The Next Species: The Future of Evolution in the Aftermath of Man (27 page)

These are set in a double row in the middle of each arm, preceded and followed by the more standard toothed suckers. The claws likely assist in holding and immobilizing struggling prey like grappling hooks as the animals are drawn to the parrot-like beak of the squid. The largest known colossal squid to date was captured off New Zealand and weighed 1,091 pounds (495 kilograms) and measured 33 feet (10 meters) in total length.

Perhaps if this deep-sea creature got bigger it would have a better chance of taking the place of the great white shark, but giant or colossal squid could also borrow a few advantages from their cephalopod brethren, cuttlefish and octopuses.

Killer whales take on much larger whales by hunting in packs, but giant and colossal squid appear to be loners. A little better communication skill could help them with pack hunting, which cuttlefish, closely related to squid, have mastered. Cuttlefish range in size from
two inches to three feet. They look like short squid. As cuttlefish swim over yellow sand, brown sand, multicolored pebbles, or even beds of white shells, they can instantly and effortlessly change colors and textures to mimic the colors and textures of the bottom so predators above can’t see them.

Cuttlefish also have a rich vocabulary of signals for hunting, reproduction, and warning. An intense striped zebra display warns other males to stay away. Roger Hanlon of the Marine Biological Laboratory at Woods Hole, Massachusetts, described in a telephone interview and an online seminar from his lab a number of elements of the cuttlefish “vocabulary” that might come in handy. These include defense against predators, communication with other cuttlefish, attracting mates, repelling or deceiving rivals, signaling alarm to others, and more.

The giant Pacific octopus is a cousin to the squid and has some of the squid’s abilities, but also a brain that beats them all. Giant Pacific octopuses can grow as large as six hundred pounds, but most weigh less than one hundred pounds. They are found in the coastal waters of the North Pacific from Japan to California. Scientists believe
octopuses are more intelligent than any of the fishes, though not as smart as most mammals.

At the Seattle Aquarium, volunteers tend to give only octopuses, seals, and sea otters names, as these animals exhibit the prerequisite personality. Roland C. Anderson, a former biologist at the aquarium, told me that giant Pacific octopuses held in their tanks will invert their bodies to expose their suckers like a panhandler when they want food. If you give it to them, they will swim back and forth in their tanks turning red, perhaps “the only example of an invertebrate showing emotion,” he said.

Give a marine animal the body of a colossal squid, the brains of a giant Pacific octopus, and the communication ability of the cuttlefish and the result could give colossal squid top or apex predator potential. Add to these the newly discovered ability of Humboldt squid to hunt collectively, and they could take the place of a great white shark,
hunting and feeding on elephant seals. The trick is to get them to come up from the depths. But elephant seals already dive to great depths to catch fish and avoid topside predators.

Nature could bypass the depth problem and go with Humboldt squid as the top ocean predator if they could get larger.
They currently live to about one and a half years of age. No one has ever recorded finding a two-year-old squid. However, their growth rate is exponential at 5 percent a day. At one and a half years they can weigh up to a hundred pounds, but if they lived to two years, explains Gilly, they could weigh up to 660 pounds. If they lived up to three years, they could weigh up to two tons. “It would be pretty scary if these things figured out how to live longer than two years,” he says.

If man takes all the great white, tiger, and bull sharks, nature could adapt, though who would reign as champion of the seas would be a matter for evolution and time to decide. Larger animals—both in the sea and on land—once existed on earth, and it’s possible that they could return without us.

A
S
Homo sapiens
came out of Africa sixty thousand to eighty thousand years ago and spread over the world, animals in their path gradually got smaller. Man was an ecological force against size. As he moved out of Africa, the large mammals he encountered disappeared. They were often the easiest to hunt and provided the most food. In Africa, large animals evolved with different hominids over millions of years, observed their tactics, and learned how to keep their distance from these lethal and tricky two-legged creatures. But animal species in Australia, New Zealand, and North America weren’t as aware.

