apple

Exploring the origins of the apple

Exploring the origins of the apple

Apples originally evolved in the wild to entice ancient megafauna to disperse their seeds; more recently, humans began spreading the trees along the Silk Road with other familiar crops; dispersing the apple trees led to their domestication

wild horses apple
Horses eating wild apples in the Tien Shan Mountains. These domesticated horses demonstrate the process of seed dispersal that wild apple trees evolved to support millions of years ago, when large monogastric mammals such as these were prominent across Eurasia. Credit: Artur Stroscherer

Recent archaeological finds of ancient preserved apple seeds across Europe and West Asia combined with historical, paleontological, and recently published genetic data are presenting a fascinating new narrative for one of our most familiar fruits. In this study, Robert Spengler of the Max Planck Institute for the Science of Human History traces the history of the apple from its wild origins, noting that it was originally spread by ancient megafauna and later as a process of trade along the Silk Road. These processes allowed for the development of the varieties that we know today.

The apple is, arguably, the most familiar fruit in the world. It is grown in temperate environments around the globe and its history is deeply intertwined with humanity. Depictions of large red fruits in Classical art demonstrate that domesticated apples were present in southern Europe over two millennia ago, and ancient seeds from archaeological sites attest to the fact that people have been collecting wild apples across Europe and West Asia for more than ten thousand years. While it is clear that people have closely maintained wild apple populations for millennia, the process of domestication, or evolutionary change under human cultivation, in these trees is not clear.

Several recent genetic studies have demonstrated that the modern apple is a hybrid of at least four wild apple populations, and researchers have hypothesized that the Silk Road trade routes were responsible for bringing these fruits together and causing their hybridization. Archaeological remains of apples in the form of preserved seeds have been recovered from sites across Eurasia, and these discoveries support the idea that fruit and nut trees were among the commodities that moved on these early trade routes. Spengler recently summarized the archaeobotanical and historical evidence for cultivated crops on the Silk Road in a book titled Fruit from the Sands, published with the University of California Press. The apple holds a deep connection with the Silk Road - much of the genetic material for the modern apple originated at the heart of the ancient trade routes in the Tien Shan Mountains of Kazakhstan. Furthermore, the process of exchange caused the hybridization events that gave rise to the large red sweet fruits in our produce markets.

Understanding how and when apple trees evolved to produce larger fruits is an important question for researchers, because fruit trees do not appear to have followed the same path towards domestication as other, better-understood crops, such as cereals or legumes. Many different wild and anthropogenic forces apply selective pressure on the crops in our fields, it is not always easy to reconstruct what pressures caused which evolutionary changes. Therefore, looking at evolutionary processing in modern and fossil plants can help scholars interpret the process of domestication. Fleshy sweet fruits evolve to attract animals to eat then and spread their seeds; large fruits specifically evolve to attract large animals to disperse them.

apple
The wild apples in the Tien Shan Mountains represent the main ancestral population for our modern apple. These trees produce large fruits, which are often red when ripe and have a varying array of flavors. These were the ancestors of the trees that people first started to cultivate and spread along the Silk Road. Credit: Prof. Dr. Martin R. Stuchtey

Large fruits evolved to attract ancient megafauna

While most scholars studying domestication focus on the period when humans first start cultivating a plant, in this study Spengler explores the processes in the wild that set the stage for domestication. Spengler suggests that understanding the process of evolution of large fruits in the wild will help us understand the process of their domestication. "Seeing that fruits are evolutionary adaptations for seed dispersal, the key to understanding fruit evolution rests in understanding what animals were eating the fruits in the past," he explains.

Many fruiting plants in the apple family (Rosaceae) have small fruits, such as cherries, raspberries, and roses. These small fruits are easily swallowed by birds, which then disperse their seeds. However, certain trees in the family, such as apples, pears, quince, and peaches, evolved in the wild to be too large for a bird to disperse their seeds. Fossil and genetic evidence demonstrate that these large fruits evolved several million years before humans started cultivating them. So who did these large fruits evolve to attract?

The evidence suggests that large fruits are an evolutionary adaptation to attract large animals that can eat the fruits and spread the seeds. Certain large mammals, such as bears and domesticated horses, eat apples and spread the seeds today. However, prior to the end of the last Ice Age, there were many more large mammals on the European landscape, such as wild horses and large deer. Evidence suggests that seed dispersal in the large-fruiting wild relatives of the apple has been weak during the past ten thousand years, since many of these animals went extinct. The fact that wild apple populations appear to map over glacial refugial zones of the Ice Age further suggests that these plants have not been moving over long distances or colonizing new areas in the absence of their original seed-spreaders.

Trade along the Silk Road likely enabled the development of the apple we know today

Silk Road apple
Venders in every Central Asian bazaar sell a diverse array of apples. This women in the Bukhara bazaar is selling a variety of small sweet yellow apples, which she locally cultivated in Uzbekistan. Some of the fruits sold in these markets today travel great distances, similar to how they would have during the peak of the Silk Road. Credit: Robert Spengler

Wild apple tree populations were isolated after the end of the last Ice Age, until humans started moving the fruits across Eurasia, in particular along the Silk Road. Once humans brought these tree lineages back into contact with each other again, bees and other pollinators did the rest of the work. The resulting hybrid offspring had larger fruits, a common result of hybridization. Humans noticed the larger fruiting trees and fixed this trait in place through grafting and by planting cuttings of the most favored trees. Thus, the apples we know today were primarily not developed through a long process of the selection and propagation of seeds from the most favored trees, but rather through hybridization and grafting. This process may have been relatively rapid and parts of it were likely unintentional. The fact that apple trees are hybrids and not "properly" domesticated is why we often end up with a crabapple tree when we plant an apple seed.

