Stories tagged evolution

Sep
19
2008

The Ambulocetus: Not looking very fearsome at the moment, but it's thinking horrible, horrible thoughts.
The Ambulocetus: Not looking very fearsome at the moment, but it's thinking horrible, horrible thoughts.Courtesy ArthurWeasley
It’s Friday, y’all, and you know what that means!

No, not falling asleep at a booth in Applebee’s (should have gone to TGIF, right?)!

No, not a methadone suppository (not from me, anyway)!

And, no, not matching butterfly tattoos (that’s a Saturday thing)!

What’s left? Why a Science Buzz creature feature, of course! Sure, Friday has never been Creature Spotlight day before, sure, and, yes, it’s unlikely that I’ll remember to do it next Friday… But, hey, we’re Buzzketeers, right? We live in the now.

And so, with a small current science introduction, the creature of the week:

The crocowhale* (also known as ambulocetus, or “walking whale”).

If you’re keeping up on your cetacean evolution paleontology, you might have noticed this story recently. The ancestors of whales, paleontologists are quite certain, were land animals. Finding the evolutionary steps of their return to the water has been a challenge, however.

The distant ancestors of whales were carnivorous ungulates (ungulates are hoofed animals), that probably looked a little like dogs (with hooves). At some point these creatures began adapting to live and hunt in and around the water, eventually evolving into fully aquatic species.

Living vertebrates that swim employ a variety of propulsion methods. Several swimming styles seem to develop in sequence as a group of animals becomes more fully adapted to living in the water: swimming with four legs, paddling with just the back legs, undulation of the hips, undulation of the tale, and finally oscillation of the tail. The sequence of whale ancestor fossils seemed to follow this pattern (with modern whales having lost their hind legs to propel themselves with just their tails), except that for a long time it appeared that the step of swimming by hip undulation.

Recent fossil discoveries, however, show a whale ancestor that appeared to have a long fluke-less tail (it didn’t have big tail fins, like a modern whale), along with long hind legs and large, webbed feet. The skeleton seems to indicate that this creature would have propelled itself by undulating its hips, using its webbed hind feet as hydrofoils. And so, la de da, we have an important step in whale evolution in the bag. But, for the creature spotlight, we’re going back a couple branches in the cetacean family tree.

Before the group had evolved to the point of the hip wiggler above (called georgiacetus, by the way), there was the ambulocetus. Ambulocetus was a creature that probably still spent some of its time on land. It was about 10 feet long, and moved around on short, powerful legs. With its eyes and nostrils located on top of its long head, it probably looked something like a furry crocodile. Indeed, paleontologists think that ambulocetus probably acted very much like a crocodile, and filled a similar ecological niche.

Ambulocetus could have waited for large prey almost entirely submerged in shallow water, with only its eyes and nostrils breaking the surface. When something worthwhile came down to the water’s edge, it could have launched its body out of the water with its particularly powerful hind legs, ambushing its prey. The ambulocetus would have then dragged its struggling meal back into the water, and waited for it to drown. Yes! Crocowhale!

Here’s a cool illustration of ambulocetus in action.

* “Crocowhale” is a brand new term, and while I’m all for you using it in everyday life, don’t put it in any biology papers or anything. Yet.

A few days ago we posted a link to an article about a push within the Church of England to apologize for its actions of the past that were critical of Charles Darwin's emerging theories of evolution 150 years ago. Now here's word that top Roman Catholic officials are saying that there is room for evolution is "more than a theory" and that there is room for it in the creation story. I believe Sarah Palin is still a creationist, however.

A British-based website has sprung urging the Anglican church of England to issue a formal apology for the church's treatment of Charles Darwin in the afternmath of his publishing the book "On the Origin of Species." This is a sure-fire topic to generate discussion, so have at it folks.

Sep
11
2008

A crurotarsan: Pretty cool, but don't put any bets on it.
A crurotarsan: Pretty cool, but don't put any bets on it.Courtesy ArthurWeasley
Just as those of us who have hands know the backs of them well, just as all of us know that the Hulk is stronger than the Thing, just as we know that it’s a good idea to keep our lips off that thing… We all know that dinosaurs are pretty awesome. They are, perhaps, the most awesome.

Dinosaurs did, after all, strut their fine stuff across the surface of the planet for more than 150 million years. How else would one explain that, if not for the fact that dinosaurs were clearly more awesome than any and all of the competition? It can’t be done.

Except…

Scientists at the American Museum of Natural History are now saying that at the outset of their reign, the during Triassic, dinosaurs succeeded where other groups did not simply because they were lucky. Dinosaurs didn’t make it because they were stronger or able to adapt more quickly, but because they did well at the craps table. As it were.

