September 5, 2007 | David F. Coppedge

Whale Sonar: Necessity Is the Mother of Invention

Biosonar is a complex ability possessed by toothed whales and dolphins, bats and some birds.  It includes both the ability to produce signals and to process the echoes to locate prey.  How could such a system evolve?  Scientists at UC Berkeley proposed an answer.  The press release promised a developing story:

Behind the sailor’s lore of fearsome battles between sperm whale and giant squid lies a deep question of evolution: How did these leviathans develop the underwater sonar needed to chase and catch squid in the inky depths?

Yet the answer was perplexing: bats and whales developed it by developing it —

Now, two evolutionary biologists at the University of California, Berkeley, claim that, just as bats developed sonar to chase flying insects through the darkness, dolphins and other toothed whales also developed sonar to chase schools of squid swimming at night at the surface.

Their answer, in other words, provided no information on the sequence of mutations that could have been acted on by natural selection to create a complex, interacting system.  It only asserted that the need to dive deep after squid somehow caused the system to be developed – by evolution.
    From that premise, they wove an evolutionary story of millions of years, based on the assumption that necessity is the mother of invention. 

….the first whales entered the ocean from land about 45 million years ago, and apparently did not echolocate….
    At the time whales developed biosonar, nautiloids dominated the oceans.  Lindberg and Pyenson propose that whales first found it possible to track these hard-shelled creatures in surface waters at night by bouncing sounds off of them, an advantage over whales that relied only on moonlight or starlight.  This would have enabled whales to follow the cephalopods as they migrated downwards into the darkness during the day….
    Over the millennia, cephalopod species in general – and especially shelled cephalopod species – fell as the number of whale species boomed, possibly because of predation by whales.  Then, about 10 million years ago, the whales seem to have driven the nautiloids out of the open ocean into protected reefs.  Lindberg said that the decline in nautiloid diversity would have forced whales to perfect their sonar to hunt soft-bodied, migrating squid….

The scientists recognized the need for better explanations:

The most convincing explanation, that echolocation allowed whales to more efficiently find food in the darkness of the deep ocean, ignores the question of evolution.
    “How did the whales know there was a large supply of food down in the dark?” asked Lindberg, noting that cephalopods are the most abundant and high-energy resource in the ocean, eaten by 90 percent of all toothed whales.  “What were the intermediate evolutionary steps that got whales down there?”

Yet the press release never did explain how the system developed – only that evolution saw a need, and by some unspecified process, developed the “sophisticated biosonar system” used by whales today:

“Whales didn’t need to have a very sophisticated sonar system to follow the nautiloids, they could just home in on the hard part,” Lindberg said.  Only later, he added, did they “develop a complex system with finer resolution to detect and capture soft-bodied squid.”

The article pointed to biosonar in bats and whales as “strong examples of convergent evolution” – a term that also hides the “how” of engineering design.  They reinforced their claim by pointing to filter-feeding baleen whales and fruit-eating bats that lack sonar because those don’t need the technology to locate their food in the dark.  Since both the sonar-equipped bats and whales are nocturnal, the authors presumed evolution provided the equipment needed to hunt at night.  They did not speculate why the nocturnal bats and whales didn’t simply switch to daytime food with their diurnal colleagues, nor why the squid didn’t just develop stealth technology to evade the sonar.
    Apparently, this is an acceptable way to explain things in biology these days.  David Lindberg, UC Berkeley professor of integrative biology, said, “thinking from an evolutionary perspective about existing data from biology, paleontology and ecology could answer questions about the origin of echolocation in bats, shrews and other animals.”  Presumably, it is now permissible to explain how something developed by saying it just developed – an odd development in scientific explanation.

OK, folks, we all just saw their shenanigans right there, which means we have developed a keen sense for seeing things in the dark – a case of convergent perspicacity.  Don’t let the ev-illusion squids get away with it.

(Visited 70 times, 1 visits today)
Categories: Mammals, Marine Biology

Leave a Reply