have long debated whether this eruption contributed to the final extinction of the Neanderthals. This new study by Benjamin A. Black and colleagues tests this hypothesis with a sophisticated climate model.

Black and colleagues write that the CI eruption approximately coincided with the final decline of Neanderthals as well as with dramatic territorial and cultural advances among anatomically modern humans. Because of this, the roles of climate, hominin competition, and volcanic sulfur cooling and acid deposition have been vigorously debated as causes of Neanderthal extinction.

They point out, however, that the decline of Neanderthals in Europe began well before the CI eruption: "Radiocarbon dating has shown that at the time of the CI eruption, anatomically modern humans had already arrived in Europe, and the range of Neanderthals had steadily diminished. Work at five sites in the Mediterranean indicates that anatomically modern humans were established in these locations by then as well."

"While the precise implications of the CI eruption for cultures and livelihoods are best understood in the context of archaeological data sets," write Black and colleagues, the results of their study quantitatively describe the magnitude and distribution of the volcanic cooling and acid deposition that ancient hominin communities experienced coincident with the final decline of the Neanderthals.

In their climate simulations, Black and colleagues found that the largest temperature decreases after the eruption occurred in Eastern Europe and Asia and sidestepped the areas where the final Neanderthal populations were living (Western Europe). Therefore, the authors conclude that the eruption was probably insufficient to trigger Neanderthal extinction.

However, the abrupt cold spell that followed the eruption would still have significantly impacted day-to-day life for Neanderthals and early humans in Europe. Black and colleagues point out that temperatures in Western Europe would have decreased by an average of 2 to 4 degrees Celsius during the year following the eruption. These unusual conditions, they write, may have directly influenced survival and day-to-day life for Neanderthals and anatomically modern humans alike, and emphasize the resilience of anatomically modern humans in the face of abrupt and adverse changes in the environment.

Wednesday, March 18, 2015

Archaeologists explore the historical processes leading up to China's political unification

Archaeologists from The Field Museum in Chicago, IL and Shandong University (Jinan, China) have investigated the historical processes leading up to China's political unification through the juxtaposition of macro- and micro-scale analysis. The study offers new perspectives on how human impacts of infrastructural investments, interactive technologies, social contracts, and ideologies that were implemented during the Qin and Han Dynasties and before have helped establish the rough spatial configuration of what is today China.

Why humans cooperate in large social groupings is a key question for contemporary research. Thus, the repeated historical renegotiation of China's continent-scale political consolidations remains a scholarly focus after more than a generation of attention.
"Two millennia ago, Rome and the Han dominated their respective regions," said Gary M. Feinman, MacArthur Curator of Anthropology at The Field Museum. "While the two were roughly equal in their spatial extents at their peaks, the bounds of the Roman Empire were never historically reconstituted. In contrast, Chinese regions were reintegrated perpetually into one political unit. Why is that?"

Feinman and his colleagues question the widely advanced perspective that China's reunifications were simply due to the periodic threats from nomadic peoples to its north. While this view is not entirely discounted, the authors argue that the persistent reunifications were in part the consequence of social and economic actions that were taken during the Bronze and Iron Ages prior, during, and just after China's first unification under the Qin emperor.

The study used two distinct sets of data: first, the authors drew on documents that mostly pertain to the macro-scale.

Beginning with the aristocratic Shang rule in the second millennium B.C., the authors cite precocious developments in urbanization, high-intensity metal production and early writing as a few of the cultural practices of the region that were later adopted by the Zhou, who were the first to consolidate a large part of central China. Writings by Confucius during this time period typify a shift in leadership and governance from aristocratic forms to more explicit moral codes and defined social expectations for all.

Eventually, centralized authority largely broke down, leaving 5-10 formerly vassal states to vie for control during the Warring States era (453-221 B.C.). One of these local polities, the Qin state, began an episode of conquest that culminated in China's political unification. Changes set in motion during these times underpinned a national identity and the course of subsequent Chinese history.

