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Forever Amber

A tree once grew on the Caribbean island of Hispaniola that had the strange ability of freezing moments in time. A member of the honey locust family known as the algarrobo, it vanished millions of years ago. Fortunately for us it left behind tiny time capsules—fragments of amber in which we can read the story of a marvelous lost world. Entombed in some fragments are the remains of plants and various animals, the most common being the bodies of insects. For sheer beauty, mystery, and the capacity to astonish, these fossils are difficult to surpass.

The algarrobo tree produced a copious, clear, sticky resin. Whenever the tree bled from borer hole or fracture it extruded the substance in quantity. Sometimes the peculiar sap must have run down the trunk like honey, encasing whatever it encountered. At other times it sat atop the wound in a glistening pool, its reflection beckoning enticingly in the dark of the forest. Then a wasp, sweat bee, or beetle attracted to the substance might tumble in. Within seconds it would be engulfed. Life was extinguished almost instantaneously, but the corpse was rendered eternal.

It has long been known that resin has preservative and antibiotic properties, for it has been used in food preservatives, in medicines, and in winemaking since ancient times. Despite great recent advances in chemistry we still do not understand exactly how amber does its magic trick of preserving things so wonderfully. This is because amber is a cocktail of chemicals, including alcohols, sugars, esters, and terpenes whose complexity defies ready analysis. Somehow the brew withdraws water from whatever it engulfs, then fixes the dehydrated tissues and excludes bacteria. To top it all off it hardens when fossilized to a brilliant, transparent, gemlike material.

Although scientists have long appreciated the amber fossils for their ability to reveal something of a vanished world, their true potential as a key to unlocking the past has been recognized only recently. The senior author of The Amber Forest, George Poinar, was the first person to extract DNA from an amber fossil—that of a stingless bee from the Dominican Republic. It is now known that amber is the only substance that can preserve DNA in any form for more than a few tens of thousands of years.

The discovery of amber’s unique ability to preserve DNA over the long term has spawned a whole new industry, which began in 1990 when Michael Crichton published his book Jurassic Park. The story was to become famous and it went on to inspire one of the most popular recent movies. At the heart of the plot lay a plan to extract the DNA of dinosaurs from blood-sucking insects preserved in amber. The fictional researchers then reconstructed the beasts, with well-known consequences.

The authors of The Amber Forest inform us that Jurassic Park is still in the realms of fantasy, for even the DNA from animals preserved in amber is badly degraded, fragmented, and strongly cross-linked with other molecules in the cell. Yet we can still hope that one day the very improbability that the remarkable properties of amber exist at all will be matched by the creation of a real rather than virtual Jurassic Park.

The process by which algarrobo resin is transformed into amber is mysterious. Within a few hundred years of being exuded the resin becomes harder, though still remaining pliable and fragrant. At this stage it is known as copal. It takes another four or five million years to transform into the brittle, glasslike, and odorless substance we know as amber. Its gemlike qualities have long been celebrated. The Taino Indians who greeted Columbus presented him with treasured pieces, but the Spanish greed for gold soon extinguished interest in amber. It was only at the beginning of the twentieth century that Dominican amber once again regained its reputation as a precious stone.

The oldest fossils preserved in amber are plant fragments from southern Scotland that are thought to be around 300 million years old. The fossils that form the subject of The Amber Forest, however, are from the Caribbean and are between 15 and 45 million years in age. Today Dominican amber is mined predominantly in the high northern range of the island known as the Cordillera Septentrional. There, miners equipped only with a hammer, chisel, candle, and sack push deep into the steep hillsides, following the deposits for up to six hundred feet, where they work in tunnels so narrow that they have to crawl to the amber-bearing rockface.

The amber they seek was not formed in the rocks that they mine, for the Cordillera Septentrional is composed of sediments that accumulated under the sea. How the amber became incorporated in these sediments is not clear, but it seems likely that it was transformed from copal to amber in ancient swamp deposits. These may then have been eroded away and the amber washed out to sea by an ancient river. The amber was subsequently buried among the shells and other remains of crabs and other small marine creatures, some of which attached themselves to the glasslike shards. After the sediments were compressed and buried deep in the earth, great movements in the earth’s crust thrust them high into the air, forming the Cordillera Septentrional. The pressure generated by these earth movements crushed and fractured many of the amber nuggets, and indeed may have destroyed most of them. Consequently it is rare to find a piece of amber larger than a golf ball without internal fractures.

