The Rift Valley in East Africa holds many secrets to our primate past. Our diminutive ancestor Lucy was discovered there and a publication this week in Nature reveals even older primate fossils, farther down our family tree.

Nancy Stevens, of Ohio University, and her colleagues have been working in a single fossil site in the Rukwa Rift Basin of Tanzania for several years. Over the course of two years, Stevens uncovered two separate fossils—a lower jawbone with several teeth, and a tooth with a jaw fragment. Each fossil represents a different, new species and remarkably, two of the oldest species ever identified from their groups.

The two primate fossils come from different groups—apes (of which we’re part) and Old World monkeys. Rukwapithecus fleaglei is the new ape species (pictured, left) and Nsungwepithecus gunnelli is the new Old World monkey (pictured, right).

Using an approach that dates multiple minerals contained within the rocks, geologists determined a precise age for the specimens—25 million years old. The age is significant because few primate fossils date back to that era, the late Oligocene.

In addition, the new discoveries can help us understand when these two groups (apes and Old World monkeys) diverged.  Time estimates from analyses of DNA sequences from living primates do not agree with those suggested by the primate fossil record. Studies of clock-like mutations in primate DNA have indicated that the split between apes and Old World monkeys occurred between 30 million and 25 million years ago. But prior to these finds, the fossil evidence had only gone back 20 million years.

“Fossils from the Rukwa Rift Basin in southwestern Tanzania provide the first real test of the hypothesis that these groups diverged so early, by revealing a novel glimpse into this late Oligocene terrestrial ecosystem,” Stevens says.

Undoubtedly, the researchers will uncover more fossils in the area to test the hypothesis. “The rift setting provides an advantage in that it preserves datable materials together with these important primate fossils,” says co-author Eric Roberts of James Cook University. Dig on!

Image: Mauricio Anton

Gourma elephants (Loxodonta africana) living near Timbuktu, Mali, make an epic journey each year in their quest for food and water. Researchers at Oxford University and the University of British Columbia found that the elephants travel across an area of 32,000 square kilometers (more than 12,000 square miles!) in the desert, marking the largest known elephant range in the world.

The animals’ extreme journey is a product of their tough life. The northernmost population of elephants in the world, wandering over a much larger range than their relatives, they frequently endure sand storms, water shortages, and temperatures over 50 degrees Celsius.

“It’s incredible these elephants have survived. They have a truly stressful life with the lack of water and food, and their giant range reflects that,” says lead researcher Jake Wall of the University of British Columbia and the conservation organization Save The Elephants.

Wall and his colleagues attached GPS collars to nine elephants in the Gourma region in Africa in March 2008 and tracked them over the next two years. In a paper published this month in the journal Biological Conservation they report that the elephants migrate south over a large path that extends into northern Burkina-Faso in West Africa.

The Gourma elephants don’t necessarily travel farther than their East and Southern African cousins, but their movements are spread out over an area 150 percent bigger than those reported in Namibia and 29 percent larger than those in Botswana, the researchers said. Interestingly, scientists also found that males and females often take different routes. In fact, they only share about a quarter of their ranges.

“We think the difference is partly because of their tolerances towards people. Bulls generally take more risks and occupy areas that have higher human densities,” explains Wall. “They also have varying food strategies, and we think that differences in the areas they occupy might be because of different vegetation types in those areas.”

Gourma elephants have been able to beat climate change induced heat and drought in their environment and have historically enjoyed relatively peaceful coexistence with the local Touareg, Fuhlani and Dogon peoples. However researchers warn that the elephants may currently be threatened by political violence in Mali and expanding human settlements.

Currently the Gourma population has an estimated 350 elephants. To prevent extinction of this species, scientists have identified 10 hotspots essential for the survival of these animals. “These elephant hot-spots should be considered conservation priorities,” Wall urges.

Zuberoa Marcos is a former biologist and current science writer based in Barcelona. She writes articles regularly for Science Today.

