Frozen Fauna of the Mammoth Steppe: The Story of Blue Babe Read online

  Tales of earlier explorers suggested that mammoths ate pinecones. Herz was disappointed to find no pinecones or larch needles, but only bits of various grasses, in the large bolus of food frozen between the mammoth’s teeth. Much of the animal’s head had been eaten away by carnivores during the two years of exposure, but enough remained for Herz to find real information about mammoths. He and his associates were the first professionally trained biologists to see a mammoth mummy “in the flesh.” Herz described hair color and length in detail, as well as other parts of the anatomy. The bare tail, for example, was short, only 14 inches (355 mm) long, with 10-inch (255 mm) hairs (fig. 1.3).

  The death of the Berezovka mammoth seems to have been almost instantaneous. It had several broken bones—ribs, shoulder blade, and pelvis—and vertebrae were wrenched to one side. There were large blood clots in the viscera. It is possible, however, that some bones were broken diagenetically by the movement of sediments after burial. Despite a good description of the carcass, it is still unclear how the Berezovka mammoth died.

  How the Berezovka mammoth was buried is likewise unknown. It may have been trapped in a cavity or mud sink as Herz suggests, but how it was buried remains a problem and probably does not relate directly to how and only indirectly to where it died. The geology of the site is sketchy, as one might assume that geologists from the early 1900s did not have a sophisticated understanding of the sedimentary features of reworked loess (fig. 1.4). The animal had about 3.6 inches (90 mm) of fat on its torso, suggesting that it was in good health and that it died in the late autumn, after a good summer’s feeding. Fortunately, the Berezovka mammoth was brought back to Petrograd and saved for posterity.

  Fig. 1.1. The Berezovka mammoth. (Drawn from photo in Pfitzenmayer 1926.) Reconstruction of the mammoth’s appearance at time of death is shown in box.

  Fig. 1.2. Tongue, penis, and tail of the Berezovka mammoth. (Drawn from photos in Pfitzenmayer 1926)

  This was the sum of our knowledge of frozen woolly mammoths for almost three-quarters of a century. Some very incomplete mummies were found in the interim, but until 1977, none was more informative than the Berezovka mammoth.

  Fig. 1.3. Comparison of mammoth and elephant tails. Mammoth tails were short and hairy compared to those of elephants. The total length of the Berezovka mammoth’s tail was about 60 cm, whereas, elephants have tails over 160 cm long. A Paleolithic drawing of a mammoth tail from Gönnersdorf in northern Germany, above, shows a relatively short structure. In this drawing one can see the anal flap characteristic of proboscidians.

  Fig. 1.4. Berezovka mammoth site. Like other early finds of Siberian mammoth mummies, the Berezovka mammoth was discovered in a naturally eroding stream bank. The mummy was exposed by slumping of the hillside above a loop of the Berezovka River. Such erosion is common in Alaska as well, usually triggered by melting of underlying ice wedges. The weight of the water-saturated soil carries it downslope. (Above) A diagrammatic portrayal of how the mammoth was exposed (taken from the photos of the Herz expedition). (Below) Aerial view of Berezovka River channels showing the eroding bank where the mummy was found.

  Dima

  Perhaps the most famous frozen mummy from the far north is Dima, a baby mammoth found in the USSR in 1977 by a placer gold miner who was using a bulldozer to strip the thawed soils from underlying frozen ground. Dima was uncovered on a terrace of the Kirgiliakh River, a tributary of the Kolyma, north of Magadan in the Soviet Far East. Dima is perhaps the best-preserved specimen of all of the frozen large-mammal carcasses found in the far north. It had not been scavenged, so the carcass was intact (fig. 1.5), and very little decomposition had taken place before the body was frozen. A team of Soviet scientists was assembled to work with the mummy; they were able to conserve and analyze the specimen soon after discovery, and their analysis was quite thorough. The team included experts in paleontology, geology, geography, botany, palynology, entomology, histology, and anatomy. Each contributed a chapter to a monograph about Dima. Unfortunately, their book (Vereshchagin and Mikhel’son 1981) has not yet been published in English.

