‘Jellyfish, not sponges, oldest animals’


This video says about itself:

23 October 2015

Put the comb jelly in the spotlight and watch it groove. The sea creatures turn into pulsating rainbows of movement under the right lighting, no disco ball needed.

From Vanderbilt University in the USA:

Forget sponges: The earliest animals were marine jellies

April 10, 2017

Summary: One of the longest-running controversies in evolutionary biology has been, ‘What was the oldest branch of the animal family tree?’ Was it the sponges, as had long been thought, or was it the delicate marine predators called comb jellies? A powerful new method has been devised to settle contentious phylogenetic tree-of-life issues like this and it comes down squarely on the side of comb jellies

When cartoonist and marine-biology teacher Steve Hillenburg created SpongeBob SquarePants in 1999, he may have backed the wrong side of one of the longest-running controversies in the field of evolutionary biology.

For the last decade, zoologists have been battling over the question, “What was the oldest branch of the animal family tree?” Was it the sponges, as they had long thought, or was it a distinctly different set of creatures, the delicate marine predators called comb jellies? The answer to this question could have a major impact on scientists’ thinking about how the nervous system, digestive tract and other basic organs in modern animals evolved.

Now, a team of evolutionary biologists from Vanderbilt University and the University of Wisconsin-Madison have devised a new approach designed specifically to settle contentious phylogenetic tree-of-life issues like this. The new approach comes down squarely on the side of comb jellies.

The method and its application to this and 17 other controversial phylogenetic relationships was published online on Apr. 10 by the journal Nature Ecology & Evolution in an article titled “Resolution of contentious relationships in phylogenomic studies can be driven by one or a handful of genes.”

For nearly a century, scientists organized the animal family tree based in large part on their judgement of the relative complexity of various organisms. Because of their comparative simplicity, sponges were considered to be the earliest members of the animal lineage. This paradigm began to shift when the revolution in genomics began providing vast quantities of information about the DNA of an increasing number of species. Evolutionary biologists started to apply this wealth of information to refine and redefine evolutionary relationships, creating a new field called phylogenomics. In most cases, the DNA data helped clarify these relationships. In a number of instances, however, it gave rise to controversies that intensified as more and more data accumulated.

In 2008, one of the early phylogenomic studies fingered the comb jellies (aka ctenophores) as the earliest members of the animal kingdom, rather than sponges. This triggered an ongoing controversy with the latest round being a massive study published last month that marshalled an unprecedented array of genetic data to support the sponges’ position as the first animal offshoot.

“The current method that scientists use in phylogenomic studies is to collect large amounts of genetic data, analyze the data, build a set of relationships and then argue that their conclusions are correct because of various improvements they have made in their analysis,” said Antonis Rokas, Cornelius Vanderbilt Professor of Biological Sciences, who devised the new approach with Vanderbilt postdoctoral scholar Xing-Xing Shen and Assistant Professor Chris Todd Hittinger from the University of Wisconsin-Madison. “This has worked extremely well in 95 percent of the cases, but it has led to apparently irreconcilable differences in the remaining 5 percent.”

Rokas and his collaborators decided to focus on 18 of these controversial relationships (seven from animals, five from plants and six from fungi) in an attempt to figure out why the studies have produced such strongly contradictory results. To do so, they got down into the weeds, genetically speaking, and began comparing the individual genes of the leading contenders in each relationship.

“In these analyses, we only use genes that are shared across all organisms,” Rokas said. “The trick is to examine the gene sequences from different organisms to figure out who they identify as their closest relatives. When you look at a particular gene in an organism, let’s call it A, we ask if it is most closely related to its counterpart in organism B? Or to its counterpart in organism C? And by how much?”

These analyses typically involve hundreds to thousands of genes. The researchers determined how much support each gene provides to one hypothesis (comb-jellies first) over another (sponges first). They labeled the resulting difference a “phylogenetic signal.” The correct hypothesis is the one that the phylogenetic signals from the most genes consistently favor.

