Halszka Glowacka is a PhD candidate at Arizona State University.  She was awarded a grant during our spring 2015 cycle for her project entitled "Biomechanical constraints on molar emergence in primates."

Halszka Glowacka in Hadar, Ethiopia

Human life history is unique among living primates. Humans grow slowly and have long lifespans coupled with short inter-birth intervals, resulting in fast reproductive rates. Among primates, there is a strong relationship between life history and the age at which the first permanent molar emerges into the mouth. Paleoanthropologists use this relationship to probe the antiquity of the unique human life history profile, but knowledge of how variation in molar emergence age arises and why it is closely associated with life history is lacking.

My study will examine molar emergence as part of a developing functionally integrated chewing system. Molars function with the jaws and chewing muscles to break down food. Developmental coordination among these parts of the chewing system is critical for food ingestion throughout life. In adult primates, the configuration of the chewing system constrains the position of molars to avoid damage to the temporomandibular joint during chewing. Using 3D coordinate data from cross-sectional ontogenetic samples of primate skulls (n = 18 species) I will determine if the position of molar emergence is constrained in the same manner, thereby regulating the timing of molar emergence.

Alouatta ontogenetic series

My research will determine how ontogenetic changes in the configuration of the chewing system drive variation in molar emergence schedules among primates and may suggest that life history is closely associated with molar emergence ages vis-à-vis its influence on facial growth rates. It will further suggest that selection for shorter faces and a prolonged growth schedule in the lineage leading to humans would have had the concomitant effect of delaying molar emergence.

Data collection, Halszka Glowacka

AuthorH Gregory

The next grantee from our spring 2015 cycle is Thierra Nalley from the California Academy of Sciences.  Her project is entitled "Ontogeny of the thoracolumbar transition in extant hominoids and Australopithecus."

Thierra Nalley and a digital reconstruction of the fossil hominin DIK 1-1

Walking on two legs, or bipedalism, is a hallmark adaptation of the human lineage. A requirement for efficient bipedalism is the ability to balance the head and torso over the hips and legs. The shape of spinal column vertebrae help make this possible, but how these vertebrae develop, and what causes variation in development, is poorly understood.

Our study will compare human vertebral anatomy to that of our closet living relatives, the apes, and demonstrate how differences in shape are achieved during development, from infants to adults. Understanding the relationships between vertebral shape, skeletal growth, and the development of adult locomotor behavior is directly relevant to many paleoanthropological questions, including those related to the origin of bipedality.

Age sequence (adult to infant, left to right) of human, first lumbar vertebrae

Results from this study will produce data on traits that may reflect an individual’s behavior and thus inform the continuing debate concerning the role of apelike traits observed in early human ancestors (i.e., were these traits simply primitive features retained from ancestors, or were they an important component of these species’ biology and behavior?). The inclusion of the juvenile Australopithecus afarensis DIK-1-1 specimen in our sample is particularly significant, because the developmental stage of the individual and its excellent preservation provides the rare opportunity to compare juvenile and adult Australopithecus afarensis anatomy. Furthermore, this project will capture and analyze, for the first time concurrently, key functional features across the vertebral column, many of which determine how vertebrae move. Documenting their development and co-variation will provide a more comprehensive understanding of spinal biomechanics.

AuthorH Gregory

Introducing Karline Janmaat from the Max Planck Institute of Evolutionary Anthropology. She was awarded a Leakey Foundation research grant in our spring 2015 cycle for her project entitled "The ecological intelligence of human rainforest foragers."

Karline Janmaat. Photo credit:  Bill Loubelo

Many primates have developed mental abilities that help them keep track of when and where energy-rich foods such as ripe fruits become available. This may help them to find such food more efficiently and to maintain large brains when times are lean. In this study, I will investigate 1) the extent with which humans use their spatio-temporal memory and planning abilities in the same forest environment that most primates live, 2) humans' species and plant-specific knowledge of the temporal distribution of tropical rainforest food and 3) how this knowledge corresponds to both that of our closest relative, the chimpanzee (Pan troglodytes), that lives in similar forests feeding on the same plant food and humans living in different environments where food can be more easily spotted by sight.

Babendjele Yaka women at a irvingia nut tree. Photo credit:  Haneul Jang

 The second part of my studies will focus on the questions whether, when and with whom human rainforest foragers share knowledge about food locations and whether information transfer (by language or behavioral reading) increases food-finding efficiency.

To answer these questions we will record the foraging behavior, travel routes and food locations of five Babendjele Yaka women and their families living in the rainforest of the northwestern Congo basin bordering the Motaba river. Each woman will be observed for 28 consecutive days within two subsequent years. In addition to our observational work on the women, we will assess the value of alternative foraging choices and conduct a variety of non-invasive food finding experiments.

 My team imcludes my Korean PhD student Haneul Jang and a Congolese PhD student Bill Loubelo. The results of our collaboration are expected to produce novel insights in to the origins of human intelligence.

PhD student Haneul Jang (L) and Kuona eating fruit. Photo credit: Karline Janmaat

Bill Loubelo (center with binoculars) recording food tree density and distribution. Photo credit:  Karline Janmaat  

Botele fishing with burning firewood in her hand. Photo credit: Karline Janmaat

Karline Janmaat in Babendjele camp. Photo credit:   Haneul Jang


AuthorH Gregory

Stacy Rosenbaum (University of California at Los Angeles) was awarded a Leakey Foundation research grant in 2010 for her project entitled "Male-immature relationships in the mountain gorilla (Gorilla beringei)." Dr. Rosenbaum and her team were recently published in the journal Animal Behaviour, and she was kind enough to provide us with a brief summary of the article.

Copyright:  Dian Fossey Gorilla Fund International

Every day, just like humans, animals have to make choices about who to socialize with. Also like humans, they generally (though not always) have the strongest bonds with their relatives. There are good reasons for this; for most of the primate lineage’s evolutionary history, it was likely highly adaptive to primarily associate with, and help, relatives. However, if you’re living in a group that includes unrelated animals, it also creates an interesting conundrum: how do you figure out who you’re related to?

For years, primatologists assumed that when monkeys and apes lived in groups where females mated with multiple males, fathers and infants couldn’t recognize one another. Thanks to advances in molecular genetics, we can now reliably determine an infant’s paternity even in wild populations where blood samples are impossible to obtain. By matching paternity to behavioral patterns, we know that fathers and infants in some species do appear to “recognize” one another. The mechanism remains unknown, though it’s likely that males are using a form of ‘bet-hedging’ based on their previous mating history with an infant’s mother.

Copyright:  Dian Fossey Gorilla Fund International

Mountain gorillas are an interesting species in which to investigate male parenting. For most of their evolutionary history, they probably lived in groups with one male and a few females and infants. Infants and males could both be confident they were related. However, today they are regularly observed in groups with multiple males. The gorillas monitored by the Dian Fossey Gorilla Fund’s Karisoke Research Center have been closely studied for the last 48 years. Because they are well habituated to human presence, we can collect both detailed behavioral and genetic paternity data. Their large, multimale/multifemale groups presented an excellent opportunity to ask an intriguing question: can one of humans’ closest living relatives recognize paternity when there are multiple possible fathers, even though we think this is likely an evolutionarily novel type of social group?

