Life Everlasting

by Bernd Heinrich

  Elephant dung is very coarse compared to any other dung I have ever seen, smelled, or felt. That is because elephants don’t eat just young juicy grass shoots; they eat whole bushes. The result of digesting them can be stuff with the consistency of moist sawdust. You don’t really notice how rough it is until a few thousand dung beetles have ravaged a pile throughout a night. By morning the beetles are done, and all that remains is a thin mat of fibrous frass about a yard wide. But when this woody stuff dries out, it becomes perfect fodder for termites.

  Termites evolved from ancient cockroaches that ate decaying wood, incorporating bacteria and protozoa into their digestive tracts to help them digest the otherwise nonnutritious cellulose. Ensconced in a large log, the termites could eat slowly; there was plenty of food for the offspring, so the adults could stay home. Eating more wood merely enlarged their home, which they make by recycling their own feces. So the more inhabitants the merrier. Living a crowded but sheltered existence, termites had evolved from their cockroachlike ancestors by about 300 million years ago.

  Even more than their cockroach relatives, termites shun the light for most of their lives. They fly from home only once, to seek a mate and start a family, which may become a colony of millions. But on average one new colony just replaces an old one, and each colony has only one reproducing female. So, since each colony sends out millions of males and females, successful reproduction (meaning raising offspring) is a lottery: if only one in a million females may win, 999,999 necessarily fail. Most of the colony residents stay all their lives in or close to their climate-controlled home. For foraging, they build long extensions of their home in the form of tunnels. Their fuel—cellulose from wood—is cheap and plentiful.

  The termites’ main potential pollutant is their feces, which contain the indigestible lignin from wood left over after they digest the cellulose. But it is this, their own feces, that they recycle as a building material for their homes and tunnels. I suspect, though, that termite feces contain some other ingredient(s), because the building material they make is remarkable, as I found out when I recently brought back a piece of a termite nest from the tropical jungle of Suriname. The material had the consistency of plastic and was to my surprise totally insoluble in water. This plasticlike material has not been researched very deeply, but I suspect that it would be found to lack the toxins, such as sex-hormone mimics, found in manufactured plastics. The termites’ evolution-tested product might substitute for what we have invented, and it would use up lignin as well, which to us is a waste product when we extract the very useful cellulose from wood.

  IV

  WATERY DEATHS

  As terrestrial animals, we automatically connect undertaking with burial, which implies a rooting to ground, usually in the place of living. But most of the globe is covered by ocean, where animals may die far from where they lived. Large carcasses like those of whales may sink miles into the cold, dark depths. Salmon may live most of their lives in the ocean, yet they come inland to die and be deposited in fresh water, and the major effects of their recycling are on land, not in the oceans where they lived. Watery deaths involve similar principles to deaths on land, but those principles are differently applied. They give us examples of how life adapts and glimpses of different worlds from those most familiar to us.

  Salmon Death-into-Life

  AT A SERIES OF SHALLOW WATERFALLS ON THE MCNEIL River in Alaska, adjacent to Katmai National Park and Preserve, the sockeye salmon migrating upstream to spawn in June, and the chum salmon in July and August, encounter a gauntlet of grizzlies. These brown bears, Ursus arctos horribilis, are the largest in the world, weighing up to 1,500 pounds. Thanks largely to Larry Aumiller, who manages the McNeil Sanctuary, people who win a select drawing to come here can see the bears within several feet. They view them unprotected by any barriers, and they are not allowed to carry guns. No one has ever been attacked, because the bears have become habituated to people and are not angered by their presence. Besides, I suspect salmon probably taste better than humans, at least as far as these grizzlies know.

  The normally solitary bears gather at the McNeil River Falls because the water is funneled to places where they can perch to intercept the fish. The salmon have by then grown for two to three years in the northern Pacific. From twenty to sixty-eight of the huge bears may come to the falls at one time. Their great size is due to their access to the rich salmon diet. During a good salmon run, they become so glutted that they cease to eat the muscle meat, instead pulling off the skin and eating only the fish’s gonads, which are engorged with roe or milt. They may also eat the salmon’s brain, another delicacy because of its high fat content. By the time they hibernate in the fall, they will have gained a couple of hundred pounds of fat.

  One might suppose that the salmon not eaten is “wasted.” From the ecosystem perspective, however, the bears’ picky eating habits provide food for others. Wherever the bears are feasting, at the McNeil Falls or other places where salmon are caught, scavengers are there to take the leavings. In this case the scavengers feasting on salmon leftovers are swarms of gulls.

  Various species of salmon run in Alaska’s rivers and in many other rivers on the west coast of America. For most of them, the upriver fight is a one-way trip. Years earlier they came down the same river and then grew to adulthood in the ocean. They returned home to reproduce and then die. Indeed, soon after they entered the fresh water of their home stream, hormones kicked in to change their physiology and, in the case of the sockeye, also their appearance; returning sockeyes grow a large jaw and a humped back and turn bright red. After spawning, they experience a sudden, physiologically assisted aging; their tissues almost literally dissolve, and they die where they were born. The change in their appearance may be related to sexual selection, since many other fish also change appearance at breeding time, as do many birds. However, their seemingly premature death is more difficult to explain on the evolutionary principle of “survival of the fittest.”