Un viaje de récord por el desierto

Por Zuberoa Marcos

Los elefantes Gourma (Loxodonta africana) que viven cerca de Tombuctú, Malí, realizan un viaje épico cada año en busca de comida y agua. Investigadores de las universidades de Oxford y British Columbia en Canadá han descubierto que viajan a través de un área de 32,000 kilómetros cuadrados por el desierto, el área de distribución más grande de elefantes conocida en el mundo.

Este viaje extremo es consecuencia de sus duras condiciones de vida. Los Gourma constituyen la población más septentrional de elefantes en el mundo y con frecuencia tienen que soportar tormentas de arena, escasez de agua y temperaturas por encima de 50 grados centígrados.

“Es increíble que estos elefantes hayan sobrevivido. Tienen una vida verdaderamente estresante con la falta de agua y alimentos y su área de distribución gigantesca así lo demuestra”, dijo Jake Wall investigador principal del estudio de la Universidad British Columbia y miembro de la organización de conservación Save the Elephants.

Wall y su equipo colocaron collares con GPS a nueve elefantes en la región africana de Gourma en marzo de 2008 y, después, siguieron sus pasos durante los siguientes dos años. En un artículo publicado este mes en la revista Biological Conservation explican que los elefantes migran hacia el sur a través de un sendero de gran longitud que se extiende hacia el norte de Burkina-Faso en el África Occidental.

Los elefantes de Gourma no hacen viajes más largos que sus primos del Este y del Sur de África, pero sus desplazamientos se extienden sobre un área un 150% mayor que la de los elefantes que viven en Namibia y 29% superior que los que hacen en Botswana. Curiosamente, los investigadores también observaron que los machos y las hembras suelen tomar rutas diferentes. De hecho, sólo comparten una cuarta parte de su área de distribución.

“Creemos que la diferencia se debe en parte a su tolerancia hacia las personas. Los machos generalmente toman más riesgos y ocupan las zonas que tienen mayor densidad humana”, dijo Wall. “Ellos también tienen distintas estrategias alimentarias y creemos que las diferencias en las áreas que ocupan pueden ser debidas a diferentes tipos de vegetación en esas regiones”.

Los elefantes de Gourma han sido capaces de superar el calor y la sequía de su entorno inducidas por el cambio climático y han disfrutado históricamente de una convivencia pacífica con los pueblos locales como los Touareg, los Fuhlani y los Dogon. Sin embargo, los investigadores advierten que, hoy en día, la supervivencia de estos animales está amenazada por la violencia política en Malí y por la expansión de los asentamientos humanos.

Actualmente, se calcula que la población Gourma está formada por unos 350 elefantes. Para evitar su extinción, los científicos han identificado 10 sitios esenciales para la supervivencia de estos animales. Wall insta a que estos lugares sean considerados como prioridades para la conservación de los Gourma.

Zuberoa Marcos es una bióloga retirada y actualmente trabaja como escritora científica desde Barcelona. Escribe de forma regular para Science Today.

Image: Chyulu Smith/Save the Elephants

The authors of the paper sequenced the entire genomes of five members of each of the following hunter-gatherer populations: forest-dwelling, short-statured Pygmies from Cameroon, and click-speaking Hadza and Sandawe individuals from Tanzania.

The fascinating findings tell us more about human origins and prove to be a bit controversial, so I wanted to get more information from the Academy’s expert in human evolution, Zeray Alemseged. Zeray’s studies of early human remains have been published in prominent journals and garnered him worldwide attention. (PBS’s NOVA filmed an extensive interview with him here last spring, in addition to being on the covers of Nature and National Geographic.)

Zeray says these populations are not well studied and their isolation offers a new view on the human genome. Their unique diets, stature and culture also enable scientists to potentially link specific attributes to genetic markers, he adds.

The researchers used an in-depth method that involves sequencing each strand of DNA more than 60 times on average. This redundancy makes the sequencing highly accurate, giving the geneticists confidence that any mutations they identify are real and not errors.