Copyright:  Dian Fossey Gorilla Fund International

It turns out, the answer is ‘probably not.’ Infants socialize with adult males based on males’ dominance rank, not paternity. Dominance hierarchies are strong amongst male gorillas. Alpha males sire the most infants in a group, but males who are lower on the totem pole also father a surprising number (in one of our samples, ~60% of infants). We found no behavioral indicators that males or infants were using paternity as a cue for selecting one another as social partners. Infants preferred males who were higher ranking than those who were lower, regardless of whether that male was dad.

Currently, we’re working on figuring out what hormonal signatures are associated with male gorillas’ parenting behaviors. Like humans, gorillas show a tremendous amount of individual variation. Some males are very paternal, playing with and grooming infants. Others, while tolerant, show little active interest. We hope to understand more about the mechanisms that drive parenting behavior under different conditions in humans and their relatives. The Leakey Foundation’s support allows us to integrate physiological and behavioral data to gain a more complete picture of the evolutionary history of the human lineage. 

You may read the full article in Animal Behaviour by clicking here.  

AuthorH Gregory
CategoriesJournal Article

The next spring 2015 Leakey Foundation grantee we would like to introduce you to is Gabrielle Russo from Stony Brook University.  Her project is entitled "Elucidating the evolutionary pathways of hominin basicranial morphology using a formal phylogenetic comparative primate approach."

Gabrielle Russo (R) and collaborator Jeroen B. Smaers

The morphology of the basicranium (base of the skull) in modern humans is distinct from that in our closest living relatives and has therefore been a central focus for paleoanthropologists seeking to understand the evolutionary pathways that led from the panin (chimpanzees and bonobos) – hominin last common ancestor to Homo sapiens.

The basicranium is typically studied using a ‘fossil to living’ approach, in which one or few features preserved for fossil hominin crania are evaluated in a hominid-centric sample in order to identify features that are primitive to hominids, derived and shared among hominins, or unique to modern humans. However, a burgeoning Mio-Pliocene fossil record and recent interpretations of the Ardipithecus ramidus skeleton highlight the potential for mosaicism and independent evolution to complicate hypotheses about evolutionary relationships.

Our study addresses this issue by generating a broad perspective of basicranial evolution that formally combines information about the taxonomic breadth (110 living species) of basicranial morphological variation with the evolutionary depth (46 million years of primate evolution) of lineage-specific patterns of morphological change. Specifically, we employ a phylogenetically-integrated approach to quantify evolutionary changes in basicranial morphology within the Haplorhini, identify the patterns and processes of change responsible for select external cranial base features that are relevant to discussions of probable early hominins, and evaluate the extent to which certain factors (e.g., locomotion, brain size) explain the observed evolutionary patterns of basicranial morphology.

Our results will provide a critical first step toward contextualizing morphological variation among living primate species within a macroevolutionary framework that reveals detailed patterns of change over time. This approach will allow recognition of how patterns of change in basicranium morphology observed in recent hominin and great ape evolution relate to those that occurred elsewhere in phylogenetic space.

Click here to visit Gabrielle Russo's web site.


AuthorH Gregory

Amanda Tan is a PhD candidate at Nanyang Technological University in Singapore. She was awarded a Leakey Foundation research grant in the spring of 2013. Here is a summary of her team's recent paper in PLOS ONE.

Researchers Catalog Variation in Stone-Tool Use by Burmese Long-Tailed Macaques

Burmese long-tailed macaques living on islands in southern Thailand use 17 different action patterns in their use of stone tools to crack open seafood.

Since 2007, a group of researchers including Leakey Foundation grantee, Amanda Tan, has been documenting variation in the tools and action patterns used by a population of coastal-living Burmese long-tailed macaques in southern Thailand, under an 8-year field project led by Michael D Gumert from the Nanyang Technological University, Singapore. These macaques use stone and shell tools to crack open a wide variety of marine bivalves, gastropods, and crustaceans, as well as plant seeds. Their findings are described in the journal PLOS ONE

To identify variation in how the macaques used tools, the researchers collected and analyzed videos of over 600 instances of tool use from 90 macaques in populations on Piak Nam Yai and Thao Islands, in Laem Son National Park Thailand. They found that the macaques used different parts of stone and shell tools: the flatter faces and edges, and the sharp points. They then catalogued a total of 17 different action patterns in macaque tool use, which varied in hand use, posture, and striking motions. They also observed over 100 macaques on Piak Nam Yai Island’s costs at over 3000 time points to determine what proportion of the population used each action pattern, and how often.

They found that 80% of the macaques used tools, each using between one and four different action patterns. Most commonly, the macaques used one-handed hammering with the points of smaller tools to crack open oysters that grew on rocks, and used one- or two-handed hammering with the faces and edges of larger tools to crack unattached shellfish that had to first be placed on anvils. Some of the macaques however, used rare or idiosyncratic action patterns. All action patterns can be viewed in a video published with the article, and on PLOS’s Youtube channel.

Burmese long-tailed macaques are the most recent addition to the small group of nonhuman primates known to use stone tools in the wild, which had previously comprised of only some populations of West African chimpanzees, and robust capuchins of South America. Compared to the nut cracking behaviour of capuchins and chimpanzees, there seems to be much greater variation in the use of different tool surfaces and striking actions in the use of stone tools by macaques.

At least some of the variation is due to the unique food types that these macaques process with stones. Macaques are the only species to regularly process oysters that grow on rocks, and these oysters require different processing techniques from the nuts that are cracked by chimpanzees and capuchins. Since oysters cannot be moved and placed on flat anvils, the macaques must chip them open with precision from different striking angles depending on the surface on which the oyster grows. As a result, the macaques have developed axe hammering, or using the sharp points of stones to chip open food items, which has not been observed in other species.

Cataloging the tools and actions involved in macaque tool use thus raises new questions about tool technologies and cultures in the primate lineage that can be explored with future study. By answering questions about how different action patterns develop and are influenced by environmental constraints and learning processes, we can gain a better understanding of how technology and culture evolves in species living in different environments, with different social systems.

Click here to read the journal article on PLOS ONE.






AuthorH Gregory

Over the next few months we will be introducing you to our new spring 2015 Leakey Foundation grantees, and the first on our list is Paola Villa from the University of Colorado Museum. She was awarded a research grant for her project entitled "Uluzzian technology in Central Italy: From Neandertals to modern humans." 

Dr. Paola Villa

Dr. Paola Villa

Current evidence suggests that modern humans evolved and dispersed from Africa into Asia and later into Europe. The arrival of modern humans in Western Europe between 35,000 and 35,000 years ago is closely associated with the demise and ultimate extinction of the local Neandertal population and the emergence of the Upper Paleolithic art and sophisticated technology. Yet Neandertals and their Middle Paleolithic culture had thrived in Europe and Asia for more than 300,000 years and it is not clear that they were inferior to modern humans in weaponry, subsistence methods or cognition. This is why the causes of the extinction of Neandertals are the subject of continuous debate among paleoanthropologists.

The period between 45,000 and 35,000 is also the time of appearance in various parts of Europe of "transitional" cultures that show similarities to the Neandertal tools but also contain more developed, Upper Paleolithic artifacts. Perhaps the colonization of Europe by modern humans proceeded in a stepwise process with multiple waves of migration but it is not always clear if the makers of these transitional industries were modern humans or Neandertals and whether their innovative elements were due to acculturation or independent invention.

The Uluzzian is an Italian transitional industry, known from sites in Northern and Southern Italy but until now completely absent from Latium (central Italy) due to a hypothesized persistence of Neandertals in the region. The Uluzzian was previously attributed to Neandertals but is now seen by some the product of modern humans, although this is also the subject of intense debate.

