Which best describes the fossil record?

A. The fossil record cannot provide evidence of evolution.

B. The fossil record provides evidence of a common ancestor to many species.

C. The fossil record provides evidence that disputes the theory of evolution.

D. The fossil record is inaccurate because scientists are not able to date fossils.

Picture of a fossil Archaeopteryx
Picture of a fossil Archaeopteryx

The correct answer is B. The fossil record provides evidence of a common ancestor to many species.

A fossil is the remains of a living organism that lived a long time ago and that has been preserved in some way. The fossil record is the cumulative knowledge of fossils that have been found in various sediments, rocks, and amber, that have been dated by relative or absolute dating methods.

These remains of organisms that once lived can be dated because the sediments or other substances that they are in can be dated. This then provides a record of some of the living organisms that once lived at various times during the history of life on earth.

The fossil record is often cited as evidence for evolution since there can sometimes be evidence of a common ancestor for different species. Transitional forms of a particular organism may also be evidence suggesting that the organism has evolved over a period of time.

New fossils are still being found and new techniques being developed to help with evolutionary analyses. Although the fossil record is incomplete and does not work well for soft-bodied organisms, it is useful for analyzing evolutionary relationships of other organisms.

Fossils

Fossils are the remains or impressions of animals and plants that once lived many millions of years ago. Examples of fossilized remains include shells and exoskeletons found in rocks, and insects that are trapped in amber.

The size of trapped organisms can vary greatly from the size of bacterial cells to gigantic animals and plants. Animal tracks and feces may also be found in sediments and rocks and can also be used to indicate that an animal once lived at a particular time. The age of the rocks and amber that organisms can be found in can often be dated.

It is difficult to know if a specific fossil is a common ancestor; however, there is evidence for individuals having common ancestry. This is most often seen in transitional fossils which show traits and features that are postulated to be between those of an ancestor and a more advanced species.

Today data from fossils and the morphological features of living organisms are often combined with molecular data and then analyzed to try to establish how species are related and what a common ancestor may be.

Research has been done on turtles for instance, where transitional morphological forms have been integrated into an overall analysis of how species may be related. Techniques have improved and new fossils are still being found, providing more evidence for evolution and how organisms are related.

Dating of fossils

Dating of fossilized remains can be done either by absolute or relative dating methods. Relative methods look at where remains are found in a set of sedimentary layers.

Older rock layers will be deeper so if one looks at a road cutting, for example, you would expect the oldest rocks to be those in the deepest of the layers (strata) of rocks.

Absolute dating is known as radiometric dating and uses the radioactive decay of isotopes to date rocks and remains. The method works because scientists know how long it takes for certain isotopes to decay. Furthermore, the most useful rocks for dating are volcanic rocks since they are formed at a particular time.

In comparison, sedimentary rocks are harder to date since they are accumulations of rocks from several sources and time periods. Dating is most often done using uranium-238, potassium-argon, and argon-argon dating.

How fossils form

There are various ways in which fossilization can occur. Dead animals and plants can become buried by sediment and the remains may become mineralized.

In some cases, only a mold remains of the organism as a hollow in the rock, which may later become mineralized to form a cast. Certain organisms such as insects became trapped in tree resin to form amber fossils.

The fossil record

The fossil record is the total record of fossilized organisms and remnants of organisms that have been found up until the present time. There are advantages and disadvantages to this record of life.

For one thing, it is important to realize that soft-bodied organisms are likely to be underrepresented in the record because they do not fossilize well in the same way that hard-bodied organisms do.

It is, therefore, more likely that a more accurate history of animals with bones and exoskeletons can be determined when compared with animals such as worms and jellyfish.

This is a challenge for evolutionary biologists who may need to rely on using presently living organisms to determine evolutionary relationships.

Many fossils can be dated by radiometric dating. These can provide a glimpse of some of the living organisms that were alive during certain geological time periods. This then can provide a record of life since it can indicate what life forms were present in the past.

Evolutionary biologists have used this as a means of postulating evolutionary relationships among organisms and in determining which organisms are more primitive versus more advanced.

Current trends

Today, the trend among evolutionary biologists is to use molecular data in addition to morphological data to try to determine how organisms are related. This is believed to provide a better overall picture of how life on earth has evolved.

It is also easier to analyze large complex data sets today using information from thousands of species. This is possible because computers today are now able to handle the analysis of large amounts of data.

Techniques for dating fossils and obtaining information from such remains have also improved. This is believed to help improve on the results obtained from evolutionary analyses.

In fact, radiometric dating methods have also improved and are now thought to have an error of only 1% compared with the past where the error was estimated at as much as 5%.

New fossils are still being found and new tools for data extraction and analysis are being developed. For example, intermediate forms have been found between the dinosaurs and the suspected bird ancestor, Archaeopteryx. This has provided a more complete picture of how birds evolved from reptilian ancestral forms.

References

  1. CQ Choi (2017). Fossil Reveals What Last Common Ancestor of Humans and Apes Looked Liked. Scientific American.
  2. SJ Gould (1993). The book of life. UK, London: Ebury Hutchinson Publishers.
  3. TR Lyson, GS Bever, BAS Bhullar, et al. (2010).  Transitional fossils and the origin of turtles. Biology Letters.
  4. MJ Benton, GW Storrs (1994). Testing the quality of the fossil record: paleontological knowledge is improving. Geology.
  5. MJ Benton (2015). Exploring macroevolution using modern and fossil data. Proceedings of the Royal Society of London B.

LEAVE A REPLY

Please enter your comment!
Please enter your name here