For Smart Animals, Octopuses Are Very Weird

For Smart Animals, Octopuses Are Very Weird

Ed Yong

It’s telling that the nautilus—the only living cephalopod that still has an external shell—bucks all of these trends. It lives for up to 20 years, reproducing several times during its life. It also has a much smaller brain than its shell-less relatives, and doesn’t seem to be anywhere as smart. The loss of the shell “has been linked to so many of the adaptations that make cephalopods special,” Amodio says.

But Ernesto Mollo from the National Research Council of Italy isn’t convinced. In a rebuttal paper, he and two colleagues argue that the evolution of intelligence takes many generations, and cephalopods would surely have been exterminated by their legion of predators if they only started that process after they had lost their protective shells. “A gradual and relatively slow evolution of intelligence would not have allowed the survival of hypothetical shell-less, but still unintelligent ancestors,” they say.

More likely, they argue, the path to intelligence began while the shells still existed, perhaps to help early cephalopods control their jet propulsion, or process the information from their well-developed eyes and many arms. “This suggests that the gradual evolution of intelligence in cephalopods facilitated the loss of the shell, and not the opposite,” Mollo and his colleagues write.

Amodio actually agrees with that...