This study challenges the definition of "domestication"' and demonstrates that there is no one-shoe-fits-all model to explain plant evolution under human cultivation. For some plants, domestication took millennia of cultivation and human-induced selective pressure - for other plants, hybridization caused rapid morphological change. "The domestication process is not the same for all plants, and we still do not know much about the process in long-generation trees," notes Spengler. "It is important that we look past annual grasses, such as wheat and rice, when we study plant domestication. There are hundreds of other domesticated plants on the planet, many of which took different pathways toward domestication." Ultimately, the apple in your kitchen appears to owe its existence to extinct megafaunal browsers and Silk Road merchants.

 

 

Press release from the Max Planck Institute for the Science of Human History / Max-Planck-Institut für Menschheitsgeschichte


Neanderthals and modern humans diverged at least 800,000 years ago

Neanderthals and modern humans diverged at least 800,000 years ago

Neanderthals and modern humans diverged at least 800,000 years ago, substantially earlier than indicated by most DNA-based estimates, according to new research by a UCL academic.

Neanderthals diverged teeth
Dental morphology. Credit: Aida Gómez-Robles

The research, published in Science Advances, analysed dental evolutionary rates across different hominin species, focusing on early Neanderthals. It shows that the teeth of hominins from Sima de los Huesos, Spain - ancestors of the Neanderthals - diverged from the modern human lineage earlier than previously assumed.

Sima de los Huesos is a cave site in Atapuerca Mountains, Spain, where archaeologists have recovered fossils of almost 30 people. Previous studies date the site to around 430,000 years ago (Middle Pleistocene), making it one of the oldest and largest collections of human remains discovered to date.

Dr Aida Gomez-Robles (UCL Anthropology), said: "Any divergence time between Neanderthals and modern humans younger than 800,000 years ago would have entailed an unexpectedly fast dental evolution in the early Neanderthals from Sima de los Huesos."

"There are different factors that could potentially explain these results, including strong selection to change the teeth of these hominins or their isolation from other Neanderthals found in mainland Europe. However, the simplest explanation is that the divergence between Neanderthals and modern humans was older than 800,000 years. This would make the evolutionary rates of the early Neanderthals from Sima de los Huesos roughly comparable to those found in other species."

Modern humans share a common ancestor with Neanderthals, the extinct species that were our closest prehistoric relatives. However, the details on when and how they diverged are a matter of intense debate within the anthropological community.

Ancient DNA analyses have generally indicated that both lineages diverged around 300,000 to 500,000 years ago, which has strongly influenced the interpretation of the hominin fossil record.

This divergence time, however, is not compatible with the anatomical and genetic Neanderthal similarities observed in the hominins from Sima de los Huesos. The Sima fossils are considered likely Neanderthal ancestors based on both anatomical features and DNA analysis.

Dr Gomez-Robles said: "Sima de los Huesos hominins are characterised by very small posterior teeth (premolars and molars) that show multiple similarities with classic Neanderthals. It is likely that the small and Neanderthal-looking teeth of these hominins evolved from the larger and more primitive teeth present in the last common ancestor of Neanderthals and modern humans."

Dental shape has evolved at very similar rates across all hominin species, including those with very expanded and very reduced teeth. This new study examined the time at which Neanderthals and modern humans should have diverged to make the evolutionary rate of the early Neanderthals from Sima de los Huesos similar to those observed in other hominins.

The research used quantitative data to measure the evolution of dental shape across hominin species assuming different divergent times between Neanderthals and modern humans, and accounting for the uncertainty about the evolutionary relationships between different hominin species.

"The Sima people's teeth are very different from those that we would expect to find in their last common ancestral species with modern humans, suggesting that they evolved separately over a long period of time to develop such stark differences."

The study has significant implications for the identification of Homo sapiens last common ancestral species with Neanderthals, as it allows ruling out all the groups postdating 800,000 year ago.

Neanderthals diverged teeth
Hominin teeth. Credit: Aida Gómez-Robles

Press release from University College London


New Jurassic non-avian theropod dinosaur sheds light on origin of flight in Dinosauria

New Jurassic non-avian theropod dinosaur sheds light on origin of flight in Dinosauria

origin of flight Ambopteryx longibrachium
a. Fossil; b. restoration, scale bar equal 10 mm; c. melanosomes of the membranous wing (mw); d. histology of the bony stomach content (bn). st, styliform element; gs, gastroliths. Credit: WANG Min

A new Jurassic non-avian theropod dinosaur from 163 million-year-old fossil deposits in northeastern China provides new information regarding the incredible richness of evolutionary experimentation that characterized the origin of flight in the Dinosauria.

Drs. WANG Min, Jingmai K. O'Connor, XU Xing, and ZHOU Zhonghe from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences described and analyzed the well-preserved skeleton of a new species of Jurassic scansoriopterygid dinosaur with associated feathers and membranous tissues. Their findings were published in Nature.

The new species, named Ambopteryx longibrachium, belongs to the Scansoriopterygidae, one of the most bizarre groups of non-avian theropods. The Scansoriopterygidae differ from other theropods in their body proportions, particularly in the proportions of the forelimb, which supports a bizarre wing structure first recognized in a close relative of Ambopteryx, Yi qi.