For example, numerous roads were built, river transport was improved, and efforts were made to connect the walls that had been built at the northern limits of three of the warring states. Once linked, they became China's Great Wall.

Following a short period of Qin rule, dynastic power shifted to the Han, who maintained many of the unifying initiatives of the Qin. Ultimately the Han Dynasty produced political, social and ideological foundations for empire that have endured for more than a millennium.

The team also analyzed the results of an 18-year systematic archaeological settlement pattern study that they implemented in a small region on the coast of the Shandong Province.

"China's first great wall, the Great Wall of the Qi state, was built east-to-west across much of what is today Shandong Province," said Feinman. "It defined the southern limits of the Qi polity, which was the last of the warring states to be engulfed by the Qin armies before unification. We were able to follow the easternmost extension of the Qi wall for 50 kilometers as it ran across the northern limits of our study region. Based on our survey, the political border that the wall demarcated in the Warring States period likely had been a kind of boundary for more than 1,500 years."

Eventually, the wall was breached and the Qin defeated the Qi state, resulting in China's first episode of unification." Our perspective draws on data from the early history of China through its first episode of unification to offer an alternative perspective as to why China has reunified several times subsequently at a more or less comparable scale," said Feinman.

The study concludes that the globally unmatched tendency for China to be politically unified so repeatedly was in large part the consequence of social constructions; of a mixture of political ideals, institutional structures and relations, unified communication technologies, commerce networks, and collective traditions and memories negotiated and adopted during the Shang, Zhou, Qin, and Han eras.

Tuesday, March 17, 2015

Wealth and power may have played a stronger role than 'survival of the fittest'

Number of reproducing males declined during global growth
Arizona State University
IMAGE: 4 to 8,000 years ago, there was an extreme reduction in the number of males who reproduced, but not in the number females. Wealth and power may have played a... view more
Credit: Sabine Deviche
The DNA you inherit from your parents contributes to the physical make-up of your body -- whether you have blue eyes or brown, black hair or red, or are male or female. Your DNA can also influence whether you might develop certain diseases or disorders such as Crohn's Disease, cystic fibrosis, hemophilia or neurofibromatosis, to name a few.

In a study led by scientists from Arizona State University, the University of Cambridge, University of Tartu and Estonian Biocentre, and published March 13 in an online issue of the journal Genome Research, researchers discovered a dramatic decline in genetic diversity in male lineages four to eight thousand years ago -- likely the result of the accumulation of material wealth, while in contrast, female genetic diversity was on the rise. This male-specific decline occurred during the mid- to late-Neolithic period.

Melissa Wilson Sayres, a leading author and assistant professor with ASU's School of Life Sciences, said, "Instead of 'survival of the fittest' in biological sense, the accumulation of wealth and power may have increased the reproductive success of a limited number of 'socially fit' males and their sons."
It is widely recognized among scientists that a major bottleneck, or decrease in genetic diversity, occurred approximately 50 thousand years ago when a subset of humans left Africa and migrated across the rest of the world. Signatures of this bottleneck appear in most genes of non-African populations, whether they are inherited from both parents or, as confirmed in this study, only along the father's or mother's genetic lines.

"Most surprisingly to us, we detected another, male-specific, bottleneck during a period of global growth. The signal for this bottleneck dates to a time period four to eight thousand years ago, when humans in different parts of the world had become sedentary farmers," said senior author Toomas Kivisild from the Division of Biological Anthropology, University of Cambridge.

Researchers studied DNA samples taken from the saliva or blood of 456 males living in seven regions of five continents including Africa, the Andes, South-Asia, near East and Central Asia, Europe and Oceania. Scientists specifically studied the Y chromosome, which is passed down through the male lineage, and the mitochondria, which is passed to offspring by the genetic mother.

After using computer and statistical modeling, they found the two extreme "bottlenecks" in human genetic history, specifically the second found only in the male lineage.

