A former Utahn, Richard A. Robison is a leading scientist in the study of the development of sidedness - the preference that humans, and some other animals, have for using one side or the other.
Until recently, sidedness was believed to be a strictly human property. Ancient cave art in which a hand was outlined in cave paintings showed that people were preferring to use one hand over the other.And as all lefties know, by far the majority of people alive today use their right hands. But this preference was generally believed to be a strictly human trait, until research about 20 years ago showed that it extended to some animals, writes Loren E. Babcock in the July issue of Natural History.
Now, Babcock added, work that he an Robison carried out shows that a right- or left-side preference goes back to some of the earliest complex animals. They found proof of it among trilobites from the Cambrian era, more than 530 million years ago.
Trilobites were small, shell-covered swimming animals that thrived in the ancient seas. They are commonly collected by fossil enthusiasts in western Utah; in fact, the trilobite is Utah's state fossil.
The discovery of sidedness is considered a major scientific advance.
Robison, a Fillmore native who is a professor at the University of Kansas, Lawrence, explained how the research came about.
A student of Robison's named Gary Vorwald wrote his master's thesis about the Cambrian fossils in the western Utah mountain range called the Drum Moun-tains.
"He was preparing his specimens, and he brought in a specimen that had a healed bite mark on the tail," Robison said.
The fossil trilobite had been attacked by a predator, then it escaped and managed to heal before it died. The bite had removed part of the trilobite's shell on one side, however, and the fossil record preserved the evidence of the injury for half a billion years.
"These healed bite marks have been described in the (scientific) literature for a long time," Robison noted.
"The next day or so, he brought in another specimen. It was bitten in almost exactly the same spot."
Within a few days, Vorwald came up with two more fossil trilobites from his collection - both with healed wounds.
"All four of these were bitten in exactly the same spot. we calculated the odds of that, and it seemed to be about a thousand to one.
"This seemed to be beyond the realm of random biting."
Vorwald wrote a small section in his thesis about the bites, and presented the paper at a national meeting. "They received a little bit of attention at that time," Robison recalled.
About two years later, another student of Robison's - Babcock, who is now an assistant professor at Ohio State University, Columbus - showed up at the University of Kansas and wrote a term paper about fossil animals. It was published in Nature Magazine soon afterward, Robison said.
"He just continued to develop information about this subject . . . I just suggested that they investigate these subject, which both of these students did."
In articles published this year in Nature Magazine and in the Journal of Paleontology, Babcock credits Robison for his part of the research.
So what does the fossil record show?
"What it indicates is that there was handedness in the broad sense, indicated by these bite marks," Robison said.
"About 75 percent (of the bites) are on the right side, versus 25 percent on the left. Which means that either the trilobites themselves were prone toward right or left movements of the body, or the predators were, or both.
"This in turn indicates the development of brain laterality." That is the use of one side of the brain for some function more than the other side.
Earlier, scientists had speculated that fossils should show evidence of the development of preferences for sidedness. But these studies present the first statistical proof of it in extremely ancient life.
"This shows evidence of brain laterality that was developed at least 500 million years ago," he said.
The likely predators from the Cambrian era were the big swimming nightmarish creatures called Anomalocaris, some of whose fossils have been found in western Utah. These animals had spiny grasping appendages that portruded from the bottoms of their heads, and grinding teeth arranged in a circular mouth.
But in searching for other signs of handedness, the scientists found that trilobites from later than the Cambrian era also had healed injuries. Anoma-lo-caris is not known to have survived beyond the Cambrian, though other predators called ammonites are known from the time of the later trilobites.
"We found . . . something on the order of 300 specimens" of trilobites with signs of healed bites, Robison said. "About half of them are Cambrian and half of them are post-Cambrian."
In both times, the injuries have about the same disproportionate number on the right side.
The injuries might mean that the predator turned swiftly to the left to grab and bite a trilobite. Or they could mean that the trilobite tended to turn to the right and was bitten on that side as they escaped.
The fossils may even show that a trilobite was better at getting away if it turned to the right, since those going the other way didn't survive to heal.
Scientists of behavior don't care so much for the details of exactly which turnings or graspings contributed to the statistics. What is important is the simple reality of the preference for one side over the other.
In Babcock's Natural History article, he says the fact that one side dominates might be vital for controlled movement by any animal. One side always takes the lead, he writes.
The fact that a minority of animals favor the opposite side may have survival value, too.
If trilobites always turned to the right, the Anomalocaris predators might learn to anticipate their movements and catch more of them. But if a minority had the opposite preference, those might tend to escape more often.