New evidence of the Sahara's age

By: Thomas Schmitt Attorney on September 23, 2019 / comment : 0 Canary Islands, Climate Change, Earth Science, Geology, North Africa, Palaeoclimate, Palaeontology

The Sahara Desert is vast, generously dusty, and surprisingly shy about its age. New research looking into what appears to be dust that the Sahara blew over to the Canary Islands is providing the first direct evidence from dry land that the age of the Sahara matches that found in deep-sea sediments: at least 4.6 million years old.

Desert dust from Africa is transported west to the Canary Islands and the CapeVerde Islands every year. Moderate Resolution Imaging Spectroradiometer (MODIS) image of "Calima" (dust storm) event on 8 March 2006, taken from the Terra satellite [Credit: Jeff Schmaltz, MODIS Land Rapid Response Team at NASA/GSFC]

"People have been trying to figure it out for several decades," said Daniel Muhs, a geologist with the U.S. Geological Survey in Denver, Colorado. "More recent studies said it was the beginning of the Pleistocene (about 2.6 million years ago). Then others say a few thousand years ago." Added to this is a model suggesting the Sahara Desert first appeared as far back as seven million years ago.

There is also other evidence that the desert has taken breaks and had wetter, greener periods interspersed with arid times. It's this sensitivity to climate -- and the Sahara's role in global climate -- that makes the region so interesting to researchers.

The new work by Muhs and his colleagues in the Canary Islands focused on thick layers of fine reddish-brown soil found among layers of volcanic rocks and dune sands on Fuerteventura and Gran Canaria islands. The islands are off the west coast of North Africa, at the mouth of a spigot that seasonally pours windblown dust off of the Sahara and across the Atlantic Ocean. Muhs presented the results at the annual meeting of the Geological Society of America in Phoenix, Arizona.

A paleosol on the island of Gran Canaria, sandwiched between basalt flows dated to 3.0-2.9 million years ago - to the Pliocene [Credit: Daniel Muhs]

Muhs's and his colleagues' mission was to find, identify, and date any layers of ancient African dust in what are called paleosols, or buried, ancient soils. In one coastal location studied, they found layers of dunes made from local shells of sea animals; in another, there were layers of lava from the volcanoes that built the islands. Both of these geologic archives contained paleosols made of very fine-grained minerals rich in quartz and mica--minerals that do not reflect the local geology of the islands. They do, however, reflect the minerals found on the nearby African mainland.

Luckily for the geologists, the lava flows that sandwich the windblown fine-grained quartz and mica layers made it possible to nail down approximate ages of the Saharan dust. This is because volcanic rocks contain minerals with what are essentially isotopic clocks that start ticking when the minerals in the lava cool and solidify. And since the layers of lava, paleosols, and other local soils are stacked chronologically with the youngest on top, the lava flows provide some boundaries of when the Sahara was dry enough to launch massive dusty storms out over the Atlantic.

In all, the researchers report eight paleosols that record African dust piling up in the Canaries between about 4.8 and 2.8 million years ago, 3.0 to 2.9 million years ago, and at about 400,000 years ago. The oldest paleosols agree with the deep-sea cores, which put the earliest Sahara dust to the Atlantic at about 4.6 million years ago.

View from the ground on the Canary Islands on 8 March 2006, when the Calima arrived [Credit: Daniel Muhs]

That's not to say the Sahara is 4.6-million-years-old. That's only as old as Muhs and his colleagues could determine based on the paleosols and lavas they found.

"We could take it further back in time if we can find the paleosols," Muhs said.

Source: Geological Society of America [September 23, 2019]

Experts sequence the genome of an endemic spider from the Canary Islands

By: Thomas Schmitt Attorney on September 05, 2019 / comment : 0 Biodiversity, Biology, Canary Islands, Evolution, Genetics

A research team of the Faculty of Biology and the Biodiversity Research Institute (IRBio) of the University of Barcelona has sequenced the genome of the spider Dysdera silvatica Schmidt 1981, an endemic species living in the laurel forests in the islands La Gomera, La Palma, and El Hierro -in the Canary Islands (Spain).

