Stories tagged evolution

Sep
06
2009

Appendix removal
Appendix removalCourtesy Drvgaikwad

Why we need an appendix

Darwin thought that our appendix was vestigial, a left over organ that no longer served any purpose. Now we know that the appendix can serve as a hiding place for good gut bacteria so they can replenish the colon after unpleasant circumstances like diarrhea or colon cleansing.

"Two years ago, Duke University Medical Center researchers said that the supposedly useless appendix is actually where good gut bacteria safely hide out during some unpleasant intestinal conditions." Scientific American

Aug
17
2009

Extinction: It may run in the family.
Extinction: It may run in the family.Courtesy Mark Ryan
Extinction 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.

LINKS

ScienceDaily story
Science News story

Jun
29
2009

Warmer climate boosts evolution: Okay, so iguanas aren't mammals, and I doubt Charles Darwin ever visited Sloppy Joe's in Key West, Florida, but the graphic still illustrates the point.
Warmer climate boosts evolution: Okay, so iguanas aren't mammals, and I doubt Charles Darwin ever visited Sloppy Joe's in Key West, Florida, but the graphic still illustrates the point.Courtesy Apollo13Ma (background photo), public domain and Mark Ryan
A 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.

LINKS
Discover magazine story
BBC story
More about evolution

Jun
28
2009

Piranha
PiranhaCourtesy AlexeyDr
While working on a river as a guide last summer I was able to tell many stories, one of which was about the infamous prout. A prout is a cross breed of piranha and trout produced by the US government in World War II. With the carnivorous teeth of the piranha and large, fast body of the trout the government hoped that the fish would become a water defence system if the war ever came to our shores and rivers. While some people will fall for this outlandish story (you would be surprised what people will believe when you speak confidently) there have been new findings in a fossil of one of the missing links between plant eating fish and present day piranhas.

Plant eating fish have two rows of flat, square teeth but, the meat eating piranha has one row of triangular teeth with sharp edges. The fossil of a Megapiranha paranensis was found in the early 1900's on a river bank in Argentina and was left sitting in a drawer unstudied until the 1980's. It consists of the jaw bone and shows a zig-zaged line of teeth that could be proof of the transition from two to one row of teeth.

Further research continues to support that this fish is a long lost ancestor of our piranha having lived 8 to 10 million years ago in the South American rivers. Although its diet is unknown it would still be an unpleasant visitor at a length of about 3 ft, much larger then any prout you may run into.

Jun
22
2009

The titans close on each other: Look at how much bigger they are than that house! But how do we know that's a werewolf and not just a normal giant wolf?
The titans close on each other: Look at how much bigger they are than that house! But how do we know that's a werewolf and not just a normal giant wolf?Courtesy JGordon
JK. The war has already been fought, Bigfoot totally won, you missed it, and remarkably little blood was spilled. Go figure.

A professor of the history of science at Kean University in New Jersey is arguing that Bigfoot, in fact, killed the werewolf. Not for really real, but in the collective mind of our society. However, Bigfoot had a secret weapon: Charles Darwin. (I’m assuming it was a silver-tipped Charles Darwin, at least.)

See, everybody has to be afraid of something, pretty much. And for a long time we were all, “I have to be afraid of something, huh? Well… I’m already sort of afraid of wolves, so why don’t we throw in this unnatural wolf/man mix thingy. I’ll be afraid of that.” And because we were too dumb to know about stuff like flesh eating disease and giant crocodiles and cancer, we were pretty satisfied being afraid of werewolves.

But then, says New Jersey science historian Brian Regal, then along comes ol’ Charles Darwin (and his silver tongue?), and begins to popularize evolution with On the Origin of Species. People start thinking, “Hey… wolf-man? Why did I ever think that was scary? That’s old, magicky nonsense. No, what makes sense is an ape-man. I’ll be afraid of that now.”

Science gave the supernatural a little boost of legitimacy, in a roundabout way. And at the cost of poor, dear wolf-man.

Or so says Brian Regal. Take it for what it’s worth; he’s an assistant professor, after all. I don’t trust assistant anythings. Especially not dental assistants. Regal will be presenting his theory to the British Society for the History of Science in Leicester, UK in July. He’s going to show how period artwork also reflects this werewolf to Bigfoot transition, which sounds pretty neat. So if you can make it to Leicester and into the British Society for the History of Science sometime in the next month, maybe you should check it out.

A brutal win!: Look—the wolf has pants. Case closed. Oh, right... this drawing isn't appropriate for more delicate viewers.
A brutal win!: Look—the wolf has pants. Case closed. Oh, right... this drawing isn't appropriate for more delicate viewers.Courtesy JGordon
I’m more than a little disappointed in the lack of an epic, bloody monster-on-monster battle here, though. So I’ll be drawing one for y’all just now, on the back of some paper I pulled out of my trash.

