Sometimes you’ll hear people cast doubts on evolution because no one has ever seen it happen. As if that’s some sort of great insight. No one has eve “seen” atomic fusion, either, but the fact that the Sun was shining this morning is pretty strong evidence that, yep, it happens. No one has ever “seen” gravity. Seen gravity’s effects, sure. But seen gravity itself? Like Ms. Ono once asked, Who Has Seen The Wind?
Evolution used to be in the same boat. The effects of evolution are visible everywhere, in every cell of every living thing on the planet. But seeing the actual process of evolution? That was another matter.
Until now. Scientists at Michigan State University (go Spartans!) have been growing bacteria in bottles for the past 21 years. Every so often, they would freeze a sample for later study. Well, “later” is now. DNA sequencing and computer analysis have advanced to the state where they can readily map the genome of each sample. And guess what? The bugs evolved exactly as evolution says they should. Mutations in the genome pop up at random intervals. Mutations that help the bug survive—like make more efficient use of food, or fend off disease—get passed on to future generations, and eventually spread through the entire colony.
Twenty-one years may not seem like enough time for a species to change. But, as Mia Sorvino said in the truly awful 1997 movie Mimic, think generations, not time. In the two decades of study, the little bacteria went through 40 thousand generations—the equivalent of roughly 800,000 years in human terms. Plenty of opportunity for evolution to do it’s thang.
And the experiment continues. Understanding mutations in bacteria might help us understand the mutations that lead to some forms of cancer. In recent generations, the rate of mutation has increased; the scientists would like to know why.
Richard Lenski, the scientist heading up the research, has put together a video explaining his work.
Courtesy coteIt’s a weird suggestion, I know, because you probably give a lot of thought to whom the various cavemen had sex with anyway, regardless of the weather. But give it a little extra thought today. Because it’s nice out, and the dark corners of your brain could use the sunlight.
So, you guys all know that we aren’t the only human species ever to exist, right? The human family tree had other branches before it got to us (take a look at our Human Spark feature for more on that), and there were times when more than one species lived in the same area, and—in all probability—had interactions with each other. Neanderthals, for instance, lived alongside modern humans for many thousands of years in ice age Europe. Keep in mind, “Neanderthal” isn’t just a synonym for “cave-man.” Neanderthals were a distinct species—they had heavier, longer skulls, and thick, strong bodies. The modern humans of ice age Europe would have looked, more or less, like us. And because the two species were living in the same area for so long, it seems pretty likely that they interacted. But did those interactions include, you know, dinner, dancing, and romantic music?
On one hand, these are sort of fightin’ words. People have suggested that Neanderthals faded into extinction as they interbred with modern humans, but when human DNA was compared with a sequence of Neanderthal DNA, it didn’t look like there was any overlap. That is, if there was any interbreeding, the Neanderthal contributions to our genes have been so diluted with human genes that it doesn’t appear that we have any Neanderthals in our family at all.
On the other hand… Well… I mean… People do all sorts of stuff… We all just want someone to love, right? Or, you know, just think of what a puppy will do to a piece of furniture. And humans and Neanderthals are a lot more similar to each other than puppies and ottomans. Too much? I don’t think so. Look at ligers. Or tigons. Or mules. Similar animals interbreed all the time, but very often they have infertile offspring. And that would explain why we don’t see any Neanderthal genes around today—everybody could have been doing it like it was 2012, but if the offspring couldn’t reproduce it wouldn’t matter to future generations.
Another factor that could explain the lack of genetic overlap (despite Paabo’s certainty of caveman/Neanderthal sexiness) is that our Neanderthal DNA sample just isn’t good enough. Mitochondrial DNA from Neanderthals doesn’t show up in modern humans, and while that’s an incredibly valuable genetic marker, it only makes up a tiny fraction of an organism’s total DNA. The Neanderthal genome hasn’t been completely sequenced yet, and that’s what Paabo means to do. Once we can fully compare the genomes, we can see if the two species became at all mixed.
Because they were definitely doing it.