Paola Villa and colleagues are studying the technology of two sites in Central Italy. One of the sites (Colle Rotondo) is a new, recently discovered open air site; the second is a cave (La Fabbrica cave) which contains Middle Paleolithic, Uluzzian and early Upper Paleolithic assemblages. The goal of their project is to clarify the nature of the Uluzzian in terms of technology and cognition of Neandertals versus modern humans.

The area has been the focus of systematic research (funded by NSF) on the Middle and early Upper Paleolithic by Paola Villa. This previous knowledge will allow her to produce a more complete picture of the process of replacement of Neandertals by modern humans in the Italian peninsula.

AuthorH Gregory

Marina Davila-Ross was awarded a grant from The Leakey Foundation in the spring of 2015 for her research project entitled "Systematically testing facial thermal imaging as a most sensitive and reliable novel technology to directly compare subtle emotion changes in apes and humans." Her work on facial expressions and laughter in chimpanzees was recently published in the journal PLOS ONE.

Chimpanzee facial expressions, vocalizations used differently during play

Chimpanzees may be able to use facial expressions and vocalizations flexibly, notably during physical contact play, according to a study published June 10, 2015 in the open-access journal PLOS ONE by Leakey Foundation grantee, Marina Davila-Ross from the University of Portsmouth, UK and colleagues.

Open mouth expressions of silent and audible laughter in chimpanzees and humans. Image from PLOS ONE paper. Davila-Ross et. al.

Open mouth expressions of silent and audible laughter in chimpanzees and humans. Image from PLOS ONE paper. Davila-Ross et. al.

The ability to flexibly produce facial expressions and vocalizations has a strong impact on the way humans communicate, but scientists' understanding of nonhuman primate facial expressions and vocalizations is limited. The authors of this study investigated whether chimpanzees produce the same types of facial expressions with and without accompanying vocalizations, as do humans. Forty-six chimpanzees were video-recorded during spontaneous play at the Chimfunshi Wildlife Orphanage, Zambia. ChimpFACS, a standardized coding system, was applied to measure chimpanzee facial movements, based on Facial Action Coding System (FACS) developed for humans.

Data showed that chimpanzees produced the same fourteen open-mouthed facial expressions when laugh sounds were present as when they weren't. Based on the data, the authors suggest that chimpanzees produce these facial expressions flexibly, without being constrained by the accompanying vocalizations. Furthermore, the data indicated that the facial expression in addition to vocalization, as well as the facial expression alone, were used differently in social play, for instance, when in physical contact with playmates and when matching playmates' open-mouthed faces. These findings support the idea that chimpanzees produce distinctive facial expressions independently from a vocalization, and that their use affects communicative meaning, as both traits are important for a more explicit and versatile way of communicating.

Click here to read the paper on PLOS ONE.

Citation: Davila-Ross M, Jesus G, Osborne J, Bard KA (2015) Chimpanzees (Pan troglodytes) Produce the Same Types of 'Laugh Faces' when They Emit Laughter and when They Are Silent.PLoS ONE 10(6): e0127337. doi:10.1371/journal.pone.0127337


AuthorMeredith Johnson

Season two field crew (l-r): Cherene De Bruyn, Lisa Rogers, Dr. Christopher Ames, Dr. Benjamin Collins. Photo credit:  Dr. Benjamin Collins.

Dr. Benjamin Collins and Dr. Christopher Ames recently concluded a second season of Leakey Foundation-funded excavations at Grassridge rockshelter. The shelter is located at the base of the Stormberg Mountains in the Eastern Cape of South Africa, approximately 200 kilometers inland from the Indian Ocean. These excavations are part of the Grassridge Archaeological and Paleoenvironmental Project (GAPP), which explores the relationships between behavioral diversity, social network formation, and climatic variability during the enigmatic late Middle Stone Age period (MSA), which spans from ~50,000 to 25,000 years ago.

Current research suggests that the late MSA was subject to periods of severe aridity and rapid climatic change. These findings have led researchers to suggest that southern Africa was sparsely populated during the late MSA, with hunter-gatherer groups forming very small, localized social networks. The paucity of archaeological sites from this period has made it difficult to explicitly test this hypothesis. However, recent research focusing on late MSA occupations in parts of southern Africa, including the preliminary findings from Grassridge, is providing evidence, such as non-local ostrich eggshell and marine shell beads, and specific stone tool types that occur throughout southern Africa, to suggest that social networks were more extensive than previously thought.

Grassridge rockshelter was initially excavated in 1979 by Dr. Hermanus Opperman, who identified rich Later and Middle Stone Age occupations at the site. The original excavations focused on the Later Stone Age (LSA) occupation, dated to between 6,000 and 7,000 years ago. Dr. Opperman’s excavation also produced a single radiocarbon date of ~36,000 years before present near the base of the MSA layers. This date, however, is near the limit of conventional radiocarbon dating, and the lower age limit of the site remained uncertain.

GAPP's main objectives for the first two field seasons were to re-evaluate the site stratigraphy, obtain a suite of dating samples from the original excavation, and begin a new excavation. Our Leakey Foundation-funded research has recently provided two new radiocarbon dates, one from near the top of the MSA sequence dating to ~35,000 radiocarbon years ago, and the other from the base of the sequence dating to >36,000 years ago. The latter date confirms that the base of the MSA sequence is older than the limit of radiocarbon dating, and luminescence methods are being pursued to determine how far back in time the Grassridge MSA sequence stretches.

We have opened a new 2 x 1 m excavation trench adjacent to the 1979 excavations. By the end of this most recent field season we had removed the overlying LSA deposit, and the first 5-10 cm of the MSA deposit. The excavations have been very fruitful, with the 3-dimensional provenience recorded for nearly 4000 artifacts – a density of ~3500 artifacts per cubic meter of sediment – and tens of thousands more pieces of bone and stone tools recovered from the excavated sediment. Other noteworthy finds include many ostrich eggshell beads, bone tools, and shell ornaments from the Later Stone Age deposits. The top 5-10 cm of MSA deposit so far excavated has produced many similar finds, and we expect this density of artifacts will continue as we proceed with our excavations of the MSA deposit in the coming field seasons.

Rock art panel documented during survey. Photo credit:  Dr. Christopher Ames.

In addition to our excavations at Grassridge, GAPP documented three rock art sites during our survey of the surrounding area. These sites are located within 5 km of each other, and contain well-preserved, vivid, and detailed panels from two or more different periods.

We are spending the next six months analyzing geological and radiocarbon dating samples, stone tools, animal bones, ostrich eggshell, and other artifacts, to elucidate what life was like for the LSA and MSA hunter-gatherers at Grassridge. These important data, coupled with ongoing excavations and research at Grassridge, will provide valuable insight for understanding the behavioral diversity observed during the enigmatic late MSA.

AuthorH Gregory

The Leakey Foundation is thrilled to announce Being Human, a new collaboration with the Baumann FoundationBeing Human organizes conversations and events to explore what it means to be human and how humans are fundamentally shaped by our evolutionary history and cultural environment.

A panel discussion at the first Being Human conference in 2012

A panel discussion at the first Being Human conference in 2012

The Baumann Foundation launched Being Human in 2012 with a conference in San Francisco and a vibrant online community. Being Human has created opportunities for people to gather and explore complex ideas and questions about the nature of the human experience from an evolutionary, scientific, and reflective perspective. 

