Last week, a new study in the journal Science highlighted the role forests could play in tackling climate change. Researchers estimated that by restoring forests to their maximum potential, we could cut down atmospheric carbon dioxide (CO2) by 25 percent — a move that would take us back to levels not seen in over a century. Though the study brings hope in the fight against climate change, other experts warn the solution is not that simple.
The study, led by scientists at ETH-Zürich, Switzerland, determined the planet has 0.9 billion hectares of land available to hold more trees — an area the size of the continental U.S. Converting those areas into forests would be a game-changer for climate change, the authors suggested.Read More
We know it best as a stringy slime dripping from noses and as viscous, discolored goop hacked up by sickened airways. But it’s so much more than that. Coating the surfaces of guts, eyes, mouth, nasal cavity and ears, mucus plays a range of important physiological roles — hydrating, cleaning, supporting good microbes and warding off foreign invaders.
“I like to call it the unsung hero of the body — it’s something that has such powerful effects over our health,” says Katharina Ribbeck, a biophysicist at MIT who with colleagues outlined the many roles of mucus in the 2018 Annual Review of Cell and Developmental Biology. Most of those functions come from the 5 percent of the substance that’s not water: various salts, lipids and proteins, most notably mucins, which give mucus its gel-like qualities — long, thread-like polypeptides coated in covalently bound chains of sugars called glycans.Read More
For the past ~40,000 years, Homo sapiens — modern humans — has been the only Homo species on Earth. But for most of our history, there were close evolutionary cousins of ours, human but not quite like us, coexisting and evolving at the same time in different regions.
Some of our now-extinct relatives, such as the Neanderthals, are well known. Others, like the recently-discovered Denisovans or Homo naledi have hardly made it into textbooks yet. And hints of even more human forms have been found in incomplete fossils and genetic patterns, although these relatives are poorly understood. Modern humans were just one of many variations on the Homo theme.Read More
What if the key to protecting our planet … was leaving it? Well, in part, at least. As worries about climate change mount, and the race to obtain resources from space heats up, some experts and über-rich CEOs are seriously considering moving our industry off-planet. That means using robots to build satellites and space stations by mining asteroids, the moon and other planets. A plot ripped from science fiction? Most definitely. But much of the technology to build this off-earth infrastructure already exists.
This contingency plan — known as in situ resource utilization — is not only necessary to reduce global warming, but could even be key to our continued growth as a species, according to Phil Metzger, a planetary scientist at the University of Central Florida. Before that, Metzger spent 30 years at NASA where he cofounded Swamp Works, a lab that develops tech for space mining and interplanetary living.Read More
(Inside Science) — Big, black wasplike things living in your toilet may sound more like a horror scene than a sanitation solution. That’s certainly what people in rural Louisiana thought in the summer of 1930, when black soldier flies infested a set of newly installed privies.
“[C]onsiderable consternation often resulted when a person lifted a privy lid and was greeted by a swarm of insects resembling wasps, or when upon leaving the privy he experienced a strange creeping and buzzing sensation due to flies being confined within his garments,” wrote researchers in an account published in 1930 in the Journal of Economic Entomology. To make matters worse, hungry local chickens tore down the privies’ foundations in search of larvae pupating in the surrounding dirt.Read More
Deepfake videos are hard for untrained eyes to detect because they can be quite realistic. Whether used as personal weapons of revenge, to manipulate financial markets or to destabilize international relations, videos depicting people doing and saying things they never did or said are a fundamental threat to the longstanding idea that “seeing is believing.” Not anymore.
Most deepfakes are made by showing a computer algorithm many images of a person, and then having it use what it saw to generate new face images. At the same time, their voice is synthesized, so it both looks and sounds like the person has said something new.Read More
More and more, researchers have been studying how your gut microbes might be making you sick. Scientists have linked these vital bugs to everything from schizophrenia, to autism, allergies and obesity. But what do the microbes look like inside the guts of super healthy people? Say, in elite athletes like marathon runners?
A research team from the Joslin Diabetes Center and Wyss Institute, both at Harvard Medical School, sampled the gut bacteria from runners a week before, and a week after, they ran the Boston Marathon. The group, led in part by microbiologist Alex Kostic, compared the samples to those from some non-elite athletes: scientists in the lab. The findings were published Monday in Nature Medicine.
The team found that most of the marathoners had a higher abundance of a bacteria called Veillonella. This group of species, or genus, lives off of lactate. Remember the last time you “felt the burn” from exercising or some other strenuous task? That’s the lactate in your muscles.
