Normally, organic material decays before fossilization occurs, leaving only the hard body parts, such as teeth and bones.
A fossil is any preserved evidence, including the remains or impressions, of an ancient organism. This includes footprints, casts of the body or burrows. Although it is extremely rare to find fossilized remains of soft-bodied organisms due to decomposition, fossil discoveries of human and shark remains have been found.
Age
While the oldest human fossils discoveries date to 195,000 years old, ancient shark remains date to more than 400 million years old. As reported by National Geographic, the 1967 discovery of two human skull fossils, dubbed Omo I and Omo II, along Ethiopia's Omo River pushed mankind to 195,000 years old--more than 35,000 years older than previously thought.
On the other hand, a dig in October 2003 uncovered the world's oldest, intact shark fossil near New Brunswick, Canada. The 409-million-year-old species, known as Doliodus prolematicus, measures 9 inches long and has scissor-like teeth in the upper and lower jaws, large fin spines and scales. This discovery predates other fossilized shark finds by 15 million years.
Preservation
Intact shark fossils are extremely rare. Conditions of oxygen depletion and rapid burial are required to suppress the decaying process and allow the preservation of the soft tissue. A 2009 National Geographic article entitled "Shark Picture: Most Complete Great White Fossil Yet" details the discovery by paleontologists in 1988 of a nearly complete fossil of a great white shark in southwestern Peru. This four-million-year-old fossil contained the spinal column, head, jaws and 222 teeth of the ancient shark.
Human fossils containing both soft and hard body parts include the mummies of ancient Egypt and the preserved human fossils in the stagnant swamps of Denmark, which included skin, internal organs and even the remains of a last meal.
Dating Process
The dating process for both human and shark fossils is similar. To determine a fossils age commonly requires dating the rocks and strata in which the specimen was found; however, this may not be possible, especially if the exact fossil location is unknown. When this occurs, geological maps of the area as well as comparative or relative dating (comparing the fossil with other known fossil finds) are utilized. If any organic material exists, scientists use carbon-14 or potassium-argon dating techniques.
Living Fossils
Palomar College describes a living fossil as any species that adapts and survives a changing environment. With each generation, bodies and behaviors change. Organisms pass these changes on to their offspring, enabling the species to survive. Living fossils are essentially today's living organisms that exhibit the same characteristics as their ancestors. The shark is classified as a living fossil, while humans are not commonly labeled as such.
Fossil Hunting
Amateur fossil hunters are more likely to find fossilized shark teeth than human fossilized remains, according to National Geographic. Sharks have existed for millions of years and shed many teeth during a lifetime, making fossilized teeth abundant. Human fossil hunting may be more difficult due to the short geological time span as well as governmental restrictions on digs.
Tags: National Geographic, ancient shark, body parts, extremely rare, find fossilized, fossilized remains
