There’s bad news about the climate. We’re driving numerous mammals, birds, and even insects, to extinction. We’re not doing very well limiting the manufacture of weapons of mass destruction. Yet this week something happened that I found unusually melancholy and dispiriting. We seem to be close to destroying the most complex and awesome product of Darwinian evolution — a mammalian super brain.
As an anatomist I have handled many human brains fixed in formalin. My living brain writing this blog and your living brain reading it weigh about 1.4 kilograms (3 pounds) each. We have about 100 billion neurons, each with up to 10 supporting cells and in continuous contact through trillions of synapses. It can give a headache thinking about something so complex, but when it comes to brain size we are pygmies compared to one other mammal.
I’ve been having nightmares about the sperm whale found on the beach in Indonesia with a stomach full of plastic waste. A sperm whale has a giant 7.8-kilogram (17-pound) brain. That is five to six times as large as ours. Perhaps there are other planets with oceans and big brained creatures, but as far as we can be certain, the brain of the sperm whale is the most complex object in existence.
It is difficult to know why sperm whales have such large brains. It could be argued that a 40-ton animal needs a big brain, but dinosaurs did quite well with small brains. Perhaps the echolocation system sperm whales use to capture squids deep in the ocean requires a lot of computing power, but bats are great echolocators and they have tiny brains. Sperm whales are social animals. Males and females communicate with a complex range of sounds. Females and carves live in groups. Pregnancy last 17 months and calves can breast feed for many years. The males fight for access to ovulating females. (Incidentally their penises are 5 to 6 feet long.) Perhaps, like us, a lot of brain power goes into social life. With a brain that big perhaps sperm whales can think about the world in a way we cannot even imagine, just as a chimpanzee cannot conceive of why we should be interested in the movement of the stars or the structure of an atom.
Human beings have had a terrible relationship with sperm whales. The Moby-Dick type Massachusetts whaling industry killed sperm whales partly for spermaceti — the unique fatty substance that gives the animal its name. An adult can have almost 2,000 liters of spermaceti in a huge cavity at the front of the skull. Spermaceti both concentrates sound waves for echolocation and serves as an energy-saving buoyancy system when the whale dives as deep as 1,500 meters. Spermaceti oil illuminated many a 19th century American home with a smokeless flame. As recently as the 1960s, a quarter of a million sperm whales were slaughtered for oil and meat. Commercial whaling was banned in 1986, but plastic floating in the sea today may prove more dangerous than yesterday’s harpoons. It is not clear whether the dead Indonesian whale collected the trash that killed it on the sea surface, or echolocated stuff that seemed like a meal far beneath the waves. Perhaps the indigestible rubbish in its stomach satiated it and it stopped looking for real food. Whatever the details, this sperm whale did not live for the 60 or more years nature intended.
I find it ineffably sad that my grandchildren may live in world where the most complex, and I would assert most sublime, product of 4 billion years of evolution that ever existed, or is likely to exist in the future, may have been destroyed by the plastic water bottles and other throw away items used by a bipedal mammal with a much smaller brain.