Peter Baumann of the Baumann Foundation

Peter Baumann of the Baumann Foundation

Peter Baumann, founder of the Baumann Foundation, said that he is "delighted to enter into this partnership with The Leakey Foundation. Both organizations share similar goals in spreading understanding of our human history and nature." With the Being Human initiative, our two organizations plan to engage Bay Area communities with an ongoing series of enlightening and entertaining events. We also plan to reach broader audiences with podcast episodes examining important questions of human evolution and behavior.

We look forward to sharing further announcements as this exciting initiative evolves.

AuthorMeredith Johnson

On April 25th The Leakey Foundation’s Board of Trustees convened for our Spring Granting Session. The Board unanimously approved the twenty-two research grants our Scientific Executive Committee presented as recommended for funding.  

Here are a few numbers from our Spring 2015 Granting Cycle:

There were 101 research grant applications: 37% were categorized as behavioral, 63% were paleoanthropology. Over 460 reviews were submitted to our grants department during this cycle.

We would like to congratulate all of our new grantees, and we look forward to sharing news and information about them and their research along the way! 

Here are The Leakey Foundation's Spring 2015 Grantees:

Iulia Badescu, University of Toronto:  Investigating the infant nutritional development of wild chimpanzees

Stephanie Bogart, University of Southern California:   Savanna chimpanzee ecology at MARS (Mount Assirik Research Site)

Marina Davila-Ross, University of Portsmouth:  Systematically testing facial thermal imaging as a most sensitive and reliable novel technology to directly compare subtle emotion changes in apes and humans

Harold Dibble, University of Pennsylvania:  New excavations at La Ferrassie (Dordogne, France): The final season

Kelsey Ellis, University of Texas at Austin:  Grouping dynamics of woolly monkeys (Lagothrix poeppigii) in Amazonian Ecuador

Davide Faggionato, Iowa State University:  Molecular and functional analysis of vision in three hominin species

Tyler Faith, University of Queensland:  Middle Stone Age of the Gwasi and Uyoma Peninsulas, Kenya

Halszka Glowacka, Arizona State University:  Biomechanical constraints on molar emergence in primates

Avi Gopher, Institute of Archaeology, Tel Aviv University:  Continued excavation in Middle Pleistocene Qesem Cave, Israel

Ashley Hammond, Stony Brook University:  Reconstructing phenotypic change of the pelvis in apes and humans

John Hoffecker, University of Colorado at Boulder:  The geochronology of the earliest Upper Paleolithic in Eastern Europe

Karline Janmaat, Max Planck Institute for Evolutionary Anthropology:  The ecological intelligence of human rainforest foragers

Carolina Mallol, Universidad de La Laguna:  Neandertal fire technology

Rebecca Miller, University of Liege:  The Middle-Upper Paleolithic transition at Trou Al'Wesse (Belgium)

Thierra Nalley, California Academy of Sciences:  Ontogeny of the thoracolumbar transition in extant hominoids and Australopithecus

Marco Peresani, University of Ferrara:  Rediscovering the Uluzzian in Italy

Susan Perry, University of California, Los Angeles:  Life histories of wild capuchins in Lomas Barbudal, Costa Rica

Gabrielle A. Russo, Stony Brook University:  Elucidating the evolutionary pathways of hominin basicranial morphology using a formal phylogenetic comparative primate approach

Christopher Stevenson, Virginia Commonwealth University:  Hydration dating of Late Pleistocene archaeological sites in eastern Africa

Paola Villa, University of Colorado Museum:  Uluzzian technology in Central Italy: From neandertals to modern humans

Amelia Villaseñor, George Washington University:  The biogeography and behavioral ecology of hominins in Pliocene Eastern Africa: A macroecological perspective

Nicolas Zwyns, University of California, Davis:  Human response to the Late Pleistocene climate change in Northern Mongolia: The Upper Paleolithic site of Tolbor 16

AuthorH Gregory

A new relative joins "Lucy" on the human family tree. An international team of scientists led by seven-time Leakey Foundation grantee Dr. Yohannes Haile-Selassie of The Cleveland Museum of Natural History has discovered a 3.3 to 3.5 million-year-old new hominin species (more closely related to humans than to chimps). Upper and lower jaw fossils recovered from the Woranso-Mille area of the Afar region of Ethiopia have been assigned to the new species Australopithecus deyiremeda. This hominin lived alongside the famous "Lucy's" species, Australopithecus afarensis. The species is described in the May 28, 2015 issue of the journal Nature.

The left edentulous half of the paratype lower jaw (BRT-VP-3/14). Photo credit: Yohannes Haile-Selassie.

The left edentulous half of the paratype lower jaw (BRT-VP-3/14). Photo credit: Yohannes Haile-Selassie.

Lucy's species lived from 2.9 million years ago to 3.8 million years ago, overlapping in time with the new species Australopithecus deyiremeda. The new species is the most conclusive evidence for the contemporaneous presence of more than one closely related early human ancestor species prior to 3 million years ago. The species name "deyiremeda" (day-ihreme-dah) means "close relative" in the language spoken by the Afar people.

Australopithecus deyiremeda differs from Lucy's species in terms of the shape and size of its thick-enameled teeth and the robust architecture of its lower jaws. The anterior teeth are also relatively small indicating that it probably had a different diet.

Casts of the jaws of Australopithecus deyiremeda, a new human ancestor species from Ethiopia, held by principal investigator and lead author Dr. Yohannes Haile-Selassie of The Cleveland Museum of Natural History. Photo credit: Laura Dempsey.

Casts of the jaws of Australopithecus deyiremeda, a new human ancestor species from Ethiopia, held by principal investigator and lead author Dr. Yohannes Haile-Selassie of The Cleveland Museum of Natural History. Photo credit: Laura Dempsey.

"The new species is yet another confirmation that Lucy's species, Australopithecus afarensis, was not the only potential human ancestor species that roamed in what is now the Afar region of Ethiopia during the middle Pliocene," said lead author and Woranso-Mille project team leader Dr. Yohannes Haile-Selassie, curator of physical anthropology at The Cleveland Museum of Natural History. "Current fossil evidence from the Woranso-Mille study area clearly shows that there were at least two, if not three, early human species living at the same time and in close geographic proximity."

"The age of the new fossils is very well constrained by the regional geology, radiometric dating, and new paleomagnetic data," said co-author Dr. Beverly Saylor of Case Western Reserve University. The combined evidence from radiometric, paleomagnetic, and depositional rate analyses yields estimated minimum and maximum ages of 3.3 and 3.5 million years.

"This new species from Ethiopia takes the ongoing debate on early hominin diversity to another level," said Haile-Selassie. "Some of our colleagues are going to be skeptical about this new species, which is not unusual. However, I think it is time that we look into the earlier phases of our evolution with an open mind and carefully examine the currently available fossil evidence rather than immediately dismissing the fossils that do not fit our long-held hypotheses," said Haile-Selassie.

Scientists have long argued that there was only one pre-human species at any given time between 3 and 4 million years ago, subsequently giving rise to another new species through time. This was what the fossil record appeared to indicate until the end of the 20th century. However, the naming of Australopithecus bahrelghazali from Chad and Kenyanthropus platyops from Kenya, both from the same time period as Lucy's species, challenged this long-held idea. Although a number of researchers were skeptical about the validity of these species, the announcement by Haile-Selassie of the 3.4 million-year-old Burtele partial foot in 2012 cleared some of the skepticism on the likelihood of multiple early hominin species in the 3 to 4 million-year range.