This species, which lives in the insular laurel forests in the Canary Islands (Spain), is a big generalist predator  that does not use a web to hunt its prey [Credit: Miquel Arnedo (UB-IRBio)]

The new study reveals the first genome sequencing of an arthropod in the Canary Islands, an archipelago with a rich biodiversity regarding endemic species that are distributed around the insular area.

Participants in the new study, published in the journal GigaScience, are the experts Julio Rozas, Miquel Arnedo, Jose Francisco Sanchez-Herrero, Cristina Frias-Lopez, Paula Escuer, Silvia Hinojosa-Alvarez and Alejandro Sanchez-Gracia (UB-IRBio).

Dysdera sylvatica: a ravening predator in the Canary laurel forests

The Dysdera genus, which belongs to the species Dysdera silvatica, includes more than 250 spider species mainly distributed around the Mediterranean area. The Macaronesian archipelagos represent the western limits of the distribution of this taxon, which reached a significant diversification in the Canary Islands, where there are about 50 endemic species currently.

"One of these species is Dysdera silvatica, integrated in an evolutionary lineage that became one of the main predators -both in abundance and diversity- in the insular terrestrial invertebrate trophic networks", notes Professor Miquel Arnedo, from the Department of Evolutionary Biology, Ecology and Environmental Sciences of the Faculty of Biology and the Biodiversity Research Institute (IRBio) of the UB.

"The species D. silvatica is a generalist predator. Unlike other spider groups, the Dysdera includes experts on hunting and consumption of terrestrial isopods. All these species live in the Canary Islands, where the crustacean trophic specialization seems to have evolved independently several times", adds the researcher, head of the research group on Arthropod Systematics and Animal Evolution of the UB.

The first genome sequencing in the Dysderoidea superfamily

This is the first sequencing of the nuclear and mitochondrial genome for a species of the Dysderoidea superfamily, and the second one known in the Synspermiata group, one of the main spider lineages. Regarding this group, the first species with the available genomic data was the brown recluse spider (Loxoceles reclusa Gertsch & Mulaik, 1940), a species distributed around the American continent and quite known for its necrotic venom.

According to the conclusions, the genome of the D. silvatica species is large (1.7 Gb) and shows a high complexity, with a high fraction of repetitive elements. According to Professor Julio Rozas (UB-IRBio), who co-led the study together with Alejandro Sanchez-Garcia, "Within this study, we created a 1.4 Gb genomic sequencing assembly, 54 % of which is built by repetitive elements"

"We identified and characterized a total of 36,000 protein-coding gens", notes Professor Julio Rozas (UB-IRBio), head of the research group on Evolutionary Genomics and Bioinformatics at the UB, part of the platform Bioinformatics Barcelona (BIB).

The D. silvatica species has a diploid chromosome set of six pairs of autosomes and two (females are XX) or one (males are X0) sex chromosomes (XX-X0), females have six non-sexual chromosome pairs (autosomes) and the XX sexual paired chromosomes. Males have six pairs of autosomes and only one X sexual chromosome.

Third generation sequencing techniques to treat a complex genome

The research study to sequence the genome of Dysdera silvatica started about five years ago with the application of next generation massive sequencing (NGS) such as Illumina. With this protocol, they created one billion short sequences (100 paired bases) that were not enough to get a quality assembly for the complex genome of the species.

Therefore, the research team completed these data with PacBio and Nanopore single molecule sequencing (SMS) techniques, "more expensive but more efficient methodologies to obtain larger genome sequencing, and provide a quality genomic assembly using the hybrid assembly strategy, combining data from the obtained sequencing through different technologies", notes Jose Francisco Sanchez-Herrero, member of the Department of Genetics, Microbiology and Statistics of IRBio and first author of the article.

