The period on our planet between 540 and 520 million years ago when most modern animal groups appeared is also known as evolution’s Big Bang. Prior to the Cambrian explosion, life was much simpler on Earth—single-celled organisms dominated the landscape.

But how did so many different organisms develop in such a short period of time? “The abrupt appearance of dozens of animal groups during this time is arguably the most important evolutionary event after the origin of life,” says Michael Lee of the University of Adelaide. “Darwin himself famously considered that this was at odds with the normal evolutionary processes.”

Lee and his colleagues decided to look into “Darwin’s dilemma,” focusing on arthropods (insects, crustaceans, arachnids and their relatives), the most diverse animal group in both the Cambrian period and present day.

“It was during this Cambrian period that many of the most familiar traits associated with this group of animals evolved, like a hard exoskeleton, jointed legs, and compound (multi-faceted) eyes that are shared by all arthropods,” explains team member Greg Edgecombe of the Natural History Museum of London. “We even find the first appearance in the fossil record of the antenna that insects, millipedes and lobsters all have, and the earliest biting jaws.”

The team quantified the anatomical and genetic differences between living animals, and established a timeframe over which those differences accumulated with the help of the fossil record and intricate mathematical models.

“In this study we’ve estimated that rates of both morphological and genetic evolution during the Cambrian explosion were five times faster than today—quite rapid, but perfectly consistent with Darwin’s theory of evolution,” Lee says.

ScienceNOW offers the numbers:

The creatures’ genetic codes were changing by about .117% every million years—approximately 5.5 times faster than modern estimates.

Unusual, perhaps, but in line with natural selection, the team indicates. The study appears in the recent edition of Current Biology.

Perhaps Darwin can get some rest now.

Image: Michael Lee

Here’s a great idea for a super-power: what if by merely emitting a sound, you could detect nearby friends and enemies in the way the sound echoes? Echoes. Echoes.

For many species of bats and dolphins, echolocation isn’t a super-power but a necessity. It allows these animals to hear predators and prey without seeing them in the dark skies or cloudy oceans. This adaptation evolved separately in these mammals—a great example of convergent evolution.

Scientists at Queen Mary, University of London were curious how this type of convergent evolution looked at the genomic level. So they compared the complete genomes of 22 mammals, including new sequences of four bat species, to look at how echolocation is expressed in the genes.

To perform the analysis, the team had to sift through millions of “letters” of genetic code using a computer program developed to calculate the probability of convergent changes occurring by chance, so they could reliably identify “odd-man-out” genes.

Remarkably, they found genetic signatures consistent with convergence in nearly 200 different genomic regions! “We had expected to find identical changes in maybe a dozen or so genes but to see nearly 200 is incredible,” explains Queen Mary team member Joe Parker. “We know natural selection is a potent driver of gene sequence evolution, but identifying so many examples where it produces nearly identical results in the genetic sequences of totally unrelated animals is astonishing.”

Although many of the gene region similarities are in genes involved in hearing, which the team expected, others are all over the place, reports ScienceNOW:

…some genes with shared changes are important for vision, but most have functions that are unknown.

The team published their findings last week in Nature.

“These results could be the tip of the iceberg,” says group leader Stephen Rossiter. “As the genomes of more species are sequenced and studied, we may well see other striking cases of convergent adaptations being driven by identical genetic changes.”

So perhaps not a super-power, but a regular occurrence…

Image: Greg Hume

Remoras could be classified as freeloaders, having evolved sucker discs on the top of their heads, which they use to attach themselves to their hosts. They hitch a ride on sharks or other large marine animals (rays, whales, turtles), even though they are fine swimmers on their own. They also eat the leftovers or possibly the feces of their host animal. Living on a large animal also protects remoras from predators.

Remoras cause no damage to their shark host, who don’t get much back from remoras, unless sharks find amusement in their oddly upside-down disc-shaped heads. Remarkably, these suckers evolved over time from the fishes’ dorsal fins.

Two recent studies, looking at a fossil remora and remora larvae, have determined how these fins develop over time into a strong sucking device.

The first study, led by Oxford University’s Matt Friedman, examined a 30 million year-old early remora fossil with a fully functioning sucker on its back.