  Fig. 1.5. Dima, a baby mammoth found in the Soviet Union. Note the “wings” of the trunk, the small ears and tail. Its relatively empty gastrointestinal tract and small size must have allowed the body to cool rapidly after death. There was little decomposition before the body was completely frozen, and even the viscera were preserved. Dima is displayed at the Zoological Museum in Leningrad.

  This team of experts generally agrees on basic data pertaining to Dima; their interpretations, however, vary widely. Each of the scientists who worked with Dima provides a scenario of his death and burial. Their report brings new life to the parable of the blind men and the elephant; each man, touching only part of the animal, describes a quite different beast.

  Dima was truly a baby mammoth, just slightly over one meter high at the shoulder. Most hair had slipped, but much was found embedded in the mud where the animal laid. In fact, the hair actually helped the scientists, most of whom arrived at the site a little over a week after discovery, to relocate the exact spot where the carcass was found, because immediately after the discovery Dima had been moved to Magadan and refrozen. Dima’s small size, lack of fat, and empty gut probably helped the carcass cool rapidly at the time of death, reducing the rate of decay so that even his viscera were well preserved. The carcass was virtually complete; only one side had been torn loose by the blade of the bulldozer at the time of discovery.

  The Soviet team found a number of points of information pertinent to a reconstruction of Dima’s death and preservation. The high quality of tissue preservation is itself unusual and indicates that the body cooled rapidly after death and was not subsequently exposed to long episodes of warm temperatures. The degree of completeness of the carcass is also unusual. Because there were no signs of scavenging by avian or mammalian carnivores, the carcass probably was not exposed to scavengers for any length of time.

  Dima was a very young animal; judging from his size and the degree of tooth eruption and wear, his age was assessed at 7 to 8 months. His gastrointestinal tract was empty of food but contained plant detritus (unetched by stomach acids) and considerable amounts of mineral particles, silt, clay, and gravel. Most of the gut material (3.5 kg) was in his colon. “Many” hairs from the animal’s own body were found in its gut, along with a few insect (Coleopteran) parts. The botanist identifying seeds from the gastrointestinal tract found them to be late summer to early winter in their degree of maturity; however, the team’s palynologist found many pollen grains in the gastrointestinal tract that had not yet reached maturity. Mineral particles were not only found in the gastrointestinal tract, but also throughout the trachea, bronchi, and alveoli of the lungs. Dima was emaciated; no fat of any kind was present.

  The animal lay on its left side, with the head pointing downslope and dipping down below the body. This position was fortunate, for it allowed the bulldozer blade to miss the head entirely. The animal was found about 2 m below the surface, where the zone of annual thaw is about 1.2 m. There was some ice around the carcass. Portions of ice were clear and others quite brownish yellow with mineral and organic particles. A very small wound was found on the lateral or outer side of Dima’s right wrist, which showed some bruised tissue but no inflammation.

  Radiocarbon dating showed that wood found immediately around the carcass had been buried from 9,000 to 10,000 yr B.P. However, a number of Soviet laboratory tests on the mummy’s tissue gave dates in the range of 40,000 yr B.P. One tissue sample submitted to a lab in Pittsburgh, Pennsylvania, gave a date of 26,000 yr B.P. Histological evidence suggested that Dima contained a considerable number of helminth eggs. Other histological evidence showed that he had been under considerable physical exertion before death.

  A few days prior to finding Dima, the same miner had unearthed a crushed horse head and legs with hooves. Because the miner thought this animal was a moose (Alces), he had not saved it, and the specimen was lost and could not b
e found. His descriptions of the hoof as “not split” helped the investigators conclude it had been a horse. Other horse bones and the bones of bison (Bison priscus) and woolly rhinos (Coleodonta antiquatus) were found in nearby sediments.

  Fig. 1.6. The Dima site. The baby mammoth was found by a placer gold miner while removing silt overburden near a small creek called Dima, shown to the right. Both the cross section and the three-dimensional diagram are reconstructed from two-dimensional illustrations published by Soviet researchers.