On March 4, 2011, Mohammed Barao, a local Afar working for the Woranso-Mille project, found the holotype upper jaw of Australopithecus deyiremeda (BRT-VP-3/1). Photo credit: Yohannes Haile-Selassie.

On March 4, 2011, Mohammed Barao, a local Afar working for the Woranso-Mille project, found the holotype upper jaw of Australopithecus deyiremeda (BRT-VP-3/1). Photo credit: Yohannes Haile-Selassie.

The Burtele partial fossil foot did not belong to a member of Lucy's species. However, despite the similarity in geological age and close geographic proximity, the researchers have not assigned the partial foot to the new species due to lack of clear association. Regardless, the new species Australopithecus deyiremeda incontrovertibly confirms that multiple species did indeed co-exist during this time period.

This discovery has important implications for our understanding of early hominin ecology. It also raises significant questions, such as how multiple early hominins living at the same time and geographic area might have used the shared landscape and available resources.

Discovery of Australopithecus deyiremeda:

The holotype (type specimen) of Australopithecus deyiremeda is an upper jaw with teeth discovered on March 4, 2011, on top of a silty clay surface at one of the Burtele localities. The paratype lower jaws were also surface discoveries found on March 4 and 5, 2011, at the same locality as the holotype and another nearby locality called Waytaleyta. The holotype upper jaw was found in one piece (except for one of the teeth which was found nearby), whereas the mandible was recovered in two halves that were found about two meters apart from each other. The other mandible was found about 2 kilometers east of where the Burtele specimens were found.

Team members crawling the area where the paratype jaw (BRT-VP-3/14) was found searching for more pieces of the specimen. Photo credit: Yohannes Haile-Selassie.

Team members crawling the area where the paratype jaw (BRT-VP-3/14) was found searching for more pieces of the specimen. Photo credit: Yohannes Haile-Selassie.

Location of the Discovery:

The fossil specimens were found in the Woranso-Mille Paleontological Project study area located in the central Afar region of Ethiopia about 325 miles (520 kilometers) northeast of the capital Addis Ababa and 22 miles (35 kilometers) north of Hadar ("Lucy's" site). Burtele and Waytaleyta are local names for the areas where the holotype and paratypes were found and they are located in the Mille district, Zone 1 of the Afar Regional State.

The Woranso-Mille Project:

Participants of the 2011 Woranso-Mille project field season. Photo credit: The Woranso-Mille project.

Participants of the 2011 Woranso-Mille project field season. Photo credit: The Woranso-Mille project.

The Woranso-Mille Paleontological project conducts field and laboratory work in Ethiopia every year. This multidisciplinary project is led by Dr. Yohannes Haile-Selassie* of The Cleveland Museum of Natural History. Additional co-authors of this research include: Dr. Luis Gibert of University of Barcelona (Spain), Dr. Stephanie Melillo* of the Max Planck Institute (Leipzig, Germany), Dr. Timothy M. Ryan* of Pennsylvania State University, Dr. Mulugeta Alene of Addis Ababa University (Ethiopia), Drs. Alan Deino and Gary Scott of the Berkeley Geochronology Center, Dr. Naomi E. Levin of Johns Hopkins University, and Dr. Beverly Z. Saylor of Case Western Reserve University. Graduate and undergraduate students from Ethiopia and the United States of America also participated in the field and laboratory activities of the project.

*Indicates a Leakey Foundation grantee.

Read More!

  1. Haile-Selassie, Y. et al. Nature 521, 483–488 (2015).
  2. Haile-Selassie, Y. et al. Nature 483, 565–569 (2012).
  3. Spoor, F. Nature 521 432–433 (2015).

This article was adapted from materials provided by the Cleveland Museum of Natural History.


AuthorMeredith Johnson

Franklin Mosher Baldwin Memorial Fellowships are awarded to graduate students who are from developing countries and would like to pursue training and/or education abroad. In providing this opportunity The Leakey Foundation hopes to equip these scholars with the knowledge and experience necessary to assume leadership positions in their home countries where there often exist extraordinary resources in the field of prehistory.

The Baldwin Fellowship was established in 1978, and its track record speaks for itself. Baldwin Fellows such as Zeresenay Alemseged, Berhane Asfew, Mzalendo Kibunjia, Jackson Njau, Agazi Negash, Emma Mbua and Fredrick Manthi (to name only a few) have gone on to productive and influential careers in the fields of paleoanthropology and primatology. 

Here are the four Baldwin Fellows from our spring 2015 cycle:

Dagmawit Abebe is a second year Baldwin Fellow from Ethiopia. She is majoring in physical anthropology at City University of New York under the sponsorship of Eric Delson. When finished with her PhD, she intends to return to her home country where she hopes to join the faculty at Addis Ababa University.

First year Baldwin Fellow Ainash Childebayeva is from Kazakhstan, and she is in the first year of her PhD studies at the University of Michigan.  Under the supervision of Abigail Bigham, Ms. Childebayeva's research focus is the analysis of human adaption genetics in high-altitude ancient Peruvian populations.

Hailay Reda is a first year Baldwin Fellow from Ethiopia. He is beginning his PhD program at the University of Oregon under the supervision of Stephen Frost.  He has extensive field experience in places such as Hadar, Wonanso-Mille and the Middle Awash Project. He is interested in studying the taxonomy and phylogeny of the Eastern African Plio-Pleistocene primates.

Abebe Taffere is a first year Baldwin Fellow who is beginning her PhD Studies at the University of Florida under the sponsorship of Steven Brandt. She intends on specializing in Late Pleistocene archaeology and lithic technology.  She would like to return to her home country of Ethiopia to work at the Authority for Research and Conservation of Cultural Heritage as the first staff member to have a PhD in archaeology.

We wish our Baldwin Fellows the very best in their studies this coming year.  We look forward to keeping you updated on their progress!

AuthorH Gregory

New research funded in part by The Leakey Foundation shows that chacma baboons within a troop spend more of their time with baboons that have similar characteristics to themselves: associating with those of a similar age, dominance rank and even personality type such as boldness. This is known as homophily, or ‘love of the same’.

Grooming. Photo courtesy of Alecia Carter.

Grooming. Photo courtesy of Alecia Carter.

This happens in humans all the time; we hang out with people who have the same income, religion, education etc. Essentially, it’s the same in baboons
— Alecia Carter

A team of researchers led by the University of Cambridge and international conservation charity the Zoological Society of London says that this may act as a barrier to the transfer of new social information to the wider troop, as previous research done by the team shows baboons of a certain age and personality type – the younger, bolder animals – are more likely to be information ‘generators’: those who solve new foraging problems.    

Given that information generators spend much of their time in the company of similar baboons, researchers say there is a risk that acquired information may end up exclusively confined to other information generators, thus decreasing the likelihood of new knowledge being disseminated to the wider troop.

Research teams tracked the same two baboon troops from dawn until dusk across Namibia’s Tsaobis Nature Park over several months each year between 2009-2014 to observe patterns of behaviour. The study is the first to monitor baboon social network structures over such a timescale and is published Wednesday in the journal Royal Society Open Science.    

“Within these big troop networks over time social preferences are generally dictated by age, rank, personality and so on,” said Dr Alecia Carter, from the University of Cambridge’s Department of Zoology, first author of the study. “This happens in humans all the time; we hang out with people who have the same income, religion, education etc. Essentially, it’s the same in baboons.”