“The remora sucker is a truly amazing anatomical specialization but, strange as it may seem, it evolved from a spiny fin,” Friedman says. “In this fossil the fin is clearly modified as a disc but is found on the back of the fish. It enables us to say that first fin spines on the back broadened to form wide segments of a suction disc. After the disc evolved, it migrated to the skull, and it was there that individual segments became divided in two, the number of segments increased, and a row of spines were developed on the back of individual segments.”

The second study looked at the development of remora from the earliest larval stages and compared it to the larval development of white perch, fish that have typical dorsal fins.

The research team found that up to a certain stage in the fish’s development, the dorsal fin develops in the same way and looks very similar in both fishes. Then, through a series of small changes, the remora’s dorsal fin begins to expand and shift toward the head. By the time the remora has reached about 30 millimeters (1.18 inches) in length, the dorsal fin has become a fully-formed two-millimeter sucking disc. It still has the components found in the dorsal fin—the tiny fin spines, spine bases and supporting bones—but the spine bases have greatly expanded.

The study confirms that the specialized sucking disc is formed by a massive expansion of the dorsal fin through small changes while the fish is developing. This completely new structure is homologous to other fish with dorsal fins and is not an evolutionary offshoot.

Fins turning into suckers? It sounds like a super-power! Well done, remoras.

Image: Dave Johnson, Smithsonian Institution

Now this raven-sized early bird has had its brain examined. Amy Balanoff and her colleagues from the American Museum of Natural History recently took CT scans of more than two dozen specimens, including modern birds, Archaeopteryx, and closely related non-avian dinosaurs such as tyrannosaurs, to size up the different species’ brain power.

“Bird-brained” is actually a misnomer. (Crows demonstrate this again and again.) Modern birds are distinguished from reptiles by their brains, which are enlarged compared to body size. This “hyperinflation,” most obvious in the forebrain, is important for providing the superior vision and coordination required to fly.

By stitching together the CT scans, the scientists created 3D reconstructions of the skulls’ interiors. In addition to calculating the total volume of each digital brain cast, the research team also determined the size of each brain’s major anatomical regions, including the olfactory bulbs, cerebrum, optic lobes, cerebellum, and brain stem.

The researchers found that in terms of volumetric measurements, Archaeopteryx is not in a unique transitional position between non-avian dinosaurs and modern birds. Several other non-avian dinosaurs sampled, including bird-like oviraptorosaurs and troodontids, actually had larger brains relative to body size than Archaeopteryx.

“If Archaeopteryx had a flight-ready brain, which is almost certainly the case given its morphology, then so did at least some other non-avian dinosaurs,” Balanoff says.

“Archaeopteryx has always been set up as a uniquely transitional species between feathered dinosaurs and modern birds, a halfway point,” she says. “But by studying the cranial volume of closely related dinosaurs, we learned that Archaeopteryx might not have been so special.”

If not unique, where should we place Archaeopteryx in the tree of life? More research is needed. The current study is published this week in Nature.

Image: Amy Balanoff, American Museum of Natural History

When you watch a pitcher wind up and throw a fastball down the middle, or a quarterback step out of the pocket and make a successful long pass, you’re seeing millions of years of human evolution and adaptations in action.

Or so say researchers Daniel Lieberman and Neil Roach. Their study, published today in Nature, determines that this uniquely human trait—high speed and high accuracy throwing—originated with our ancestors Homo erectus, two million years ago.

Darwin speculated that by freeing up the arms, bipedalism may have enabled our hominin ancestors to hunt effectively using projectiles. But scientists had been unable to pinpoint the exact time throwing became viable.

“When we started this research,” Roach says, “we asked: How do we do it? What is it about our body that enables this behavior, and can we identify those changes in the fossil record?”

The researchers began by creating a complex model that incorporated current research about the biomechanics of throwing. Using that model, they were able to explore how morphological changes to the body—wider shoulders, arms that are higher or lower on the body, the ability to twist the upper body independently of the hips and legs, and the anatomy of the humerus—affect throwing performance.

They also studied 20 experienced human throwers during overhand baseball pitching, demonstrating that several derived anatomical features that enable elastic energy storage and release at the shoulder are central to our ability to throw powerfully and accurately. (Video is available of these mechanics on Harvard’s website.)