Courtesy Mark RyanWhen the first Archaeopteryx skeleton came to light in 1861 just two years after the publication of Charles Darwin’s On the Origin of Species, it was hailed as not only the earliest known bird but also as proof of evolution. The rare specimen (known as the London specimen) appeared to be somewhat of a chimera of both dinosaurian and bird features. Thomas Huxley, a fierce proponent of Darwin’s work, even suggested that birds were the descendents of small meat-eating dinosaurs. It took more than a century for the idea to become widely accepted. Today most paleontologists divide dinosaurs into two groups: avian dinosaurs (birds) and non-avian dinosaurs, the branch that died out at the end of the Cretaceous.
"For a long time, Archaeopteryx was considered the archetypical bird primarily because it had feathers, although it retained typical dinosaur features like a long tail and teeth,” said Mark Norell, Chair of the Division of Paleontology at the American Museum of Natural History. “But the discovery of classical bird features like feathers and wishbones have recently been found in many non-avian dinosaurs blurring the line of what constitutes a bird."
Now, a new study by Norell and co-author Gregory Erickson, a vertebrate paleontologist at Florida State University, shows that 150 million year-old Archaeopteryx (Greek for “ancient wing”) may have been much more like a non-avian dinosaur than a bird (avian dinosaur), at least in its bone structure and growth rate.
"Dinosaurs had a very different metabolism from today's birds,” Erickson said. “It would take years for individuals to mature, and we found evidence for this same pattern in Archaeopteryx and its closest relatives.”
For their research, the team removed tiny, 250-micron slivers of bone from the remains of several Archaeopteryx fossils, and from the bones of primitive but younger bird fossils (Jeholornis prima and Sapeornis chaochengensi, and Confuciornis sanctus) found recently in China. They also examined the bone structure of closely related non-avian dinosaurs such as Velociraptor mongoliensis.
Those samples from the Archaeopteryxes showed high bone-density, annual growth lines (a reptilian trait), and very small blood vessels similar to the bones sampled from the non-avian dinosaurs. The location of bone cells also appeared flattened and parallel – more like that of a velociraptor – and much different from the hollow, vascularized (i.e. filled with blood vessels), rapid growing bones found in younger-aged bird fossils, and most birds today. (Flightless birds such as ostriches and penguins have solid bones.)
"Although the genealogy of birds is well understood, the genesis of modern bird biology has been a huge mystery,” Norell said. “We knew that they are a kind of dinosaur, but we now know that the transition into true birds—physiologically and metabolically—happened well after Archaeopteryx."
What this implies is that Archaeopteryx was more of a dinosaur than it was a bird – at least in its metabolism and how fast it matured – and that the traits considered necessary for flight – such as light, hollow bone structure – evolved from a dinosaur body-plan sometime after Archaeopteryx.
"We show that avian flight was achieved with the physiology of a dinosaur," Erickson said.
The study can be found in a recent edition of the online journal PLoS ONE.
Courtesy Mark RyanRecently discovered fossils out of China add strong evidence to the theory that birds descended from dinosaurs. The fossil remains of a new feathered dinosaur, named Anchiornis huxleyi, were discovered in rock strata thought to be at least 10 million years older than that at Solnhofen, Germany. This is exciting news. Since the 19th century the quarries at Solnhofen have produced several skeletons of the feathered Archaeopteryx which has long been considered the first bird. But now it appears that feathers arose several millions of years before Archaeopteryx showed up in the fossil record. Professor Xu Xing of Chinese Academy of Science in Beijing reported his findings in the science journal Nature, and at the Society of Vertebrate Paleontology's annual convention being held this week at the University of Bristol in England.
Courtesy Paul SerenoA new meat-eating dinosaur that looks like a scaled-down version of Tyrannosaurus rex has been uncovered in northeast China.
Raptorex kriegsteini would have been about 100 times smaller than its tyrannosaur descendents, weighing in at only about 150 pounds and about eight or nine feet in length; a punk compared to the forty-foot, six-ton T. rex.
But the new discovery possesses the same puny forelimbs, massive legs, oversized head, crushing jaws, and large olfactory bulb as the T. rex. Only much smaller. In fact, the entire body length of Raptorex would be less than twice that of just the skull of a Tyrannosaurus rex (9 feet verses 5 feet).
The fossil was found in Mongolia and sold on the open market. The buyer contacted paleontologist Paul Sereno, who agreed to describe it, but only on condition the buyer agreed to turn it over to science. The Sereno et al. study appears in Science Express, the online edition of the journal Science.