Their results suggest that different human populations evolved distinctly in order to reap nutrition from local foods and defend against infectious disease. They also identify new candidate genes that likely play a major role in making Pygmies short in stature.

Scanning these sequences, the researchers found 13.4 million genetic variants or mutations—locations in the genome where a single nucleotide differed from other human sequences—and astonishingly, 3 million are new to science.

These new variants can represent the gene expressions unique to these populations, Zeray explains. This study is quite significant in making these genetic links to function and attributes that are phenotypic.

Zeray reminds us that these genetic studies aren’t just for mapping our ancestry, but also for mapping our future. He offers two separate examples—first, personalized medicine could tailor to specific gene regions. Second, “If we can link variants to diet, isolation and environment,” Zeray says, citing this current study’s examples, “then we can also understand what future climate change might look like for our species and how to prepare for it.”

Finally, the study finds genetic evidence that these direct ancestors of modern humans may have interbred with members of an unknown ancestral group of hominins. Zeray remarks that this particular finding—of a potential new species—reminds us why, in this technological age, paleoanthropology is a transdisciplinary endeavor requiring both fossil discovery AND genetic research.

So he’ll wait for more evidence, along with the rest of us…

The origin of our species was once firmly rooted in eastern Africa, but a new discovery may have shifted those roots much further to the south.

Exactly when and from where our species, Homo sapiens, first evolved and left Africa has been the subject of fierce debate. Most fossil and genetic evidence placed these origins in eastern Africa between 150,000 and 200,000 years ago. But a new study published earlier this month online in the Proceedings of the National Academy of Sciences reveals that our species may have evolved in southern, not eastern Africa.

Most Africans south of the Sahara are descended from early farmers spreading from western Africa about 8,000 years ago. But nestled within this vast dispersal of farmers are pockets of hunter-gatherers: The Khomani Bushmen of the Namibian Desert, the Pygmies of the central African rainforests, and the click-speaking Hadza and Sandawe of Tanzania. These peoples’ anatomy, culture, and language are distinct from their neighbors, and many believe that they offer a window into our species’ earliest days. But genetic data of these groups has been limited, and many questions on their origins remain.

The study’s authors, led by Brenna Henn of Stanford University, sought to fill in the gaps. “We started [this] project because southern Africa has been poorly sampled. Very few other studies have ever published on them in the last decade, certainly never with more than a dozen individuals,” says Henn.

Henn and colleagues analyzed over 55,000 individual points on the genomes of people from six hunter-gatherer populations, comparing them alongside other African populations. The team used this data to construct a genetic map of prehistoric Africa.

Not only had the hunter-gatherers been genetically isolated from the farming groups for thousands of years, they were also genetically distinct from each other.

In addition, long before the farmers swept across the continent, these hunter-gatherer groups were already well-established in their respective locales.

How does this relate to modern human origins? By using genomic data and a computer model, the team found the most likely starting point to be closest to the most ancient populations: southern Africa. Other experts have hypothesized this to be the case, and recent archaeological discoveries and climatic evidence have lent additional support to the fact that this region of Africa hosted our most ancient ancestors.

But the team has many questions left to answer. Henn and her colleagues also detected rapid evolutionary change among the groups, which may trace back thousands of years. They found that the Hadza of Tanzania have been going through a rapid decline, called a bottleneck, but have yet to understand why. “We would like to know when this bottleneck started – did it happen when the agriculturalists moved in?  Why don’t all hunter-gatherer populations show this signature?” says Henn.

Anne Holden, a docent at the California Academy of Sciences, is a PhD trained genetic anthropologist and science writer living in San Francisco.

Image of the Khomani courtesy of Brenna Henn

A new study, published online today in the journal Science, only adds to the conundrum. From the New York Times:

“This is a huge milestone, but unfortunately it raises more questions than it answers,” said Jeffrey Rose, an archaeologist at the University of Birmingham in England.

The study is based on several stone tools found in the United Arab Emirates. The tools date to around 125,000 years ago.  They are similar to those found  belonging to humans in East Africa. In addition, the area is beyond the known boundaries of Neanderthals. Did these tools belong to modern humans? Were Homo sapiens in Arabia that long ago?

