Nearly 2 million years ago, three hominin genera – Australopithecus, Paranthropus and the earliest Homo erectus lineage – lived as contemporaries in the karst landscape of what is now South Africa, according to a new geochronological evaluation of the hominin fossil-rich Drimolen Paleocave complex.
Combined with other evidence, authors Andy Herries et al. argue that the site reflects a period of transition in southern Africa driven by climatic variability, one marked by endemic species, like Australopithecus, going extinct, while new migrants – Homo and Paranthropus – moved in. In their study, Herries and colleagues describe the geological context and age of two hominin crania fossils recently recovered from Drimolen, representing Homo and Paranthropus.
Using a combination of electron spin resonance, paleomagnetism and uranium-lead dating, Herries et al. pieced together the chronology of the Drimolen Main Quarry (DMQ). The results show that the Homo and Paranthropus fossils recovered from the region date to 2.04-1.95 million-years-old, which establishes both as the oldest definitive examples of their respective species (H. erectus and P. robustus).
“If correct, Herries [et al.’s] results provide the most precisely dated remains in South Africa [and] add more than a hundred thousand years to the first appearance dates of at least H. erectus,” writes Leakey Foundation grantee Susan Antón in a related “Perspective” article in the journal Science.
The crania ages also indicate that early Homo and Paranthropus hominins lived at the same time as their older Australopithecus cousins roughly 2 million years ago, which suggests a period of transition at the site; as endemic species, like Australopithecus, went extinct, new migrants – Homo and Paranthropus – moved in, the authors suggest. What’s more, the relative simplicity of the geological context of DMQ as revealed by the new geochronological techniques challenges the perceived complexity of other similarly aged South African paleocave sites, suggesting that much of what is known about the stratigraphy in these hominin-bearing sites may need to be reevaluated, according to the authors.
This article from press materials provided by the American Association for the Advancement of Science.
Science is a collaborative endeavor and long-term projects require the work of multiple generations of researchers. At the 2019 meeting of the American Association of Physical Anthropologists, The Leakey Foundation set out to document the academic “families” of biological anthropology.
With support from donors, The Leakey Foundation has been providing research grants since 1968 and educational fellowships since 1978. The Anthropology Portrait Project, generously funded by Leakey Foundation Executive Director, Sharal Camisa, illustrates the impact of Leakey Foundation grants over time. “Mentorship is fundamental to growth in most professions, especially science,” said Camisa, “Collaboration is critical to the advancement of knowledge. This project symbolizes a multigenerational and multidisciplinary approach to human origins research and underscores the value of mentorship and collaboration.”
People who received their first grants from The Leakey Foundation decades ago have now mentored several “generations” of scientists who have gone on to receive Leakey Foundation grants of their own.
This project is focused on the relationships between mentors and mentees, as well as collaborative groups like labs and long-term field research projects. Some portraits are of individual scientists.
The next phase of this project will be a series of interviews and articles on mentorship and collaboration.
Within our extended primate family consisting of lemurs, monkeys, and apes, humans have the largest brains. Our closest living relatives, chimpanzees, weigh about two-thirds as much as us, yet our brains are about 3.5 times larger.
Ours are also organized differently, and take longer to grow and mature. This extended period of development leads to a particularly long childhood for humans – one that requires extra parental care and protection.
Brains consume a large amount of energy. For a species that has a small brain at birth and a large one in adulthood, growth must either occur rapidly, or over a long time, or through a combination of both.
Researchers first observed exceptionally large brains in the human fossil record from about 300,000 years ago. However, the slower rate of brain development, which is now unique to humans, began more than three million years ago in the australopithecine lineage. These two-footed hominins from Africa are thought to be ancestral to our genus, Homo.
What triggered the evolutionary brain expansion in hominins, and how this relates to human behavior, remain hotly debated topics among palaeoanthropologists.
The Dikika child
In 2000, an Ethiopian team uncovered an astonishing find in the country’s Dikika region: the skeleton of an ancient baby with a nearly complete skull.
Dated to about 3.3 million years ago, this youngster belonged to the same genus and species as the iconic australopithecine adult female Lucy – Australopithecus afarensis.
In a new paper published in Science Advances, we reveal that Lucy’s species shows surprising similarities and differences with both chimpanzees and humans. But in order to make these comparisons, we first needed to work out two critical details:
1. exactly how old was the Dikika child when it died?
2. how did its brain size compare to adult members of its species, such as Lucy?
X-rays to the rescue
Brains do not fossilize, but as they grow and expand during childhood, the tissues surrounding them leave their mark inside the skull.