Unlike other flying dinosaurs, namely birds, these two species have membranous wings supported by a rod-like wrist bone that is not found in any other dinosaur (but is present in pterosaurs and flying squirrels).

Until the discovery of Yi qi in 2015, such a flight apparatus was completely unknown among theropod dinosaurs. Due to incomplete preservation in the holotype and only known specimen of Yi qi, the veracity of these structures and their exact function remained hotly debated.

As the most completely preserved specimen to date, Ambopteryx preserves membranous wings and the rod-like wrist, supporting the widespread existence of these wing structures in the Scansoriopterygidae.

WANG and his colleagues investigated the ecomorphospace disparity of Ambopteryx relative to other non-avian coelurosaurians and Mesozoic birds. The results showed dramatic changes in wing architecture evolution between the Scansoriopterygidae and the avian lineage, as the two clades diverged and underwent very different evolutionary paths to achieving flight.

Interestingly, forelimb elongation, an important characteristic of flying dinosaurs, was achieved in scansoriopterygids primarily through elongation of the humerus and ulna, whereas the metacarpals were elongated in non-scansoriopterygid dinosaurs including Microraptor and birds.

In scansoriopterygids, the presence of an elongated manual digit III and the rod-like wrist probably compensated for the relatively short metacarpals and provided the main support for the membranous wings. In contrast, selection for relatively elongated metacarpals in most birdlike dinosaurs was likely driven by the need for increased area for the attachment of the flight feathers, which created the wing surface in Microraptor and birds.

The co-occurrence of short metacarpals with membranous wings, versus long metacarpals and feathered wings, exhibits how the evolution of these two significantly different flight strategies affected the overall forelimb structure. So far, all known scansoriopterygids are from the Late Jurassic and their unique membranous wing structure did not survive into the Cretaceous.

This suggests that this wing structure represents a short-lived and unsuccessful attempt to fly. In contrast, feathered wings, first documented in Late Jurassic non-avian dinosaurs, were further refined through the evolution of numerous skeletal and soft tissue modifications, giving rise to at least two additional independent origins of dinosaur flight and ultimately leading to the current success of modern birds.

Life reconstruction of the bizarre membranous-winged Ambopteryx longibrachium. Credit: Chung-Tat Cheung

Press release from the Chinese Academy of Sciences


Cambrian explosion oxygen

Oxygen variation behind evolutionary surges and extinctions during the Cambrian explosion

Oxygen variation controls episodic pattern of Cambrian explosion: study

Early Cambrian sections of the Lena River in Siberia. Credit: ZHU Maoyan

The Cambrian Explosion around 540 million years ago was a key event in the evolutionary history of life. But what exactly controlled the Cambrian Explosion has been a subject of scientific debate since Darwin's time.

A multidisciplinary study, published on May 6 in Nature Geoscience by a joint China-UK-Russia research team, gives strong support to the hypothesis that the oxygen content of the atmosphere and ocean was the principal controlling factor in early animal evolution.

In past decades, important fossil discoveries revealed a puzzling pattern of episodic radiations and extinctions in early animal evolution. This pattern coincides with dramatic fluctuations in the carbon isotopic composition of seawater, according to study co-author ZHU Maoyan from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences.

Lower Cambrian strata along the Aldan and Lena rivers in Siberia consist of continuous sequences of limestone with abundant fossils and reliable age constraints, making these rocks ideal for analysing ancient seawater chemistry. The isotopic signatures of the rocks correlate with the global production of oxygen, allowing the team to determine oxygen levels in shallow sea water and the atmosphere during the Cambrian Period.

The study is the first to show that the pattern of episodic radiations and extinctions in early animal evolution closely matches extreme changes in atmospheric and oceanic oxygen levels. This result strongly suggests that oxygen played a fundamental role in the Cambrian Explosion of animals.

"The complex creatures that came about during the Cambrian Explosion were the precursors to many of the modern animals we see today. By analysing carbon and sulphur isotopes found in ancient rocks, we are able to trace oxygen variations in Earth's atmosphere and shallow oceans during the Cambrian Explosion. We found that evolutionary radiations follow a pattern of 'boom and bust' in tandem with the oxygen levels," said Dr. HE Tianchen, study lead author and postdoctoral researcher at the University of Leeds.

According to Prof. Graham Shields, study co-author from UCL Earth Sciences, this is the first study to show clearly that our earliest animal ancestors experienced a series of evolutionary radiations and bottlenecks caused by extreme changes in atmospheric oxygen levels. The result was a veritable explosion of new animal forms during more than 13 million years of the Cambrian Period.

Study co-author Dr. Benjamin Mills, from the School of Earth and Environment at Leeds, said, "The Siberian Platform gives us a unique window into early marine ecosystems. This area contains over half of all currently known fossilised diversity from the Cambrian Explosion."

"This has been an incredibly successful and exciting joint study. The question of the Cambrian Explosion trigger has puzzled scientists for years. Now, the results give us convincing evidence to link the rapid appearance of animals as well as mass extinction during the early Cambrian with oxygen," said co-author Andrey Yu Zhuravlev from Lomonosov Moscow State University.

Study co-author YANG Aihua from Nanjing University said, "In the last decade, progress has been made in the Cambrian Explosion; this study shows the interactions between the biodiversity of animal and environment during the early Cambrian."