After the marathon, these lactate-eating bacteria in the runners’ guts went nuts, or “bloomed,” in bacteria lingo. Now, the researchers have pieced together how these bacteria might give elite athletes a boost — and how they might be able to share that boost with the rest of us.
The researchers gave some lab mice Veillonella from the runners — rodent probiotics, if you will — and tested their running endurance. Mice with the marathoner’s microbes ran for 13 percent longer than those without before hitting exhaustion.
Then, they looked at the microbiomes of a bigger cohort of endurance athletes — adding ultra-marathoners and Olympic trial rowers to their study — and saw that Veillonella bloomed after exercise in them, too. More, they found the genes that were switched on in the microbes, and figured out how they were breaking down lactate into another compound, propionate.
This all makes sense until you think about why the lactate built up in muscles would end up in the athletes’ colons at all. Researchers already knew most of the break-down of lactate happens in the liver. So the researchers decided they should trace some lactate through the body to see if any ended up in the gut. They laced some lactate with a heavier version of the element carbon, called an isotope. Then they injected this into the rodent test subjects, waited a few minutes, killed them and opened up their guts to look for the substance. The team found that some of this lactate did indeed end up in the mice’s colons.
At this point, it seemed to the scientists like it was all adding up. If Veillonella eat lactate, maybe these athletes don’t feel so much of the burn, allowing them to do well at these high-endurance events. But, the researchers learned, the story is more complicated than that. When they looked at post-exercise mice with and without Veillonella in their systems, the animals’ lactate levels weren’t that different.
Instead, they looked closer at the propionate the gut bacteria were producing from the lactate. They gave mice (with no Veillonella) propionate enemas to see what effect the compound would have in the gut.
The propionate increased their treadmill endurance, just like the Veillonella had. The added endurance wasn’t because the elite athletes had less lactate, it was because they had more propionate.
What, exactly, the propionate is doing isn’t totally settled yet, but this compound is known to do a couple of things in the body. It’s anti-inflammatory, and it can serve as an energy source to cells in the gut. It might also increase some nervous system capacities.
But before you run out to get a propionate enema (please don’t — Kostic says that would be “highly unadvisable”), there may be a better solution.
Jonathan Scheiman, another lead author of the work, started on this research when he was a researcher at the Wyss Institute. But he’s since left to start a biotech startup called FitBiomics.
“There’s a real big desire and push [at Wyss] to not keep discoveries bottled up in the lab and find ways to translate them into the real world,” Scheiman says.
FitBiomics is working on how to turn Veillonella into a probiotic that’s available over the counter. This could give run-of-the-mill athletes a little boost, but more importantly, it could give sedentary people more capacity to exercise.
“Is it possible that introduction of a bug that might be missing in their microbiome, Veillonella, might help change that?” asks Kostic. “That’s, from a health perspective, I think the most important potential outcome.”
Scheiman says he was motivated to do this research thanks to his past as a college athlete. “When I didn’t make the NBA I got a Ph.D. in microbiology as a backup,” he says.
“[I’m] just really excited about the notion of working with the most fit and healthy people in the world and trying to understand what makes them unique and perform at an optimal level,” says Scheiman. “Can we translate that information into consumer health applications?”
“As an athlete and now as a scientist,” says Scheiman, “I think what excites me the most is bridging communities together to kind of create something entirely unique.”
When the Neanderthal genome was first sequenced in 2010 and compared with ours, scientists noticed that genes from Homo neanderthalensis also showed up in our own DNA. The conclusion was inescapable: Our ancestors mated and reproduced with another lineage of now-extinct humans who live on today in our genes.
When the Denisovan genome was sequenced soon after, in 2012, it revealed similar instances of interbreeding. We now know that small populations from all three Homo lineages mixed and mingled at various times. The result is that our DNA today is speckled with contributions from ancient hominin groups who lived alongside us, but did not survive to the present day. Genes from Denisovans and Neanderthals are not present in everyone’s DNA — for example, some Africans have neither, while Europeans have just Neanderthal genes. But, these genetic echoes are loud enough to stand out clearly to scientists.
On one level, it’s not shocking that DNA from other human groups resides within us. H. sapiens today is the result of millions of years of evolution; we can count numerous species of ancient hominin among our ancestors. But the Neanderthal and Denisovan contributions to our genetic makeup happened far more recently, after H. sapiens had already split from other human groups. Those interbreeding events, also called introgressions, did not create a new species of human — they enriched an already existing one. Some of the traits we acquired are still relevant to our lives today.
