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Geology and Comparative Anatomy
The period of Buffon and Lamarck also witnessed the contribution of geology to the undermining of Genesis doctrines and paved the way for a proper scientific explanation of species origins. James Hutton (1726-1797), the 'father' of historical geology, and William Smith (1769-1539), the originator of stratigraphy, are two key contributors to this narrative.
The Pioneers of Geology
The period of Buffon and Lamarck also witnessed the contribution of geology to the undermining of Genesis doctrines and paved the way for a proper scientific explanation of species origins. James Hutton (1726-1797), the 'father' of historical geology, and William Smith (1769-1539), the originator of stratigraphy, are two key contributors to this narrative. These two pioneers successfully decoded the tale hidden in the earth's crust. Several layers of compressed sediments formed the earth's crust. The majority of them were carrying some fossils. Sometimes the fossils were only found in one stratum. However, the same group of fossils was frequently found in numerous adjacent levels.
Again, some of them were not exact duplicates. While they formed a linked series, they did show variations. The forces responsible for what we observe as geological deposits also affect the earth's shape. They not only existed during geological ages, but they still exist today. They have had a consistent impact on the earth's crust. What exactly are these forces? The primary factors are −
Rapid unswelling of submerged land to form mountains
Subsidence of land beneath the sea
Erosion of land mass owing to wind impact on exposed soil
Silting of river beds
Silt transfer and deposition in the sea
An important implication of the above uniformitarian interpretation of geological strata is the concept of a geological time scale, which can span millions of years, to account for natural events. We are interested in this because, as you might expect, massive periods are required for any theory of species evolution based on progressive, heritable changes in living creatures.
Baron Cuvier and Comparative Anatomy
Fossils are made up of the shells of both marine invertebrates and terrestrial and aquatic animals. Identification and interpretation of vertebrate fossils had to wait until the subject of comparative anatomy was established. Remember that Buffon had previously brought attention to the underlying structural commonality among animals diverse in appearance and behaviour.
Baron Cuvier (1769-1832) advanced comparative anatomy research with scientific accuracy. Based on a thorough investigation of the anatomy of living species, he concluded that there were only a limited number of body designs in the animal kingdom. As a result, he proposed four primary groups: Vertebrata, Mollusca, Articulata, and Radiata.
He also recognised the tight relationship between structure and function. He believed that anatomy should be seen 'holistically,' that is, regarding the animal as a whole about its adaptation to the specific environment in which it lives. For example, adaptation to flight in birds requires not only the transformation of the vertebrate forelimbs into wings but also the spongification of the main bones to make them light and packed with air sacs, allowing them to fly. No part can be fitted to perform a specific function unless other connected parts are also modified.
Cuvier's belief and comprehensive knowledge of the comparative anatomy of modern species enabled him to solve the puzzle of fragmentary fossil remains. It is unusual to come across the fossilised remnants of a whole animal. An image of the entire animal must often be conjured up from a few isolated bones - even a single bone! It reminds you of Sherlock Holmes' technique!
He noticed a "remarkable succession in the appearance of the different species" after evaluating the anatomical characteristics of the age of the fossil-bearing rocks. He realised that the geologically younger alluvial layers included animal forms more comparable to modern species than the strata reflecting more distant (geological) epochs. As a result, the rocks indicated a progressive increase in the complexity of biological beings.
So, what has this brief examination of pre-Darwinian theories on the genesis of biological forms and their probable links taught us? The pieces of a coherent scientific explanation began to fall into place gradually. However, no one person has yet got the vision to connect all of the seemingly disparate data - and theories - into a coherent theory. We may sum them up as follows −
Consider the earth's age in a few hundred million years.
Species are neither immutably fixed nor immortal. The application of comparative anatomy concepts indicates the unity of body design within the major groups of the animal world, whether of present or fossil species. Simultaneously, variations on the fundamental subject are seen. The stratigraphic strata of the earth's crust include fossil remnants that indicate increased form complexity through time.
Some regard the notion of species diversity by transmutation to be a distinct possibility.
The Lamarckian hypothesis of acquired character inheritance is the closest anybody can give a mechanism for such alterations.
Expression of Variability
A genotype is encoded genetic information for a particular phenotype under a limited set of environmental variables. In other words, a phenotype that occurs due to a genotype-environment interaction is represented by a structure or function of an organism that may be influenced by natural selection. Let us look at an instructive example of sickle cell anemia, a genetic illness in which the allele displays differently in different contexts due to natural selection.
A faulty chain of hemoglobin causes sickle cell anemia in roan. HbS, or aberrant hemoglobin, varies from native hemoglobin (HbA) by one amino acid. A substitutional mutation occurs when glutamic acid is replaced by valine at the sixth position from the amino-terminal end of a three-chain polypeptide. The aberrant mRNA has GUA or GUG instead of the triplet GAA or GAG, which codes for glutamic acid in regular chains. Deoxygenated HbS precipitates out of the solution as elongated crystals. The production of crystals causes a distinctive distortion of RBCs, causing the cells to take on a crescent or sickle shape, thus the name sickle cell anemia.
The period of Buffon and Lamarck witnessed the contribution of geology to the undermining of Genesis doctrines and paving the way for a proper scientific explanation of species origins. James Hutton and William Smith were two key contributors to this narrative. Baron Cuvier advanced comparative anatomy research with scientific accuracy.
Cuvier proposed four primary groups of body designs and recognised the relationship between structure and function, allowing him to solve the mystery of fragmentary fossil remains. Pre-Darwinian theories suggest a progressive increase in the complexity of biological forms, but no one has yet connected all of the disparate data into a coherent theory.
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