Recognising life in stone
The ancient Greek Xenophanes saw seashell fossils on mountains and guessed the land had once been sea, and Shen Kuo in Song-dynasty China recorded a similar idea in his Dream Pool Essays. Yet for a long time many believed fossils were stones that grew into lifelike shapes. In 1665 Robert Hooke showed under the microscope that fossil wood shares the structure of living wood, and in 1669 Nicolaus Steno compared shark teeth with "tongue stones", arguing that fossils are real remains and setting out the law of superposition — lower strata were laid down first. In 1815 William Smith used the distinctive fossils of each layer to make the first geological map of Britain.
How fossils form and how old they are
Most dead organisms decay, but if quickly buried in mud or sand, hard parts like bones and shells may survive, and minerals in groundwater can turn them to stone. Traces of activity — footprints, burrows, dung — are trace fossils; insects trapped in resin become amber fossils. Only a tiny fraction of organisms fossilise, so the record has many gaps. Georges Cuvier's studies of vanished animals such as mammoths showed that extinction really happens, leading to the study of mass extinctions. Fossils are dated by the order of strata and by the decay rates of radioactive elements: radiocarbon dating, developed by Willard Libby and colleagues around 1949, works on organic material up to about 50,000 years, while uranium or potassium–argon methods date rocks millions to billions of years old.
Fossils as evidence of evolution
In On the Origin of Species (1859) Charles Darwin admitted the fossil record was imperfect but argued it shows life changing over long periods (natural selection). Since then transitional fossils have filled in the story: Archaeopteryx (1861), the Cambrian animals of Canada's Burgess Shale, "Lucy", a roughly 3.2-million-year-old human ancestor found in Ethiopia in 1974, and Tiktaalik, found in 2004 and described in 2006, between fish and four-legged animals. In 2005 Mary Schweitzer's team reported soft-tissue-like structures in a Tyrannosaurus bone, whose nature is still debated. Korea's southern coast, including Goseong, has some of the world's notable dinosaur trackways. Fossil pollen and shells reveal past climates such as ice ages, and coal and oil — fossil fuels — also derive from ancient life.
FAQ
- Can we bring back dinosaurs with DNA from fossils?
- Most scientists think not with current science. DNA breaks down over time; the oldest DNA sequenced so far is about two million years old, and DNA from 66-million-year-old dinosaurs is not expected to survive.
- Can anyone take fossils home?
- It depends on country and site. Many fossil localities are legally protected, and collecting there can be an offence, so photograph a find and report it to the relevant authority.
Sources reviewed: 2026-10-26
References
- Hooke, R. (1665). Micrographia: or some physiological descriptions of minute bodies made by magnifying glasses. London: J. Martyn and J. Allestry.
- Steno, N. (1669). De solido intra solidum naturaliter contento dissertationis prodromus. Florence.
- Cuvier, G. (1812). Recherches sur les ossemens fossiles de quadrupèdes. Paris: Deterville.
- Smith, W. (1815). A Delineation of the Strata of England and Wales, with Part of Scotland. London: J. Cary.
- Darwin, C. (1859). On the Origin of Species by Means of Natural Selection. London: John Murray.
- Arnold, J. R., & Libby, W. F. (1949). Age determinations by radiocarbon content: checks with samples of known age. Science, 110(2869), 678–680.
- Johanson, D. C., & White, T. D. (1979). A systematic assessment of early African hominids. Science, 203(4378), 321–330.
- Gould, S. J. (1989). Wonderful Life: The Burgess Shale and the Nature of History. New York: W. W. Norton.
- Schweitzer, M. H., Wittmeyer, J. L., Horner, J. R., & Toporski, J. K. (2005). Soft-tissue vessels and cellular preservation in Tyrannosaurus rex. Science, 307(5717), 1952–1955.
- Daeschler, E. B., Shubin, N. H., & Jenkins, F. A. (2006). A Devonian tetrapod-like fish and the evolution of the tetrapod body plan. Nature, 440(7085), 757–763.