Question

Please answer the following questions in this discussion board:

So far we have really only discussed relative dating methods, but things like stratigraphy and time markers/index fossils can be powerful tools to help us understand the past.

How do you think these tools help us understand evolution in a broader context? Do you think Darwin's ideas would have been more quickly and readily accepted if these sorts of things had been more common knowledge at the time?

word limit 150-200

Answer 1

It is difficult for today's students of archaeology to imagine an era when chronometric dating methods were unavailable. However, even a casual perusal of the large body of literature that arose during the first half of the twentieth century reveals a battery of clever methods used to determine the relative ages of archaeological phenomena, often with considerable precision.
Stratigraphic excavation is perhaps the best known of the various relative-dating methods used by prehistorians. Although there are several techniques of using artifacts from superposed strata to measure time, these are rarely if ever differentiated. Rather, common practice is to categorize them under the heading `stratigraphic excavation'. This text distinguishes among the several techniques and argues that stratigraphic excavation tends to result in discontinuous measures of time - a point little appreciated by modern archaeologists.

Although not as well known as stratigraphic excavation, two other methods of relative dating have figured important in Americanist archaeology: seriation and the use of index fossils. The latter (like stratigraphic excavation) measures time discontinuously, while the former - in various guises - measures time continuously. Perhaps no other method used in archaeology is as misunderstood as seriation, and the authors provide detailed descriptions and examples of each of its three different techniques.

Each method and technique of relative dating is placed in historical perspective, with particular focus on developments in North America, an approach that allows a more complete understanding of the methods described, both in terms of analytical technique and disciplinary history.

The Fossil Record as Evidence for Evolution. Fossils tell us when organisms lived, as well as provide evidence for the progression and evolution of life on earth over millions of years.

Fossils are the preserved remains or traces of animals, plants, and other organisms from the past.
Fossils are important evidence for evolution because they show that life on earth was once different from life found on earth today.

Usually only a portion of an organism is preserved as a fossil, such as body fossils (bones and exoskeletons ), trace fossils (feces and footprints), and chemofossils (biochemical signals).
Paleontologists can determine the age of fossils using methods like radiometric dating and categorize them to determine the evolutionary relationships between organisms.

Fossils are the preserved remains or traces of animals, plants, and other organisms from the past. Fossils range in age from 10,000 to 3.48 billion years old. The observation that certain fossils were associated with certain rock strata led 19th century geologists to recognize a geological timescale. Like extant organisms, fossils vary in size from microscopic, like single-celled bacteria, to gigantic, like dinosaurs and trees.

Fossils provide solid evidence that organisms from the past are not the same as those found today; fossils show a progression of evolution. Fossils, along with the comparative anatomy of present-day organisms, constitute the morphological, or anatomical, record. By comparing the anatomies of both modern and extinct species, paleontologists can infer the lineages of those species. This approach is most successful for organisms that had hard body parts, such as shells, bones or teeth. The resulting fossil record tells the story of the past and shows the evolution of form over millions of years.

The Law of Fossil Succession is very important to geologists who need to know the ages of the rocks they are studying. The fossils present in a rock exposure or in a core hole can be used to determine the ages of rocks very precisely. Detailed studies of many rocks from many places reveal that some fossils have a short, well-known time of existence. These useful fossils are called index fossils.

Stratigraphy is the chronological study of sedimentary rocks. Among the different group of rocks. Only sedimentary rock are amenable to such study because of the principle of the order of superposition. Stratigraphy • (Strata= a set of sedimentary beds, graphy= description) reveals various details of the history of the earth during the different periods of geological past, from the beginning till the present. • Through stratigraphy we can know the past details of climate, geography, glaciations, orogeny, eperogeny, evolution and migration of plants and animals. • Thus as this branch of geology reveals the history of our planet, it is called as “Historical Geology”.

The aim of stratigraphy are :

(i) To study the chronological sequence of scattered strata of different places
(ii) To correlate them with that of the worldwide or established regional chronological framework.
(iii) To interpret the geological history of the earth as a whole from the forgoing data.  Such a study paves the way for the arrangement of the sedimentary rock in the chronological sequence in which they were laid on the surface of earth.

In the mid-nineteenth century, both Charles Darwin and Alfred Wallace proposed that older species of life give rise to younger ones. According to Darwin, this change or evolution is caused by four processes: variation, over-reproduction, competition, and survival of those best adapted to the environment in which they live. Darwin’s theory accounts for all of the diversity of life, both living and fossil. His explanation gave scientific meaning to the observed succession of once-living species seen as fossils in the record of Earth’s history preserved in the rocks. Scientific theories are continually being corrected and improved, because theory must always account for known facts and observations. Therefore, as new knowledge is gained, a theory may change. Application of theory allows us to develop new plants that resist disease, to transplant kidneys, to find oil, and to establish the age of our Earth. Darwin’s theory of evolution has been refined and modified continuously as new information has accumulated. All of the new information has supported Darwin’s basic concept—that living beings have changed through time and older species are ancestors of younger ones. The fossil record. Fossil remains have been found in rocks of all ages. Fossils of the simplest organisms are found in the oldest rocks, and fossils of more complex organisms in the newest rocks. This supports Darwin's theory of evolution, which states that simple life forms gradually evolved into more complex ones.