La Brea Tar Pits Essay Example

at Exposition Park in 1913. Among the Pleistocene fossils found and put on display: mammoths, mastodons, saber-toothed cats, the giant ground sloth and dire wolf, the California lion, weighing over a thousand pounds, the ground stork, the golden eagle (800 of these) and one solitary human, a female named the La Brea Woman. The Saber-Tooth Tiger Perhaps the most iconic of these finds is that of the Smilodon, or the North American saber tooth tiger.

The great predator likely ended up in the pit due to following prey into the sticky tar — the La Brea lab now holds 166,000 pieces of more than 2200 separate cats. (Kreiner 2000) Now extinct, and with no living ancestors in North America, the saber tooth tiger generated significant interest among paleontologists — why did the tiger evolve such long fangs? The hunting tactic of the tiger required and encouraged long teeth: a computer simulation of Smilodon "moves more like a bear than a cat. He's better equipped to pounce from ambush than he is to run down game" (Kreiner 2000, p. ) and those saber-like fangs were crucial for not only a quick kill, but to hook into the flesh of the huge beasts upon whom the tiger pounced. Smilodon prey included many other members of the La Brea bestiary. Ancient Los Angeles was "a damper, warmer, more heavily vegetated place where camels, horses, buffalo one-fifth larger than today's version and even mastodons roam." (Kreiner 2000, p. 2).

Smilodon vanishes from the fossil record some 3000 years after human beings enter the picture, leading to the possibility that humans either outcompeted the tiger for prey animals or directly wiped out

the animal itself.Some scholars suggest that humans may have initially scavenged off Smilodon kills, arguing "that the dental specializations of sabertooths would have precluded them from dismembering carcasses and consuming all the flesh; thus, they would have left behind substantial amounts of protein for scavengers. " (Stanford and Bunn 2001, p. 113) These scavengers would include humans, but also other creatures such as jackals, birds, etc.

However, this is not the only theory. Stanford and Bunn (2001) go on to note that:Other evidence concerning sabertooth cat feeding behavior comes from a study of tooth fracture in Smilodon fatalis from the Pleistocene Rancho La Brea deposits of California... Tooth fracture in extant carnivores is associated with heavy carcass utilization and bone-eating…, and Smilodon broke its teeth regularly, especially its incisors. Given this evidence, and the fact that modern big cats often use their rough tongues to rasp flesh off bones, it seems probable that sabertooths were quite capable of both dismembering and thoroughly finishing a kill up to the bone-cracking stage.p. 113)

Thus, while the teeth may have been impressive, they were not invulnerable, and likely worked much the same way current big cats use their smaller teeth. This also works as evidence to the idea that humans may have scavenged off saber-tooth kills. Again, the La Brea samples come in handy: "Four large carnivores are well represented at La Brea—the sabertooth cat Smilodon fatalis, the giant American lion, Panthera atrox, the dire wolf, Canis dirus, and the coyote, C. latrans.All four exhibit a remarkably high incidence of teeth that fractured in life, three to five times the incidence observed in extant large predators such as the lion

and spotted hyena." (Stanford and Bunn 2001, p. 115)

Interaction with Scavengers and Humans What was going on with the large number of broken teeth — teeth broken in life, that is, and not via the process of fossilization? One theory is that "kleptoparasitism as the explanation for the high incidence of broken teeth in Rancho La Brea carnivores.They argued that high predator densities led to more frequent kleptoparasitism, which favored increased carcass utilization and thus tooth fracture. " (Stanford and Bunn 2001, p. 115) "Kleptoparasitism" simply means that other animals, including perhaps humans, would steal the meat of a downed prey animal. To avoid this, the saber-tooth and other La Brea predators would spend more time with their prey animal carcasses, eating them more closely even at the risk of tooth damage.

It is also known that as the number of humans increased, the number of giant predators decreased.While we still do not know for sure whether the humans hunted predators (presumably to eliminate threats rather than as food), outcompeted them for prey, or whether there were climactic changes that encouraged human settlement while limiting opportunities for big prey animals due to the decline in vegetable matter, their food source, leading to a cascade of food source collapses. Non-Megafauna The shift in climate 10,000 years ago took a toll on many different types of animals that can now be found in La Brea. Barlow (2000) notes that " only a half dozen species of Pleistocene dung beetles were fortuitously reserved in the La Brea tar pits of California, along with the bones of ground sloths, sabertooth cats, dire wolves, and carrion-feeding birds. " (Barlow 2000, p.

209) Interestingly, despite being from a far older group of species, insects such as beetles may be considered more evolutionarily suited to their environments.

Insects are more likely to exist today, unchanged, than are any of the giant Ice Age"megafauna" they have been found alongside in the La Brea tar pits. Indeed, as mentioned above, neither the tiger, elephant, nor the lion have any living ancestors alive today in North America. Yet of these six beetles, two (possibly four) are extinct," Barlow (2000) continues. "The dung beetle extinctions are not surprising; when the megafauna vanished, beetles who nurtured their young in dung were even more vulnerable to extinction than were the large-seeded plants who depended on animals for transportation. " (Barlow 2000, p.209)

The connection between dung beetles and the sheer amount of dung available is well-known today, partially due to the investigation of fossils at La Brea. As Janzen (1983) notes:The Santa Rosa dung beetle fauna is probably a mere remnant of what was once supported by the Pleistocene megafauna. With the extinction of ground sloths, gomphotheres, glyptodonts, horses, etc. , the dung beetles that survived would have been those that could survive on the very diffuse and small-particle dung rain that is generated by humans and the many small species of vertebrates in a tropical deciduous forest.