A synchrotron is a machine that accelerates electrons close to the speed of light and directs them around a large ring. By forcing electrons to travel in a circular direction with magnetic fields, extremely bright light is produced that can be filtered and adjusted for research purposes.
A benefit of this approach is that permanent impressions of brain folds on the bone can provide clues about key aspects of the brain’s organization. Synchrotron imaging can also provide powerful insights into dental development.
The truth is in the tooth
A seldom recognized fact about humans and other primates is that our milk (baby) teeth and first molars are marked with a line formed at birth. Similar to the growth rings of a tree, cross-sections of teeth also reveal daily growth lines reflecting the body’s internal rhythms during childhood.
Having access to precise records of the Dikika child’s teeth, we were able to determine how old the child was when it died. Our team’s dental experts calculated an age of 861 days, about 2.4 years.
This means the infant grew its molar teeth rapidly – similar to chimpanzees, and faster than humans. Surprisingly, however, its rate of brain development seemed to have shifted from the fast lane to the slow lane.
Extending brain growth
Virtual models of australopithecine brain cases reveal members of Lucy’s species had a chimpanzee-like brain organization, but grew for a longer period of time.
Our estimates suggest that by 2.4 years old, australopithecine children had brains that were only about 70% as big as adults, while average chimpanzees of the same age would have completed more than 85% of their brain growth. Thus, this species may bridge the gap between the long childhoods humans enjoy today, and the shorter ones of our ape-like ancestors.
Among primates in general, different rates of growth and maturation are associated with varied strategies of caring for infants. Slowing brain development is a way to spread the energetic needs of highly dependent offspring over many years. And this can be linked to a long reliance on caregivers.
Lengthening the period of brain growth also stretches out a species’ highly impressionable learning period. Extended brain growth in Lucy’s species may have provided a basis for the subsequent evolution of the brain and social behavior in our ancestors.
These baby steps would have been critical for the long childhood that is now often regarded as a keystone of human uniqueness.
Genetic information from an 800,000-year-old human fossil has been retrieved for the first time. The results, funded in part by The Leakey Foundation, shed light on one of the branching points in the human family tree, reaching much further back in time than previously possible.
An important advancement in human evolution studies has been achieved after scientists retrieved the oldest human genetic data set from an 800,000-year-old tooth belonging to the hominin species Homo antecessor.
The findings by scientists from the University of Copenhagen (Denmark), in collaboration with colleagues from the CENIEH (National Research Center on Human Evolution) in Burgos, Spain, and other institutions, are published today (April 1st, 2020) in Nature.
“Ancient protein analysis provides evidence for a close relationship between Homo antecessor, us (Homo sapiens), Neanderthals, and Denisovans. Our results support the idea that Homo antecessor was a sister group to the group containing Homo sapiens, Neanderthals, and Denisovans”, says Leakey Foundation grantee Frido Welker, Postdoctoral Research Fellow at the Globe Institute, University of Copenhagen, and first author on the paper.
Reconstructing the human family tree
By using a technique called mass spectrometry, researchers sequenced ancient proteins from dental enamel, and confidently determined the position of Homo antecessor in the human family tree.
The new molecular method, palaeoproteomics, developed
by researchers at the Faculty of Health and Medical Sciences, University of
Copenhagen, enables scientists to retrieve
molecular evidence to accurately reconstruct human evolution from further back
in time than ever before.
The human and the chimpanzee lineages split from each
other about 9-7 million years ago. Scientists have relentlessly aimed to better
understand the evolutionary relations between our species and the others, all
now extinct, in the human lineage.
“Much of what we know so far is based either on the results of ancient DNA analysis, or on observations of the shape and the physical structure of fossils. Because of the chemical degradation of DNA over time, the oldest human DNA retrieved so far is dated at no more than approximately 400.000 years,” says Enrico Cappellini, Associate Professor at the Globe Institute, University of Copenhagen, and lead author on the paper.
“Now, the analysis of ancient proteins with mass spectrometry, an approach commonly known as palaeoproteomics, allows us to overcome these limits,” he adds.
The fossils analyzed by the researchers were found by
palaeoanthropologist José María Bermúdez de Castro and his team in 1994 in
stratigraphic level TD6 from the Gran Dolina cave site, one of the
archaeological and paleontological sites of the Sierra de Atapuerca, Spain.