  The heads of large vertical polygonal ice wedges surrounded Dima (fig. 1.6). These reached 7 to 8 m in depth and were about 1.3 to 1.4 m across, creating a polygonal core about 15 to 20 m across. Dima lay within one of these cores, yet he was stratigraphically well above the tops (dorsal surfaces) of the ice wedges. He lay on top of a 10 m terrace of the Kirgiliakh River, not in the river’s floodplain. The material covering him was unsorted clay, silt, sand, and gravel from the side slope of this Kirgiliakh River, near a small side drainage called Dima. From pollen found in and around Dima, the team’s botanists were able to describe the vegetation as mostly herbaceous, a dry tundra-steppe with some trees in the valleys.

  Interpretations of the Dima Mummy

  N. K. Vereshchagin, a famous figure in Soviet paleozoology who has conducted the bulk of recent research on Soviet frozen mummies, was the senior scientist on the Dima project. He developed the most complete theory about Dima’s death and preservation, and his interpretations are a baseline from which to compare the ideas of other researchers.

  Vereshchagin argues that early hunters killed Dima’s mother and wounded Dima in the leg. Dima must have escaped and hid. Without his mother he was unable to get milk and began to starve. Not knowing what to eat, he consumed silt and plant detritus. Exhausted, Dima came to a pool to drink, collapsed into the pool, and drowned, inhaling the silt in the water in the process. The cold water preserved the body, but the carcass still underwent some maceration, causing the hair to slip. It froze in the ice that winter and was thus preserved. New flows of mud and waste rock from upslope buried the animal the next spring. Vereshchagin argues that Dima must have died during late summer, because that would have been the time of maximum thaw. He thinks Dima is of a very late age, nearer the time of the surrounding wood (9,000–10,000 yr B.P.) that the skin dates (40,000 yr B.P.), but he recognizes the problematic incongruity of dates.

  To account for these differences in dates, several of the Soviet scientists who studied Dima proposed or implied the retransporation of a 40,000-year-old carcass into later sediments; others argue that the ice in which Dima was frozen was never thawed. Supporters of redeposition claim that little hair was associated with the carcass and that the hair was left behind during retransport. N. A. Shilo and E. E. Titov, two geologists, are among those proposing the reburial of Dima during the Holocene, perhaps by an earthquake. However, they propose that the death was accidental, not caused by humans, and they rely on the “lost mother” scenario to explain Dima’s starved condition. They suggest the animal fell into a polygon pond during early winter, froze, and was covered by a seismic landslide the next spring.

  I. A. Dubrovo, another geologist, finds evidence that Dima did not die from drowning in a polygon pond but rather fell into a thermokarst pit, starved, and was subsequently buried by snow, then covered by solifluction (the slow sag of soil downslope every summer as winter frost thaws) soon thereafter, probably within a month. To answer the question of why Dima was not rescued by his mother, Dubrovo also employs that lost-mother scenario.

  S. Timordiaro and V. K. Riabchun, a geographer and a permafrost specialist, respectively, contend that mummification requires surface exposure for an extended period before burial. They realize that scavengers would have eaten an exposed animal and proposed that Dima’s body was guarded by his mother—the opposite of Vereshchagin’s lost-mother scenario. They propose that following a period of desiccation, the baby mammoth was buried by a mud flow of at least 1.5 m, providing a cover that kept it from decomposing. They identified the ice enclosing Dima as neither vein ice (polygonal ice-wedge ice) nor frozen pond ice, but as segregated ice, ice withdrawn when water-saturated soil freezes. They also argue that a water-saturated mudflow retransported Dima, removing its hair in the process.

  V. V. Ukraintseva’s study of pollen percentages shows a surrounding vegetation dominated by woodless communities (67% grass pollen), similar to what we see today in cold mountain steppes. Pine, birch, and willow were distributed along the river valleys. However, V. P. Nikitin, examining the macrofossils in the gastrointestinal tract, concludes Dima lived in a swampy tundra. Ukraintseva found many immature pollen grains, which suggest the animal died in the spring. On the other hand, the mature seeds Nikitin found in the gut indicate to him a death in late summer or early fall. Nikitin also subscribes to the lost-mother scenario and frozen thermokarst trap. He thinks Dima probably used his trunk to pull at the edges of the pit, getting soil and plant detritus on his trunk and carrying this material to his mouth, accounting for the strange gut contents. Ukraintseva interprets the almost empty stomach as indicative of an animal trapped in sticky mud, unable to work its way out, starving and desperate, finally eating plant detritus and mineral particles.