With the introduction of a cow and horse megafauna, the dung beetles have again a resource that comes in one- or two-kilogram packets in large numbers.However, it should be a long time before the species richness again climbs to the level that was probably supported by the Pleistocene megafauna, since there is no nearby source area with a rich

fauna of large dung beetles from which more species may immigrate. (pp. 279-280) Research like that of Janzen (1983) is based on what was discovered at La Brea in the decades before.

Thus, the La Brea fossil pool is not only useful for the understanding of what went on in downtown Los Angeles, but what happened in the Pleistocene era (the so-called "Ice Age" in hich evolution encouraged the creation of gigantic land mammals to an extent not seen before or since) in general. The megafauna can in some way be seen as lynchpins of the era – as they were unique to the environment of the time and not seen before or since. Their collapse had profound, if geologically short-term, effects of related species such as insects and plant life. Humans and Guesses Of humans of the era, we know little. The tar pits were such a rich find as animals lack the cognitive ability to avoid the pits, and thus they got stuck with some frequency.Predators followed prey into the pits frequently, as we can tell from the treasure trove of over 2000 saber-tooth tigers alone.

As mentioned above, only one human was found, the La Brea woman, and her early on, near the top of the pit (suggesting a relatively recent death). We know little about her, indeed, Dixon (1999) sums up quite a bit of our knowledge in a single paragraph: In 1914, a human cranium, mandible, and some postcranial bones were recovered from Pit lo at Rancho La Brea (the well-known California tar pits), in Los Angeles, California. The skull was that of an adult female about 25 years of age.According to

Robert Heizer (cited in Kroeber 1962:416), there was apparently no inventory of the postcranial elements. A.L. Kroeber, the author of the brief manuscript describing this find, never completed analysis of the discovery, and his report was published after his death. Based on identification of avifauna also from Pit 10, it was suggested that the remains of La Brea woman may have been early Holocene in age. Subsequently, Berger (1975) has reported a 14C determination of 9,000 ± 80 B. P. for the La Brea human. (p. 139) Interestingly, La Brea was used to disprove some supposition about humans.In the 1880s, a peculiar fossil track was found in Nevada, amidst similar ones by known megafauna – mammoths, elks, etc.

– and by other animals such as cats and dogs. This strange track was believed to be by some to be a shod human, suggesting that Ice Age man had not only hunted mammoth and other huge animals, but had also developed the technology to make sandals or moccasins. Lockley (2000) notes that the controversy even attracted the attention of Mark Twain, who had an interest in human origins. As it turns out, however, the track was not of human provenance. Lockley (2000) explains:Even though we now know that humans existed in America during the Ice Age and were mammoth hunters, consensus now holds that the Carson City tracks were made by ground sloths--the theories of Mark Twain not withstanding. The discovery of the ground sloth Mylodon at the La Brea tar pits in Los Angeles, which are of the same age, supports the identification of the track maker.(p. 253)

Because of the sheer richness of the La Brea

area, paleontologically speaking, the relatively rare track mark of the giant ground sloth is fairly common, and La Brea tracks could be compared to the rare tracks elsewhere to allow for identification.Given the very limited information physical anthropologists, archeologists, and paleontologists have, it can easily be imagined that without La Brea, the track that looked like a sandal could have led to a significant wild goose chase, with many PhD theses and speculative journal articles written about the economy and artifacts of "the sandal wearers of Nevada", a group of humans that just did not exist at all. While fortunate for the humans of the era, it is unfortunate for us moderns that more people did not get stuck in the muck and drown in the Ice Age tar.If there were only more human skeletons, and perhaps some artifacts, at La Brea, we would know far more about the way life was lived in North America tens of thousands of years ago. Conclusions Despite its inadequacies and distortions, the fossil record fits the major predictions based on comparative studies of living organisms.

The plant and animal life that has evolved and diversified during the past can be better understood today within the context of large-scale changes in the physical and biological environments of the world.The continual redistribution of landmasses through continental drift has markedly influenced the levels of biological variety evolving in isolation and the composition of fauna and flora freely migrating or prevented from migrating between one landmass and another. Though today's North America contains no elephants, no rhinos, no lions, and no tigers, we know that at some point these huge creatures existed here,

and we know much of how they lived, thanks to how they died. The La Brea tar pits were a treasure trove of fossil remains.While oriented toward megafauna, as these were the animals most likely to find themselves trapped and drowning in the tar, we were able to learn much about the Ice Age ecology, and even got a glimpse of human life in the era thanks to the massive number of animal remains that have been retrieved.

While now almost a subject of kitsch – the pits are frequently referenced in television shows and movies (Futurama, Miracle Mile) as a tourist attraction, and are most frequently visited by Los Angeles-area schoolchildren – the scientific knowledge taken from the pits cannot be overstated.The state university system of California and the city and county of Los Angeles not only put themselves on the map with their embrace of the find, they have helped us map the Pleistocene era in a way that would not have otherwise been possible had the pits never been found.

Works Cited

1. Barlow, C. (2000) The Ghosts of Evolution: Nonsensical Fruit, Missing Partners, and Other Ecological Anachronisms.
2. New York: Basic Books. Dixon. E. J. (1999) Bones, Boats & Bison: Archeology and the First Colonization of Western North America Albuquerque: U of New Mexico Press.
3. Franks, K. A. & Lambert, P. F. (1985) Early California Oil: A Photographic History, 1865-1940.
4. College Station, TX: Texas A UP. Janzen, D. (1983) "Seasonal Change in Abundance of Large Nocturnal Dung Beetles in a Costa Rican Deciduous Forest and Adjacent Horse Pasture. " Oikos 41: 274-83. Kreiner, J.
5. (2000) "Science Fleshes out Saber-Toothed Tiger. " Washington Times 25 November:
   

2. Lockley, M. (2000) The Eternal Trail: A Tracker Looks at Evolution. Cambridge, MA: Perseus Books.