Initial observations led to conclude that Homo antecessor was the last common
ancestor to modern humans and Neanderthals, a conclusion based on the physical
shape and appearance of the fossils. In the following years, the exact relation
between Homo antecessor and other
human groups, like ourselves and Neanderthals, has been discussed intensely
Although the hypothesis that Homo antecessor could be the common ancestor of Neanderthals and modern humans is very
difficult to fit into the evolutionary scenario of the genus Homo, new
findings in TD6 and subsequent studies revealed several characters shared among
the human species found in Atapuerca and the Neanderthals. In addition, new
studies confirmed that the facial features of Homo antecessor are very
similar to those of Homo sapiens and very different from those of the
Neanderthals and their more recent ancestors.
“I am happy that the protein study provides evidence that
the Homo antecessor species may be closely related to the last common
ancestor of Homo sapiens,
Neanderthals, and Denisovans. The features shared by Homo antecessor with these hominins clearly appeared much earlier than previously thought. Homo
antecessor would therefore be a basal species of the emerging humanity
formed by Neanderthals, Denisovans, and modern humans”, adds José María
Bermúdez de Castro, Scientific Co-director of the excavations in Atapuerca and
co-corresponding author on the paper.
Findings like these are made possible through extensive collaboration between different research fields: from paleoanthropology to biochemistry, proteomics, and population genomics.
Retrieval of ancient genetic material from the rarest fossil specimens requires top-quality expertise and equipment. This is the reason behind the now ten-years-long strategic collaboration between Enrico Cappellini and Jesper Velgaard Olsen, Professor at the Novo Nordisk Foundation Center for Protein Research, University of Copenhagen and co-author on the paper.
“This study is an exciting milestone in palaeoproteomics. Using state of the art mass spectrometry, we determine the sequence of amino acids within protein remains from Homo antecessor dental enamel. We can then compare the ancient protein sequences we ‘read’ to those of other hominins, for example, Neanderthals and Homo sapiens, to determine how they are genetically related”, says Jesper Velgaard Olsen.
“I really look forward to seeing what palaeoproteomics
will reveal in the future”, concludes Enrico Cappellini.
The study of human evolution by palaeoproteomics will continue in the
next years through the recently established EU-funded “Palaeoproteomics to
Unleash Studies on Human History (PUSHH)” Marie S. Curie European Training
Network (ETN), led by Enrico Cappellini, and involving many of the co-authors
on the paper.
The research is funded by VILLUM FONDEN, the Novo Nordisk Foundation, and the Marie Sklowowska-Curie Actions Individual Fellowship and International Training Network programs, with additional funding from The Leakey Foundation.
Harmonie Klein is a PhD candidate at the Max Planck Institute for Evolutionary Anthropology. She received a Leakey Foundation grant in 2019 for her project entitled: “Hunting strategy and food sharing in wild central African chimpanzees.”
Q: Have you always been interested in science?
Harmonie Klein: As far as I remember, I always wanted to work with animals, in nature. I have a strong memory from my childhood of finding a small dead baby bird on the ground. I remember observing it from every angle, opening its beak or its wings, taking notes in a small notebook and drawing it. But strangely, I always said I hated science. My goal was really to study animal behavior to better understand this fascinating wild world, but it was not science for me. Naturally, I began an ethology course at university and suddenly one day, I realized with surprise that I was a scientist.
Q: How did you become interested in your current field?
Harmonie Klein: During graduate school, I first studied human impact on a ring-tailed lemur group in a zoo. Then I worked on vocal plasticity and development in the grey mouse lemur to better understand the origin of babbling in humans. These first experiences were my first contact with primates and I became interested in better understanding humans through studying other primates. Thus, I decided to focus on apes, our closest relative and went to the Loango Chimpanzee Project (LCP), Gabon, to habituate wild chimpanzees. There, I made my first observation of chimpanzees hunting mammals. I was fascinated by this behavior and its similarities with human hunter-gatherer societies.
Q: Tell us about your Leakey Foundation-funded project.
Harmonie Klein: The extraordinary degree of cooperation exhibited by humans seems unrivaled in the animal kingdom with group hunting and meat sharing having been suggested as milestones in the evolutionary trajectory of human sociality and life history traits. In humans, meat is an important food resource and meat sharing allows high energetic and social benefits. Besides, successful hunting results in higher reproductive success for good hunters. Therefore, hunting is considered a cooperative act in humans and sharing is motivated by a reward for the invested labor.
Chimpanzees (Pan troglodytes), one of humankind’s closest living relatives, are known to frequently hunt and consume the meat of a variety of vertebrates (ranging from birds to reptiles and to mammals), and share a wide variety of foods such as meat, fruit, and honey. Cooperation in hunting and meat sharing has been described in some chimpanzee populations through collaborative hunting, defined roles, and a reward of more meat for hunters than for non-hunters. However, such observations have not been made at other sites and, even today, cooperation is still considered by some scholars as a uniquely human trait. In addition, food sharing has been claimed as specific to humans while in chimpanzees, food sharing has been seen as only marginally important.