“There’s a lot of evidence for some type of introgression from ancient hominins into modern humans, particularly modern humans out of Africa,” says Adam Siepel, a computational biologists at the Cold Spring Harbor Laboratory. “I don’t think there’s any real question among experts in the field as to whether the evidence overwhelmingly supports that event.”
Some evidence also suggests that there may be more than two additional human groups lurking in our DNA, what researchers sometimes call “ghost lineages.” Modern humans living in Africa may have interbred with one or more hominin species there, resulting in even more addition to our current DNA. And a recent study of modern-day Indonesians suggests that what we call Denisovans was actually three separate groups of hominins, at least one of which can be thought of as its own species. The ancestors of Asians and Melanesians mated with at least one of these groups, and possibly more.
Scientists have begun to unravel our tangled past in a few different ways. For groups like the Neanderthals and Denisovans, where their DNA still survives in some fossils, it’s been easiest. After sequencing their genomes, archaeologists simply compared them with our own. Finding stretches of our DNA that look strikingly similar to those from an ancient group is a strong indication that our ancestors interbred with them at some point.
Those genes could have come from even further back, of course, from the last common ancestor we shared with Neanderthals and Denisovans. But the split happened so long ago that most regions of the DNA we share with other human groups has seen mutations that make them look distinct in each group. Any genes that seem to be a direct match, then, are a strong indication of interbreeding.
For the majority of ancient hominin species that we know of, though, we have bones but no DNA. The molecules that make up the delicate double helix break apart over time, especially in the hot and humid environments where most of our ancestors lived. But archaeologists have unearthed faint echoes of additional ancient hominins in our own DNA by running genomic data through statistical algorithms meant to pick out telltale variations. Several papers have suggested that hidden ancestors lurk in our genomes. But the margins for error are large.
The mathematical models scientists use to find ghost lineages in genetic data are complex, but usually boil down to a search for clusters of genes in specific groups of humans today that set them apart from other modern human populations. A team of researchers did just this recently with a collection of 161 genomes from modern-day Indonesians. They compared this genetic information with the genomes of Denisovans and Neanderthals, as well as other humans today.
The researchers found signatures of Denisovan DNA in the Indonesians — no surprise — but also saw hints that the ancient hominins were actually three distinct groups. They shared a common ancestor but began to drift apart genetically as they spread across Asia and the Pacific. One of the groups was as different from the Denisovans found in Siberia as it was from Neanderthals. The researchers say that means it likely deserves to be called its own species, though they don’t have the fossils to make the designation official.
“If we’re going to call Neanderthals and Denisovans by a unique name, which we do, then we should probably call this other group by another name,” says Murray Cox, a computational biologist at Massey University in New Zealand, a co-author of the study.
New finds may give us tangible evidence of this Denisovan cousin, but for now its only remains are snippets of DNA tucked inside the genomes of some modern human populations.
Those Denisovan-like ghosts are not alone, though. Other researchers looking at the DNA of African hunter-gatherers today have used similar methods to find what they say is evidence that the ancestors of those groups mated with other hominins on the continent tens of thousands of years ago.
Perhaps the largest study, published in 2011, looked at the DNA of 61 Africans from the Mandenka, Biaka and San tribes. They compared these genomes to two models of human populations, one of which assumed the Africans’ ancestors interbred with ancient human groups, and one which didn’t. The model that included gene flow from archaic hominins produced results that more closely matched up to actual human populations in the region.
Based on their modeling, the researchers say that around two percent of the African genomes they sequenced came from a mysterious group of ancient hominins. The two interbred somewhere around 35,000 years ago.
Another study looking at a gene, called MUCL7, that encodes for a protein in our saliva. They found further evidence of a ghost lineage in Africans. The MUCL7 gene has a few variants in humans today, and the researchers say that one can be traced back to an ancestor that was something other than H. sapiens. A paper examining the genomes of 15 people from the Hadza, Sandawe, Baka, Bakola and Bedzan tribes also found evidence of interbreeding, though again they were unable to say whom it might have been.
The genes that many of us have inherited from other human groups remain, in many cases, active in our bodies today. Genes from Neanderthals and Denisovans affect the functioning of our immune systems today. Neanderthal genes have been suggested to affect both the body’s keratin (which makes up our hair, among other things) and how we react to UV light. These genes were likely picked up after humans migrated north from Africa to Europe, where trysts with our Neanderthal cousins may have helped fast-track our own adaptations to the cold climate.
A unique gene from Denisovans has also been found in modern-day Tibetans, high in the Himalayas. Known as EPAS1, it alters how their bodies produce hemoglobin, a protein in red blood cells that carries oxygen. The gene helps move oxygen around their bodies more efficiently at altitude, and has likely been instrumental in allowing them to colonize the miles-high world of the Tibetan Plateau.