In this fashion, they determined that comb jellies have considerably more genes which support their “first to diverge” status in the animal lineage than do sponges.

Another contentious relationship the researchers addressed was whether crocodiles are more closely related to birds or turtles. They found that 74 percent of the shared genes favor the hypothesis that crocodiles and turtles are sister lineages while birds are close cousins.

In the course of their study, they also discovered that in a number of contentious cases one or two “strongly opinionated genes” among all the genes being analyzed appear to be causing the problem because the statistical methods that evolutionary biologists have been using are highly susceptible to their influence.

In some cases, such as the controversies over the origins of flowering plants and modern birds, they determined that the removal of even a single opinionated gene can flip the results of an analysis from one candidate to another. In cases like this, the researchers were forced to conclude that the available data is either inadequate to support a definitive conclusion or it indicates that the diversification occurred too rapidly to resolve.

“We believe that our approach can help resolve many of these long-standing controversies and raise the game of phylogenetic reconstruction to a new level,” Rokas said.

Ancient bird Archaeopteryx and Donald Trump


This video says about itself:

23 May 2014

In 1860 in Germany, an unusual fossil was found that shocked the world. It seemed to be a strange combination of a dinosaur and a bird. It was the 150 million-year-old fossil of Archaeopteryx. The skeleton looked like a normal two-legged meat-eating dinosaur, but it had one very special feature: feathers. Its feathers are how it got its name, which means “ancient wing”.

By Peter Frost in Britain:

Archaeopteryx takes to the skies

Friday 24th March 2017

The fossil which proved the evolutionary link between dinosaurs and birds is on tour. PETER FROST explains why this scientific discovery is still relevant today

CHARLES DARWIN published his earth-shattering book On the Origin of Species in 1859. The book outlined the theory of evolution that is still, despite its compelling evidence, being argued about today, especially in the United States bible belt and even in President Donald Trump’s White House.

Part of Darwin’s argument predicted finding fossil evidence for the transitional stage between dinosaurs and what would become birds. At the time of his writing, Darwin predicted that evidence would be uncovered to prove his theory. Critics scoffed and noted the absence of any fossil evidence.

Then in 1861, just two years after his book was published, the fossil of a single feather was uncovered in the limestone layers of Solnhofen in Bavaria, southern Germany. It was clear evidence for the transitional fossil between dinosaurs and birds that Darwin had predicted. The great scientist was vindicated, to the dismay of his critics.

That same year more proof arrived when the first complete specimen of Archaeopteryx was discovered. That first skeleton, later to be known as “the London specimen,” was unearthed near Langenaltheim, Germany. It finally proved the link between dinosaurs and birds.

The fossil was given to local physician Karl Haberlein in return for medical services. Over the years, ten more fossils of Archaeopteryx have surfaced all in the same limestone layers of Solnhofen.

These fossil archaeopteryx have since become key evidence for the origin of birds, the transitional fossils debate and the confirmation of evolution.

The original German fossil was purchased by Britain in 1863 for £700 and was kept initially at the British Museum. When the Natural History Museum opened in South Kensington in 1881, the fossil became one of its most important exhibits.

Until this year it had never left the museum, but since March 18 it has been the star exhibit in a travelling exhibition at the National Museum of Nature and Science in Tokyo.

At first glance the fossil might seem to be just a ragtag assortment of bones, but on closer inspection you can understand why Archaeopteryx is so interesting and important.

Today, the thin limestone slabs that contain the bones of this pivotal creature are considered priceless. If one ever came to auction it would sell for millions of pounds.

The delicate stone has been carefully reinforced using a strong plastic resin but is still incredibly delicate. Museums officials are satisfied the iconic fossil will come to no harm in transit or during its time on display in Japan.

The Archaeopteryx fossil has beautiful impressions of feathers and wings — like a bird. But then it also displays the claws, the long bony tail and the serrated teeth more normally associated with dinosaurs.

Archaeopteryx was roughly the size of a small chicken, with broad wings that were rounded at the ends and a long tail compared to its body length.

