Despite having a less convoluted birth canal, Neandertals felt the difficult pangs of childbirth just like modern humans do, according to a recent study of a female Neandertal pelvis unearthed in Israel more than 70 years ago.

Unlike our ape and monkey relatives, human babies are about the same size as the birth canal, making for a “difficult” passage, the two male authors write. (How’s that for an understatement?)

In fact, the human birth canal is twisted, wider than it is long in some places, and longer than it is wide in others. This means that babies must twist as they make their egress: entering the birth canal sideways, the baby must rotate so its head is down, and then rotate again to allow its shoulders to pass.

When did the ape’s birth canal evolve into the twisted, and painful, human version? Timothy Weaver and Jean-Jacques Hublin used CT scans to reconstruct a birth canal from pelvic bone fossil fragments from a Neandertal and compared this to data from pelvic bones from modern humans.

Weaver and Hublin’s reconstruction suggest that the Neandertal’s birth canal was less twisted than that of modern humans. But the pelvic area in Neandertals and modern humans is similar, suggesting that even though Neandertal babies didn’t have to twist as much during delivery, their size relative to the birth canal was close enough to insure a painful passage.

The results mean that changes in childbirth probably occurred “quite late in human evolution, during the last few hundred thousand years.”

A word of caution - this type of research relies on intact fossils. The pelvis survives very poorly, which is why scientists must rely on sophisticated reconstruction techniques. The current study is based on bone from a single Neandertal, making it difficult to take normal variations present within a species into account.

You know the cliché that science knows no borders? The current study was written by a scientist in the United States and one in Germany - examining a specimen discovered in Israel by a British archaeologist - using imaging technology developed by scientists from South Africa and the United Kingdom (one of whom worked in the United States).

Source: “Neandertal birth canal shape and the evolution of human childbirth” by Timothy D. Weaver and Jean-Jacques Hublin published April 20 online in PNAS (doi: 10.1073/pnas.0812554106).

Evidence from human hunter-gatherer societies suggests that more successful male hunters have higher reproduction success, an outcome a new study on chimpanzee behavior could help explain.

Two scientists from the Max Planck Institute for Evolutionary Anthropology in Germany have published an association between meat exchange and sex in a population of wild chimpanzees. Researchers studied 49 chimps, 5 adult males and 14 adult females, in Taϊ National Park in Côte d’Ivoire between 2003 and 2006.

Females copulated more frequently with males who shared meat with them on at least one occasion, than with males who never shared meat with them, the authors found. Their statistical model showed that other social interactions, such as grooming, did not significantly affect males’ mating success.

Researchers also found that it was the act of sharing meat that was important. The amount of meat shared did not correlate with mating frequency.

Chimps are promiscuous, so scientists had little problem recording copulation — 262 copulations during 1,814 hours of study. Only voluntary meat sharing was scored. “Cases of theft in which the male screamed, cried or aggressed against the female after the transfer, were excluded from the analysis.” Scientists recorded the frequency and the amount of meat transferred in each case.

To be clear, researchers are not saying this is a case of you give me meat and we copulate a few hours later. Meat exchange is part of a long-term strategy, and whether similar behavior occurs in humans requires further study.

Source: “Wild Chimpanzees Exchange Meat for Sex on a Long-
Term Basis” by Cristina M. Gomes and Christophe Boesch, published online April 8 in PLoS One (doi:10.1371/journal.pone.0005116).

How cool is this poster?

Mike Rosulek used Charles Darwin’s portrait in a parody of the Obama campaign posters designed by Shepard Fairey.

The Obama campaign posters were so popular that they were imitated by politicians in other parts of the world – during her campaign for prime minister of Israel, Tzipi Livni used posters with a Fairey-like image of her over the word “Believni.”

Mike is a graduate student in computer science at the University of Illinois. In August he will graduate and head to the University of Montana as an assistant professor. His specialty is theoretical aspects of cryptography.

“I wanted to do something clever for Darwin’s 200th birthday,” Mike told me. A few months ago he made a self-portrait parody of the iconic Fairey poster, which inspired him to try the same using Darwin’s visage. “The concept of evolution fit nicely with the Obama campaign’s rhetoric of change, so the slogan ‘(Very gradual) change we can believe in’ practically wrote itself.” You can find more variations on this theme on Mike’s blog.