My study will shed new light on this debate and allow us to better understand the evolution of cooperation in humans by focusing especially on hunting and food sharing behaviors of the newly habituated chimpanzees of the Rekambo community in Loango National Park, Gabon. I will especially try to determine the underlying degree of cooperation during hunts, the nature of meat sharing patterns, and the impact of food resources on food sharing patterns in Central African chimpanzees.
Q: How did you feel when you received your grant?
Harmonie Klein: I have been working with the Loango Chimpanzee Project (LCP) for three years with the goal of realizing this PhD project, but due to the uncertain future of the MPI primatology department at this time, there was no possibility of funding. I did not give up and I worked on the LCP hunting data, I wrote, with colleagues and supervisors, two papers on tortoise predation and hunting behaviors in central African chimpanzees. Having acquired substantial knowledge on this topic, my supervisors finally decided we should try to initiate this project and I applied for a Leakey Foundation grant.
So, how can I describe my feeling when I got my grant? It represents the achievement of all my previous efforts, the achievement of my professional but also personal career aspirations, and the rewarding of a mature project that I thought about and worked on for a long time. This grant gives me the opportunity to collect all the data I need to complete my study, which is very exciting to me. It finally gives me the opportunity to finish my PhD, to become a doctor in primatology and to evolve in my career. And of course, it will also allow me to bring new evidence of chimpanzee behavioral diversity and to shed new light on an important debate around the existence of cooperation in apes and a better understanding of human evolution.
Q: What excites you about your work?
Harmonie Klein: The Rekambo community offers unique research possibilities since the chimpanzees frequently hunt a wide variety of animal taxa. In addition, they share meat and other resources across a wide variety of contexts (mammals, tortoises, honey, fruits) and they provide food before requests without any previous begging, a rare observation in chimpanzees (1.2% of the sharing). Moreover, the unique open primary forest (visibility up to 50 meters), enables the simultaneous observation of several participants in a hunt. Finally, a very exciting aspect of this project is the fact that Loango chimpanzees are one of the lesser-known sub-species of the Pan genus (Pan troglodytes troglodytes). Chimpanzees present a high variation of behavior across all of Africa between groups and sub-species and the Rekambo community already shows different behaviors. Thus, this project will also enable direct quantitative comparisons with other chimpanzee populations and allow us to investigate whether differences in hunting and sharing behaviors across populations are related to demographic, ecological or sub-species differences.
Q: Can you tell us about something interesting you’ve discovered?
Harmonie Klein: A crazy discovery, is the one we made in 2016: Rekambo chimpanzees use a percussive technique to open the shells of the tortoises (Kinixys erosa) they hunt. Tortoise predation happened often, mostly by adult males and seems to require physical abilities to break open the carapace. A research assistant and I also observed a chimpanzee storing a half-eaten tortoise in a tree and coming back the next day to finish it. This could be evidence of future planning in chimpanzees, though further observations are needed to assess it. Reptile consumption was never reported before in wild chimpanzees after more than 60 years of research. This is why studying wild animals is so fascinating! You can always discover new things even after years of research.
Q: What is most challenging about your work?
The physical demands of this work can be a challenge. Living in an isolated setting is also difficult sometimes.
Q: What are you working on right now?
Harmonie Klein: Right now I am working on my data collection protocol to prepare for my departure to the field. The next step is to spend a year in the field, in the LCP, following the Rekambo chimpanzees every day. I am also still working on a paper describing the general pattern of hunting in central African chimpanzees.
Q: Why do you think research like yours is important?
Harmonie Klein: First, studying wild animals allows us to better understand their behavior, ecology, habits, and the world we live in. Then it gives us tools to improve wild animal conservation, which is essential and a real concern.
Secondly, studying new populations and new sub-species, in chimpanzees but also other taxa, will lead to a better understanding of the behavioral variety of a species across the world.
Finally, apes are our closest living relatives, offering valuable perspectives into the causes and evolution of individual, social, and reproductive human actions. Acquiring knowledge about human evolution is essential for understanding our current behaviors and anatomy.
Studying the hunting and food sharing patterns of chimpanzees at Loango, and comparing these patterns with other well-studied populations will permit a better understanding of the contexts in which cooperative hunting has evolved in humans. Therefore, I hope my research will help The Leakey Foundation in its mission to increase scientific knowledge and public understanding of human evolution.