Its feathers were very similar in structure to modern-day bird feathers. Unlike modern birds, Archaeopteryx had small teeth as well as a long bony tail, features which the species shared with other dinosaurs of the time.

Directors of modern dinosaur films may have used their computers to make Archaeopteryx into a soaring elegant flyer — something like a giant condor. In reality, it was probably an ungainly beast capable only of flapping flight from one low shrub to another.

In a world where more and more fundamentalist religious views are arguing against the science of evolution, it is important that the convincing evidence of fossils is made as widely known as possible.

President Trump and Vice-President Mike Pence were asked for their thoughts on evolution and Darwin. Pence told Congress he believed in teaching creationism in schools to balance out the theory of evolution.

In answer to a journalists question, he replied: “Do I believe in evolution? I embrace the view that God created the heavens and the Earth, the seas and all that’s in them.”

Pence wants the biblical story of creation taught in biology class alongside evolution.

With backwoodsman Trump as president, it will certainly happen.

Sadly the pair of them are in good company as many people in the United States agree with them.

While the majority of people in Europe and in many other parts of the world accept evolution, the United States lags behind.

Today, four in every 10 adults in the US believe that humans have existed in our present form since the beginning of time. In many religious groups, that number is even higher.

Perhaps then it is good news that the remarkable Archaeopteryx fossil is making the journey to Tokyo as just one of 300 exhibits from the collection of London’s Natural History Museum.

The travelling exhibition features all sorts of objects, including many animals that inspired Darwin directly and demonstrate the truth of evolution.

The artefacts range from a lion from the royal menagerie to an exquisite glass model of an octopus. All have a fascinating science backstory.

“Science is a global endeavour fuelled by wonder and curiosity. So it has been an ambition for us to share these extraordinary treasures with a wider audience,” Natural History Museum director Sir Michael Dixon told us.

“They are the essence of the scientific exploration that inspired pioneers and continues today at the Natural History Museum.”

Other destinations for this exciting touring exhibition beyond Japan will be announced in due course, but I doubt they will be welcome in Trump and Pence’s Washington.

Computer game on evolution of bird flight


This video from the USA says about itself:

Flap to the Future – American Robin

7 February 2017

HELFUL TIP: I play through the level twice. Skip to 3:02 for former personal best time.

Wowza, wowza! A bird game! Of course I’m going to play it longer than I should.

Cornell Lab of Ornithology sent out an email today about this game, so I tried it out and maybe got somewhat good at the American Robin stage. It’s a super easy stage assuming you have a good path routed and can pull off a few tight maneuvers. Though my time is very beatable, I’ll leave it as is since it seems that my new best times aren’t being posted on the leaderboards for some reason. I could always go back and restart my file to have a new best time posted, but I really don’t want to lose the random generated name I currently have on my account. I’ll just have to deal with my initial 05:30.17 minute clear time on the leaderboards.

EDIT: The leaderboards are now functional beyond the initial completion of a level! However, I accidentally reset my game like an idiot, and as such, Lilac-feathered Friendly Heron will forever be displayed with mediocre completion times.

My current mobile name is now Agile Tourmaline-backed Heron, and my current PC name is Least-bearded Fluffheron.

From the Cornell Lab of Ornithology in the USA:

Video Game Lets You Scamper, Glide, and Flap Through the Evolution of Flight

Skip through time and explore how birds mastered the skies with our new video game. Start as an earthbound dinosaur and then feel the thrill of feathered wings and flapping flight. Then jump ahead 100 million years from now to imagine the future of flight. The game is free, mobile-friendly, and runs in a web browser. There’s no app download necessary—just an interest in dinosaurs, flight, or video games. Visit Bird Academy to play (and—bonus—find out your very own fanciful bird name).

Horse evolution, new study


This video says about itself:

7 August 2015

The “evolution of the horse” occurred over a period of 50 million years, transforming the small, dog-sized, forest-dwelling “Eohippus” into the modern horse. Paleozoologists have been able to piece together a more complete outline of the evolutionary lineage of the modern horse than of any other animal.