To test for the personality traits of ‘boldness’ – essentially an assertive curiosity – the researchers planted unfamiliar foods on the edge of paths commonly used by baboon troops. These stimuli included hard-boiled eggs and small bread rolls dyed red or green. The research team then measured the time spent on investigating the new foodstuff, and whether they ate it, to determine a scale of boldness for members of the baboon troops.

“Our analysis is the first to suggest that bolder and shyer baboons are more likely to associate with others that share this personality trait,” said Dr Guy Cowlishaw from the Zoological Society of London, senior author of the study. “Previous studies in other animals – from chimps to guppies – suggests that time spent in the company of those with similar personalities could promote cooperation among individuals.

“Why baboons should demonstrate homophily for boldness is unclear, but it could be a heritable trait, and the patterns we’re seeing reflect family associations.”    

Perhaps surprisingly, says Carter, gender was not a particular obstacle to social interaction, with females preferring to groom males. This is, in part, due to the obvious sexual engagements for breeding, but also as a tactic on the part of females to curry favour with particular males for the sake of their offspring.

“Chacma baboon males will often commit infanticide, killing the babies of rivals. Female baboons try and get around this by being as promiscuous as possible to confuse the paternal identity – so males find it harder to tell if they are killing a rival’s offspring or their own,” added Dr Carter.

“They will also try and form bonds with particular males in the hope that they will protect their offspring and let the babies forage in good places with them – although males tend to be fairly lazy when it comes to this; it’s up to the babies to follow the males to good food.” 

The text in this work is licensed under a Creative Commons Attribution 4.0 International License. It was provided by the University of Cambridge.


AuthorMeredith Johnson
Chimpanzees are wily enough to adapt in some ways when people encroach on their turf. Kimberley Hockings, CC BY-NC-ND

Chimpanzees are wily enough to adapt in some ways when people encroach on their turf. Kimberley Hockings, CC BY-NC-ND

In the mid 20th century, when paleoanthropologist Louis Leakey sent three pioneering women to study great apes in their natural habitats, the Earth’s wilderness was still untouched in many places. Jane Goodall went to Gombe in Tanzania to study chimpanzees; at first she could only study them with binoculars from far away because the chimps would not let her approach. In those days, Gombe was not the tiny island of forest surrounded by villages and crop fields it is today. In the neighboring country of Rwanda, Dian Fossey became the first researcher to be accepted by wild mountain gorillas. In the 1960s, her “gorillas in the mist” had not yet suffered the severe impact of war and refugees. The third of Leakey’s Angels Birutė Galdikas, arrived in Borneo to study the red apes, orangutans. When she started her work in 1971, oil-palm plantations and loggers were just beginning to force orangutans into increasingly small patches of rain forest.

A baby mountain gorilla born today has never known a pristine environment free of threat from people. Bradford Duplisea CC BY-NC-ND

A baby mountain gorilla born today has never known a pristine environment free of threat from people. Bradford Duplisea CC BY-NC-ND

When these pioneering women started studying great apes in their pristine forests, the Earth had just entered a time characterized by the tremendous impact of humans on every ecosystem of our planet, what many scientists call a new epoch: the Anthropocene. Hunting, poaching and logging was taking place in the 1960s and 1970s, but the scale of the problem has dramatically increased since then.

As researchers studying great apes in the wild, we’re fully aware that there are few, if any, untouched forests left in tropical Africa and Southeast Asia. Chimpanzee sites across equatorial Africa are suffering human disturbance, but little is known about the ways in which these apes are surviving alongside their human neighbors. The unfortunate situation of declining habitat provides an interesting opportunity for science: we can study these apes in novel situations they’ve never had to deal with before and we can look for clues about our own evolutionary past.

The Bossou chimpanzees employ an old mechanism to adapt to a more recent dangerous situation.

Responding to new pressures

Is the behavior of our closest evolutionary cousins changing as human settlements and roads push into their habitats? We’ve observed that the chimpanzees of Bossou (Guinea), a field site under severe human pressure, increase their waiting time when they have to cross a large road with heavy human and vehicle traffic and wait less time before crossing a narrow, quieter road. Adult male chimpanzees are more likely to lead and bring up the rear when crossing the larger, more dangerous road with a group, in an attempt to protect vulnerable individuals in the road-crossing party, such as infants.

Apes now also need to cope with increased competition from human beings for resources such as fruits. Chimpanzees are developing new strategies to access resources that are shared with people. Adult males are more likely to take the risk to enter the village to raid human crops than females and younger individuals are; sometimes they bring these crops back to the safety of the forest to share with females. Researchers in Uganda have recorded nocturnal crop-raiding by chimpanzees. Typically, they haven’t previously been observed in activities after dark and this suggests that they are aware that the risks are lower under the cover of darkness.

Chimpanzee in Bossou demonstrates how to carry nuts and stone tools with just two feet on the ground. Jules Dore CC BY-NC-ND

Chimpanzee in Bossou demonstrates how to carry nuts and stone tools with just two feet on the ground. Jules Dore CC BY-NC-ND

Novel situations appear to trigger novel behaviors on the part of great apes. For example, we’ve recently reported how chimpanzees in Bossou exhibit bipedal behavior when they need to transport unpredictable and valuable resources, including fruits. Normally chimpanzees move around on four legs. When chimpanzees go to a village to crop-raid papayas, it’s a risky behavior since frequently the fruits grow very close to people’s houses. To minimize their exposure, chimpanzees try to carry as much as possible at once, sometimes as many as three large papayas. By running on two feet, they can carry more of a resource that might not even be available next time they return.

When apes are confronted with new human-induced challenges, we’re able to study the flexibility of ape cognition. Can they figure out how to solve problems they would never encounter if people weren’t a part of their lives? Bossou chimpanzees, for example, have been seen deactivating snares that hunters place in the forest to catch animals that will be eaten as bush meat. They’ve figured out how to free themselves from these traps, and even more amazingly it appears that they transmit the knowledge throughout their group. It’s a surprising and intelligent way of solving the problem, and something researchers haven’t observed in many other animals.<

Villagers in Bossou watch chimps carrying out a papaya raid mission.                                      Susan Carvalho CC BY-NC-ND

Villagers in Bossou watch chimps carrying out a papaya raid mission.                                      Susan Carvalho CC BY-NC-ND

Different apes living side by side

The study of how these apes face new challenges may also teach us about our own evolutionary past. Researchers René Bobe and Bernard Wood, at George Washington University’s Center for the Advanced Study of Human Paleobiology, are focused on understanding living primates and ancient human fossils to learn about our origins and evolution. They work closely with us and our colleagues studying ape responses to modern-day threats to learn about our own evolution.

For example, how do modern ape species living in the same habitats at the same time interact with one another? During the course of our evolution over many millennia, we know that human ancestors faced severe climatic and environmental changes. Some species survived and continued to evolve. Others went extinct. At various times human ancestors and close evolutionary cousins shared the same environments, much like chimpanzees and gorillas do today in parts of Africa. But we know little about how some of these ancient species competed for space and resources.

Our own species survived these challenges to become the only ape able to colonize the entire planet, and to have in its hands the survival of all other remaining apes. By looking at how great apes coexist now, we might find clues into our own evolutionary past. For instance, the chimpanzees who choose to run on two feet when rushing back to the forest with village crops hint at which pressures may have contributed to our ancestors becoming bipedal.