The researchers said studying genetic history is important for understanding underlying levels of genetic variation. Having a high level of genetic diversity is beneficial to humans for several reasons. First, when the genes of individuals in a population vary greatly, the group has a greater chance of thriving and surviving -- particularly against disease. It may also reduce the likelihood of passing along unfavorable genetic traits, which can weaken a species over time.

According to Monika Karmin, a leading author from University of Tartu, Estonia, their findings may have implications related to human health.

"We know that some populations are predisposed to certain types of genetic disorders," said Karmin. "Global population evolution is important to consider, especially as it relates to medicine."

"When a doctor tries to provide a diagnosis when you are sick, you'll be asked about your environment, what's going on in your life, and your genetic history based on your family's health," added Wilson Sayres, who is also with ASU's Biodesign Institute. "If we want to understand human health on a global scale, we need to know our global genetic history; that is what we are studying here."

The researchers believe this will be relevant for informing patterns of genetic diversity across whole human populations, as well as informing their susceptibility to diseases.

Wilson Sayres said the next step is to continue the research by gathering a greater number of DNA samples, increasing the diversity of the samples, and working with anthropologists and sociologists to gain a broader perspective on the findings.

Wednesday, March 11, 2015

Neandertals modified white-tailed eagle claws 130,000 years ago

Discovery sheds new light on cognitive abilities of human predecessors


Krapina Neandertals may have manipulated white-tailed eagle talons to make jewelry 130,000 years ago, before the appearance of modern human in Europe, according to a study published March 11, 2015 in the open-access journal PLOS ONE by David Frayer from University of Kansas and colleagues from Croatia.

Researchers describe eight mostly complete white-tailed eagle talons from the Krapina Neandertal site in present-day Croatia, dating to approximately 130,000 years ago. These white-tailed eagle bones, discovered more than 100 years ago, all derive from a single time period at Krapina. Four talons bear multiple edge-smoothed cut marks, and eight show polishing facets or abrasion. Three of the largest talons have small notches at roughly the same place along the plantar surface.

The authors suggest these features may be part of a jewelry assemblage, like mounting the talons in a necklace or bracelet. Some have argued that Neandertals lacked symbolic ability or copied this behavior from modern humans, but the presence of the talons indicates that the Krapina Neandertals may have acquired eagle talons for some kind of symbolic purpose. They also demonstrate that the Krapina Neandertals may have made jewelry 80,000 years before the appearance of modern humans in Europe.

"It's really a stunning discovery. It's one of those things that just appeared out of the blue. It's so unexpected and it's so startling because there's just nothing like it until very recent times to find this kind of jewelry," David Frayer said.

Epoch-defining study pinpoints when humans came to dominate planet Earth

The human-dominated geological epoch known as the Anthropocene probably began around the year 1610, with an unusual drop in atmospheric carbon dioxide and the irreversible exchange of species between the New and Old Worlds, according to new research published today in Nature.

Previous epochs began and ended due to factors including meteorite strikes, sustained volcanic eruptions and the shifting of the continents. Human actions are now changing the planet, but are we really a geological force of nature driving Earth into a new epoch that will last millions of years?

Scientists at UCL have concluded that humans have become a geological power and suggest that human actions have produced a new geological epoch.

Defining an epoch requires two main criteria to be met. Long-lasting changes to the Earth must be documented. Scientists must also pinpoint and date a global environmental change that has been captured in natural material, such as rocks, ancient ice or sediment from the ocean floor. Such a marker - like the chemical signature left by the meteorite strike that wiped out the dinosaurs - is called a golden spike.

The study authors systematically compared the major environmental impacts of human activity over the past 50,000 years against these two formal requirements. Just two dates met the criteria: 1610, when the collision of the New and Old Worlds a century earlier was first felt globally; and 1964, associated with the fallout from nuclear weapons tests. The researchers conclude that 1610 is the stronger candidate.