  S. P. Il’inskii found mineral particles throughout the respiratory system and proposed that Dima died either of suffocation under a large block of dusty silt or from drowning in silty water. Widening of the pulmonary alveoli suggested death by asphixia. Heart muscle hemorrhaging and other damage were found, suggesting great exertion just before death, which Il’inskii interpreted as running. E. I. Ivanova found many cysts and eggs of helminths, which she contended could have contributed to the animal’s death.

  Dima’s Case and Others: Varying Views

  This brief summary does not do justice to the detailed discussions by Dima’s investigators, but it does indicate the great diversity of interpretations. Several issues still warrant further discussion and analysis, particularly the carbon-14 dates. I do not know what to make of the one Rochester, New York, U.S., date of 26,000 yr B.P. and the Soviet dates, from two different labs, of around 40,000 yr B.P. I suspect the Rochester date may be incorrect, but this disparity in dates should be pursued.

  As to the general pattern of surrounding vegetation, Ukraintseva’s steppe reconstruction agrees with many subsequent studies. The northern extent of pine and birch also agrees with the general picture of northward extension of tree species during the slightly warmer and wetter period of the interstade (Hopkin’s Beringian Boutellier Interval or marine isotope stage 3). The pollen and macroplant fossils indicate a dry, grassy landscape with some tree species growing along valley bottoms.

  Dima’s ontongenetic age is an important factor in determining the season in which he died. Among northern ungulates, timing of parturition has evolved to coincide with the first growth of plants in spring. I think woolly mammoths would also have had their young in the spring, for two reasons. The first concerns the mother: lactation is a costly endeavor, and the protein-rich greenery of spring helps the mother recover from winter and nurture her young. The second reason involves the young: a calf must maximize growth during its first summer or it stands no chance of surviving the lean times of its first winter.

  Winter forage is so poor in available nutrients that northern ungulates do not grow and even fail to maintain body condition over the winter. In less than five months, they must recover winter energy debts and build reserves for the next year. Young of the year face the same rigors as the adults. Unlike Asian and African elephants, which may be born any time of the year, baby mammoths must have arrived synchronously, in the early spring. Therefore, if the interpretations of autumn death are correct, it would not seem possible for Dima to be 7 to 8 months old. Nor would a spring death be consistent with that age, for then Dima would have had to have been born in the previous January or February, arriving in −40° F (−40°C) temperatures and winds. Wet fur and amnionic membranes would h
ave frozen immediately. Determining Dima’s age depends on a clear assessment of the season of death.

  The presence of mature seeds and immature pollen in the gut indicates, to me, that the young mammoth ingested seasonally mixed plant detritus and that plant studies alone cannot specify season of death. One reason an autumn death seems most logical is that the carcass would not be subject to lengthy decay or scavenging. If Dima did drown, the body would have bloated with enzymatic activity from its own heat after death and floated to the surface. Scavengers could have penetrated Dima’s relatively thin hide. The quality of preservation and lack of scavenging suggest fairly rapid cooling and freezing, but all evidence argues against a winter death. Mud in the gastrointestinal tract, silt in the respiratory system, and skeletal parts of Coleopteran beetles are incongruent with death in winter. An autumn death seems most likely. For this reason, I think the estimate of Dima’s age may be incorrect.

  Birth in spring and death in autumn would make Dima approximately 4 months, or 1 year and 4 months old. I think the animal’s size is consistent with an estimate of 4 months. The very rapid growth rates of mammoths during the short summer season would probably have been slightly higher than those of elephants, for young elephants enjoy a longer growing season and even grow year-round in places where forage permits. Elephants average 85 cm at the shoulder at birth and weigh about 120 kg, sometimes even as much as 160 kg (Hanks 1979). Dima was slightly over 100 cm tall and weighed an estimated 120 kg in life. This amount of growth, a 15% to 20% increase in shoulder height, can be expected during the first year of life. Northern ungulates, remember, complete a year’s growth during their first four months because resources to support growth are simply unavailable all winter. Dima would have been about four months old in September.