Human beings and chimpanzees currently share the same habitats, as do human beings and orangutans. Studies of modern sympatric apes – that is, different ape species that live in the same area and encounter one another frequently – can help us answer crucial evolutionary questions: which apes can adapt to rapid environmental change? What characteristics help them do that? How do apes avoid conflict when they must share resources with other apes?

Researchers are interested in whether a more or less specialized diet could be a barrier for adapting to a changing habitat. We also wonder about how apes avoid conflict when facing the need to share resources with other apes. One study in Congo reported interesting cases of chimpanzees and gorillas eating in the same tree at the same time. What is their way of avoiding conflict and sharing resources and space? They feed at different heights of the tree and eat different parts of the plants!

Eating and sharing papaya after crop raiding. Susana Carvalho CC BY-NC-ND

Eating and sharing papaya after crop raiding. Susana Carvalho CC BY-NC-ND

Apes' ability to adapt doesn’t mean they should have to

The problem of apes adapting to human-dominated ecosystems has to be approached carefully. We dedicate our lives to trying to save these fascinating animals, and the last thing we want is to misuse the ability of apes to survive as a justification to continue the destruction of their remaining habitats. Some might argue that if wildlife can survive in highly human-influenced areas, then why put so much effort into conservation?

However, for apes to survive this new epoch, the Anthropocene, we need to understand how apes modify their behavior under human impact. We need to understand the limits of ape adaptability. Apes cannot adapt to urban areas, unlike some monkeys such as baboons and macaques. They do not survive in cities and towns. It’s imperative to understand the limits beyond which they cannot survive.

Susana Carvalho is a Postdoctoral Scientist in Human Paleobiology at George Washington University.

This article was originally published on The Conversation.
Read the original article.

AuthorMeredith Johnson

Every good story starts at the beginning. In the first episode of Origin Stories we talk with Carol Ward about one of the first things that distinguished our ancestors from the other primates, the weird way we walk around.

Carol Ward is Curator’s Professor and Director of Anatomical Sciences in the integrative anatomy program at the University of Missouri, where she directs the Ward Laboratory. Her lab is interested in the evolution of the skeleton below the neck in early African primates. Most of their work at the lab involves studying the functional morphology of modern primates and other mammals to explore what it can tell them about locomotor adaptation and evolutionary history. She’s also a paleoanthropologist who conducts field work at a site called Kanapoi in the West Turkana Basin in Kenya. Her project is called the West Turkana Paleo Project.

Professor Carol Ward overlooking Kanapoi in the West Turkana Basin in Kenya. Photo courtesy of the West Turkana Paleo Project.

Professor Carol Ward overlooking Kanapoi in the West Turkana Basin in Kenya. Photo courtesy of the West Turkana Paleo Project.

In this episode we learn about a discovery that helped answer a question about one of our most famous fossil ancestors, LucyLucy is an Australopithecus afarensis, and her skeleton was discovered in 1974 by Donald Johanson. We knew that Lucy and her species could move around on two feet by looking at things like the pelvis and femur. We also had the Laetoli footprints, which were discovered by Mary Leakey in 1978, but scientists were still missing an important piece of evidence. Lucy’s skeleton was missing something very important…the feet.

Lucy Australopithecus afarensis AL 288-1. Image via Wikimedia Commons.

Lucy Australopithecus afarensis AL 288-1. Image via Wikimedia Commons.

Donald Johanson and his colleague William Kimbel, both from the Institute of Human Origins at Arizona State University, found some new fossils at a site in Ethiopia near where Lucy was discovered. They invited Carol Ward to come to the National Museum of Ethiopia to examine them.

The new research facility at the National Museum of Ethiopia.

The new research facility at the National Museum of Ethiopia.

Photo illustration courtesy of Carol Ward.

Photo illustration courtesy of Carol Ward.

The results of Carol Ward's visit to Ethiopia and her subsequent research were published in the journal Science in 2011. You can read the abstract of the paper “Complete Fourth Metatarsal and Arches in the Foot of Australopithecus afarensis” by Carol Ward, William Kimbel and Don Johanson here. The full paper is free to read with registration on Science‘s website.

AuthorMeredith Johnson
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Sarie Van Belle and howler monkeys

In December 2014, three time Leakey Foundation grantee Dr. Sarie Van Belle, of the University of Texas at Austin, was awarded a research grant for her project entitled "Paternity and kinship in socially monogamous saki and titi monkeys."

This study will examine paternity and kinship patterns in two closely related primate species (the red titi monkey, Callicebus discolor, and the equatorial saki monkey, Pithecia aequatorialis) at the Tiputini Biodiversity Station in Yasuni National Park and Biosphere Reserve, Ecuador.  Both species have been described as monogamous, a social system traditionally defined as an exclusive mating relationship between one adult female and one adult male.  However, extrapair paternity, multi-adult groups, and replacements of pairmates by intruders have become increasingly acknowledged in other purportedly monogamous primate species.  Genetic analyses that evaluate rates of extrapair paternity and the associated population genetic structure in socially monogamous species will enhance our understanding of aspects of this social system not readily documented with behavioral observations alone. 

This comparative study has the power to identify social or ecological factors crucial in the functioning and maintenance of pair-living and monogamy, particularly because saki and titi monkeys differ in the nature of male-female relationships, the level of male care provided to offspring, and the participation of each sex to territory defense.  Such analyses can contribute importantly to our understanding of the selective pressures under which monogamy evolved in primates, from which the evolution of monogamy in humans, which emerged in early hominins, can be inferred.  

AuthorH Gregory

by H. Gregory

This is the first in a series of articles written for those of you who might appreciate a little extra background information on the science behind some of the projects we share with you. Enjoy!

In this year's Spring/Summer AnthroQuest we describe how Getty Grant recipient Thure Cerling is using stable isotope analysis of tooth enamel from fossil primates in order to determine the percentages of C 3 and C 4 plants that contributed to the their diets, and in December Oliver Paine updated us on his team’s progress in analysing the mechanical and nutritional properties of C4 plants in savannah habitats . Though these projects approach the questions from somewhat different angles, they will undoubtedly help us gain a greater understanding of early hominin diets, behavior and environment. Perhaps we should take this opportunity to review some of the basic science behind the study of C 3 and C 4 plants as they relate to human evolution.

Carbon: The Building Block of Life

Yes it is! With its four valence electrons, Carbon (C) is quite suited to act as the backbone in the molecules that are the foundation of life as we know it (proteins, the nucleic acids of DNA, lipids, etc.). Carbon exists naturally in three forms (or isotopes). Remember, in non-ionized atoms the number of negatively charged electrons spinning around the nucleus is equal to the number of positively charged protons in the nucleus. Typically the number of neutral neutrons in the nucleus is equal to the number of protons. In the case of isotopes, the number of neutrons is variable.

If an isotope is stable, then unless some outside force acts upon it, this isotope will sit around and do its thing, stably, forever. Unstable isotopes (or radioisotopes) will not. They will emit energy in the form of ionizing radiation until this instability is sufficiently resolved. The end result may be a more stable isotope of the same element or even another element altogether. This is the process behind what we call radioactive decay.

Of the naturally occurring carbon isotopes, one of them is a radioisotope called 14C. (The 14 tells us that the atom contains the usual 6 electrons, 6 protons and 6 plus an additional 2 neutrons.) This radioisotope exists in trace amounts and is mainly created when carbon atoms in the upper atmosphere encounter cosmic radiation. It takes in the thousands of years for this isotope to decay into a stable nitrogen atom (14N).

