In chapter 1, Shubin details the process which field paleontologists like himself narrow down a long list of possible excavation sites to very reliable ones. Using his "everythings" analogies, he explains that a single column or rocks can hold billions of years of evolutionary history. However he also explains that due to the ever expanding nature of our society, it has become increasingly difficult to find and properly excavate good dig sites. In detail, explain the system he uses to find reliable dig sites as well as the type of terrains that produce the best results. Furthermore, explain how we as a culture are making it increasingly difficult to find good dig sites.
-Robbie Thomashow
diehardcubsfan93@comcast.net
It is said that paleontologists have an easier time finding dig sites nowadays because they have more knowledge on the geology of areas. They also have easier access to information because they can use the Internet to decide whether the site has appropriate conditions. Even though this is true, it is still difficult for plaeontologists to find fossils.
ReplyDeleteFossil sites are rare. There are three major factors that paleontologists look for. The first factor is that they look for rocks of the right age. They also look for rocks that are the right type to preserve fossils and rocks that are exposed to the surface. Fossils are not arranged randomly in the world. Most of the time, newer rocks are layered on top of older ones but there are sometimes faults in which the older rocks will end up on top which can throw paleontologists off.
Layers can also differentiate species of animals. The lowest layers would have little visible evidence of life. The next set of layers would contain impressions of early life forms such as jellyfish-like things. Higher layers would contain organisms with skeletons, appendages, and organs. The next layers would have the first animals with backbones. People would be found in even higher layers. We can use these columns of fossils to help predict where other fossil sequences can be found.
Shubin categorizes creatures in the zoo to help find fossils. He categorizes any animal with a head and two eyes as “everythings” and then adds descriptors of each animals traits to the word. By creating subsets such as “everythings with limbs and walks upright” Shubin says they can predict fossil order. As more descriptors are added, the later the creature is in the order.\
The environment is definitely a factor in finding fossils. Different rocks leave distinct rock layer signatures. Igneous rocks are ruled out because no organism can survive in it or in metamorphic rocks. The most ideal place to preserve fossils are sedimentary rocks which are formed by a gentle process in which fossils can form. Therefore the best places to look for fossils would be deserts such as the Sahara or the Gobi Desert.
Societal expansion has led to destroying of many possible fossil sites. The human need for more space has led to people pushing past their original habitat. They now develop over possible excavation sites in order to satisfy their, which eventually makes it harder for paleontologists to find fossils.
-Adnan Jahan
(adnanjahan@gmail.com)
As Adnan stated in his post, some believe that paleontologists have an easier time finding fossils due to greater access to information, but scientists also have technology that aids them in uncovering fossils in sites that they were not able to explore before. In 2009, scientists uncovered the skeletons of 2 pliosaurs, a reptile from 150 million years ago. Many believed that the arctic contained less fossils because of the lower temperatures there, but the fossils were simply reserved deeper down under hard permafrost surfaces. In order to uncover these fossils, the scientists had to use jackhammers. Before such technology was available, scientists had no way of uncovering such fossils. ((http://www.nytimes.com/2009/03/17/science/17foss.html)
ReplyDeleteBut technology can only take us so far when uncovering fossils. In actuality there are plenty of fossil dig sites around the world, but what is slowing down the process of uncovering fossils is the slow process of digging out the fossils. In once site in Fredericksburg, east of the Mississippi, volunteers have been working for 20 years to uncover fossils, but during that time they have only worked on 4,000 square feet of the site. Technological advances allowed these scientists to dig further down, but technology could not aid them in chiseling with spades and paintbrushes, a job that must be done carefully and slowly. It is because fossils are so fragile that this process takes so much time. Fossils are so precious to begin with, and working so fast that they become damaged would be detrimental. (http://www.washingtonpost.com/national/paleontologists-find-hoard-of-fossils-even-a-whales-skeleton-near-va-quarry/2011/03/10/ABskRpV_story.html)
While Adnan brings up a good point about urbanization leading to fewer dig sites available to people, we are currently seeing even more discoveries than in the past, not only due to our technological advance, but also increased knowledge about paleontology. For example, just a few days ago, the over 7,600 fossils were found in a dig in Zhucheng, China. These fossils were said to be the largest bones found in the world. Scientists have been digging at this site, known for its bones since the 1960s, and since then, more than 50 tons of fossils have been uncovered. Scientists were able to find all of these fossils, not because they were digging in a remote location, but rather because technology enabled them to dig deeper down and uncover even more fossils, despite the fact that digging at the site had already been going on for 50 years.
Now the question is, what makes for a good fossilization site. As Adnan stated, sedentary rock is a good place to look for fossils, but even more important than looking for specific types of rocks is looking for an environment that enables the animal to become properly fossilized. Bacteria often eats away at corpses before they have the opportunity to fossilize, so animals must die in locations where they are protected from other animals. Animals that are buried in sand, soil, or mud often fossilize the best. This is seen with all of the fossils uncovered at the dig site in Zhucheng china. Scientist at the University College Dublin discovered that the site was once a flood plain. The dinosaur bodies probably washed up there and were then fossilized. Seabeds or riverbeds are very good for fossilization, because they provide the proper protection to the corpse, so that fossilization can occur. (http://www.bbc.co.uk/nature/fossils) (http://www.myfoxphoenix.com/dpps/news/scientists-identify-new-dinosaur-zhuchengtyrannus-magnus-dpgoha-20110405-fc_12631534)
Anna Leng (annaissbananas@gmail.com)