See, the reptiles that survived the Permian extinction would eventually give rise to dinosaurs and a group called “crurotarsans.” The only living descendants of the crurotarsans are crocodiles and their ilk, but during the Triassic the group included a wide range of large predators, armored herbivores, and agile little crocodilians. At the end of the Triassic, however, the crurotarsans became almost entirely extinct, while the dinosaurs flourished.

When one group dies out and another succeeds under the same conditions, scientists usually expect to find that the “winning” group has a greater range of physical traits, or appears to be able to adapt much faster. The study done by the AMNH indicates the opposite in this case: as a group, the crurotarsans had twice the range of body plans as the dinosaurs, and seemed to be adapting just as fast. Subjected to the changing environmental conditions at the end of the Triassic, the greater variety of body designs should have given the crurotarsans a leg up in surviving to the Jurassic.

Not only should they not have died out, but the scientists behind the study say that if they could have bet—during the Triassic—who would dominate the planet for the next 130 million years, they would have picked the crurotarsans, not dinos. It just so happened that the crurotarsans were hit particularly hard at the end of the Triassic. Of all the extinction-inducing changes that could have occurred, the planet went through one that the crurotarsans couldn’t deal with: global warming. Dumb luck.

It seems like the study was missing something, however. What was it about global warming (or about the crurotarsans) that made them die out, even with their great diversity? Even if luck was the reason, what was the mechanism?

I’m inclined to think that the dinosaurs’ coolness had something to do with it. Sort of an opposite James Dean effect.

How about that, though? But for the roll of the biological dice, children across the world could have lunch boxes and notebooks covered in crurotarsans.

The last laugh

by Gene on Jul. 11th, 2008

Author Jim Holt consults Darwin and Copernicus and declares: laughter will be mankind’s most enduring legacy.

Jun
20
2008

For decades, scientists have been growing microbes in their labs and watching them evolve new traits. Most of the changes tend to be simple things, like an increase in size or growth rate.

But Dr. Richard Lenski of Michigan State University (just 2 miles from my house!) recently witnessed a major evolutionary leap--as it was happening. Twenty years ago, he took a colony of E. coli, a common bacteria, and split it into 12 identical populations. He’s been watching ever since to see if the strains evolve in different directions.

A few years ago, one of them did. One of his study strains suddenly evolved the ability to eat citrate, a molecule found in citrus fruits. No other E. coli in the world can do this, not even the other strains in Dr. Lenski’s lab. Even given several extra years and thousands of extra generations, the other strains are still citrate-averse. What’s more, the bacteria evolved this mutation entirely on their own, without any prodding or genetic manipulation from the researchers.

Lenski had saved frozen reference samples of all of his strains at regular intervals. Going back and growing new cultures from these samples, he again finds that only those from one strain ever evolve the citrate-eating habit – and only those sample less than about 10 years old. Lenski figures that some mutation happened around that time in one strain – and one strain only – that would later lead to citrate eating. He and his lab are now working on figuring out exactly what that mutation is.

Jun
03
2008

I'm too sexy for light feathers: Barn swallows with darker chest feathers do better with the ladies than those with lighter feathers, a study shows. On top of that, those that have their feathers darkened increase their production of testosterone.
I'm too sexy for light feathers: Barn swallows with darker chest feathers do better with the ladies than those with lighter feathers, a study shows. On top of that, those that have their feathers darkened increase their production of testosterone.Courtesy Mdf
Sorry guys, but our perceptions of what makes us manly have taken a severe hit with this new scientific discovery.

Evolutionary biologists working with barn swallows in New Jersey have found that a little extra black make-up applied to the chest feathers of male swallows increases their “hook-ups” with female swallows.

The lighter colored males typically are smaller, less genetically attractive versions of the species and hence their low procreation rate. But as they say, a little dab will do you, and with the help of ink from a marker, life changes for the male swallows.

The researchers actually had done earlier testing that showed the feather coloring change to be an aid for male swallows. But in this latest round of research, they found that maleness-enhancing impacts from the color change. They treated males had increases in the amount of testosterone they produced and even trimmed down in weight.

Full details of the study are available here at the Current Biology website. I just hope that the Hair Club for Men and Grecian Formula yahoos don’t get wind of this new information.

New fossil evidence indicates that the ancestors of modern kangaroos walked on four legs, had fangs and climbed trees -- a sobering thought. Meanwhile, scientists studying marsupial flatulence have discovered that kangaroo gas contains no methane, and thus does not contribute to greenhouse gasses. A spokesman for kangaroos said he was glad no kangaroos were involved in changing the Earth's climate.

I mean, really -- what more do you need to know?

Basically, dinosaurs had a very efficient respiratory system, similar in many respects to that of diving birds, who must make the most of each breath. This provides yet more evidence that birds evolved from dinosaurs.