"Many of these traits have never been seen in anything but the big brutes," Sereno said. "That's what's so surprising about the whole thing, from tooth to limbs to even the space for the brain, we see things we used to think were just exclusive to the big tyrannosaurids in the late Cretaceous. But there they are."
Despite its reduced size the new dinosaur would still have been a formidable predator to its prey. But the find means the blueprint for the famous Tyrannosaurus rex goes way back in the family line, something not expected.
Learn more from Paul Sereno himself in this video from the University of Chicago.
Raptorex (which means “king of thieves) lived in the Early Cretaceous about 125 million years ago, and several tens of millions years before its famous descendent italicizedT. rex roamed the Earth in the waning days of the dinosaurs.
Courtesy kookr and McflyIer (composite) via FlickrRemember how odd it felt to learn the Rolling Stones' song, I Wanna Be Your Man, was written by the Beatles' Lennon & McCartney? Or that off-putting twinge of “hmmm” you experienced when hunky hipster Tom Jones covered Kiss, a song written and originally performed by Prince (AKA The Artist Formerly Known as Prince, AKA His Glyphship, AKA The Artist, AKA Prince (again))? Or the unsettling angst brought on by Celine Dion screaming through AC/DC’s You Shook Me All Night Long? In each case, it’s not like they were terrible renditions (I’ll leave that judgement to the music critics), but there was just something not quite right about it. They all just seemed so... unnatural.
Well, as it turns out, it may be a more common natural phenomenon than previously thought. At least in the world of birds. And I’m not talking about Roger McGuinn’s band.
Researchers at Oxford have discovered two different species of antbird in South America whistling the same territorial tune to help eliminate mating competition. They’re claiming it’s the first such discovery.
Although the two birds belong to the same family (Thamnophilidae) they are distinct species (Hypocnemis peruviana and Hypocnemis subflava). Genetic tests done by the researchers showed the two species separated from a common ancestor about three millions years ago. This means the territorial song developed before they split off from their common ancestor.
During the study (the results of which appear in the current issue of Evolution) the scientists made recordings of the songs of males of both species listen here and played them back to competitors in their territories. The reaction in each was similar.
"When we played the song of the [rival] species, the resident bird responded as aggressively as it did to its own species," said Dr Joe Tobias, who led the research along with colleague Nathalie Seddon.
Even though the territorial songs remained similar after the split, other characteristics (such as plumage color and mating calls) diverged along very different paths, and probably aid in preventing confrontation and crossbreeding between the two species.
In effect, the territorial songs of these birds are more or less interchangeable in design and function. Given that they last shared a common ancestor more than 3 million years ago, it is almost equivalent to humans and chimpanzees - which diverged around 5 million years ago - using the same language to settle disputes over resources.
– Dr. Joe Tobias in a press release
So, this kind of cross-species convergence - with different types singing the same song - may not be such an unnatural thing. But then again, Britney Spears did do a cover of the Stones’ (I Can’t Get No) Satisfaction.
Courtesy Mark RyanIn the latter days of summer my wife and I took a drive up the Gunflint Trail and visited the Magnetic Rock Trail, a spur trail jutting off the Gunflint near Gunflint Lake. Our original plans of lounging about the North Shore of Lake Superior had been scuttled by a mix-up in our cabin reservations, so I saw it as an opportunity to check out first-hand some of the local geology. I had visited the MRT briefly once before and my reasons for wanting to make the 50-mile drive from Grand Marais to revisit the trail were three-fold: stromatolites, meteorite impact ejecta, and, of course, magnetic rocks
Well, as it turns out, I wasn’t very successful,
Courtesy Mark RyanReaders may recall the Ham Lake forest fires raged along the Gunflint Trail in the early summer of 2007, destroying several hundred acres of the surrounding forest along with resorts and private property. The fire, it was later determined, was started by a legal campfire in the vicinity of Ham Lake that had gotten out of hand and spread quickly through the region. It was the second forest fire to rage through the Magnetic Rock Trail (MRT) in the past two decades (there was also a controlled burn in 2002). The latest fire removed much of the pine canopy that covered the area, opening it to more sky and sunlight, and new vistas of the surrounding terrain.