Press release from the Chinese Academy of Sciences

Oxygen linked with the boom and bust of early animal evolution

Cambrian explosion oxygen
This is a fossilized trilobite Aldonaia from the Cambrian Period. Credit: Andrey Zhuravlev, Lomonosov Moscow State University

Extreme fluctuations in atmospheric oxygen levels corresponded with evolutionary surges and extinctions in animal biodiversity during the Cambrian explosion, finds new study led by UCL and the University of Leeds.

The Cambrian explosion was a crucial period of rapid evolution in complex animals that began roughly 540 million years ago. The trigger for this fundamental phase in the early history of animal life is a subject of ongoing biological debate.

The study, published today in Nature Geoscience by scientists from the UK, China and Russia, gives strong support to the theory that oxygen content in the atmosphere was a major controlling factor in animal evolution.

The study is the first to show that during the Cambrian explosion there was significant correlation between surges in oxygen levels and bursts in animal evolution and biodiversity, as well as extinction events during periods of low oxygen.

Dr Tianchen He, study lead author and postdoctoral researcher at the University of Leeds, began this research while at UCL. He said: "The complex creatures that came about during the Cambrian explosion were the precursors to many of the modern animals we see today. But because there is no direct record of atmospheric oxygen during this time period it has been difficult to determine what factors might have kick started this crucial point in evolution.

"By analysing the carbon and sulphur isotopes found in ancient rocks, we are able to trace oxygen variations in Earth's atmosphere and shallow oceans during the Cambrian Explosion. When compared to fossilised animals from the same time we can clearly see that evolutionary radiations follow a pattern of 'boom and bust' in tandem with the oxygen levels.

"This strongly suggests oxygen played a vital role in the emergence of early animal life."

Study co-author Professor Graham Shields from UCL Earth Sciences, said: "This is the first study to show clearly that our earliest animal ancestors experienced a series of evolutionary radiations and bottlenecks caused by extreme changes in atmospheric oxygen levels.

"The result was a veritable explosion of new animal forms during more than 13 million years of the Cambrian Period. In that time, Earth went from being populated by simple, single-celled and immobile organisms to hosting the wonderful variety of intricate, energetic life forms we see today."

Cambrian explosion oxygen
This is a fossilized giant arthropod Phytophilaspis from the Cambrian Period. Credit: Andrey Zhuravlev, Lomonosov Moscow State University

The team analysed the carbon and sulphur isotopes from marine carbonate samples collected from sections along the Aldan and Lena rivers in Siberia. During the time of the Cambrian explosion this area would have been a shallow sea and the home for the majority of animal life on Earth.

The lower Cambrian strata in Siberia are composed of continuous limestone with rich fossil records and reliable age constraints, providing suitable samples for the geochemical analyses. The isotope signatures in the rocks relate to the global production of oxygen, allowing the team to determine oxygen levels present in the shallow ocean and atmosphere during the Cambrian Period.

This is the Lena River in Sakha (Yakutia), Siberia. Credit: Andrey Zhuravlev, Lomonosov Moscow State University

Study co-author Dr Benjamin Mills, from the School of Earth and Environment at Leeds, said: "The Siberian Platform gives us a unique window into early marine ecosystems. This area contains over half of all currently known fossilised diversity from the Cambrian explosion.

"Combining our isotope measurements with a mathematical model lets us track the pulses of carbon and sulphur entering the sediments in this critical evolutionary cradle. Our model uses this information to estimate the global balance of oxygen production and destruction, giving us new insight into how oxygen shaped the life we have on the planet today."

Study co-author Maoyan Zhu from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, said: "Understanding what triggered the Cambrian explosion requires multidisciplinary study. That's why with Graham Shields we organized together such a multidisciplinary team funded by NERC and NSFC in past years. I am so excited about the results through this collaborative project."

"On the other hand, it took a long time to get this result. We already got samples from Siberia in 2008. The sections in Siberia are difficult to access. It took time for us to organize the expedition and collect the samples there. Without support from Russian colleagues, we could not do the project."

Study co-author Andrey Yu Zhuravlev from Lomonosov Moscow State University said: "This has been an incredibly successful and exciting joint study. The question of the Cambrian Explosion trigger has puzzled scientists for years. Now, the results give us convincing evidence to link the rapid appearance of animals as well as mass extinction during the early Cambrian with oxygen."

###

Further information

The paper Possible links between extreme oxygen perturbations and the Cambrian radiation of animals is published in Nature Geoscience 06 May 2019. (DOI: 10.1038/s41561-019-0357-z)

Full list of authors: Tianchen He, Maoyan Zhu, Benjamin J. W. Mills, Peter M. Wynn, Andrey Yu. Zhuravlev, Rosalie Tostevin, Philip A. E. Pogge von Strandmann, Aihua Yang, Simon W. Poulton and Graham A. Shields

This work was facilitated and supported by a joint Sino-UK-Russia research collaboration.