The scientists say the 1492 arrival of Europeans in the Americas, and subsequent global trade, moved species to new continents and oceans, resulting in a global re-ordering of life on Earth. This rapid, repeated, cross-ocean exchange of species is without precedent in Earth's history.

They argue that the joining of the two hemispheres is an unambiguous event after which the impacts of human activity became global and set Earth on a new trajectory. The first fossil pollen of maize, a Latin American species, appears in marine sediment in Europe in 1600, becoming common over subsequent centuries. This irreversible exchange of species satisfies the first criteria for dating an epoch - long-term changes to Earth.

The researchers also found a golden spike that can be dated to the same time: a pronounced dip in atmospheric carbon dioxide centred on 1610 and captured in Antarctic ice-core records (1). The drop occurred as a direct result of the arrival of Europeans in the Americas. Colonisation of the New World led to the deaths of about 50 million indigenous people, most within a few decades of the 16th century due to smallpox. The abrupt near-cessation of farming across the continent and the subsequent re-growth of Latin American forests and other vegetation removed enough carbon dioxide from the atmosphere to produce a drop in CO2. Thus, the second requirement of a golden spike marker is met.

The researchers have named the 1610 dip in carbon dioxide the 'Orbis Spike'. They chose the Latin word for 'world' because this golden spike was caused by once-disconnected peoples becoming globally linked.

Lead author, Dr Simon Lewis (UCL Geography and University of Leeds), said: "In a hundred thousand years scientists will look at the environmental record and know something remarkable happened in the second half of the second millennium. They will be in no doubt that these global changes to Earth were caused by their own species. Today we can say when those changes began and why. The Anthropocene probably began when species jumped continents, starting when the Old World met the New. We humans are now a geological power in our own right - as Earth-changing as a meteorite strike."

He added: "Historically, the collision of the Old and New Worlds marks the beginning of the modern world. Many historians regard agricultural imports into Europe from the vast new lands of the Americas, alongside the availability of coal, as the two essential precursors of the Industrial Revolution, which in turn unleashed further waves of global environmental changes. Geologically, this boundary also marks Earth's last globally synchronous cool moment before the onset of the long-term global warmth of the Anthropocene."

The authors also considered the merits of dating the Anthropocene to 1964, which saw a peak in radioactive fallout following nuclear weapons testing. This marker is seen in many geological deposits, and by the 1960s human impact on the Earth was large. However, the researchers note that while nuclear war could dramatically alter Earth, so far it has not. While the fallout from nuclear bomb tests is a very good marker, the testing of nuclear weapons has not been - in geological terms - an Earth-changing event.

The beginning of the Industrial Revolution, in the late 18th century, has most commonly been suggested as the start of the Anthropocene. This linked a clear turning point in human history, and the rise of atmospheric carbon dioxide from fossil fuel use is a long-term global environmental change of critical importance. However, the researchers did not find a golden spike at that time because most effects were local, while the global exponential rise in carbon dioxide was too smooth an increase to form a precisely dated marker (2).

The authors' new paper ends by highlighting some implications of formally defining the Anthropocene.

Co-author, geologist Professor Mark Maslin (UCL Geography) said: "A more wide-spread recognition that human actions are driving far-reaching changes to the life-supporting infrastructure of Earth will have implications for our philosophical, social, economic and political views of our environment. But we should not despair, because the power that humans wield is unlike any other force of nature, it is reflexive and therefore can be used, withdrawn or modified. The first stage of solving our damaging relationship with our environment is recognising it."

An official decision on whether to formally recognise the Anthropocene, including when it began, will be initiated by a recommendation of the Anthropocene Working Group of the Subcommission of Quaternary Stratigraphy, due in 2016 (3).