Courtesy Mark Ryan
Courtesy Mark RyanBut as destructive as forest fires can be, they do have their upside. Forests are quick to revitalize after fires. New trees soon rise up from the ashes, and evidence of that in the MRT was apparent in the many jack pines (Pinus banksiana) we saw sprouting up everywhere. But trees aren’t the only affected flora. A lot of the groundcover gets incinerated as well, sometimes exposing patches of bedrock. In the case of the Magnetic Rock Trail, it meant new outcrops of the Gunflint Iron Formation were uncovered, revealing fresh unexplored exposures.
The Gunflint Iron Formation is a mass of iron ore taconite that spans from the Arrowhead region of Minnesota eastward into Ontario, Canada with the majority of the formation located on the Canadian side of the border. Most iron formations on Earth were formed around the same time, about 2 billion years ago during the Middle Pre-Cambrian (Early Proterozoic) times. A shallow sea (the Animikie) covered much of northern Minnesota and eastern Ontario at the time. The sea teemed with cyanobacteria in the form of stromatolites; thick microbial mats that helped oxygenate the Earth’s atmosphere and metabolize iron out of solution through photosynthesis. The iron-oxide sediments later became the iron ranges that span across northern Minnesota and Canada. Much of the rock along the Magnetic Rock Trail is composed of magnetite (Fe3 O4) inter-bedded with layers of chert or shale. Magnetite is the most magnetic of all the naturally occurring minerals, hence its name. The Gunflint Iron Formation is particularly resistant to erosion on the Minnesota side probably due to its nearness to the Duluth Complex intrusives. These influxes of magma moved into the area around 1.1 billion years ago, adding tremendous heat to the existing strata. The portion of the Gunflint Iron Formations (that located in Minnesota) closest to the heat source shows the most resistance to erosion.
Courtesy Jim Miller, MN Geological Survey (top) Mark Ryan (bottom)Preserved within some of the newly exposed outcrops along the MRT are fossil records of these stromatolites, representing some of the oldest fossils found in Minnesota. Gunflint stromatolites contain large numbers of fossils that can be seen under a scanning electron microscope. I had been told that you can walk off the main path and find some of these ancient fossils, so I searched off-trail for a while and found what I thought were stromatolites, and took photos of them.
But later when I consulted with geologist Mark Jirsa, he wasn’t so sure.
“You're looking at thin bedding in the iron formation that dips shallowly in comparison to the dip of the outcrop surface,” he wrote me. “The result is a swirly look, that looks deceptively like stromatolite mounds.”
Jirsa was in the field when I contacted him, and his Internet capability was limited, so when he tried to send me some photos of what the stromatolites actually looked like, they didn’t come through. However, his colleague, geologist Jim Miller (who also supplied welcomed assistance with this post) sent me a stromatolite photo he had taken at MRT.
Personally, I can’t tell the difference, but then I’m no geologist. so I have to bow to the professionals.
My second quest – to locate and photograph ejecta from the Sudbury Impact – wasn’t successful either. The aforementioned Mark Jirsa discovered this record of a 1.85 billion-year-old meteor impact in 2007. I wrote a previous post about it that same year so I won’t go into those details (you can read it here) but I will bring you up to speed on how he’s since interpreted the find.
Briefly, the Sudbury Impact Crater is located in Ontario, Canada, and was made by a meteorite about 10-miles in diameter that slammed into the Earth 1.85 million years ago. The 150-mile wide crater is the second largest known on the planet. The collision sent a tremendous firestorm of superheated material into the atmosphere, and some of it coalesced like hailstones and landed 480 miles away in northeastern Minnesota. This is what Jirsa discovered two years ago: a layer of ejecta mixed with torn up pieces (breccia ) of the Gunflint Formation, and all of it overlain by a younger layer of slate known as the Rove Formation. He published an article about it in Astronomy magazine, and there’s also a PDF file downloadable from Minnesota Geological Survey website (the link is located in the upper left of the MGS homepage).
What Jirsa found was quite remarkable: a layer of churned-up rocks laid down above the Gunflint Iron Formation. The odd jumble of rock included berry-shaped rocks known as accretionary lapilli, intermixed with the Gunflint Iron Formation rock. According to his interpretation, what is seen in the layer essentially shows the events of a single day in the geological record. And a nasty day it must have been.