The horse belongs to the order Perissodactyla, the members of which all share hooved feet and an odd number of toes on each foot, as well as mobile upper lips and a similar tooth structure. This means that horses share a common ancestry with tapirs and rhinoceroses. The perissodactyls arose in the late Paleocene, less than 10 million years after the Cretaceous–Paleogene extinction event. This group of animals appears to have been originally specialized for life in tropical forests, but whereas tapirs and, to some extent, rhinoceroses, retained their jungle specializations, modern horses are adapted to life on drier land, in the much harsher climatic conditions of the steppes. Other species of “Equus” are adapted to a variety of intermediate conditions.

The early ancestors of the modern horse walked on several spread-out toes, an accommodation to life spent walking on the soft, moist grounds of primeval forests. As grass species began to appear and flourish, the equids’ diets shifted from foliage to grasses, leading to larger and more durable teeth. At the same time, as the steppes began to appear, the horse’s predecessors needed to be capable of greater speeds to outrun predators. This was attained through the lengthening of limbs and the lifting of some toes from the ground in such a way that the weight of the body was gradually placed on one of the longest toes, the third.

From Science News:

Horse evolution bucks evolutionary theory

Speciation events not accompanied by big changes in teeth and body size

BY RACHEL EHRENBERG, 2:00PM, FEBRUARY 9, 2017

A cautionary tale in evolutionary theory is coming straight from the horse’s mouth. When ancient horses diversified into new species, those bursts of evolution weren’t accompanied by drastic changes to horse teeth, as scientists have long thought.

A new evolutionary tree of horses reveals three periods when several new species emerged, scientists report in the Feb. 10 Science. The researchers found that changes in teeth morphology and body size didn’t change very much during these periods of rapid speciation.

“This knocks traditional notions that rapid diversification of new species comes with morphological diversification as well,” says paleontologist Bruce MacFadden of the University of Florida in Gainesville. “This is a very sophisticated and important paper.”

The emergence of several new species in a relatively short time is often accompanied by the evolution of special new traits. Classic notions of evolution say that these traits — such as longer teeth with extensive enamel — are adaptive, enabling an animal to succeed in a particular environment. In horses, the evolution of such teeth might permit a shift from browsing on leafy, shrubby trees to grazing on grasses in open spaces with windblown dust and grit.

“You can’t live on a grassland as a grazer and have short teeth,” says MacFadden, an expert in horse evolution. “You’ll wear your teeth down and that’s not a recipe for success as a species.”

Similarly, a big change in body size can indicate a move to a new environment. Animals that live in forests tend to be smaller and more solitary than the larger herd animals that live in open grasslands.

Paleontologist Juan Cantalapiedra and colleagues compiled decades of previous work to create an evolutionary tree of 138 horse species (seven of which exist today), spanning roughly 18 million years. The tree reveals three major branchings of new species: a North American burst between 15 million and 18 million years ago, and two bursts coinciding with dispersals into Eurasia about 11 million and 4.5 million years ago.

The researchers expected to see evidence of an “adaptive radiation,” major changes in teeth and body size that allowed the new horse species to succeed. But rates of body size evolution didn’t differ much in sections of the family tree with low and high speciation rates. And rates of change in tooth characteristics were actually lower in sections of the tree with fast speciation rates, the team reports.

“It’s very tempting to see some change in body size, for example, and say, ‘Oh, that’s adaptive radiation,’” says Cantalapiedra, of the Leibniz Institute for Evolution and Biodiversity Science at the Museum für Naturkunde in Berlin. “But that’s not what we see.”

Cantalapiedra and his collaborators speculate that during the periods of rapid speciation, the environment was so expansive and productive that there just wasn’t a lot of competition to drive the evolution of adaptive traits. Perhaps, for example, North American grasslands were so rich and dense that there was enough energy for various species to evolve without having to develop traits that gave them an edge.

That scenario might be special to horses, says MacFadden, but it might not. Similarly, classic adaptive radiation scenarios might be true in many cases, but as this work shows, not always.