Monday, March 9, 2015

Millions of modern men found to be descendants of 11 Asian dynastic leaders

  • University of Leicester researchers discover that many modern men have genetic links to ancient figures such as Genghis Khan
  • Study suggests that millions of modern Asian men are descended from 11 ancient leaders, including Genghis Khan
  • Sample examined the Y chromosomes of 5,000 Asian men from 127 populations

Historical nomadic and mobile populations allowed for Y chromosomes to be spread far and wide
Geneticists from the University of Leicester have discovered that millions of modern Asian men are descended from 11 powerful dynastic leaders who lived up to 4,000 years ago - including Mongolian warlord Genghis Khan.

The study, which is funded by the Wellcome Trust and published in the journal European Journal of Human Genetics, examined the male-specific Y chromosome, which is passed from father to son, in more than 5,000 Asian men belonging to 127 populations.

Most Y-chromosome types are very rare, but the team discovered 11 types that were relatively common across the sample and studied their distributions and histories.

Two common male lineages have been discovered before, and have been ascribed to one well-known historical figure, Genghis Khan, and another less-known one, Giocangga. The Leicester team found genetic links via a chain of male ancestors to both Genghis Khan and Giocangga, in addition to nine other dynastic leaders who originated from throughout Asia and date back to between 2100 BC and 700 AD.

The project's leader, Professor Mark Jobling from the University of Leicester's Department of Genetics, said: "The youngest lineages, originating in the last 1700 years, are found in pastoral nomadic populations, who were highly mobile horse-riders and could spread their Y chromosomes far and wide. For these lineages to become so common, their powerful founders needed to have many sons by many women, and to pass their status - as well as their Y chromosomes - on to them. The sons, in turn, could then have many sons, too. It's a kind of trans-generation amplification effect."

First author of the study, Patricia Balaresque (now at Université Paul Sabatier in Toulouse), added: "Identifying the ancestors responsible for these lineages will be difficult or impossible, as it would rely on finding their remains and extracting and analysing ancient DNA. This hasn't yet been done for Genghis Khan, for example, so the evidence remains circumstantial, if pretty convincing."

Friday, March 6, 2015

Precise dating of ancient charcoal found near skull in Manot Cave , Israel

A partial human skull unearthed in 2008 in northern Israel may hold some clues as to when and where humans and Neanderthals might have interbred. The key to addressing this, as well as other important issues, is precisely determining the age of the skull. A combination of dating methods, one of them performed by Dr. Elisabetta Boaretto, head of the Weizmann Institute's D-REAMS (DANGOOR Research Accelerator Mass Spectrometry) laboratory, has made it possible to define the period of time that the cave was occupied and thus the skull's age. The combined dating provides evidence that Homo sapiens and Homo neanderthalensis could have lived side by side in the area.

The Manot Cave, a natural limestone formation, had been sealed for some 15,000 years. It was discovered by a bulldozer clearing the land for development, and the first to find the partial skull, which was sitting on a ledge, were spelunkers exploring the newly-opened cave. Five excavation seasons uncovered a rich deposit, with stone tools and stratified occupation levels covering a period of time from at least 55,000 to 27,000 years ago.

Dating the skull presented a number of difficulties. "Because it was already removed from the layer where it was presumably deposited," says Dr. Elisabetta Boaretto, "we had to look for clues to tell us where and when it belonged in the setting of the archaeological record in the cave."

The age of the skull was first determined to be 54.7 thousand years old by a technique known as the uranium-thorium method, which was applied to the thin mineral deposit on the skull. But the estimated possible error in that type of method is plus or minus 5.5 thousand years. To obtain independent confirmation of the date, a different type of dating was required, e.g., radiocarbon dating.

To narrow down the possible range of the skull's age and determine when the skull's owner had lived in the cave, the archaeological team led by Prof. Israel Hershkovitz of Tel Aviv University, Dr. Ofer Marder of Ben Gurion University and Dr. Omry Barzilai of the Israel Antiquities Authority turned to Dr. Boaretto. She and her team participated in the excavation of the cave and applied radiocarbon dating to carefully selected charcoal remains, so that the whole cave, and thus the timing of human occupation, was mapped. 

