Johns Hopkins Magazine - April 1994 Issue

Science and Technology

Research Findings and News: The beetle-browed boy, etc.

Fossil boy: Not really big for his age

In his day, "fossil boy" was probably just like any other member of his species, Homo erectus. He probably spent a good portion of his time hunting rhinoceros and hippopotamus, then chipping away pieces of their flesh with his stone ax.

Today, however, he is unique among his species--because 80 of his bones have been recovered and now reside in the Kenya National Museum in West Turkana. "This is the most complete skeleton of any early hominid ever found," says Hopkins anatomist Alan Walker. (Not until people started burying their dead are near-complete skeletons found.)

Walker and paleoanthropologist Richard Leakey recently published The Nariokotome Homo erectus Skeleton (Harvard University Press, 1993), the findings of their decade-long research on the fossil boy's bones. In 1984, an archaeological team led by Leakey discovered the first fragments of the skeleton on the western side of Kenya's Lake Turkana (near the Nariokotome River). Judging by the curve and thickness of the matchbook-sized piece of skull, it clearly came from Homo erectus, the species immediately predating our own, which lived from about 1.8 million to about 400,000 years ago. For four years after the first discovery, Walker, Leakey, and their colleagues sifted through 1,500 tons of sand to unearth the boy's bones and piece them together. They have also pieced together what he looked like and how he died.

Although Walker has studied the fossil boy for a decade, he still talks excitedly about the project, rushing to finish his sentences and looking into your face as though searching for a mutual spark of interest.

"We first looked at the boy's age," then his body shape and size, says Walker. From analysis of the boy's teeth (his molars were still coming in) and the length of his bones, they determined that he was a 5 foot 3 inch 10-year-old. As an adult, he would have been 6 foot 1 inch tall--much taller than anyone had expected.

"When we found him, we first thought he was just a big kid," says Walker. Scientists had believed that early hominids like Homo erectus were on the short side. But then Walker and Hopkins anatomist Christopher Ruff analyzed the remains of several other Homo erectus skeletons unearthed at other sites and found that the boy was of average stature. "These people were bigger than modern populations," says Walker. "Now we think that most modern populations are dwarfed" in comparison to their ancestors.

The fossil boy is the only early hominid skeleton found that includes both skull and body bones, which allowed the researchers to speculate on the boy's intelligence, comparing brain weight to body weight. (Brain weight alone is not an accurate measure of intelligence.) "It turns out Homo erectus was not very brainy," says Walker. "They weren't advanced over the previous people, Homo habilis."

The beetle-browed boy lacked expanded frontal lobes, the brain structures responsible for most higher human functions, although he probably did have Broca's area, the brain structure responsible for language and certain other functions. He also appears to have lacked the neurons that control the abdomenal and thoracic muscles necessary for speech. So he probably could not talk, but he could make sounds and communicate, just as modern-day primates can. Walker believes that language itself evolved some 40,000 years ago, about the same time that written symbols appear in the archaeological record.

Piecing together the skeleton was a painstaking task because the bones were scattered across an 80-square-foot region. When the boy died, 1.6 million years ago, the area was a seasonal muddy swamp, says Walker. "He ended up face down, his head bobbing in the ripples," he says. (An abscessed tooth suggests he may have died from an infection, but the scientists do not know for sure.)

"The individual bones got kicked backward and forward on the shore," probably by elephants and hippos, Walker says. One leg bone was bent into a sort of carpenter's square as though from a hefty weight. In the end, the bones were buried in the mud--an indelicate burial but one which spared them from gnawing predators. And that's why his skeleton is so complete today. --MH

A loss to neuroscience

David Olton, a Hopkins professor of psychology in the School of Arts and Sciences and a pioneer in the field of learning and memory, died February 1 of pancreatic cancer. He was 51.

Olton, who came to the psychology department in 1969, was known throughout the world for his research on the hippocampus, a brain structure heavily involved in learning and memory. Using rat models, he deduced that the hippocampus plays a role in short-term memory. In recent years, he used animal models to investigate memory loss caused by aging and Alzheimer's disease. He recently was elected a councilor to the Society for Neuroscience. "His loss has cast a real pall over this department," says professor of psychology Stewart Hulse, who had known Olton for 25 years. "We'll miss him."

Olton played an active role in advising students. "He was very much concerned with making sure everyone was taken care of," says Hulse. "He was sort of a father-figure. He was great at teaching students to be professionals. He'd tell them, 'When you go to a meeting, here's how you get known.'"

On January 15, more than 120 colleagues, former students, friends, and family members from around the world attended a "Fest for David Olton" on his birthday, which included lectures on research spawned by his work. Olton called it "the best birthday party of my life."

Readers wishing to contribute to a fund supporting work relating to Olton's research may send a check to the Psychology Department, Johns Hopkins University, 224 Ames Hall, Baltimore, MD 21218. --MH

A better solar cell?

The drawer holds a clutter of small glass laboratory slides, each of which sports a square of color--salmon, mustard, apple-blossom, plum, whatever. Chemistry professor Gerald Meyer pulls out a purple one, blobs on a few drops of iodine/iodide solution, and clips in place a clear slide. It's as if he were making an iodine sandwich.

Thirty seconds later, held out the window into sunshine, this impromptu solar cell generates enough power to run a solar calculator. In series, three cells will yield some 1 volts, about as much as a battery.

That amount of power is not exciting in itself, but it's exciting commercially because not only would such solar cells be easy to make, as the demonstration suggests--"unbelievably easy," adds Meyer--but also they would be cheap. The key ingredient is titanium dioxide, which is a commercially important white pigment. Because it scatters light so very well, titanium dioxide is what makes paint white and paper opaque, and it costs far less than gallium arsenide, the key ingredient in solid solar cell devices like those used in spacecraft.

The Department of Energy's National Renewable Energy Laboratory, which funds the work, is enthusiastic. "With some minor improvements," says Meyer, "these could be marketable in the next few years." They might see use as memory devices, electro-optical switches, or in chemical sensing.

To make the cells (they are photo-electrochemical solar cells, to be precise), Meyer and a Hopkins colleague, Peter Searson of the Whiting School's Department of Materials Science, worked with their students to refine a technique developed by a Swiss team two years ago. In this method, a slip of conductive glass is bombarded with tiny clusters of titanium dioxide (TiO2). The clusters aggregate to form a porous, nano-structured film, which is then annealed and soaked in a solution ofdye. The dye bonds with the TiO2 to produce the color on the slides in the drawer.

When light (photons) hits the finished cell (the iodine "sandwich"), the light excites the dye molecules, causing them to inject electrons into the titanium dioxide (a semiconductor material). The electrons find their way through the semiconductor film and, voilą, you have electricity to be stored in a battery or "do any kind of useful work you want," says Meyer.

Meanwhile, the dye molecules are ready to go again--they've renewed themselves by accepting new electrons from the iodide. "They're molecular-level electron pumps," says Meyer. As long as the photons keep coming, each dye molecule pumps several thousand electrons a second. "In a sense this is mimicking nature," adds Searson, "in that the layer of dye molecules works rather the way chlorophyll does on a leaf, harvesting light."

As well as their ongoing study of the fundamental electron transfer events, the team is working to make the cells more efficient, perhaps by synthesizing new dye molecules. "The field is wide open," says Meyer. "There's lots of room for creativity." --EH

Written by Elise Hancock and Melissa Hendricks.

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