Nutcracker man was really a grass eater

Paranthropus boisei (nicknamed ‘nutcracker man’), a hominid living from 2.3 to 1.2 million years ago, was long thought to have had a diet consisting mainly of nuts and seeds. It certainly had the massive jaws and molars required to tackle that sort of fare. However, new research on P. boisei’s fossilized teeth has shown that the hominids were mis-nicknamed. In fact, the creatures ate mostly grasses.

Thure Cerling of the University of Utah and his colleagues from the University of Colorado, Stony Brook University, the Turkana Basin Institute, and the National Museums of Kenya used carbon isotope ratios to determine what the animals ate.

Plants use different metabolic pathways to incorporate carbon into their cells, and thus into the entire food chain. Briefly, C₃ carbon fixation (used by about 95% of the plants on Earth) results in a different ratio of the isotopes carbon-12 and carbon-13 than does C₄ carbon fixation (used mainly by grasses and sedges). Cerling’s team found that the carbon isotope ratios in 24 teeth from 22 different P. boisei individuals indicated that the creatures’ diets was about 77% C4 plants. This is comparable to grass-eaters of the time, such as the ancestors of modern zebras.

Meanwhile, Peter Ungar and his colleagues from the University of Arkansas examined microscopic scratches and wear patterns in the enamel of the P. boisei teeth. These too indicate a pattern of dining on grasses, rather than of cracking nuts or other hard objects. Taken together, we have strong evidence that at least one member of the hominid family was competing with the local cows at the dinner table.

You can see explanations by Peter Ungar in the following two clips, both from the National Science Foundation.

Targeting tumors with nanoparticles

The idea of using nanoparticles to target tumors is not new. What is new is the idea of using differences in acidity to direct nanoparticles specifically to tumors. This idea was conceived and successfully tested in mice by Paula Hammond and her colleagues from MIT.

Because tumors grow much more rapidly than neighboring tissues, they use much more oxygen and consequently are more acidic than normal cells. Hammond’s team took advantage of this difference in designing their multilayered nanoparticle capsules. The outer layer of each nanoparticle protects it from degradation in the bloodstream, but falls apart in the acidic vicinity of cancer cells. The next layer is positively charged, allowing the capsule to be absorbed through the tumor cell wall. Inside the final layer could be an anti-cancer drug, or a cell labeling system such as a quantum dot.

The polymer coating (light blue) is shed as the particle approaches a tumor, exposing positive charges. Those charges help the particle be absorbed through the tumor cell membrane.

Image: Stephen Morton.

The good news is that this system should be effective against any type of cancer. Rather than targeting markers specific to a few types of tumors, the traditional approach of nanotechnology, these new nanoparticles accumulate in regions of rapid growth, the hallmark of just about any cancer we might wish to eradicate.

The bad news is that even Hammond does not expect to see human trials for five to ten years. Such is the pace of medical science.

Just for fun: Fission Chain Reaction

The advanced placement chemistry class at Horizon Science Academy Cleveland High School was set the task of explaining how a fission chain reaction works. They came up with the demonstration below. According to the students, "several fingers were harmed in the making of this video."

Hat tip: Pharyngula.

Improved gas masks

Researchers led by Michael Sailor of the University of California, San Diego have found a way to make gas masks safer. The team incorporated carbon nanofiber sensors into the masks that indicate when the masks’ filters are saturated, and thus no longer usable.

Gas masks contain canisters of activated charcoal. As a person breathes through the gas mask, airborne toxins stick to that charcoal, leaving the inhaled air free of contaminants. However, as the charcoal filter becomes saturated, it becomes less effective. Eventually, the filter becomes completely clogged and the mask is useless. In the past, the decision of when to discard a used gas mask was based purely on the number of hours of usage. Depending on where that mask had been, this could mean either continuing to use an ineffective, and thus highly dangerous mask, or throwing away a perfectly good mask.

Sailor’s innovation was to add nanofiber sensors to the filters. These thin fibers (each less than half as wide as a human hair) are assembled into photonic crystals that change color as they absorb toxins.

As Sailor explains,

Because these carbon nanofibers have the same chemical properties as the activated charcoal used in respirators, they have a similar ability to absorb organic pollutants.

People who use gas masks equipped with these sensors can be secure in the knowledge that the nanofibers will indicate when the masks are no longer protective.

Caption: Repeating bands of greater density give this bundle of carbon nanofiber photonic crystals a characteristic color. When the porous fibers absorb chemicals, they change color, making the material a sensitive optical sensor for chemical vapors.

Credit: Timothy Kelly, UCSD Chemistry and Biochemistry

Tagging caterpillars for ambush

Plants have evolved a great many defenses against herbivores. A common strategy is to produce trichomes (hair-like projections) that physically block small insects, and/or exude toxic chemicals. The wild tobacco (Nicotiana attenuata), uses its trichomes for a different purpose. These trichomes are composed of acyl sugars that label any caterpillars that eat them with an ant attractant.

After ingesting the acyl sugars, both the caterpillars themselves and their poop (frass in entomology speak) exude a distinctive odor. Alexander Weinhold and Ian Baldwin from the Max Planck Institute found that predatory ants are attracted to that odor. In short order, ants arrive on the scene and carry the hapless caterpillars back to their nests for consumption. Thus, by providing a small sugar meal to herbivorous caterpillars, the plants call in ants to rid them of the little invaders.

My favorite part of this story is an experiment in which the researchers marked grains of rice with an equivalent amount of the frass odor to see whether ants would be lured to the rice. Sure enough, ants rushed out to collect the rice and carry it back to their nests. Back in the ant nest, I envision the ants grumbling, “these are the worst caterpillars I’ve ever had!”

A freshly hatched Manduca sexta larva (tobacco hornworm) consumes trichomes of wild tobacco (Nicotiana attenuata).

Credit: MPI Chemical Ecology: Ian Baldwin, Alexander Weinhold.

Top ten new species for 2010

Arizona State University’s International Institute for Species Exploration and a committee of international taxonomists have selected their picks for the top 10 new species described in 2010. The list was made public on May 23, the birthday of Carolus Linnaeus, the father of modern taxidermy.

Taxonomists are classifiers, or groupers. They figure out how each organism is connected to every other organism on Earth. Part of that process involves identifying and sorting newly discovered species. By some estimates, as many as 10 million species remain unknown to science, although thousands are discovered each year. The top ten list is an effort to bring attention to Earth’s biodiversity and to support the study and public display of natural history.

Among other organisms, the list contains a spider that spins the largest webs yet known with silk that’s ten times stronger than kevlar, a bioluminescent mushroom, an iron-eating bacteria found on the wreck of the Titanic, a fanged leech and the Louisiana Pancake Batfish, pictured below.

An image of Halieutichthys intermedius taken by one of its discoverers, Prosanta Chakrabarty.

Here’s the full list with pictures and descriptions of why each species was selected.

If you’d like to nominate your favorite species for next year, you can do so here. But remember, to qualify, the species must have been officially described for the first time in 2011.