UK institutes: UCL; University of Leeds; Lancaster University; University of Oxford

Chinese institutes: Nanjing Institute of Geology and Palaeontology, CAS; University of Chinese Academy of Sciences; Nanjing University

Russian institute: Lomonosov Moscow State University

 

Press release from the University of Leeds

 


Denisovans Tibetan Plateau Baishiya Karst Cave Xiahe mandible

First hominins on the Tibetan Plateau were Denisovans

First hominins on the Tibetan Plateau were Denisovans

Denisovan mandible likely represents the earliest hominin fossil on the Tibetan Plateau

Denisovans Tibetan Plateau Baishiya Karst Cave Xiahe mandible
The Xiahe mandible, only represented by its right half, was found in 1980 in Baishiya Karst Cave. Credit: © Dongju Zhang, Lanzhou University

So far Denisovans were only known from a small collection of fossil fragments from Denisova Cave in Siberia. A research team led by Fahu Chen from the Institute of Tibetan Plateau Research, CAS, Dongju Zhang from Lanzhou University and Jean-Jacques Hublin from the Max Planck Institute for Evolutionary Anthropology now describes a 160,000-year-old hominin mandible from Xiahe in China. Using ancient protein analysis the researchers found that the mandible’s owner belonged to a population that was closely related to the Denisovans from Siberia. This population occupied the Tibetan Plateau in the Middle Pleistocene and was adapted to this low-oxygen environment long before Homo sapiens arrived in the region.

Denisovans - an extinct sister group of Neandertals - were discovered in 2010, when a research team led by Svante Pääbo from the Max Planck Institute for Evolutionary Anthropology (MPI-EVA) sequenced the genome of a fossil finger bone found at Denisova Cave in Russia and showed that it belonged to a hominin group that was genetically distinct from Neandertals. "Traces of Denisovan DNA are found in present-day Asian, Australian and Melanesian populations, suggesting that these ancient hominins may have once been widespread," says Jean-Jacques Hublin, director of the Department of Human Evolution at the MPI-EVA. "Yet so far the only fossils representing this ancient hominin group were identified at Denisova Cave."

Mandible from Baishiya Karst Cave

In their new study, the researchers now describe a hominin lower mandible that was found on the Tibetan Plateau in Baishiya Karst Cave in Xiahe, China. The fossil was originally discovered in 1980 by a local monk who donated it to the 6th Gung-Thang Living Buddha who then passed it on to Lanzhou University. Since 2010, researchers Fahu Chen and Dongju Zhang from Lanzhou University have been studying the area of the discovery and the cave site from where the mandible originated. In 2016, they initiated a collaboration with the Department of Human Evolution at the MPI-EVA and have since been jointly analysing the fossil.

While the researchers could not find any traces of DNA preserved in this fossil, they managed to extract proteins from one of the molars, which they then analysed applying ancient protein analysis. "The ancient proteins in the mandible are highly degraded and clearly distinguishable from modern proteins that may contaminate a sample," says Frido Welker of the MPI-EVA and the University of Copenhagen. "Our protein analysis shows that the Xiahe mandible belonged to a hominin population that was closely related to the Denisovans from Denisova Cave."

Primitive shape and large molars

The researchers found the mandible to be well-preserved. Its robust primitive shape and the very large molars still attached to it suggest that this mandible once belonged to a Middle Pleistocene hominin sharing anatomical features with Neandertals and specimens from the Denisova Cave. Attached to the mandible was a heavy carbonate crust, and by applying U-series dating to the crust the researchers found that the Xiahe mandible is at least 160,000 years old. Chuan-Chou Shen from the Department of Geosciences at National Taiwan University, who conducted the dating, says: "This minimum age equals that of the oldest specimens from the Denisova Cave".

"The Xiahe mandible likely represents the earliest hominin fossil on the Tibetan Plateau," says Fahu Chen, director of the Institute of Tibetan Research, CAS. These people had already adapted to living in this high-altitude low-oxygen environment long before Homo sapiens even arrived in the region. Previous genetic studies found present-day Himalayan populations to carry the EPAS1 allele in their genome, passed on to them by Denisovans, which helps them to adapt to their specific environment.

"Archaic hominins occupied the Tibetan Plateau in the Middle Pleistocene and successfully adapted to high-altitude low-oxygen environments long before the regional arrival of modern Homo sapiens," says Dongju Zhang. According to Hublin, similarities with other Chinese specimens confirm the presence of Denisovans among the current Asian fossil record. "Our analyses pave the way towards a better understanding of the evolutionary history of Middle Pleistocene hominins in East Asia."

 

 

Press release from the Max Planck Institute for Evolutionary Anthropology / Max-Planck-Institut für evolutionäre Anthropologie in Leipzig 

Tibetan plateau first occupied by middle Pleistocene Denisovans

Baishiya Karst Cave
Fieldwork in the Baishiya Karst Cave and surrounding regions. Credit: ITP

The Tibetan Plateau, as Earth's "Third Pole," was reported to be first occupied by modern humans probably armed with blade technology as early as 40 ka BP. However, no earlier hominin groups had been found or reported on the Tibetan Plateau until a recent study was published by Chinese researchers.

A joint research team led by CHEN Fahu from the Institute of Tibetan Plateau Research of the Chinese Academy of Sciences and ZHANG Dongju from the Lanzhou University reported their studies on a human mandible found in Xiahe, on the Northeastern Tibetan Plateau. The findings were published in Nature.

The researchers found that the mandible came from an individual who belonged to a population closely related to the Denisovans first found in Siberia. This population occupied the Tibetan Plateau in the Middle Pleistocene and adapted to this low-oxygen environment long before the arrival of modern Homo sapiens in the region.

So far, Denisovans are only known from a small collection of fossil fragments from Denisova Cave in Siberia. Traces of Denisovan DNA are found in present-day Asian, Australian and Melanesian populations, suggesting that these ancient hominins may have once been widespread.