The authors of the study propose that the conditions may have favorable for leaving Africa for the peninsula during this time. From Brian Switek’s blog in Wired:

Lower sea levels may have opened a path, and increased rainfall would have made the Jebel Faya area [in the UAE] less arid than it is today.

No remains were found in the area, so the tool-users cannot be definitively confirmed. And theories of human migration always spark debate. Scientists in varying articles regarding the publication call the study “provocative”, an “audacious claim” and find “not a scrap of evidence” indicating the tools belonged to modern humans. Perhaps Alison Brooks, an archaeologist at George Washington University, puts it best on NPR:

Certainly it’s a very intriguing find, and it should hopefully spur research in all kinds of places and directions that haven’t been undertaken before.

Image: Science /AAAS

The rainforest belt in West Africa stretches nearly 3,000 miles from the coast of Sierra Leone through the Guinean rainforest in Ghana, through Nigeria and Cameroon, to the Congolian rainforest. Over millions of years, the forest has expanded and shrunk with climate change and an aridification trend over the past several hundred thousand years.

The discovery by Adam D. Leaché, PhD, a herpetologist with UC Berkeley’s Museum of Vertebrate Zoology, and Matthew K. Fujita demonstrates the wealth of biodiversity still surviving in the patches of tropical rainforest in West Africa, and the ability of new DNA analysis techniques to distinguish different species, even when they look alike.

Having collected numerous specimens of the six-inch gecko, the scientists decided to see whether studying the genetic diversity among the geckos could tell them something about the history of the rainforest belt.

“We tended to find this gecko, Hemidactylus fasciatus, throughout our travels in West Africa,” said Leaché. “Despite the fact that it is recognized as one species, using new methods we have established a high probability that it is composed of at least four species.”

Leaché and Fujita found sufficient genetic differences among the 50 geckos collected from 10 different forest patches to identify four distinct species. The different species were found in different forest patches, suggesting that the species divergence was driven by the isolation of gecko populations from one another after gaps developed in the rainforest.

“These rainforests are classified as one of the biodiversity hotspots on the planet, yet they are one of the most endangered areas on the earth,” Leaché said. “Human deforestation is accentuating the process of habitat destruction.” If our knowledge of the diversity of geckos expanded four-fold in these few patches, imagine what remains to be discovered in the rest of the rainforest belt in West Africa.

Found several years ago in Ethiopia, a large team of interdisciplinary scientists (including paleontologists, geologists and microbiologists) studied the amber for the past five years. It dates back 95 million years to the Cretaceous period.

It is known that dinosaurs roamed Africa during that period, but the fossils found inside the amber displayed many more diverse forms of life. The amber held fossilized ants and other insects, spiders, ferns, fungi and even bacteria. The ant finding is significant because it is one of the oldest ant fossils found and could reveal more about ant evolution. Until now, paleontologists thought ants originated in North America or South Asia (the oldest fossils had been found there), but it now seems that Africa could have been their starting point.

In addition, the amber deposit may provide fresh insights into the rise of flowering plants during the Cretaceous. “The first flowering plants appeared and diversified in the Cretaceous,” says lead author Alexander Schmidt of the University of Göttingen in Germany. “Their rise to dominance drastically changed terrestrial ecosystems, and the Ethiopian amber deposit sheds light on this time of change.”

Amber is fossilized tree resin that sometimes contains animals and plant material. The researchers do not know from which tree this amber originated. According to author Paul Nascimbene, of the Division of Invertebrate Zoology at the American Museum of Natural History, “This amber could be from an early flowering plant or a previously-unknown conifer that is quite distinct…”

Amber from the Cretaceous period is primarily found in North America and Eurasia.  This Ethiopian amber is the first major discovery of its kind from the African continent.  And the diversity of life discovered in this deposit promises to reveal new information about Africa’s evolutionary past.

Image courtesy of PNAS/ Matthias Svojtka