Other genetic endowments have proven more problematic. Some genes from Neanderthals have been implicated in depression and myocardial infarctions, as well as allergies. Where some genes from ancient species help our immune systems, others may predispose us to disease: lupus, Crohn’s disease and type-2 diabetes, among others.
Like many family legacies, our extra-sapien genetic inheritance is complex. Scientists have more work to do before they understand the true implications of our multi-species past, including the ways that it continues to shape our present. Indeed, even finding evidence for ghostly genes can be problematic.
The evidence for ghost lineages is building, but when scientists must rely solely on genetic evidence, it is difficult to make an airtight case for the existance of another species. There are numerous factors that can muddle the stories our genes tell, making it difficult to tell a true signal of an ancient population from background genetic noise. What kind of evolutionary pressures a population is under, the size of that population, to what extent it has mixed with other human populations and things like genetic bottlenecks — an event where just a fraction of a population survives to produce offspring — all add uncertainty to geneticists’ work. What appear to be ghosts are sometimes no more than metaphorical curtains blowing in the wind.
A recent paper in Nature Communications illuminates some of the shortfalls of this method. In it, three researchers from Spain and Estonia say that they’ve found evidence of a ghost lineage in the DNA of people of Asian and Oceanian descent based on a complex statistical analysis and machine learning algorithms.
They started by constructing an artificial genome using a computer program that simulates genetic information and then paired it with demographic models of ancient humans. This gave them an “in silico” genome that they could compare with real ones, says study co-author Oscar Lao, a population geneticist at the Centre for Genomic Regulation in Barcelona. They ran these simulations millions of times.
Where the two matched up, they then looked at what in the artificial genome’s evolutionary history led to that cluster of genes, with the implication that what created that DNA in the computer genome may also have happened in real life. Averaging the results over millions of simulations gave them what they say is an approximation of a real genome.
They then attempted to fit the data into a few different scenarios describing the interactions between various lineages of ancient humans. The one that fits best, they say, is a model that includes a heretofore unknown group of ancient hominins interbreeding with modern humans. These people would have been a hybrid of Neanderthals and Denisovans, the authors say.
It would also explain why Asians today have more Neanderthal DNA than Europeans do — not only did their ancestors mate with the Neanderthals at some point, they also interbred with this hybrid group in Asia. The work is another reminder that hominins were a diverse bunch, says Lao.
“What it’s suggesting is that the picture of archaic genetic diversity was quite complex,” he says. “It was not only Neanderthals waiting until anatomically modern humans appeared, but there were other archaic populations from which we don’t have archaic remains so far.”
It’s a compelling story, boosted by the discovery last year of a first-generation Neanderthal-Denisovan hybrid in Denisova cave in Siberia. But other researchers aren’t convinced.
There are just too many unknowns at the moment for us to run simulations of this kind, Siepel says.
“It’s a question where you have to write down a fairly complicated model to distinguish between those scenarios and that model is almost certainly unrealistic in many respects,” he says.
Sharon Browning, a research professor of biostatistics at the University of Washington, agrees.
“The reality of human history is pretty complex,” she says. “If you simplify too much and don’t capture the right aspects of what really happened then you’re going to be comparing different models, all of which are wrong.”
Browning also studies the genetics of ancient hominins, and she says her own work found no evidence of the population that Lao and his colleagues saw.
Instead, a recent paper from her lab looking at traces of Denisovan DNA in modern genomes found two distinct Denisovan-like groups. One looked genetically similar to the single Denisovan genome we’ve sequenced, from Siberia. The other group looked to be only distantly related, though.
It’s a finding that matches up, at least in broad outline, with the recent suggestion that the Denisovans were more than one species. If so, both Browning and Cox may have found evidence of the same ghost lineage distantly related to Denisovans. Or perhaps they each picked out different groups entirely, hinting that there was much greater diversity among ancient hominins than we realize.
As scientists claim evidence of unknown populations in our shared past, it’s reasonable to wonder how many more there might be to find. What evidence we have so far of ghost lineages amounts mostly to hints, without (by definition) solid proof to back them up. Indeed, we may have already hit the limits of what is observable when it comes to picking out ancestors in our DNA. The Neanderthal and Denisovan additions amount to just a fraction of the genomes of some modern human populations.
“Any other introgression that’s out there is going to be quite a small proportion [of our DNA],” Browning says. Most of the DNA segments that look like they came from another species have probably been found, she says. “There’s not a lot left to work with that might be something else.”