Three minutes after the initial fireball impact at Sudbury, seismic waves from earthquakes measuring more than magnitude-10 on the Richter Scale reached the Animikie basin, ripping loose the iron formation off the seafloor crust, and redistributed it along a submarine slope. Within 10 minutes, a firestorm of molten material hailed down from the sky covering the region with from 3 to 10 feet of ejecta in the form of accretionary lapilli. Ultra-hurricane-force winds measuring up to 1400 mph(!) blasted over the shallow sea soon after, followed by the coup de grace – titanic tsunamis the likes of which have never been seen since which tossed everything into a stew of breccia (jumbled rock) and berry-shaped ejecta.
This day of horror took place sometime in the 48 million year interim that separates the Gunflint Iron Formation and the time the sediments of the Rove Formation were laid down above it. The entire concoction was later baked and metamorphosed by the intrusive magmas of the Duluth Complex.
How hard could it be to find evidence of a mess like this? Well, considering the MRT covers a large area, and since I had no information pinpointing any locations, it was like looking for a needle in a haystack – a very large haystack. In the end, I soon gave up because I really didn’t know what I was looking for and I realized how futile it probably would be. However, I’ve sure learned a whole lot about it now.
Courtesy Mark RyanInitially, I thought at least my third quest – finding magnetic rock – would be a complete success because just about every rock exposed along the MRT is highly magnetic (I had a magnet with me and I can attest to that fact – see photo). It made sense that the whole reason the trail is called the Magnetic Rock Trail is because of all the magnetic rocks found there. But I’ve since learned I was once again totally wrong. The trail is name after a single large magnetic rock that’s about 1.5 miles up the trail. This 30-foot monolith stands upright and obvious in the middle of the forest and its notoriety dates back to early native American times. It is a chunk of the Gunflint Iron Formation – and highly magnetic like the rest of the rock in the area – but is deemed an erratic moved into place from a short distance away by glaciers during the last Ice Age. Had I read any of the brochures I had collected on our trip sometime other than when I got home, I would have known this before I even got there. But as it was, we didn’t walk that far into the trail so we missed it completely. Oh, well.
Courtesy Mark RyanBut even though my three main objectives for visiting the MRT were pretty much complete washouts, there was one unexpected surprise that will probably draw us back to the region next year: blueberries.
Courtesy Mark RyanWild blueberries (Vaccinium angustifolium) were all over the place. The low-bush berries thrive in sandy, acid soils of forest clearings, and in rocky areas around pines forests – just the type of environments you find around the MRT. So, once I finished with my failed geological studies, I assisted my wife in picking as many wild blueberries as we needed. We kept them in our cooler for the ride home, and as Mrs. R is prone to do, she jumbled all the berries together into a viscous concoction, all within a flakey crust that was heated over time at a very high-temperature.
The result looked something like the Sudbury Impact ejecta layer found near the Magnetic Rock Trail, but it was much more delicious, and a great way to end the summer.
Courtesy Mark RyanExtinction is a fact of life. Species rise up, consume energy, reproduce, radiate to fill their range, and die off. It happens all the time. In fact, nearly 99% of all creatures that have ever lived on Earth have gone extinct. That’s just the way it is. Sometimes the cause for extinction is minor – a subtle change in the environment such as increased competition for a food source or the introduction of a harmful contaminate or virus. Other times it can be more heavy-handed, like when a giant asteroid hurls in from outer space and slams into the planet sending the biosphere into a tizzy, and wiping out entire faunas. Either way it sucks big time.
But now there may be a third, more insidious reason. Extinction could be built into the genes of some unfortunate creatures, and according to the new study, it may be get passed on as an ancestral species branches out into new ones. Meaning extinction is a family affair.
The research team, composed of Kaustuv Roy of the University of California, Gene Hunt from the Smithsonian Institute, and David Jablonski of the University of Chicago, studied a whole gamut of extinction patterns in shelled marine animals such as clams, mussels and scallops. Their paper, which appeared recently in the journal Science, suggests that propensity for extinctions could be passed on through the whole groups of species that share common ancestors.
"Biologists have long suspected that the evolutionary history of species and lineages play a big role in determining their vulnerability to extinction, with some branches of the tree of life being more extinction-prone than others," said Roy, a biology professor at UC San Diego.