The Amber Forest is profusely illustrated, and to look into an amber ellipse and see there the microscopic inhabitants of a tiny pool preserved for eternity, or a pair of beetles mating, is the best way to gain an appreciation of the miracle of preservation that amber has wrought. It’s a strange sort of fossilization, for it can preserve an intimate moment—the laying of an egg or the taking of a meal—and yet provide almost nothing by way of a historical setting for these fundamental acts. Thus, for example, we know that a mother millipede assiduously carried her single young about, cradled carefully in her forefeet, and yet we have no idea whether the perfectly preserved creatures last breathed 15 or 45 million years ago. We do not know whether they lived in a forest that resounded with the nocturnal cries of owls and the morning howling of monkeys, or whether rhinoceros, tapir, or sloth crossed their path. The forest may have been seasonally dry or eternally steamy, and we do not even know whether Hispaniola existed as an island at the time the algarrobo trees shed their deadly, embalming tears.

A reader trying to understand the nature of the amber-producing forest through the fossils illustrated in The Amber Forest is in very much the same position as a person trying to make sense of a greatly enlarged newspaper photograph from very close up. They can see the individual dots of ink making up the image very well, but the portrait as a whole is lost in the detail. That is because for all of their beauty the amber fossils can give us little direct feeling for what the ancient forest was like.

The sight of so many splendid amber fossils left me with a longing to know in a more intimate way what the world that they inhabited might have been like. The Poinars make an attempt to reconstruct the ecology of the ancient forest, but ultimately they fail to provide, for me at least, a sense of what it might have been like to wander in those ancient groves. For that we must turn to other sources, in particular the works of early travelers who ventured into the wilderness where the descendants of the algarrobo tree still grow.

One such was the eccentric wanderer Charles Waterton, who in 1812 left the town of Stabroek in Dutch Guiana in search of the mysterious Wourali poison, as curare was then known. His adventure—which he described in his Wanderings in South America—would take him deep into the rain forests of South America.* There Waterton saw “the green-heart, famous for its hardness and durability; the hackea for its toughness, the ducalabali, surpassing the mahogany,… the locust tree, yielding copal; and the hayawa and olou trees, furnishing a sweet-smelling resin.”

Waterton says of the copal forest (in his rather florid style) that

the crowing of the hannaquoi will sound in thine ears like the day-break town clock, and the wren and thrush will join with thee in thy matin hymn to thy creator, to thank him for thy night’s rest. At noon thy genius will lead thee to the troely, one leaf of which will defend thee from both sun and rain. And if, in the cool of the evening, thou hast been tempted to stray too far from thy place of abode, and art deprived of light to write…the firefly…will be thy candle. Hold it over thy pocket book, in any position which thou knowest will not hurt it, and it will afford thee ample light. And when thou hast done with it, put it kindly back again on the next branch to thee. It will want no other reward for its services.

Evening in Waterton’s copal forest was an enchanted time: “The hayawa tree perfumes the woods around; pairs of scarlet aras [macaws] are continually crossing the river. The maam sends forth its plaintive note, the wren chants its evening song. The caprimulgus wheels in busy flight around the canoe, while whip-poor-will sits on the broken stump near the water’s edge, complaining as the shades of night set in.”

While The Amber Forest does not give the reader a larger, more fulfilling sense of the algarrobo forest, it more than makes up for it with a plethora of astonishing detail. Indeed the great strength of The Amber Forest lies in revealing and explaining the intimate moments in the lives of long-vanished, tiny creatures. For me the most extraordinary, if diminutive, of these intimate moments is fixed forever in a tiny fragment that has preserved the bodies of over five hundred once-living specks. They belong to an enigmatic, microscopic species that is represented in all stages of development. Their precise identification is still disputed, but they may be the tiny bear-like creatures known as tardigrades. Alongside them are preserved the strands of fungi on which they fed, while scattered throughout are the bodies of giant single-celled amoeba-like creatures, mites, and a single pseudoscorpion, all of which were carnivores and presumably preyed on the tiny hoard. Here is a miniature and fragile world preserved in toto. Just how amber could first engulf, then preserve, such a fragile spectacle defies comprehension.

Many of the larger creatures reveal the drama of life in that ancient forest. Peering out from one piece of amber is an ant, still apparently struggling mightily to free itself from a strand of spider silk. In another a butterfly is caught in a section of an orb-weaver’s web. It hangs helplessly, hoping perhaps by inaction to escape detection by the spider, just as I have seen countless moths and butterflies do today. In another tiny piece an entire flight of spiderlings has been overwhelmed just moments before they were ready to balloon off into the world. Had they not met their sticky end they would have been carried aloft on threads high above the rain forest, to come to rest perhaps far across the sea.

  1. *

    Charles Waterton, Wanderings in South America (London: Thomas Nelson and Sons, 1891; first published 1826).

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