  According to human standards and to our standard (simplified) ideas of so-called survival of the fittest, one might say there should not be an accelerated rush to death. However, according to most evolutionary logic, there is no point to living on after reproduction. Indeed, one might posit that at this point in human evolutionary history, our genes, on average, contribute to our demise, since we as a species continually collect more deleterious genetic mutations while having little or no natural selection that removes them. As we live longer and longer, medical costs will continue to rise. However, even by a strictly materialistic interpretation, we humans contribute much more than just our genes to future generations. This contribution is itself part of our genome as social beings in a complex world requiring skills to survive and prosper. The evidence for this interpretation is in our longevity. Our long postmenopausal life can be rationalized as being adaptive because old people, like old elephants, are able to pass on experience and knowledge to their offspring to help them survive and prosper. It seems to me that a similar argument can be made with regard to the salmon’s seemingly premature death—that, as I’ll explain, it is an indirect genomic mechanism of contribution to future generations.

  After swimming perhaps hundreds, if not thousands, of miles upstream and spawning, a salmon has only a small chance of surviving the trip back to the sea, living another year, and making the trip back up to spawn. Therefore, rather than “save” anything for the very uncertain future, it might as well use everything it has now. And the only contribution that makes any conceivable difference is to ensure that the salmon’s one reproductive effort is the maximum. This in itself would explain a lack of investment for future living, but does it explain what amounts to suicide rather than a gradual or unassisted decline?

  Given that animals have had strong selective pressure to repair their wounds and avoid being eaten, we may wonder why these salmon literally give up and offer themselves to the predators/scavengers long before we surmise they must. Why should the salmon’s m
igration to ocean and back be more difficult the second time as opposed to the first? Only one in hundreds may make it the first time, so why should the slim chances of making it a second time be less privileged? The relevant point is that the salmon presumably could feed after spawning and at least potentially recover for another try. But they don’t. Instead, their behavior has two effects: it is in essence a starvation, because it ensures that they will exhaust themselves at some point. It also assures, however, that they will not eat their own or others’ eggs and young. I believe that the second effect is the major selective pressure; self-imposed mortality helps the survival of their offspring. Recall that the fish are returning to their home stream and to the specific area in which they were born. This is the area to which their offspring will also eventually return and where their relatives are. And if not eating their own young and relatives is not enough selective pressure, another, even more indirect effect might enhance and would at least not detract from the selective benefit of offering themselves. Namely, this: the massive influx of their bodies helps create and maintain their ecosystem. The counterargument to the scenario I am proposing is that “cheater” fish who do not commit hara-kiri could potentially be selected for and replace those who offer themselves and benefit the group. In the case of the salmon, this didn’t happen.

  As I mentioned earlier, some of the salmon are taken by predators on their way up to the spawning grounds, but most are eaten on those grounds. The annual die-off of thousands, and in aggregate millions, of bodies creates a feeding bonanza greater than anything like that at the McNeil River Falls. Brown bears all the way up the West Coast and into Alaska feast on the dead and dying salmon, along with gulls, bald eagles, ravens, otters, crows, magpies, jays, and raccoons. These scavenging animals do what bears traditionally do in the woods, and the salmon are thus the “delivery packages” that bring nitrogen, phosphorus, and other nutrients from the ocean into the rivers and surrounding forests. Availability of nitrogen is a limiting factor in tree growth, so the salmon not only make big bears, they also help make big trees. In turn, the trees’ roots, which hold the moisture of frequent and heavy rains, “make” the watershed and perhaps also the conditions needed for spawning.

  The epic migrations of salmon and their spawning have always fascinated us, and the lives of peoples all over the world have depended on them. How much more fascinating they are, it seems to me, if seen as one of the most highly evolved death-into-life cycles in nature.

  Other Worlds

  IN 1970 A SPERM WHALE CARCASS WASHED ONTO A BEACH near Florence, Oregon. Officials of the Oregon Highway Division, in consultation with the United States Navy, were concerned about the unbearable stench such a huge carcass would produce for a year or more and were at a loss about what to do at first. They decided to break up the carcass and thus facilitate its removal by scavengers. To accomplish this, they surrounded the whale with twenty cases (a half-ton) of dynamite. Soon after the fuse was lit, there was a stupendous rain of blubber chunks for 800 feet all around, one of which smashed a car a quarter of a mile away. These results, curiously, had not been fully anticipated.

  Another stranded sperm whale (sixty tons), which beached near Tainan City in Taiwan in January 2004, also made headlines. This one was loaded onto a truck and taken to a university to be autopsied. But when the truck arrived, permission was denied. Later, on its way to a wildlife reservation for disposal of the carcass, the truck drove through the center of Tainan, where, on a busy street, the gases produced by internal decay caused the whale to explode. Aside from the nauseating gas, a shower of entrails and blood rained down on shops and people, and although the crowd tried to disperse, the hubbub stopped traffic for hours.

