Fossils
- Fossils are defined as preserved remains or traces of an organism and in order for fossilisation to occur, there has to be a rapid burial, a lack of oxygen and the remains must be preserved (BioNinja 2010). The rapid burial will produce a large amount of pressure on the remains and the absence of oxygen will stop bacteria from decomposing the remains. If there are scavengers, the remains will not remain in the same location or in a full fossil form. As these conditions are highly specific and somewhat hard to come by, there are many gaps within the fossil record.
- The fossil record is the collection of all fossil and within this we are able to determine ancestral relations and the way in which species evolved. However, as such required conditions are extremely hard to come across, the gaps in the fossil record minimises the amount of fossils that archaeologists have to analyse. Because of this, archaeologists may not be able to date fossils that pre-exist 70,000 years ago and this leads only to further debacle about our ancestral path.
- As preservation of remains only occurs to the harder parts of an organisms, fossilised remains that archaeologists uncover are usually only in fragments (BioNinja, 2010). This posses potential problems for archaeologists, as only having fragments of hominid remains leads to speculation and a lack of finality of our history (See figure 2.1 at left). Furthermore, if the small fragments that are unearthed are too small or destroyed through the fossilisation process, archaeologists will be unable to compare the fossils found with those of previous fossils. This will result in the newly discovered being somewhat invaluable as it cannot be placed within our history accurately.
- As time goes on, the chance that fossils have become degraded increase. Fossils of 70,000 years of age or older can be difficult to analyse as in the time that they have been fossilised, many events could have occurred resulting in a loss of continuity of the fossil. Such issues involve the moving of the earth, which interferes with the fossilisation process. If these events do alter the fossil remains, it can become difficult to obtain fossil evidence for archaeologists to analyse and further add to the fossil record.
- Dating fossils is an integral part of determining evolutionary theories and stages within a species evolution. There are two methods which are utilised in order to date fossil: Relative dating and Absolute dating
- Relative dating involves a rough estimate of the age of a fossil through the use of geological evidence. Within this method, they reference the principle of superposition, which examines the strata in which fossil are found and then dating the fossils according to the stratigraphy. Furthermore, the principle of correlation, where the same strata in different locations containing the same fossils can be concluded to be the same age. This technique in turn has its issues, as the movement of the Earth can disturb fossils and ultimately destroy the strata in which fossils are located, reducing the chance of dating fossil evidence
- The second form of dating is the absolute dating method, that utilises radiometric data analysis. This technique compares the ratio between the observed abundance of a naturally occurring radioactive isotope and its decay products using known decay rates (Wikipedia, 2015). There are certain types of radioactive isotopes that can be used. Carbon-14 to Nitrogen-14 analysis is only effective in dating samples around 50,000 years of age as carbon has a half life of 5730 years. This means it is not as accurate in dating hominid fossils. Secondly, there is Uranium-238 to Lead-207 dating, which is far more beneficial in dating older fossils as it has a half life of 704 million years.
- Absolute dating has less issues surrounding it and although it can provide the age of certain fossils, the ancestral relationships between remains and species is still up to interpretation, ultimately leading to varying models of evolutionary paths.
Figure 2.1: Lucy out of Africa.. (2013, February 21). Retrieved September 23, 2015, from https://pearlsofprofundity.wordpress.com/2013/02/21/lucy-out-of-africa/