Darwin as art
Darwin as artCourtesy Public domain
In commemoration of the bicentennial of Charles Darwin’s birth, the Fitzwilliam Museum in Cambridge, England has just opened a new exhibit called Endless Forms: Charles Darwin, Natural Science and the Visual Arts. The exhibition centers on how Darwin was influenced by the visual arts and how artists in turn were influenced by Darwin’s work. The show opened today and runs until October 4, 2009. Not planning a trip to England this year? Then you’ll just have to be happy watching a preview of the show here.

Jun
10
2009

It will be a brutal fight: No one should expect to emerge unchaffed.
It will be a brutal fight: No one should expect to emerge unchaffed.Courtesy Joe Shlabotnik
For years now, members of the robust camp of biologists—paleontologists in particular—arguing that birds evolved directly from dinosaurs have kneeled on the thighs and arms of paleontologists who believe that birds did not evolve from dinosaurs, slapped their scrawny bellies pink, and rubbed dirt and grass in their bifocaled faces. And it was only right—the birds from dino people are bigger, and their veiny biceps ripple with the science of a substantial fossil record, while the clammy palms and toast-rack ribcages of the alternate theory paleontologists positively reek of onions and contrary opinions for the sake of argument. It’s only natural.

I mean, we have fossil impressions of feathers on dinosaurs, analogous bones and body-structures in birds and theropod dinosaurs (theropods, again, are two-legged meat-eaters, like T-Rex, velociraptor, etc.), similar bird-dinosaur proteins (take a look at that last link—Liza listed a bunch of other stories in that post)… the list goes on. Some paleontologists pretty much consider birds to be dinosaurs themselves (little dinos that never went extinct). The book is closed. It’s not even fun beating up on those other paleontologists anymore, because… what’s the point? You wouldn’t beat up on a worm, would you?

Ah, but these worms may have gotten their hands on something soft in this fight, and they’re about to give it a twist…

Check it out—like a hammer from nowhere, or sudden and blatant disregard for the no-scratching rule, the birds-didn’t-evolve-from-dinosaurs people have a new weapon, and they’re back on their feet.

Before we go on, I’m just going to emphasize something real quick here: nobody is saying that birds didn’t evolve, or that they didn’t evolve from something very different from birds as we know them. The question is, from what did birds first evolve, and when?

See, the winning theory is that some theropod dinosaurs began getting smaller and more birdlike in the Jurassic period (with a couple interesting exceptions eventually getting bigger and more birdlike later on, but that’s a different story.) These dinosaurs got little, and feathery, and probably started living in trees, and adapted to leaping, gliding, and eventually flying. By the late Jurassic, we have the archaeopteryx, a feathered, toothed, clawed, and bony-tailed flying machine. By the Cretaceous, there are plenty of pretty normal-looking birds around. Easy-peasy, and there are all those fossils I mentioned before.

“Oh yeah?” say the other paleontologists, “Well what about… this?!” And with that, they flick the back of their hand into the crotch of the unsuspecting bird-dino scientists.

“What are you… aaaaaaahh….” They ask.

Birds, say the alternate theory dudes, don’t have the right legs to be descended from dinosaurs. It’s so obvious, even jerks like you should have seen it.

See, birds need to breath lots of air to be able to fly (it’s hard, I’ve tried). To breath more efficiently, birds have air-sacs in addition lungs. Running all over their bodies (even in their bones) the air-sacs help pump lots of air through the birds' respiratory systems. Fossilized bones appear to show the presence of air sacs in some dinosaur species, too, and this has been seen as further evidence for the bird dinosaur link.

The new argument doesn’t dispute that everybody loves air-sacs. It points out that birds can only move their legs in a very limited way, to keep from collapsing some of their air-sacs when they breath. Birds’ femurs (their thigh bones) are largely fixed—when they walk or run, most of the movement comes from their lower legs. All other walking and running animals—including dinosaurs—have moveable thighs.

This difference, some scientists believe, is great enough that fixed-legged birds couldn’t have evolved from moving-legged dinosaurs. They might have evolved alongside dinosaurs, sharing a common ancestor, possibly one of the thecodonts. Thecodonts were dinosaur-like (but definitely not dinosaurs) and they lived during the Triassic period. Some thecodonts evolved into dinosaurs, and the group died off by the end of the Triassic.

“That’s… all?” says mainstream paleontology, straightening up and cracking its knuckles. “Someone is about to get slapped.”

“…Hiss!” say the other guys, squaring their Gollum-like shoulders.

Until I know a little more about the research, I think I have to side with the traditional birds evolved from dinosaurs argument. The alternative theory folks point out that birds are found much earlier in the fossil record than the dinosaurs they are supposed to have evolved from, but it seems to me that that’s more of a problem of overlap than of a gap—couldn’t later bird-like dinosaurs just be the descendants of the dinosaur-to-bird transitional species? It’s not as if anyone thinks that we look at individuals in the fossil record and say, “ok, you evolved from this one, which evolved from this one” etc. If birds didn’t evolved from dinosaurs like the ones we find from the Cretaceous, then we’re left with a huge gap between thecodonts and archaeopteryx and his pals. And it would have to be some pre-dinosaur thecodont, because I feel like the independent evolution of air-sacs, feathers, and everything else in both lines would be a little too much convergent evolution otherwise.