Tiger tail seahorses, new research


This 2013 video shows baby tiger tail seahorses, one day old.

From Science News:

Genome clues help explain the strange life of seahorses

by Cassie Martin

4:30pm, December 14, 2016

A seahorse’s genetic instruction book is giving biologists a few insights into the creature’s odd physical features and rare parenting style.

Researchers decoded a male tiger tail seahorse’s (Hippocampus comes) genome and compared it to the genomes of other seahorses and ray-finned fishes. The analysis revealed a bevy of missing genes and other genetic elements responsible for enamel and fin formation. The absence of these genes may explain their tubelike snouts, small toothless mouths, armored bodies and flexible square tails, the team reports online December 14 in Nature.

Although H. comes may be short a few genes, the seahorse has a surplus of other genes important for male pregnancy — a trait unique to seahorses, sea dragons and pipefish. These genetic differences suggest the tiger tail seahorse has evolved more quickly than its relatives, the researchers conclude.

Origin of the universe, evolution of life, new film


This video from the USA says about itself:

Voyage of Time IMAX® Trailer

30 June 2016

Voyage of Time: The IMAX Experience, a 40-minute, giant-screen adventure narrated by Brad Pitt, which immerses audiences directly into the story of the universe and life itself, will be shown exclusively in IMAX® theatres. For more info, visit here.

From Science News:

‘Voyage of Time’ is Terrence Malick’s ode to life

Film offers an artistic take on science

By Erin Wayman

4:38pm, October 7, 2016

Condensing billions and billions and billions of years into a 45-minute film is a tall order. But director Terrence Malick took on the challenge with Voyage of Time. The film, now playing in IMAX theaters, surveys the 13.8-billion-year history of the universe and even looks eons into the future when we — life on Earth, the planet and the entire solar system — are gone.

Starting with the Big Bang, Voyage of Time progresses through highlights of the past, with a central focus on the evolution of life. Malick, best known for directing visually rich dramas such as The Thin Red Line and The Tree of Life, presents breathtaking cinematography, using locales such as Hawaii’s lava-oozing Kilauea volcano as stand-ins for the past. Stunning visualizations and special effects bring to life the formation of the planets, the origin of the first cells, the demise of the sun and other events that scientists can only imagine.

The film marks Malick’s first attempt at documentary filmmaking. If you can call it that. Viewers hoping for a David Attenborough–style treatment of the subject matter will be disappointed. The film is more evocative, with moody scenes that provide little explication. And what narration (by Brad Pitt) there is tends to be philosophical rather than informative.

Serious science enthusiasts may find some reasons to quibble with the movie. For one, it’s hard to grasp the true immenseness and scale of cosmic time. With so much screen time devoted to the evolution of life, many viewers may not realize just how relatively recent a phenomenon it is. After the Big Bang, more than 9 billion years passed before Earth began to form. It took many hundred thousand more years before the first microbes emerged.

Malick’s treatment of evolution may also rankle some viewers. At times, the narration seems to imply life was destined to happen, with the young, barren Earth just waiting around for the first seeds of life to take root. At other times, the narration imbues evolution with purpose. Pitt notes, for instance, that perfecting a leaf took eons. Yet perfection is something evolution neither achieves nor strives for — it’s a process that lacks intentionality.

These critiques aside, Malick sought to tell an accurate story, enlisting an accomplished group of scientists as advisers, including Lee Smolin of the Perimeter Institute for Theoretical Physics in Waterloo, Canada. Smolin says he was impressed with the end result. “It’s a very unusual film,” he says, likening it to a visual poem or piece of art.

And that’s probably the best mindset to watch Voyage of Time: Just sit back, soak in the dazzling visuals and contemplate the wonders of nature.

Human evolution, fire and smoke


This video says about itself:

Smoking Causes Cancer, Heart Disease, Emphysema

20 jul. 2012

This 3D medical animation created by Nucleus Medical Media shows the health risks of smoking tobacco.