This study confirms for the first time that Denisovans not only lived in East Asia but also on the high-altitude Tibetan Plateau. It also indicates that the previously found possible introgression of Denisovan DNA (EPAS1) into modern Tibetans and Sherpas, who mainly live on the high-altitude Tibetan Plateau and surrounding regions today, is probably derived or inherited locally on Tibetan Plateau from Xiahe hominin represented by this Xiahe mandible.

The reported Xiahe mandible was found on the Tibetan Plateau in the Baishiya Karst Cave in Xiahe, China. Researchers managed to extract collagen from one of the molars, which they then analysed using ancient protein analysis. Ancient protein data showed that the Xiahe mandible belonged to a hominin population closely related to the Denisovans from Denisova Cave.

The robust primitive shape of the mandible and the very large molars still attached to it suggest that this mandible once belonged to a Middle Pleistocene hominin sharing anatomical features with Neandertals and specimens from the Denisova Cave.

Attached to the mandible was a heavy carbonate crust. By applying U-series dating to the crust, the researchers found that the Xiahe mandible is at least 160,000 years old, representing a minimum age of human presence on the Tibetan Plateau.

The similarities between the Xiahe mandible and other Chinese specimens confirm the presence of Denisovans among the current Asian fossil record. The current study paves the way towards a better understanding of the evolutionary history of Middle Pleistocene hominins in East Asia.

 

Press release from the Chinese Academy of Sciences


brain fossils neuroanatomy

Brain, shape and fossils

Brain, shape and fossils

Emiliano Bruner has just published a paper on the shape of the brain over human evolution, which reviews the evolutionary relationship between humans and the other primates, as well as the most recent methods for comparing the principal variations between brain and cranium

brain fossils neuroanatomy
Credit: Emiliano Bruner

Emiliano Bruner, a paleoneurologist at the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), has just published an overview article in the Journal of Comparative Neurology, on studies of changes in brain shape over the course of human evolution, which considers the evolutionary relationship between humans and the other primates.

Evolutionary neuroanatomy must integrate two different sources of information: fossils and living species. The fossils furnish data on the process of evolution, while living species do the same for the product of evolution. Unfortunately, the fossil record is incomplete and fragmented, and often cannot support validations for specific evolutionary hypotheses. Extant species can offer more comprehensive indications, but they do not represent ancestral groups or primitive forms.

Specifically, this paper reviews the limitations on studies of evolutionary neuroanatomy and the different contributions made by analyses of living primates and extinct hominins. For instance, the great apes are still interpreted as primitive biological models, even though these are species that have evolved independently of the path traced by the human genus. “Macaques or chimpanzees are frequently used as proxy for human ancestral conditions, despite the fact they are divergent and specialized lineages, with their own biological features”, says Bruner.

With regard to the fossils, these can furnish more direct information about the evolutionary process, but the limitations of the samples often do not allow scientific testing of our hypotheses, leading to a lot of guesswork. In fact, as Bruner explains, “independent lineages, such as the Neanderthals, ought not to be confused with ancestral modern human stages”.

Endocranial molds
The paper also introduces the most recent methods for computed morphometrics and biomedical image analysis, describing the principal variations in brains and endocranial molds (endocasts) for modern humans and extinct hominins, in addition to the spatial relationship between brain and cranium in the human genus.

Finally, it proposes integrating anatomical and cultural information with what is known in neurobiology when formulating hypotheses about cognitive evolution. One example would be the evolution of the parietal cortex and its schemes of cerebral connections.

This paper, entitled Human paleoneurology: shaping cortical evolution in fossil hominids, has been published in a volume dedicated to the evolution of the cerebral cortex, edited by Verónica Martínez-Cerdeño and Stephen Noctor, of the University of California at Davis (USA).

 

Full bibliographic information

 

"Human paleoneurology: shaping cortical evolution in fossil hominids", edited by Verónica Martínez-Cerdeño and Stephen Noctor Journal of Comparative Neurology (0). doi: 10.1002/cne.24591

Press release from the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH) / ES


Ardipithecus ramidus Ardi bipedalism quadrupedalism

Human ancestors were 'grounded,' new analysis shows

Human ancestors were 'grounded,' new analysis shows

Primates adapted to living on the ground, adding new chapter to human evolution

 

Ardipithecus ramidus bipedalism
An evolutionary tree depicting the relationships among living apes, Ardi, and modern humans. Each branch on the tree represents a species and their intersections represent their common ancestors. The dots represent hypothetical evolutionary changes associated with the evolution of ground-living adaptations in the common ancestor of African apes and humans as well as the evolution of bipedalism, which is supported by the analysis. This shows that human bipedalism evolved from an ancestral form similar to the living African apes. Credit: Thomas Prang, NYU

African apes adapted to living on the ground, a finding that indicates human evolved from an ancestor not limited to tree or other elevated habitats. The analysis adds a new chapter to evolution, shedding additional light on what preceded human bipedalism.

"Our unique form of human locomotion evolved from an ancestor that moved in similar ways to the living African apes--chimpanzees, bonobos, and gorillas," explains Thomas Prang, a doctoral candidate in New York University's Department of Anthropology and the author of the study, which appears in the journal eLife. "In other words, the common ancestor we share with chimpanzees and bonobos was an African ape that probably had adaptations to living on the ground in some form and frequency."