Man entered Australia about forty thousand years ago, and the continent lost over 85 percent of its large mammals within a period of only about five thousand years. According to UC Berkeley’s Charles Marshall, “That’s about a one percent change every fifty years. So if you are twenty and you look at the world around you and then you are seventy and you look again, do you notice the one percent difference? Probably not. Even the extinction of large animals in Australia took five thousand years, which, though geologically fast, was still creeping on human time scales.
But we’re not creeping anymore. People who do work in tropical rain forests, they go back five years later, and some of these areas are totally
gone.”

New Zealand had an assortment of very different creatures before man. Writes Jared Diamond in
The Third Chimpanzee
, “The scene was as close as we shall ever get to what we might see if we could reach another fertile planet on which life had evolved.” The most successful of New Zealand’s animals was the giant moa, an ostrich-like bird that stood over ten feet tall and weighed over five hundred pounds. New Zealand had different species of moa, the giant being the largest, instead of bison. It had songbirds and bats instead of mice, and huge eagles instead of leopards.

Polynesian settlers first landed in New Zealand only about a thousand years ago, and within a few centuries managed to annihilate the local fauna. Approximately 50 percent of New Zealand species disappeared, including all the large birds and most of the flightless ones. Moas were exploited for food and their skins and bones. Their eggshells served as water containers. The remains of approximately a half million giant moas ended up in archaeological sites, many times more than would have been alive at any one time. The
settlers apparently hunted giant moas for generations before they went extinct, as man almost did in North America with the buffalo.

The extermination of many of the large animals in North America occurred from thirteen thousand to ten thousand years ago. Some scientists speculate that a sudden cold reversal of temperature that hit earth from eleven thousand to ten thousand years ago, known as the Younger Dryas event, caught millions of species unprepared. Others think it was the quickly rising temperature at the end of this event that killed off the furry creatures.

Still others believe it was the Clovis people whose fossilized bones and other relics became dominant in archaeological excavations dated about thirteen thousand years ago. Of course, there are earlier sites with evidence of human habitation in both North America and South America before this time, but this period is notable because it is when Clovis populations gathered en masse and their fluted stone arrow points, a characteristic tool, started showing up
frequently.

Some believe that the demise of megafauna was itself the cause of sudden cold reversal. It may have cut off a large, important source of the strong greenhouse gas methane: the four-chambered stomachs of the animals themselves, which expelled the gas by burping (not passing gas). In other words, the
early hunters shut off all the methane that the large animals were releasing to the environment, and this itself caused the Younger Dryas onset of cold by temporarily shutting off the greenhouse gas that was making things warmer.

Blaire Van Valkenburgh, a vertebrate paleontologist at the University of California, Los Angeles, agrees that humans weren’t the sole cause of all the extinctions, “but they were an additional force that acted upon an ecosystem that had been in balance, but with the arrival of the Clovis people quickly became out of balance,” she told me when I visited her office.

When Clovis man appeared, he was a new carnivore that was competing with the saber-and scimitar-toothed cats, which now had to share their meals with a skillful new predator. Groups of large cats preyed on bison and horses, though there is also evidence of them following mammoth herds and attacking young mammoths. Man was essentially an uninvited guest that the cats had to deal with, and there wasn’t enough food to go around. Humans were the tipping point. After his arrival, North America’s large animal populations started to disappear.

Van Valkenburgh believes that further proof of the competition between man and megafauna is found in the condition of the teeth of saber-and scimitar-toothed cats and the large dire wolves. These
predators show heavier tooth wear and more broken teeth than modern-day beasts like cougars and gray wolves, though some of that was present even before humans arrived. Increased competition with
Homo sapiens
may have aggravated an already competitive situation.