  These mistakes were not repeated in 2007 at another whale carcass (seventy tons) that washed onto a beach in Ventura, California. This carcass attracted a huge crowd, but the Ventura County Parks Department had bulldozers dig a fifteen-foot-deep hole in the sand rather than fragmenting it by dynamite. The whale may, however, already have been punctured, as it (along with another whale around that time) was likely a fatality from a collision in the busy shipping lane of the Santa Barbara Channel. Unfortunately, most of the sand around the carcass washed away. Oil and rotting flesh leaked out, making nearby beaches uninhabitable.

  We don’t know how whale carcasses would have been disposed of in the Early Pleistocene and before. But beaching on land would have been rare, so scavenger specialists would probably not have evolved specifically to handle whale carcasses on land—just as we humans haven’t worked out an appropriate protocol for this situation. Any stranded whales would have been used opportunistically by dire wolves, condors, and perhaps the American lion and saber-toothed cats who happened to be near.

  THE NATURAL PROCESS of whale recycling presumably begins near the surface of the water. We know little about a whale’s natural death, but we can imagine a scenario of what it may look like. Perhaps the whale weakens from old age and then drowns. I suspect that a weakened whale might easily become prey to orcas (killer whales), who hasten its death. After the orcas have taken their fill, the blood would attract large sharks, such as the great white, and various smaller sharks would come flocking to fresh meat. The whale’s body cavity would be breached, organs removed, and the lungs deflated. What happens then?

  The whale carcass begins to sink, drifting through a netherworld of dark, cold water populated by an assemblage of creatures that are specialized to live off the largess that comes down from above. These creatures seem bizarre to us because they are configured differently from those we know well. Some of the fish have light-generating organs, including one that resembles a lantern suspended from a stiff rod. Some have mouths that are larger than their bodies, with huge teeth. There are females who carry around tiny males that are like parasites embedded in their flesh, an adaptation that compensates for the difficulty of meeting a mate—something we take for granted in a world of light.

  But these creatures don’t catch all the manna that drifts down. Some parts of the whale continue to drift all the way to the bottom. Below a depth of 150 meters, photosynthesis cannot occur, so only animals, not plants, exist at lower depths. Those that have adapted to survive there either live on the largess from above or they catch and eat each other. Many are transparent. No light would be visible to us in this deep-water world, but the eyes of some of the animals are enlarged and especially well developed; those with some vision can more easily prey on those who see less and swim above them. Still farther down, where there is absolutely no light from above and no animal can see images, as we do by the light reflected from objects, the animals generate their own light. Prey animals obviously do not “want” to be seen, but they may need to be visible in order to be found by potential mates. At these depths beyond sunlight, there is a continuous light show of flashing and glowing blue lights that have different meanings, from (presumably) attracting mates to luring prey to faking out potential predators; one copepod has been observed to discharge its own light-generating matter (bacteria?) into the water to hide its location, much as some octopi conceal themselves by squirting ink. This is the world of the “engulfer eel,” which hangs in the water and presents a long tail to make contact with drifting edible debris or swimming animals. It has a mouth big enough to swallow animals its own size. A forty-meter-long colonial jellyfish has plenty of surface area for contact with drifting food particles. Here lives the fangtooth, a grotesque fish with an appropriate name. It moves very slowly and uses sensory filaments extending from its body to detect nearby objects in the dark by touch or subtle movements of the water.

  Finally, the whale, after sinking through strange dark worlds for many miles, comes to rest at the bottom. Here temperatures are near the freezing point, and bodies could potentially pile up forever in this refrigerator. But whales have been on earth in recognizable form since the Eocene, about 54 to 34 million years ago, and through all this time they must have been recycled, or the oceans would now be
filled to the brim with their cold carcasses. Such a massive food bonanza as whale carcasses, drifting down to the ocean bottom over millions of years, would presumably have prompted a retinue of specialized scavengers to evolve to make use of them. Until recently we had no idea who these scavengers were or how they recycled the world’s largest mammals.

  Most of the oceans’ ecosystems are ultimately dependent on the sun’s energy captured at the surface. In the last decades, however, two new ecosystems have been discovered that suggest other possibilities for life. Deep in the ocean trenches, we now know, vents like belching chimneys spew out water heated to 400 degrees F and containing hydrogen sulfide (familiar to us as the rotten-egg smell), and some bacteria are able to use this chemical as an energy source. In this deep-water ecosystem, life is driven by chemosynthesis rather than photosynthesis. Shrimp and other organisms graze on the bacterial mass the way antelope graze on grass. Some of these bacteria have also evolved to live in symbiosis with animal cells. This is similar to the way chloroplasts evolved from algae living in symbiosis with cells and to the way bacteria evolved into mitochondria, allowing animals to live off plants or plant eaters. In this recently discovered ecosystem of the “smokers,” sulfide-eating bacteria feed worms, clams, crabs, and potentially many more organisms. A second newfound ocean-bottom ecosystem is fed by methane gas generated from “cold seeps.” The methane is first captured by bacteria living in symbiosis with other organisms and feeding on the carbon compounds scavenged from them.