The way that humans walk--striding bipedalism--is unique among all living mammals, an attribute resulting from myriad changes over time.

"The human body has been dramatically modified by evolutionary processes over the last several million years in ways that happened to make us better walkers and runners," notes Prang.

Much of this change is evident in the human foot, which has evolved to be a propulsive organ, with a big toe incapable of ape-like grasping and a spring-like, energy-saving arch that runs from front to back.

These traits raise a long-studied, but not definitively answered, question: From what kind of ancestor did the human foot evolve?

In the eLife work, Prang, a researcher in NYU's Center for the Study of Human Origins, focused on the fossil species Ardipithecus ramidus ('Ardi'), a 4.4 million-years-old human ancestor from Ethiopia--more than a million years older than the well-known 'Lucy' fossil. Ardi's bones were first publicly revealed in 2009 and have been the subject of debate since then.

In his research, Prang ascertained the relative length proportions of multiple bones in the primate foot skeleton to evaluate the relationship between species' movement (locomotion) and their skeletal characteristics (morphology). In addition, drawing upon the Ardi fossils, he used statistical methods to reconstruct or estimate what the common ancestor of humans and chimpanzees might have looked like.

Here, he found that the African apes show a clear signal of being adapted to ground-living. The results also reveal that the Ardi foot and the estimated morphology of the human-chimpanzee last common ancestor is most similar to these African ape species.

"Therefore, humans evolved from an ancestor that had adaptations to living on the ground, perhaps not unlike those found in African apes," Prang concludes. "These findings suggest that human bipedalism was derived from a form of locomotion similar to that of living African apes, which contrasts with the original interpretation of these fossils."

The original interpretation of the Ardi foot fossils, published in 2009, suggested that its foot was more monkey-like than chimpanzee- or gorilla-like. The implication of this interpretation is that many of the features shared by living great apes (chimpanzees, bonobos, gorillas, and orangutans) in their foot and elsewhere must have evolved independently in each lineage--in a different time and place.

"Humans are part of the natural world and our locomotor adaptation--bipedalism--cannot be understood outside of its natural evolutionary context," Prang observes. "Large-scale evolutionary changes do not seem to happen spontaneously. Instead, they are rooted in deeper histories revealed by the study of the fossil record.

"The study of the Ardi fossil shows that the evolution of our own ground-living adaptation--bipedalism--was preceded by a quadrupedal ground-living adaptation in the common ancestors that we share with the African apes."

 

Press release from the New York University


Middle Pleistocene asian Hualongdong Hualong cave

Middle Pleistocene human skull reveals variation and continuity in early Asian humans

Middle Pleistocene human skull reveals variation and continuity in early Asian humans

Middle Pleistocene asian Hualongdong
The Hualongdong Middle Pleistocene human skull and the collapsed cave site, with the fossil-bearing breccia in beige aournd the limestone blocks. Credit: WU Xiujie and Erik Trinkaus

A team of scientists led by LIU Wu and WU Xiujie from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences reported the first ever Middle Pleistocene human skull found in southeastern China, revealing the variation and continuity in early Asian humans. Their findings were published on April 30 in Proceedings of the National Academy of Sciences (PNAS).

Excavations in Middle Pleistocene cave deposits in southeastern China yielded a largely complete skull that exhibits morphological similarities to other East Asian Middle and Late Pleistocene archaic human remains, but also foreshadows later modern human forms.

Fossil evidence for human evolution in East Asia during the Pleistocene is often fragmentary and scattered, which makes evaluating the pattern of archaic human evolution and modern human emergence in the region complicated.

Middle Pleistocene asian Hualongdong Hualong cave
The virtual reconstruction of the Hualongdong 6 human skull, with mirror-imaged portions in gray, plus two of the few stone tools from the site. Credit: WU Xiujie

WU Xiujie and his colleagues reported the recent discovery of most of a skull and associated remains dating to around 300,000 years ago in Hualong Cave (Hualongdong). The features of the Hualongdong fossils complement those of other East Asian remains in indicating a continuity of form through the Middle Pleistocene and into the Late Pleistocene.

In particular, the skull features a low and wide braincase with a projecting brow but a less prominent midface, as well as an incipient chin. The teeth are simple in form, contrasting with other archaic East Asian fossils, and its third molar is either reduced in size or absent.

According to the authors, the remains not only add to the expected variation of these Middle Pleistocene humans, recombining features present in other individuals from the same time period, but also foreshadow developments in modern humans, providing evidence for regional continuity.

 

Press release from the Chinese Academy of Sciences


Gobihadros mongoliensis Hadrosauridae Mongolia dinosaurs

Meet Gobihadros, a new species of Mongolian hadrosaur

Meet Gobihadros, a new species of Mongolian hadrosaur

This dinosaur sheds light on the evolution of hadrosaurs, dominant herbivores of the Late Cretaceous

Gobihadros mongoliensis Hadrosauridae Mongolia dinosaurs
These are skeletal reconstructions of Gobihadros mongoliensis. Credit: Tsogtbaatar et al, 2019

The complete skeletal remains of a new species of Mongolian dinosaur fill in a gap in the evolution of hadrosaurs, according to a study released April 17, 2019 in the open-access journal PLOS ONE by Khishigjav Tsogtbataaar of the Mongolian Academy of Science, David Evans of the Royal Ontario Museum, and colleagues.