Ecology, evolution and reproductive behaviour

From a global perspective, the study brings new views to know more about the genetic bases of the eco-phenotype change that takes place during the adaptive radiation phenomena over biological evolution.

In particular, the models from the Dysdera genus in the Canary Islands, the genome sequencing of this first species can bring valuable information on the underlying genetic architecture in the phenotype and physiological changes related to the trophic specialization, as well as the underground environment adaptations, a natural environment where some species got used to live exclusively in the lava tubes.

Regarding their reproductive behavior, the Dysderidae family includes species that show a cryptic female choice mechanism, that is, a reproductive strategy which consists on the female's post-copulatory choice of a male's sperm to fertilize their ova. This choice is conducted through a complex system of diverticulum and glands associated with the female vulva. Knowing the features of the genome of a species from this family could contribute to determine the genetic bases of this behavior, through a comparative study of several regions of the genome under different selective constrictions between sexes, and among species with different sexual strategies.

Last, the study provides useful resources to treat studies on other evolutionary and essential issues, such as the origins and evolution of products with medical and commercial interests produced by spiders (venom, silk, etc.).

Source: University of Barcelona [September 05, 2019]

North Africans were among the first to colonize the Canary Islands

By: Thomas Schmitt Attorney on March 20, 2019 / comment : 0 Anthropology, Canary Islands, Genetics, North Africa

People from North Africa are likely the main group that founded the indigenous population on the Canary Islands, arriving by 1000 CE, reports a new study by Rosa Fregel of Stanford University, USA and Universidad de La Laguna, Spain, and colleagues, published in the open-access journal PLOS ONE.

A petroglyph in the Canary Islands [Credit: WikiCommons]

Numerous studies of the culture and genetics of indigenous people living in the Canary Islands, an archipelago off the coast of Morocco, point to North African Berbers as the founders, but more recent human activities -- such as the Spanish conquest, the start of sugarcane plantations and the slave trade -- have changed the indigenous population's genetic makeup.

To shed light on who first colonized the archipelago, researchers analyzed 48 ancient mitochondrial genomes from 25 archaeological sites across the seven main islands. They selected mitochondrial genomes because, since they are inherited directly from the mother, they are especially consistent and useful for tracking human migrations.

The researchers discovered lineages that have only been observed in Central North Africa, and others that have a wider distribution including both West and Central North Africa, and, in some cases, Europe and the Near East. They also identified four new lineages specific to the Canary Islands, which, when analyzed together, are consistent with radiocarbon dating evidence showing that people reached the islands by 1000 CE.

Additionally, the researchers found that the distribution of the different lineages on each island varies depending on the island's distance from the continent, which supports previous studies finding that the islands experienced at least two distinct early migration events.

The Canary Islands lineages discovered in this study fit into a larger pattern of Mediterranean migration through North Africa, as part of the Neolithic expansion of humans from the Middle East to Europe and Africa. The presence of these Mediterranean lineages suggests that the Berbers had already mixed with Mediterranean groups at the time that they colonized the islands.

The authors add: "Using next-generation techniques, we have been able to obtain ancient DNA of the indigenous population of all the seven Canary Islands for the first time. Our results indicate that mitochondrial DNA diversity is variable within the archipelago, suggesting that the colonization of the islands was a heterogeneous process and that the different islands had different evolutionary histories."

Source: Public Library of Science [March 20, 2019]

Two mummified Guanche children discovered inside cave on volcanic island of Tenerife

By: Thomas Schmitt Attorney on December 09, 2018 / comment : 0 Archaeology, Canary Islands, Indigenous Cultures

A pair of spider-hunters stumbled across the mummified remains of two babies that lived 500 years ago in a Tenerife cave. The mummified infants are believed to be Guanche children, the aboriginal inhabitants of the Canary Islands before the Spanish conquest which began in 1402.