ID#: ANH12071

Transcript:

Every time you smoke a cigarette, toxic gases pass into your lungs, then into your bloodstream, where they spread to every organ in your body. A cigarette is made using the tobacco leaf, which contains nicotine and a variety of other compounds. As the tobacco and compounds burn, they release thousands of dangerous chemicals, including over forty known to cause cancer. Cigarette smoke contains the poisonous gases carbon monoxide and nitrogen oxide, as well as trace amounts of cancer-causing radioactive particles. All forms of tobacco are dangerous, including cigars, pipes, and smokeless tobacco, such as chewing tobacco and snuff.

Nicotine is an addictive chemical in tobacco. Smoking causes death. People who smoke typically die at an earlier age than non-smokers. In fact, 1 of every 5 deaths in the United States is linked to cigarette smoking.

If you smoke, your risk for major health problems increases dramatically, including: heart disease, heart attack, stroke, lung cancer, and death from chronic obstructive pulmonary disease.

Smoking causes cardiovascular disease.

When nicotine flows through your adrenal glands, it stimulates the release of epinephrine, a hormone that raises your blood pressure. In addition, nicotine and carbon monoxide can damage the lining of the inner walls in your arteries. Fatty deposits, called plaque, can build up at these injury sites and become large enough to narrow the arteries and severely reduce blood flow, resulting in a condition called atherosclerosis. In coronary artery disease, atherosclerosis narrows the arteries that supply the heart, which reduces the supply of oxygen to your heart muscle, increasing your risk for a heart attack. Smoking also raises your risk for blood clots because it causes platelets in your blood to clump together. Smoking increases your risk for peripheral vascular disease, in which atherosclerotic plaques block the large arteries in your arms and legs. Smoking can also cause an abdominal aortic aneurysm, which is a swelling or weakening of your aorta where it runs through your abdomen.

Smoking damages two main parts of your lungs: your airways, also called bronchial tubes, and small air sacs called alveoli. Cigarette smoke irritates the lining of your bronchial tubes, causing them to swell and make mucus. Cigarette smoke also slows the movement of your cilia, causing some of the smoke and mucus to stay in your lungs. While you are sleeping, some of the cilia recover and start pushing more pollutants and mucus out of your lungs. When you wake up, your body attempts to expel this material by coughing repeatedly, a condition known as smoker’s cough. Over time, chronic bronchitis develops as your cilia stop working, your airways become clogged with scars and mucus, and breathing becomes difficult.

Your lungs are now more vulnerable to further disease. Cigarette smoke also damages your alveoli, making it harder for oxygen and carbon dioxide to exchange with your blood. Over time, so little oxygen can reach your blood that you may develop emphysema, a condition in which you must gasp for every breath and wear an oxygen tube under your nose in order to breathe.

Chronic bronchitis and emphysema are collectively called chronic obstructive pulmonary disease, or COPD. COPD is a gradual loss of the ability to breathe for which there is no cure.

Cigarette smoke contains at least 40 cancer-causing substances, called carcinogens, including cyanide, formaldehyde, benzene, and ammonia. In your body, healthy cells grow, make new cells, then die. Genetic material inside each cell, called DNA, directs this process. If you smoke, toxic chemicals can damage the DNA in your healthy cells. As a result, your damaged cells create new unhealthy cells, which grow out of control and may spread to other parts of your body. Cigarettes can cause cancer in other parts of your body, such as: in the blood and bone marrow, mouth, larynx, throat, esophagus, stomach, pancreas, kidney, bladder, uterus, and cervix.

Smoking can cause infertility in both men and women. If a woman is pregnant and smokes during pregnancy, she exposes her baby to the cigarette’s poisonous chemicals, causing a greater risk of: low birth weight, miscarriage, preterm delivery, stillbirth, infant death, and sudden infant death syndrome. Smoking is also dangerous if a mother is breastfeeding. Nicotine passes to the baby through breast milk, and can cause restlessness, rapid heartbeat, vomiting, interrupted sleep, or diarrhea.

