What People Owe Fish: A Lot

New York Times Article

What People Owe Fish: A Lot


By NATALIE ANGIER
Published: February 19, 2008

Being a resolute hydrophobe who has no more desire to go for a swim than might a kitten in a bag or Luca Brasi in “The Godfather,” I admit I never thought of myself as a large, scaleless fish out of water.

Yet after reading Neil Shubin’s brisk new book, “Your Inner Fish,” and speaking with other researchers who use fish to delve into the history of vertebrates in general and ourselves in particular, I realize that many traits we take pride in, the body parts and behaviors we exalt as hallmarks of our humanity, were really invented by fish.

You like having a big, centralized brain encased in a protective bony skull, with all the sensory organs conveniently attached? Fish invented the head.

You like having pairs of those sense organs, two eyes for binocular vision, two ears to localize sounds and twinned nostrils so you can follow your nose to freshly baked bread or the nape of a lover’s irresistibly immunocompatible neck? Fish were the first to wear their senses in sets.

They premiered the pairing of appendages, too, through fins on either side of the body that would someday flesh out into biceps, triceps, rotating wrists and opposable thumbs.

Or how about that animated mouth of yours, with its hinged and muscular jaws; its enameled, innervated teeth; and a tongue that dares to taste a peach or, if it must, get up and give a speech? Fish founded the whole modern buss we now ride.

The fish’s tale of firsts is a tall one. “The backbone that holds us upright, that’s a fish invention,” Dr. Shubin, a paleontologist at the University of Chicago and the Field Museum, said in an interview. “The cranial nerves that we use to control the muscles in our jaw, that we use to talk and to hear, they relate to a fish’s gill arches. The basic wiring in our skull, the body plan we take for granted, that’s part of our story. It’s all from fish.”

Our inner fish extends beyond physicality. New research reveals that many fish display a wide range of surprisingly sophisticated social behaviors, pursuing interpersonal, interfishal relationships that seem almost embarrassingly familiar.

“Fish have some of the most complex social systems known,” Michael Taborsky, a behavioral ecologist at the University of Bern in Switzerland, said. “You see fish helping each other. You see cooperation and forms of reciprocity.”

Dr. Taborsky and his colleagues have studied the social lives of African cichlids, colorful freshwater fish from Lake Tanganyika. The cichlids live in relatively large groups of 10 or so individuals, a dominant breeding pair and a retinue of adult and adolescent helpers. The helpers share in all duties, Dr. Taborsky said. They defend territory, they help keep the nests tidy and they clean, fan and oxygenate the breeding pair’s eggs. When the eggs hatch into larvae, the helpers take up the babies in their mouths for cleaning — all the while forgoing their own breeding efforts.

Significantly, the helper fish are often unrelated to the royal pair over whose spawn they so officiously fawn. What’s in it for the helpers? “We call it pay to stay,” Dr. Taborsky said. “Helpers are allowed to stay in the territory and gain security and protection against predators. But they have to pay rent, so to speak, or they risk being expelled.”

In laboratory experiments, the researchers have shown that when subordinate cichlids are temporarily prevented from performing their duties, the fish compensate at the first chance by ostentatiously redoubling displays of helpful behaviors.

Researchers have identified many other surprising analogies between humans and fish. Dr. David Reznick of the University of California, Riverside, has discovered that female guppies go through a kind of menopause, surviving well beyond their reproductive life span, a finding that may bear on the evolution of menopause among women.

Catherine L. Peichel of the Fred Hutchinson Cancer Research Center in Seattle has determined that the fish are awfully human, particularly in their migratory prowess.

“Sticklebacks migrated out of their ancestral marine habitat and invaded lots of new environments over an evolutionary time frame of about 10,000 generations,” Dr. Peichel said. “That’s roughly the same number of generations since humans migrated out of Africa and adapted to habitats all over the world. It’s a parallel process.”

Even some of the same genes that shifted format in human migrations, like those responsible for skin pigmentation, also changed as sticklebacks ventured from salt water to fresh.

If everything we can do fish can do wetter, we should not be surprised. “The vertebrate family tree,” Dr. Shubin said, “is really a tree of fish.”

Some 30,000 species of fish are alive, a figure that represents more than half of all known backboned beings and encompasses Ripley’s oddities like fish that fly, fish that climb trees and fish that change from male to female and back again.

Fish are also the oldest group of vertebrates, the earliest possessors of rudimentary teeth, skulls and spinal cords having arisen from wormlike predecessors maybe 550 million years ago. That means that fish have had a long time to experiment with body plans and strategies.

Spurring the evolution of the vertebrate body plan, Dr. Shubin said, was a benefit of being an active predator. The origin of jaws and teeth “was a great equalizer,” he said, adding, “It allowed smaller fish to eat bigger fish.”

The advent of teeth demanded protection against those teeth, and the earliest skulls were little more than thousands of tiny teeth fused together. Through the pairing of sense organs up front, in the well-shielded head, fish gained spectacular new powers to seek food and slink from the seekers.

“The increasingly competitive landscape was a cauldron for the invention of new things,” Dr. Shubin said — including, 365 million years ago, the power to hoist your scaly self out of the sea and begin sampling the plants and arthropods that preceded you on dry ground.

In 2004, Dr. Shubin and his colleagues reported discovering the fossil of one such pioneer, a half-fish, half-amphibian creature they named Tiktaalik. Plucky Tiktaalik had rudimentary shoulders and enough upper body muscle to do push-ups, and so the beefcake era was born.