“Large predators tend to exhibit heavier tooth wear and greater numbers of broken teeth when they consume carcasses more completely, actively feeding on bones,” Van Valkenburgh and coauthor William J. Ripple wrote in a paper in
BioScience
. “The predators, which were much more abundant than the humans, most likely killed the vast majority of the megafauna.” The addition of the new human predator was more the straw that broke the camel’s back rather than the lead cause of the extinction.

How did these mammals get so big in the first place? While the dinosaurs were still alive, mammals scurried around under the feet of their much larger neighbors, occasionally taking refuge under bushes, in tree hollows, or in underground burrows. But once the asteroid fell from the sky and the dinosaurs disappeared, mammals started growing, and growing, and growing.

It began about 65 million years ago and peaked about 30 million years later.
Animals grew about eight orders of magnitude (× 10, × 10, × 10 . . . eight times) rather quickly, but it took them about 30 million years to max out. The maximum of seventeen to eighteen tons for a land mammal has remained constant over time, in different places, and with different species, says Felisa A. Smith, a professor of biology at the University of New Mexico.
Indricotherium
, a hornless rhino-like herbivore that weighed approximately seventeen tons and stood eighteen feet at the shoulders, lived in Eurasia about 34 million years ago. It was the largest land mammal that ever existed.
Indricotherium
would have towered over a modern African elephant.

The colder the climate gets, the larger the animals, since they conserve heat better. Xiaoming Wang from the Natural History Museum of Los Angeles County and Qiang Li of the Chinese Academy of Sciences recently uncovered a large woolly rhino in the foothills of the Himalayas in the southwestern Tibetan Plateau. The animal stood perhaps six feet tall and was twelve to fourteen feet long. It had two great horns, one sprouting about three feet long from the tip of its nose, while the other arose from between its eyes. The Tibetan woolly rhino was stocky like today’s rhino but had long, thick hair. It is one of the giant mammals like woolly mammoths, giant sloths, and saber-toothed cats that became extinct. It is thought to be about
3.7 million years old. Over a million years older than the previous oldest woolly rhino fossil ever found.

The Tibetan woolly rhino lived at a much warmer time when northern continents were free of the massive fields of ice that came later with the Ice Age. But, residing in the Tibetan Plateau, this animal grew accustomed to the cold at high elevations and was “pre-adapted” to it. Thus, when the Ice Age arrived, these cold-tolerant rhinos simply descended from the highlands and began to spread throughout Eurasia. The Tibetan Plateau might have served as breeding grounds for these and other giant Ice Age mammals.

Professor Smith, whom I meet in her lab at the University of New Mexico and who towers over me in her cowboy boots, has been researching size in animals for many years and believes size is one of nature’s most important adaptations to climate change.

Smith currently studies the size of present and ancient large pack rats (also known as wood rats) at Death Valley National Park in California, details of which she discovers by studying their middens, the refuse tossed out of a pack rat nest. She uses this evidence as clues to their environment and ecology. She can tell the size of the animal and indirect information about the climate by examining the size of the animal pellets or feces in a pack rat’s midden. She also gets teeth and bones from these middens, which are used to confirm the identity of the species constructing the nest. She showed me some samples of these middens in her lab and even invited me to pick one up, which I did, cautiously. She asked what I thought of the smell, and I told her it smelled sweet, to which she responded, “You’re a born pack rat midden researcher!” since that smell was actually pack rat urine, which the animal uses to hold the pieces together.

According to Smith, the relationship of body mass and temperature has proven so predictable
it’s known as Bergmann’s rule (named for Carl Bergmann, a German biologist):
For broadly distributed mammal groups, the larger-size species are found in colder environments and the smaller sizes are found in warmer places.

Smith studies ancient pack rat middens because they provide detailed fossil evidence of the times when they were created. Pack rats are collectors of twigs, leaves, small rocks, fecal pellets, and anything they find and deposit in the large piles of debris in front of their nests. The middens provide protection from predators and insulation from climate swings. When they are constructed on rocky outcrops, they can last for thousands of years and can be carbon-dated. A single mountain may contain dozens of middens spanning thirty thousand years or more.