"Background extinctions" are the normal extinction rates that occur between major extinction events (e. g. killer asteroids), and usually don’t include those caused by human activity. (I don’t see why not – are we not part of Nature?) Anyway, when the team analyzed ‘background rates” from the Jurassic to the present they were struck by how some of the marine species with the highest rate of extinction during those “normal” times were also the most vulnerable (along with their close relatives) during major extinction events.
"Big extinctions have a filtering effect. They tend to preferentially cull the more vulnerable lineages, leaving the resistant ones to proliferate afterwards," Hunt said.
This means extinction isn't as random as we’d like to think, and actually tends to affect entire genera not just species within them. These clustered extinctions chop off larger branches from the family tree and cut deeper into the lineage history.
"Now we know that such differential loss is not restricted to extinctions driven by us but is a general feature of the extinction process itself," Roy said.
The study, according to evolutionary biologist Charles Marshall of Harvard University, shows how fossils are an important record of evolution’s workings.
"Only by analyzing the past do we get a direct sense of the rules by which evolution has worked and will continue to work,” he said.
Courtesy adolson13Did things just get a little… sexier in here? By “in here” I mean in my local metro area? So did things just get a little… sexier in the Twin Cities?
Oh ho, I think they just did. I took my shoes off the write this post, and that’s part of it, but that’s not where it starts. No, it starts with thousands upon thousands of young adults—in the blazing prime of their life, really—with one thing on their minds, and not much time on their hands.
Yep, the mayflies have hatched. That is, they hatched about a year ago, and have just now completed their final moults into adulthood. Now they have anywhere between a day and just half an hour to do what needs to be done. In their case, it’s sex that needs to be done. Other than vague efforts at avoiding premature death via fish mouth or windshield, adult mayflies haven’t got a lot of distractions—while immature naiad mayflies spend months paddling around at the bottoms of streams and lakes eating algae, their mouthparts are vestigial (useless) when they reach maturity, and their digestive tracks are full of air. (Exactly when this occurs is based on temperature and humidity, so all the mayflies in a particular area will become mature at the same time.) So, as a young mayfly, asking a prospective mate out for dinner would be pretty much pointless even if you had the time.
It might seem kind of crazy evolving into a creature that only lives for a few hours and can’t do anything but fly around and try to have sex. But if that’s all you have to do, you can invest all your resources into ensuring that you reproduce, and if your whole generation is doing it at more or less the same time, your chances are pretty good. Plus, time is relative, and there are probably those who’d say that a life of just flying around and having sex would be okay. Assuming you didn’t get eaten by a walleye.
I’m going to put up a boring ol’ picture of a mayfly here, just so you know what to look for when you’re trying to avoid thousands-strong airborne orgies over the next couple of days. Hopefully, though, I’ll have some pictures of actual swarming mayflies soon. (I know where to find some, but if y’all are already on top of things, don’t hesitate to post your own!)
Courtesy Apollo13Ma (background photo), public domain and Mark RyanA study out of New Zealand says a warmer climate speeds up molecular evolution in mammals. The concept isn’t exactly a new one. Scientists have known that a warmer environment increases the pace of microevolution for other types of life, such as some plants and marine animals, but evidence that it affects mammals – which are warm-blooded (meaning their temperature is regulated internally) – has not been observed before.
Lead researcher, Len Gillman from Auckland University of Technology, said the result of the study was “unexpected”.
""We have previously found a similar result for plant species and other groups have seen it in marine animals. But since these are 'ectotherms' - their body temperature is controlled directly by the environment - everyone assumed that the effect was caused by climate altering their metabolic rate.""
Since DNA can potentially mutate each time a cell divides into two copies of itself, the faster (and more often) these divisions take place, the more chances advantageous mutations will be passed onto subsequent generations, and the faster microevolution takes place.
Gillman and his crew traced and compared small genetic changes in 130 pairs of related species that lived in different latitudes, focusing on a single gene in each pair. They then compared the gene against that of a common ancestor, and were able to determine which of the two mammals’ DNA had mutated (microevolved) more rapidly. The changes were small-scale, but the species living in the more tropical environment showed a faster pace in its level of molecular evolution.
The results of the study appear in Proceedings of the Royal Society B.