American Scientist

The largest of New Zealand’s now extinct moas, giant flightless birds that could reach 3.6 meters in height with their necks stretched upward, weighed about 230 kilograms, and had brain volumes of only about 60 milliliters. Moas had adapted to life on islands that had been isolated from other land for some 80 million years; there, without much in the way of predators (at least until humans arrived), they didn’t have much to fear—and they didn’t need to be smart. The moa had the brains it needed to survive, but it lacked the “smarts” we associate with greater intelligence, such as learning, tool use, and complex sociality. By contrast, corvids and parrots adapted to environments in which it was advantageous to evolve brains that were larger than their body size might seem to warrant.

Size is all relative, explains Daniel T. Ksepka in “Bird Brain Evolution,” and it’s not as simple as the ratio of brain size to body size. To determine across the fossil record when birds might have evolved more intelligence, Ksepka and his colleagues developed a measure of how big of a brain would be expected for a given body size. Humans have brains about seven times bigger than expected for our body size; moas had the smallest relative brain sizes of all birds.

But what happens when there is very little organismal “real estate” for a brain to occupy? How do the brains of extremely tiny animals function to allow them to understand what’s going on in their environments? In “Insect Decision-Making,” Shannon B. Olsson and Pavan Kumar Kaushik discuss the ways they have used virtual reality arenas to figure out what’s going on inside the brain of a fly. The natural world is too uncontrolled to isolate different inputs a fly could receive, so Olsson and Kaushik keep the fly in one spot and change the virtual world around it, which allows them to look at one fly behavior at a time. Olsson and Kaushik detail the different puzzles they had to solve to make their flies act the same way in virtual reality that they would in a natural environment.

Ksepka notes that birds such as corvids and parrots are good at solving puzzles, and that puzzles have a long history of serving as a measure of intelligence. As Henry Petroski mentions in this issue’s Engineering column, “All Things Cryptic,” humans can’t help themselves when it comes to puzzles: We consider them to be the epitome of thinking, and we can’t leave them alone. This tendency has allowed us to have fun with riddles and word puzzles, but it has also had rippling effects in cybersecurity, cryptocurrency, and international espionage.

Petroski opines that scientists see nature as a universe of puzzles. Indeed, other fascinating creatures in this issue have been at the center of research conundrums. In the Perspective column, “Conservation Across Borders,” Arturo Ramirez-Valdez explains why population counts for giant sea bass have been so flummoxing and what the numbers can tell scientists about how to handle conservation data going forward. And this issue’s Infographic, “Watchdogs of the Savanna,” discusses new research into the physiology of giraffes, explaining what keeps their blood flowing throughout their very long necks.

If humans can’t help themselves when it comes to a puzzle, let’s hope that one riddle we find a solution for is how to deal with climate change. In this issue’s Arts Lab, “Artists as Architects of Wildfire,” Robert Louis Chianese discusses artworks that bring the effects of fire right up to the viewer, by using debris from fires as the artistic medium. His hope, and that of the artists as well, is that these works will raise the consciousness of viewers, and encourage us to focus our intelligence on cracking this immediate but complicated puzzle. —Fenella Saunders (@FenellaSaunders)