“We try to push these bits of anatomy back in time, if you will, to see how that affects performance,” Roach says. “The important thing about our experiments is that they went beyond just being able to measure how the restriction affects someone’s ability to throw fast and accurately—they allowed us to figure out the underlying physics. For example, when a thrower’s velocity dropped by 10 percent, we could trace that change back to where it occurred.

“In order to test our evolutionary hypotheses, we needed to link the changes we’d seen in the fossil record to performance in terms of throwing,” he continues. “This type of analysis allowed us to do that.”

This throwing ability was incredibly important for our ancestors, the researchers say. It helped them become more successful hunters and carnivores, paving the way for a host of later adaptations, including increases in brain size and migration out of Africa.

However, while speed and accuracy proved a crucial development for early hunters, the study’s authors warn that repeated use of this motion can result in serious injuries in modern throwers, especially in young baseball players, who often suffer from laxity and tearing in the ligaments and tendons of their shoulders.

“I think it’s really a case of what we evolved to do being superseded by what we’re now asking athletes to do,” Roach says. “Athletes are overusing this capability that gave early humans an evolutionary advantage, and they’re overusing it to the point that injuries are common.”

Image: Rick Dikeman/Wikipedia

Just like humans, some birds have better luck than others. From city life to dance moves to penises, the natural endowments of birds vary in so many ways! Several recent science publications demonstrate diversity in the bird world, so we thought we’d provide a sampling for you…

A study last week in the Proceedings of the Royal Society B determines that city birds keep much longer hours than their forest-dwelling brethren. Researchers studied European blackbirds (Turdus merula) in different environments in Germany and discovered that the artificial lights and noises of the city mean the blackbirds start their activities earlier in the day and keep on going later in the evening.

In fact, studies in the lab revealed that the city birds’ biological clocks were sped up compared to the forest birds’. And the authors are convinced that birds aren’t the only animals affected by city life. From the abstract:

Urban environments can significantly modify biologically important rhythms in wild organisms.

City dwellers, take note!

Australia’s superb lyrebird males possess some of the most brilliant plumage in the avian world, and researchers have now determined that the feathered creature is also a brilliant song-and-dance bird. Scientists found that the birds have a distinct dance for each of four distinct songs. Wired posted a short video of a male lyrebird strutting its stuff that you have to hear and see to believe!

This mating ritual demonstrates that “the coordination of independently produced repertoires of acoustic and movement signals is not a uniquely human trait,” according to a recent publication in Current Biology.

Maybe the male lyrebirds song-and-dance routine makes up for the fact that these males have no penises. 97% of birds simply lack the organ, using an opening called the cloaca instead. Originally, all birds had penises, but along the evolutionary path, most birds lost them. There are theories for why the organ was no longer needed (lighter for flight, more female control over mates), but the reason is still not known.

However, a new study, also in Current Biology, uncovers the mechanism behind the loss. Researchers compared embryos of the well-endowed Pekin duck (it has a corkscrew penis that can grow the entire length of its body) to those of the cloaca-ed rooster and found that both embryos begin to form penises, but around day eight or nine, the roosters’ stop growing. The scientists determined that one gene, Bmp4, caused the rooster embryo’s penis to stop growing.

Carl Zimmer, writing in the New York Times, explains why this research not only paints a bigger picture of bird evolution, but also illustrates how understanding these genetic mechanisms can help humans, too.

Superb lyrebird image: Melburnian/Wikipedia

In life, you must make choices. You can’t succeed at everything. For example, Tiger Woods is an excellent golfer, but a terrible husband. Shaquille O’Neal? Great at basketball, but acting? Not so much. (Bo Jackson could be the exception.)

Penguins realized this about 70 million years ago, when they gave up flying for diving and swimming. Now, a study in the Proceedings of the National Academy of Sciences explains why.

Researchers from the University of Manitoba studied murres, a type of auk—a family of birds that is similar to penguins but not at all related. Apparently, this species didn’t get the message about excelling at one skill. The murres both fly and swim. But research shows the dual skills come at a very high cost.

The scientists measured the energy usage of the birds. According to National Geographic News Watch,

They injected the birds with stable isotopes of oxygen and hydrogen to serve as tracers to mark the physical costs of their activities.