But future archaeological finds — providing real, hard evidence — could surprise us, especially if we can extract DNA from the remains. The evidence for Denisovan DNA in our genome, for example, would likely be quite tenuous had we not been able to sequence their DNA, Siepel says.
“I’m sure that would be very controversial, if we were just trying to hypothesize the existence of that species from the introgressed fragments in modern humans,” he says.
Future finds may turn today’s ghost lineages into tangible species, once-living and breathing humans who merged their genetic histories with ours. Their bodies may be gone, but their DNA lives on.
The rocket’s flare is sudden and brilliant, a blurring horizontal column of whooshing fire. Just as quickly, the bright jet flickers out of existence, the few seconds of burn enough complete the test.
A pause in the control room, then applause ripples around. The group retires to a test cell nearby, where there are speeches and photos; a giant ribbon is cut.
Sierra Nevada Corporation (SNC) has just completed the first test of their Vortex rocket at a brand new test facility in central Wisconsin. It’s an upper stage rocket, far smaller than the behemoths SpaceX and Blue Origin use to escape the pull of Earth’s gravity, meant to help spacecraft move and maneuver once they reach space.Read More
More than 100,000 years ago, humans lived in the caves that dot South Africa’s coastline. With the sea on their doorstep and the Cape’s rich diversity of plant life at their backs, these anatomically modern Homo sapiens flourished. Over several millennia, they collected shells that they used as beads, created toolkits to manufacture red pigment, and sculpted tools from bones.
Now some of these caves, along the country’s southern coast, have shed light on humanity’s earliest-known culinary experiments with carbohydrates, a staple in many modern diets. Small pieces of charred tubers found at the Klasies River site in South Africa date back 120,000 years, making them the earliest-known evidence of H. sapiens cooking carbs, according to recent research published in the Journal of Human Evolution.
The study joins a suite of new findings that illuminate the evolution of our ancestors’ diet. For example, in recent years, scientists have determined that hominins have been eating meat for at least 2.6 million years —
with some researchers contending that hominins were butchering bones for marrow as much as 3.4 million years ago. And hominins were roasting nuts, tubers, and seeds about 780,000 years ago. Humans specifically, as another South African find revealed, ate shellfish some 164,000 years ago. And last year, ancient crumbs revealed that H. sapiens has been eating bread for 14,400 years.
Cynthia Larbey, an archaeologist at Cambridge University in the United Kingdom and lead author of the new study, suspects that roasting tubers provided critical nutrition to our species. “It was the way we were able to continue feeding ourselves as we moved and migrated,” she says. Hunting was difficult and unreliable, so “it was a skill to be able to find food as they moved to different ecologies.”
For the study, an international team of researchers excavated blocks of rock and compacted earth from the Klasies River cave floor and identified the remains of small fire pits within them. The team then used a technique called micromorphology, in which one excavates each block in tiny layers or sheets. They then removed the charred fragments and looked at them under an electron microscope.
“When you put something into a fire that’s still fresh, it has water in it,” explains Larbey. “When it cooks quickly, the escaping steam distorts the cells.” Using an electron microscope, the researchers detected this distortion, which suggests the tubers were likely not used as kindling. In addition, the charred pieces of tubers appeared often enough in the ancient hearths that researchers ruled out the possibility they had fallen into the fire by accident.
“This is really a very nice find,” says Simcha Lev-Yadun, a paleobotanist at the University of Haifa in Israel. Lev-Yadun was part of the team that discovered evidence of hominins roasting nuts and tubers 780,000 years ago.
Larbey and her colleagues believe that early modern humans’ consumption of cooked starches could have aided our species significantly. The Klasies River inhabitants had to have possessed the knowledge to identify the correct plants from their leaves, remember their location, avoid toxic tubers, and recognize ripeness. These abilities enabled humans to reliably find food, even while on the move.
In addition, starches are a source of energy-rich sugars; when cooked, that energy is more readily accessible to the body and able to support the development of human brains and fetuses. Consumption of cooked starches, the researchers argue, was therefore evolutionarily advantageous.
Although previous studies have shown that a meat-based diet was critical for brain development, a growing body of scholarship argues that easily digestible carbohydrates were also necessary to meet the energy demands of growing brains. “This new paper provides compelling evidence to support this idea, at least for those humans living at the site [at the time],” says Peter Ungar, an anthropologist at the University of Arkansas, who was not involved in the study.
Early humans, this study and others suggest, were versatile and consumed a variety of items, including both starchy plant material and animal protein, Ungar says. Diets likely varied with food availability and personal preference, much as they do in the present-day.