Money from the sale of Mike’s designs will go to the National Center for Science Education, a nonprofit organization that defends the teaching of evolution in public schools in the United States.

So far more than 500 items have been sold, bringing in more than $1,500.

Mike used a public-domain photograph of Darwin as an old man and generated the Fairey-like image himself, without using an automated online tool, working a couple of hours a day for three days.

The tributes to Darwin take so many creative forms. When will the Alfred Wallace version be available?

Washington is wild about Abraham Lincoln, who was born 200 years ago today. In the nation’s capital, where the Lincoln Memorial anchors one end of the National Mall, it’s easy to forget that today marks another bicentennial, the 200th anniversary of the birth of Charles Darwin.

Darwin and Lincoln are more similar than you might think.

Both were controversial: Lincoln emancipated the slaves and waged an unpopular civil war to keep the United States united; Darwin’s idea that natural selection is the purposeless mechanism by which animals evolve was criticized as incompatible with religious beliefs.

Both emphasized fundamentals: Lincoln stressed equality, the bedrock of democracy. Darwin stressed evolution by natural selection, the bedrock of biology.

Both were talented writers. Lincoln’s speeches are part of the canon of American history; his second inaugural address is widely acknowledged as extraordinary. (“Both parties deprecated war, but one of them would make war rather than let the nation survive, and the other would accept war rather than let it perish.”) Darwin’s books also have stood the test of time. “On the Origin of Species” and “The Descent of Man” are classics. (“It may be said that natural selection is daily and hourly scrutinizing, throughout the world, every variation, even the slightest; rejecting that which is bad, preserving and adding up all that is good; silently and insensibly working, whenever and wherever opportunity offers, at the improvement of each organic being in relationship to its organic and inorganic conditions of life.”)

Both are featured on currency. Lincoln’s profile is on the United States’ 1 cent coin, Darwin’s visage can be found on a British £2 coin. Lincoln’s coin, although of small value, is ubiquitous. Darwin’s coin is new and commemorative and much more valuable than a penny – not that this is a competition.

Happy Birthday, Charles Darwin!

Our eyes, like cameras and microscopes, focus light using lenses – that’s refraction. For example, look at an object through water, like a straw in a filled glass, and the object will appear distorted.

Many telescopes, on the other hand, focus light using mirrors – that’s reflection.

Crustaceans such as scallops, lobsters and prawns have mirrors in their eyes, but this phenomenon had never been observed in vertebrates, until last month, when a team of scientists from Germany, the United Kingdom and the United States discovered the Brownsnout spookfish uses reflection to see.

Mirrors are common in animal eyes, but they usually aren’t used to focus light, like a lens. The eye-shine of cats is due to a reflective membrane, the tapetum lucidum, that sits behind the retina. Incoming light (refracted through the lens) that doesn’t get captured by photoreceptors in the retina is reflected back into the photoreceptors by the tapeta. “Light-doubling” systems like this are prevalent in nocturnal animals like sharks, crocodiles, and spiders.

In this picture of the spookfish, looking down at the head (in science jargon this is a dorsal view, anterior to the top), you can see that each eye has two parts that receive light. One part faces up, toward the ocean’s surface as the fish swims, and focuses light using refraction. These main parts appear colored in the photo. The second part of each eye faces downward (black in the photo), and contains stacks of crystals that reflect light onto the retina, enabling the spookfish to produce brighter images of the deep.

The spookfish Dolichopteryx longipes has been described only once before, in a 1973 paper. It was a dead, preserved specimen so authors had to make assumptions – some that turned out to be erroneous – about its anatomy. Kudos to Hans-Joachim Wagner and colleagues for collecting a live spookfish from a depth somewhere between 600 and 800 meters in the South Pacific.

Perhaps the most impressive aspect of the study is a technical one: having only a single specimen left the authors little margin for error in their examination. I’ve spent months slicing zebrafish tissue into thin sections and examining them under the microscope. Even on the best days no sample was perfect, but I had dozens of samples available. Wagner and colleagues only had one. If they had botched their preparation, we might never have learned that at least one vertebrate animal uses reflection to form images.

Source: “A Novel Vertebrate Eye Using Both Refractive and Reflective Optics” by Hans-Joachim Wagner, Ron H. Douglas, Tamara M. Frank, Nicholas W. Roberts, and Julian C. Partridge, published in Current Biology, January 27, 2009.