The team found that when flying, the murres’ sustained the highest metabolic rates ever measured for any animal. (Previously, the bar-headed goose held the record, but they are the world’s high-altitude flying champions.) In fact, the energy costs of the murres were 33% higher than the biologists expected after doing biomechanical modeling of the bird. The birds are sufficient swimmers, but researchers found that the birds’ energy costs while swimming were higher than penguins, who are specialists in the sea.

Lead-author Kyle Elliott remarks in both Nature News and ScienceNOW that the murres are at “the edge of what a bird can do.” And the team suggests that such high flight costs may have led aquatic birds, like penguins, to develop their wings for  propelled diving in response to foraging opportunities at increasing depths, behavioral adaptations that led, finally, to flightlessness.

In short, good flippers don’t fly well. But they’re great for swimming and diving. Fine choice, penguins.

Image: Ken FUNAKOSHI/Flickr

At Science Today, we love stories that highlight bioinspiration—tales that reveal how close inspection of the natural world lead to problem-solving in the human realm. Engineering-wise, nature has had millions of years of trial and error to get things right, so why not learn from evolution and adaptation?

This week, the Academy will open Built for Speed, a new exhibit that explains the adaptations by fast fish and marine mammals that make them swift and speedy underwater and how boat designers use a similar process of adaptations to create ultrafast sailboats to compete in the America’s Cup race.

To get ready for Built for Speed, we’re featuring a few recent news stories about robots inspired and refined by the study of nature. Enjoy!

UC Berkeley

One of the leaders in bio-inspired robots is right across the Bay from the Academy. Biologists and engineers at UC Berkeley have been collaborating for several years on biological inspiration. And the researchers find inspiration from the most unlikely of sources. We’ve covered their gecko-inspired bot, but earlier this year news outlets featured Cal cockroach robots. Did you know that cockroaches are able to balance without using their brains? According to Discovery News, this is fabulous news for robot builders:

… One of the recurring challenges of designing a mobile robot is writing an algorithm that keeps it from falling over.

VELOCIRoACH, is a Berkeley roach bot and happens to be one of the fastest robots in the world. TAYLRoach uses its tail to make fast turns. New Scientist says that smaller is better for these robots:

Small-legged robots are being developed for search and rescue, for situations where a location is inaccessible or too dangerous for humans.

More Insect-bots

Berkeley isn’t the only academic biorobotic institution. Last week, Harvard scientists published their engineering breakthrough—the first flying insect-like robot. Ten to fifteen years in the making, this bug-bot was inspired by the biology of a fly. It has submillimeter-scale anatomy and two wafer-thin wings that flap almost invisibly, 120 times per second! Check out the video.

Do you feel like you’re being watched? Another publication last week describes a new camera, inspired by insect eyes. Made of 180 tiny lenses, the camera can take panoramic pictures that offer similar compound views to those of ants, bees and praying mantises. According to Ed Yong in National Geographic, this tiny biomimetic camera is “ideal for surveillance. Perhaps in the future, we’ll be watched by man-made flies on the walls.” Creepy!

Speaking of creepy, how about small robots that work together like a colony of ants? French and American scientists wanted to understand how individual ants, when part of a moving colony, orient themselves in the labyrinthine pathways that stretch from their nest to various food sources. They hope their robotic findings reveal “possible improvements for the design of man-made transportation networks,” according to an abstract in PLoS Computational Biology.

Snakes and Seahorses and Birds, Oh My

Want more? How about a soft snake robot that slithers? A robotic arm as flexible and protected as a seahorse’s tail? Airplane wings fashioned after the wings of a herring gull? What about a swimming and crawling robot as efficient as a salamander? All of the above? Help yourself—many of the links above have videos detailing the creations.

Speedy Virtual Robots

Finally, just because it’s super cool, check out this video on Discover’s site. Researchers at the University of Wyoming and Cornell created a computer program to design fast virtual robots. Each robot could be made out of four different materials, and only the fastest would “reproduce.”

Essentially, the researchers incentivized forward motion, so the faster the robot, the more successful it would be in the evolutionary race.

You have to see the simulations created in this “Evolution in Action.”

Image of insect-eye camera: John A. Rogers, University of Illinois at Urbana-Champaign