It is interesting to note that the decay of 14C provides scientists with a useful tool in dating biological material, otherwise known as radiocarbon dating. By measuring the percentage of 14C remaining in non-living biological material and comparing these numbers to known values of the environment, one can estimate the age of this material. (Remember, once an animal or plant is dead, it would not be incorporating new 14C into its body.)

12C and 13C are the stable isotopes of carbon. 12C exists much more abudnantly on earth at 99%. Except for the trace amounts of 14C, 13C makes up the rest. Also, it turns out that these isotopes are utilized in different amounts by C3 and C4 plants.

Carbon Fixation

We should probably go back to our high school science classes, all the way back to the chapter on photosynthesis. This is the biochemical process by which plants use the sun’s energy, water (H2 O) and carbon dioxide (CO2) to create sugar, otherwise known to us animals as food. The process by which the inorganic CO2 is integrated into an organic sugar is called carbon fixation, and C3 and C4 plants “fix” the carbon in different manners.

C3 Pathway (or Calvin Cycle)

C3 plants are by far the most common type of plant on earth (~95%). They mostly live in environments with a moderate amount of sunlight, moderate temperatures and plenty of water, and they use the C 3 carbon fixation pathway (or Calvin cycle) to integrate the CO2 into a three carbon sugar, hence C3.

Except for humans, modern primates have a mostly C3 derived diet. They eat a range of foods (fruits, insects, leaves), all similar to those foods that would be sourced from a tropical canopy.

C4 Pathway (or Hatch-Slack Pathway)

C4 plants (tropical grasses and sedges) use the C4 carbon fixation pathway (often referred to as the Hatch-Slack pathway) to incorporate CO2 and H2O into a four carbon molecule. This process takes more energy than C3 fixation; however, C4 fixation is more efficient when it comes to its utilization of H2O and CO2. Therefore C4 plants typically live in environments with more sun (open environments), longer growing seasons and less water. The C4 pathway is a relatively recent adaptation, probably arising due to changing environment.

What do humans eat? Our diets consist of about 50% C4 derived foods. Corn, millet and rice are examples. We also eat the meat of animals that graze upon C4 plants.

So yes, it makes sense that plants have adapted to different environments. In turn, animals have adapted as well, but what about these carbon isotopes?

As I mentioned, C3 and C4 plants utilize different amounts of the 12C and 13C isotopes. This means that their bodies contain different ratios of these isotopes. For example, C3 plants have less 13C in their tissue than compared to what naturally occurs in the atmosphere. C4 also have less 13C, but this “fractionation” is less severe. This is all due to the manner in which these plants fix carbon. The biochemical pathways have differing affinities for the lighter and heavier isotopes. Without getting too deep into the chemistry, this is due to the fact that 12C can “slide” through the C3 pathway more easily than 13C can. Same is true with the C4 pathway, just not as much. The result is that the isotopic signatures of these plants are different, and the 13C/12C ratios can be measured using isotope-ratio mass spectronomy, which can measure the known behaviors of these isotopes.

Please note, I have left out CAM plants, which utilize both carbon fixation pathways. These types of plants are usually restricted to desert environments.

Cerling and Paine

Let us return to the two projects that began this conversation. Dr. Cerling is examining the 13C/12C ratios in the tooth enamel of fossil primates from Kenya. Though the ratio in tooth enamel is not exactly the same as that of the diet of the animal, this “enrichment” percentage is known, and Dr. Cerling will be able to determine the relative amounts of C3 and C4 derived food in the diet of these primates.

I keep saying derived because there are limitations to this analysis. You cannot determine whether the animal got this 13C/12C ratio from eating C3 and C4 plants or if it ate meat of an animal that ate such plants or if it was a combination of the two. However, this ratio does give us information on where these animals derived their food. As we have now learned, these C3 and C4 plants grow in dissimilar environments.

As research on early hominin diets progresses, using stable isotope analysis as well as dental microwear analysis, we are finding that perhaps our early ancestors consumed more C4 plants than earlier thought.

So, this begs the question, what exactly did they eat? If our ancestors were roaming savanna habitats through different seasons, what types of plants might they have eaten at different times? What parts of the plants might they have focused their attention, and how would they have satisfied their energetic requirements on such a diet? Oliver Paine’s project will help us begin to answer these and many more questions.

As you can see, a great amount can be learned by utilizing the properties of C3 and C4 plants as a tool to investigate the diets and environment of our early ancestors and relatives. We look forward to sharing the the results of these and other scientists in the time to come!

AuthorH Gregory

Rob Blumenschine's Leakey Speaker Series talk, "Olduvai Gorge and the Origin of Human Ecological Dominance," is coming up on April 22, 2015 at the California Academy of Sciences. Rob will discuss how humans have become one of the most adaptable and ecologically dominant species through intelligence and technology. What makes Rob so qualified to discuss this topic?

Rob has worked with the Comprehensive Olduvai Database Initiative (CODI) to expand upon the groundbreaking work of Louis and Mary Leakey at Olduvai Gorge for over two decades. Rob and his colleague Dr. Fidelis Masao have co-directed CODI's Olduvai Landscape Paleoanthropology Project (OLAPP) since 1989, which is the longest-running of current projects at CODI. OLAPP focuses on reconstructing Olduvai's ancient landscapes and identifying signs of Homo and hominid land use, such as tool making. This project has uncovered over 20,000 stone artifacts and 25,000 vertebrate specimens. It has also uncovered nine new Homo and hominid individuals including OH 65, a Homo habilis maxilla excavated in 1995 by Rob and his team. OH 65 shed new light on variation within Homo habilis. Read further about OH 65 in the Scientific American article "Tanzanian Fossil May Trim Human Family Tree."

Rob is not only passionate about the science, but scientific outreach as well. 

“The study of our past and our origins is not just of interest to scientists and maybe to a lay public when a big fossil discovery is made; but that the field has broad relevance to each of our lives, and the society in which we live.” - Rob Blumenschine

 Rob currently is the Chief Scientific, Education, and Fundraising Strategist at the Paleontological Scientific Trust (PAST) of Johannesburg, South Africa. PAST is a non-profit dedicated to Africa’s ancient natural and cultural heritage providing public outreach, student support, technical training, youth development, research support and publication and conference support.

Join The Leakey Foundation and Rob Blumenschine on Earth Day, April 22, 2015 at 7:00 PM at the California Academy of Sciences for "Olduvai Gorge and the Origin of Human Ecological Dominance."

Tickets are available for purchase online at Calacademy.org. General Admission is $15, Leakey Foundation Members, California Academy of Sciences Members, and Seniors are $12. 

For more about Rob Blumenschine watch this interview.

AuthorArielle Johnson
CategoriesSpeaker Series

Origin Stories is our new podcast about what it means to be human and the science behind what we know about ourselves. We'll have interviews and stories from scientists about their research on a vast and fascinating range of topics. We'll learn about the biology and the millions of years of evolution that shape the way we look and act today.

Our first full episode comes out in late April, and we'll have monthly episodes after that. 

When it's released, you'll be able to find it on iTunes, Soundcloud, Stitcher, or your favorite podcast app. We'll also post episodes here on our website. We hope you'll listen, subscribe, and tell your friends! 

AuthorMeredith Johnson
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