Other health effects of smoking include: low bone density and increased risk for hip fracture among women; gum disease, often leading to tooth loss and surgery; immune system dysfunction and delayed wound healing; and sexual impotence in men.

From Leiden University in the Netherlands:

Are modern humans simply bad at smoking?

Published on 21 September 2016

Scientists looked for the genetic footprint of fire use in our genes, but found that our prehistoric cousins – the Neanderthals – and even the great apes seem better at dealing with the toxins in smoke than modern humans.

Mixed blessing

The art of making and using fire was one of the greatest discoveries ‘ever made by man’, wrote Charles Darwin. Besides providing protection against cold temperatures, the use of fire in food preparation and the introduction of energy-rich cooked foods in our prehistoric diet had a major impact in the development of humankind. However, fire use comes at a cost. Exposure to the toxic compounds in smoke carries major risks for developing pneumonia, adverse pregnancy outcomes in women and reduced sperm quality in males, as well as cataracts, tuberculosis, heart disease, and chronic lung disease. In short, the use of fire is a mixed blessing.

Debate

This mixed blessing, however, put researchers at Leiden University and Wageningen University on the trail of finding genetic markers for the use of fire in prehistoric and recent humans. The use of fire is notoriously difficult to ‘see’ for archaeologists, and this has led to strong disagreement over the history of its usage. A very early start is advocated by Harvard primatologist Richard Wrangham, who argues that our Homo erectus ancestors were already using fire around two million years ago. However, numerous excavations and intensive research carried out by archaeologists in Europe and the Near East suggest that control of fire occurred much later, around 350,000 years ago.

Genetic markers for fire use

In order to bring fresh data into this ‘hot’ debate, the Leiden/Wageningen team studied the biological adaptations of prehistoric and recent humans to the toxic compounds of smoke: fire usage implies frequent exposure to hazardous compounds from smoke and heated food, which is expected to result in the selection of gene variants conferring an improved defence against these toxic compounds. To study whether such genetic selection indeed occurred, the team investigated the gene variants occurring in Neanderthals, in Denisovans (contemporaries of the Neanderthals, more related to them than to modern humans), and in prehistoric modern humans.

Tobacco

Single nucleotide variants in 19 genes were tested that are known from modern tobacco-smoking studies to increase the risk of fertility and reproduction problems when exposed to smoke and hazardous compounds formed in heated food.

These genes were compared with variants observed in Neanderthals and their Denisovan cousins, and were also studied in chimpanzees and gorillas, two closely related species that are obviously not using fire, and are therefore not exposed to smoke on a regular basis.

Neanderthal more efficient in handling smoke?

In a study now published in PLOS ONE, the team shows that Neanderthals and the Denisovan predominantly possessed gene variants that were more efficient in handling the toxic compounds in smoke than modern humans. Surprisingly, these efficient variants were also observed in chimpanzees and gorillas, and therefore appeared to be evolutionary very old (ancestral) variants.

Plant toxins

The less efficient variants are observable from the first modern human hunter-gatherers for which we have genetic information onward, i.e. from about 40,000 years ago. The efficient defence against toxic compounds in chimpanzees and gorillas may be related to the toxins in their plant food. Smoke defence capacities in humans apparently hitchhike on those adaptations, developed deep in our primate past. Our prehistoric ancestors were probably already good at dealing with the toxic compounds of smoke, long before they started producing it through their campfires. What allowed for the emergence of less efficient hazardous chemical defence genes in modern humans is a question for future research.

Traces of long-lost human cousins may be hiding in modern people’s DNA, a new computer analysis suggests. People from Melanesia, a region in the South Pacific encompassing Papua New Guinea and surrounding islands, may carry genetic evidence of a previously unknown extinct hominid species, Ryan Bohlender reported October 20 at the annual meeting of the American Society of Human Genetics. That species is probably not Neandertal or Denisovan, but a different, related hominid group, said Bohlender, a statistical geneticist at the University of Texas MD Anderson Cancer Center in Houston. “We’re missing a population or we’re misunderstanding something about the relationships,” he said: here.