Dinosaurs of the family Hadrosauridae were widespread and ecologically important large herbivores during the Late Cretaceous Period, but little is known about their early evolution. In recent years, many new species closely related to Hadrosauridae have been filling in this picture, but few complete remains are known from the early part of the Late Cretaceous, which is when the group originated.

In this study, Tsongbataar and colleagues describe a new species closely related to Hadrosauridae, Gobihadros mongoliensis. The species is represented by numerous specimens, including one virtually complete skeleton measuring almost three meters long. The new dinosaur was discovered in the Bayshin Tsav region of the Gobi Desert in Mongolia from rocks dating to the early part of the Late Cretaceous. Anatomical analysis reveals that this species doesn't quite fit into the family Hadrosauridae, but is a very close cousin, making it the first such dinosaur known from complete remains from the Late Cretaceous of central Asia.

Comparing Gobihadros to Asian species within Hadrosauridae, the researchers conclude that Gobihadros did not directly give rise to later Asian hadrosaurs. Instead, those Asian hadrosaurs appear to have migrated over from North America during the Late Cretaceous. Gobihadros and its close Asian relatives seem to disappear as these new hadrosaurs enter Asia, suggesting that the invaders might have ultimately outcompeted species like Gobihadros. However, the authors caution that more fossil data is still needed to properly resolve the ages and locations of these dinosaurs during this important transition period.

The authors add: "The article describes, for the first time, extraordinary well-preserved fossil material of hadrosauroid dinosaur as a new genus and species from the early Late Cretaceous in Mongolia. We hope that it will be very useful material for further study of the evolution of hadrosauroids, iguanodintians and ornithopods as well. However, the relationships of other taxa are well-resolved, and in combination with biostratigraphic data, suggest that hadrosaurids from the Maastricthian of Asia migrated from North America across Beringia in the Campanian, and replaced non-hadrosaurids such as Gobihadros."

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Citation: Tsogtbaatar K, Weishampel DB, Evans DC, Watabe M (2019) A new hadrosauroid (Dinosauria: Ornithopoda) from the Late Cretaceous Baynshire Formation of the Gobi Desert (Mongolia). PLoS ONE 14(4): e0208480. https://doi.org/10.1371/journal.pone.0208480

Funding: Funding for this project was provided by Hayashibara Museum of Natural Sciences. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing Interests: The authors have declared that no competing interests exist.

 

Press release from the Public Library of Science (PLOS)


human face hominins evolution

Need for social skills helped shape modern human face

Need for social skills helped shape modern human face

The modern human face is distinctively different to that of our near relatives and now researchers believe its evolution may have been partly driven by our need for good social skills

This is professor Paul O'Higgins from the University of York. Credit: University of York

The modern human face is distinctively different to that of our near relatives and now researchers believe its evolution may have been partly driven by our need for good social skills.

As large-brained, short-faced hominins, our faces are different from other, now extinct hominins (such as the Neanderthals) and our closest living relatives (bonobos and chimpanzees), but how and why did the modern human face evolve this way?

A new review published in Nature Ecology and Evolution and authored by a team of international experts, including researchers from the University of York, traces changes in the evolution of the face from the early African hominins to the appearance of modern human anatomy.

They conclude that social communication has been somewhat overlooked as a factor underlying the modern human facial form. Our faces should be seen as the result of a combination of biomechanical, physiological and social influences, the authors of the study say.

The researchers suggest that our faces evolved not only due to factors such as diet and climate, but possibly also to provide more opportunities for gesture and nonverbal communication - vital skills for establishing the large social networks which are believed to have helped Homo sapiens to survive.

"We can now use our faces to signal more than 20 different categories of emotion via the contraction or relaxation of muscles", says Paul O'Higgins, Professor of Anatomy at the Hull York Medical School and the Department of Archaeology at the University of York. "It's unlikely that our early human ancestors had the same facial dexterity as the overall shape of the face and the positions of the muscles were different."

human face hominins evolution
These are skulls of hominins over the last 4.4 million years. Credit: Rodrigo Lacruz

Instead of the pronounced brow ridge of other hominins, humans developed a smooth forehead with more visible, hairy eyebrows capable of a greater range of movement. This, alongside our faces becoming more slender, allows us to express a wide range of subtle emotions - including recognition and sympathy.

"We know that other factors such as diet, respiratory physiology and climate have contributed to the shape of the modern human face, but to interpret its evolution solely in terms of these factors would be an oversimplification," Professor O'Higgins adds.

The human face has been partly shaped by the mechanical demands of feeding and over the past 100,000 years our faces have been getting smaller as our developing ability to cook and process food led to a reduced need for chewing.

This facial shrinking process has become particularly marked since the agricultural revolution, as we switched from being hunter gatherers to agriculturalists and then to living in cities - lifestyles that led to increasingly pre-processed foods and less physical effort.

"Softer modern diets and industrialised societies may mean that the human face continues to decrease in size", says Professor O'Higgins. "There are limits on how much the human face can change however, for example breathing requires a sufficiently large nasal cavity."

"However, within these limits, the evolution of the human face is likely to continue as long as our species survives, migrates and encounters new environmental, social and cultural conditions."

 

 

The Evolutionary History of the Human Face is published in Nature Ecology and Evolution. The review was carried out in collaboration with colleagues from international institutions including the New York University College of Dentistry, the Natural History Museum, Arizona State University and Universidad Complutense de Madrid.

Press release from the University of York