Plus… I’m not clear on why dinosaurs couldn’t have just evolved to have a fixed leg later on, when they needed more efficient respiratory systems for flying. Their mode of locomotion would have necessarily been changing anyway…

“Hiss!!”

Interesting, though, right?

What do y’all think? Is this ridiculous? Or are we too attached to the mainstream model of bird evolution that we’re unable to keep an open mind to new ideas?

What makes humans unique? Do we have characteristics that make us different from other animals? PBS will be broadcasting a three-part series on the topic this fall. In advance of the series premiere, the producers want you to tell them why humans are special. You can submit a photo, a video, or text. Some entries will appear on screen, so make a grab for your 15 seconds of fame, and send in your ideas.

Jun
02
2009

Giant tortoise under threat
Giant tortoise under threatCourtesy sly06 (adapted by Mark Ryan)
Evolution of mosquitoes on the Galapagos Islands could endanger the islands’ famous giant tortoises and other reptile wildlife. On the mainland the black marsh mosquito Aedes taeniorhynchus normally feeds on mammals and birds, but scientists from the University of Leeds, the Zoological Society of London (ZSL), the University of Guayaquil and the Galapagos National Park have discovered that the island version of the blood-sucking insect has evolved a craving for reptilian blood, particularly that of the Galapagos tortoises and marine iguanas.

Genetic studies show the mosquitoes arrived on the archipelago about 200,000 years ago, giving them plenty of time to adapt to the island environment. Unlike its mainland counterpart which lives and breeds mainly in the lowlands and coastline salt marshes, the island mosquito can also breed as much as 15 miles inland and at altitudes up to 2000 feet above sea-level.

“The genetic differences of the Galapagos mosquitoes from their mainland relatives are as large as those between different species, suggesting that the mosquito in Galapagos may be in the process of evolving into a new species,” said Arnaud Bataille, PhD student at the University of Leeds and ZSL.

Mosquitoes can carry diseases such as West Nile and avian malaria that could potentially devastate the island fauna. Although none of these diseases have been detected in the Galapagos mosquitoes the researchers fear an infected mosquito brought in from the mainland via such modes as tourist transportation could potentially infect the island mosquitoes. If that happens the islands’ wildlife population could be at risk, because the long isolated Galapagos fauna wouldn’t have built up immunities to such an invasion.

But as a countermeasure, the Ecuadorian government has introduced a requirement for planes flying to Galapagos to be treated with insecticide before each flight, although similar controls have yet to be implemented for ships traveling to the islands.

“It is absolutely vital that these control measures are maintained and carried out rigorously, otherwise the consequences could be very serious indeed,” said Dr Simon Goodman, of Leeds’ Faculty of Biological Sciences and Co-author of the study which is published online in the US journal Proceedings of the National Academy of Sciences.

BBC story
Physorg.com story

May
19
2009

Darwinius  masillae
Darwinius masillaeCourtesy PLoS
There you were, thinking that lemurs were barely your relatives. It’s okay, I understand. I mean, Prosimians? Really? Sure, we’re all members of the primate family, but, like, two steps removed, like those cousins in Kentucky your mom pretends don’t exist. Or something. Prosimians are the non-human evolutionary line, how primitive. Prosimians are like NASCAR, and Anthropoids, like apes and humans, are like the DAR.

But, just like every president has an embarrassing brother, so too are we related to those furry simple primates. Now, we have proof! Scientists have found a 47 million years old human ancestor, the link between these early primates and human evolutionary lineage.

“Ida,” or Darwinius masillae, was actually discovered in 1983 by a private collector, although the fossil now belongs to the Natural History Museum of Oslo. An international team of scientists has been secretly conducting an in-depth study of Ida for the past two years. Now her skeleton is 95 percent complete.The fossil is significantly older than most fossils that explain human evolution, and, unlike Lucy and other famous primate fossils, this fossil was not found in Africa’s Cradle of Mankind; Ida is a European fossil (someone call Guinness, I just set a world record for using the word “fossil” the most times in a sentence).

Arms and hands of Darwinius  masillae
Arms and hands of Darwinius masillaeCourtesy PLoS
Ida was preserved with a full stomach, so we know that she was an herbivore. I hope that in 47 million years, scientists discover me and determine that humans subsisted mainly on a diet of Cheetos and grape soda. That would be pretty awesome. Her skeleton is pretty similar to that of modern-day lemurs, but she lacks a grooming claw and a row of teeth fused together called a “toothcomb.” She also has nails instead of claws, and teeth similar to small monkeys. She had forward facing eyes, like ours, and opposable thumbs.

Foot structure of Darwinius masillae
Foot structure of Darwinius masillaeCourtesy PLoS
What really links Ida to humans is a bone in her foot, called the talus. Her talus is nearly identical to your talus, only a lot smaller. Ida serves as a sort of “missing link,” a key part of the story of human evolution. So, you know, no big.