The agreement between the two methods -- carbon and uranium-thorium -- provided the necessary support for the "correction" in the original uranium-thorium dating of the skull, which then helped fix the true age of the skull at around 55,000 years.

The date and shape of the Manot Cave skull provides some intriguing evidence that humans and Neanderthals might have interbred sometime during the human trek out of Africa, most likely as the former passed through the Middle East before spreading out north and east. The 55,000-year-old partial skull is the first evidence of a human residing in the region at the same time as Neanderthals, whose remains have been found at several nearby sites. Archaeologists are now searching for more evidence of ancient human habitation in the cave. 

If, indeed, the mixing between humans and Neanderthals took place in this area, it would suggest that the owner of the skull and his kin may have been the ancestors of all modern non-Africans.

Evidence for the human genus -- Homo --now goes back 2.8 million years

A fossil lower jaw found in the Ledi-Geraru research area, Afar Regional State, Ethiopia, pushes back evidence for the human genus -- Homo -- to 2.8 million years ago, according to a pair of reports published March 4 in the online version of the journal Science. The jaw predates the previously known fossils of the Homo lineage by approximately 400,000 years. It was discovered in 2013 by an international team led by Arizona State University scientists Kaye E. Reed, Christopher J. Campisano and J Ramón Arrowsmith, and Brian A. Villmoare of the University of Nevada, Las Vegas.

For decades, scientists have been searching for African fossils documenting the earliest phases of the Homo lineage, but specimens recovered from the critical time interval between 3 and 2.5 million years ago have been frustratingly few and often poorly preserved. As a result, there has been little agreement on the time of origin of the lineage that ultimately gave rise to modern humans. At 2.8 million years, the new Ledi-Geraru fossil provides clues to changes in the jaw and teeth in Homo only 200,000 years after the last known occurrence of Australopithecus afarensis ("Lucy") from the nearby Ethiopian site of Hadar.

Found by team member and ASU graduate student Chalachew Seyoum, the Ledi-Geraru fossil preserves the left side of the lower jaw, or mandible, along with five teeth. The fossil analysis, led by Villmoare and William H. Kimbel, director of ASU's Institute of Human Origins, revealed advanced features, for example, slim molars, symmetrical premolars and an evenly proportioned jaw, that distinguish early species on the Homo lineage, such as Homo habilis at 2 million years ago, from the more apelike early Australopithecus. But the primitive, sloping chin links the Ledi-Geraru jaw to a Lucy-like ancestor.

"In spite of a lot of searching, fossils on the Homo lineage older than 2 million years ago are very rare," says Villmoare. "To have a glimpse of the very earliest phase of our lineage's evolution is particularly exciting."

In a report in the journal Nature, Fred Spoor and colleagues present a new reconstruction of the deformed mandible belonging to the 1.8 million-year-old iconic type-specimen of Homo habilis ("Handy Man") from Olduvai Gorge, Tanzania. The reconstruction presents an unexpectedly primitive portrait of the H. habilis jaw and makes a good link back to the Ledi fossil.

"The Ledi jaw helps narrow the evolutionary gap between Australopithecus and early Homo," says Kimbel. "It's an excellent case of a transitional fossil in a critical time period in human evolution."

Global climate change that led to increased African aridity after about 2.8 million years ago is often hypothesized to have stimulated species appearances and extinctions, including the origin of Homo. In the companion paper on the geological and environmental contexts of the Ledi-Geraru jaw, Erin N. DiMaggio, of Pennsylvania State University, and colleagues found the fossil mammal assemblage contemporary with this jaw to be dominated by species that lived in more open habitats--grasslands and low shrubs--than those common at older Australopithecus-bearing sites, such as Hadar, where Lucy's species is found.

"We can see the 2.8 million year aridity signal in the Ledi-Geraru faunal community," says research team co-leader Kaye Reed, "but it's still too soon to say that this means climate change is responsible for the origin of Homo. We need a larger sample of hominin fossils, and that's why we continue to come to the Ledi-Geraru area to search."