The mummified infants are believed to be Guanche children, the aboriginal inhabitants of the Canary Islands  before the Spanish conquest which began in 1402 [Credit: CEN/Cabildo Tenerife]

One child was wrapped in animal skin and is better preserved than the other, with soft tissue and organs in tact. The other infant is more degraded and only skeletal fragments remain. It is believed the cave is a burial site dating back to the 15th century. It is the first found on the island since 1969.

Sergio Marrero and Domingo Garcia, locals on the island, were looking for a rare white spider when they ventured inside the cave near the town of Guia de Isora in western Tenerife, Director of the Canarian Institute of Bioanthropology, Conrado Rodriguez-Maffiotte, said: 'The remains date before the 16th century for certain, but we need to carry out more tests to confirm that.'     

One child was wrapped in animal skin and is better preserved than the other, with soft tissue and organs in tact.  The other infant is more degraded and only skeletal fragments remain  [Credit: CEN/Cabildo Tenerife]

The mummified Guanche infants are not believed to be twins but their relationship is still being determined  through DNA analysis. Experts are also working on establishing their cause of death  [Credit: CEN/Cabildo Tenerife]

It was reported that animal remains were also found in the cave that is believed to be made from lava and sits  at 4,500 feet (1,390 metres) above sea level [Credit: CEN/Cabildo Tenerife]

The mummified Guanche infants are not believed to be twins but their relationship is still being determined through DNA analysis. Experts are also working on establishing their cause of death. Dr Rodriguez-Maffiote said: 'I have never seen a ritual burial of two babies together.'

It was reported that animal remains were also found in the cave that is believed to be made from lava and sits at 4,500 feet (1,390 metres) above sea level. Lava for the cave likely came from Mount Teide, the active volcano that sits atop the island in the archipelago of the west coast of Africa.

Lava for the cave likely came from Mount Teide, the active volcano that sits atop the island in the archipelago  of the west coast of Africa [Credit: CEN/Cabildo Tenerife]

The Guanche civilisation was eventually destroyed after the Spanish invaded the islands. They were hunter-gatherer  tribes who lived a lifestyle much like it is supposed that people lived in the Stone Age and may have  buried their dead in caves [Credit: CEN/Cabildo Tenerife]

Soldiers took Lanzarote and Fuerteventura quite easily, but the primitive inhabitants of the other five islands - Tenerife,  Gran Canaria, La Palma, La Gomera and El Hierro - fought back. Tenerife was the last to be conquered in 1496  [Credit: CEN/Cabildo Tenerife]

The Guanche civilisation was eventually destroyed after the Spanish invaded the islands. Guanches were the aboriginal inhabitants of the Canary Islands. They were hunter-gatherer tribes who lived a lifestyle much like it is supposed that people lived in the Stone Age.

Soldiers took Lanzarote and Fuerteventura quite easily, but the primitive inhabitants of the other five islands - Tenerife, Gran Canaria, La Palma, La Gomera and El Hierro - fought back. Tenerife was the last to be conquered in 1496.


In 2017, the first genome-wide data from the Guanches confirmed they were of North African origin. There are suggestions that the light-skinned people descended from the Berbers of North Africa, possibly Libya. It is believed that they migrated to the archipelago around 1,000 BC from North Africa.

What we do know of the mysterious people is derived from the work of Spanish Chroniclers and from archaeological discoveries.

Earlier this year, a studemt at the University of Dundee recreated the face of a Guanche woman who lived  more than 600 years ago using forensic techniques and 3D scanning. Karina Osswald recreated the face of a Guanche woman using her skull.

A woman who died more than 600 years ago, before the Canary archipelago was invaded by Spanish sailors, was brought back to life using forensic techniques and 3D imaging. The civilisation went extinct soon afterwards and little traces remain of the Gaunche people [Credit: PA]

She said: 'The true identity of the Guanche people has long remained a mystery – with the literary accounts of invading Spaniards being some of the only real information left about these intriguing indigenous people.

'During this project, I ended up learning so much about the Guanche and I hope her image will inspire others to find out more about this ancient population.'

Author: Joe Pinkstone | Source: DailyMail [December 09, 2018]