The Historical Development of the Theories of Evolution

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“Evolution means a change in living organisms over a long period of time.” Over the years an abundance of ideas and proposals of concepts have been forwarded to account for such a change within organisms – with the theories of various scientists and philosophers including: Aristotle, Lamarck, Alfred Wallace, Charles Darwin, Gregor Mendel as well as the more modern scientists – Gould and Eldridge. Over time the theories concerning evolution have developed through the advancements within the areas of technology. Technology has the capability of leading to new changes in how scientists consider evolutionary relationships between humans and other primates as it opens up a means to discover new ideas and methods. These issues are raised and covered within this written report that presents the historical development of the theories of evolution.

Introduction

Assessment of how each scientist was influenced by society and culture and the knowledge available at their time. A description on how evolutionary thought has changed since Darwin proposed his theory of natural selection.

Toongabbie Christian School – HSC Biology Assessment Task 1

Module: Blueprint of Life

Task: Written Report

“Evidence of evolution suggests that the mechanisms of inheritance, accompanied by selection, allow change over many generations.”

Featuring DNA hybridization as a means to enhance scientific knowledge about evolution.

Description of an advance in technology leading to changes in how scientists consider evolutionary relationships between humans and other primates.

Advances in Technology Altering Evolutionary Thought

Featuring the evolutionary theories and contributions of Aristotle, Lamarck, Wallace, Darwin, Mendel, Gould and Eldridge

History of Evolutionary Theories

Contents:

Evolution

Aristotle was a Greek philosopher dating back to ancient Greek times – he lived between 384 – 322 BC. Aristotle was a philosopher and his views upon biology and physical sciences provide a basis on which one of the first “evolutionary-related” theories was developed. From the work of Aristotle, the idea known as the “The Great Chain of Being” was developed. “The Great Chain of Being” was a notion formulated by Aristotle to account for the possible relationship links between living things. It was used as a means of classification during the ancient Greek times. His idea was that all living matter and organisms could be placed within a hierarchical order from the lowest and the most basic up to the highest and most complex – relating to “perfection”, with the highest being God or divinity. Aristotle’s “The Great Chain of Being” therefore suggests all living material is organized and placed within a system from “lowest” to “highest” and within this system all positions are fixed. That is, that Aristotle suggests that it is impossible to increase the position of an object within the hierarchy as each species were created independently. This notion therefore opposes the traditional idea of evolution – that living organisms change and develop over time, as within “The Great Chain of Being” species could never change.

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Aristotle’s contribution to evolutionary theories is therefore one that arises more through context rather than content. Aristotle was one of the first philosophers/scientists to propose a concept that accounts for relationship links between varying species. His theory did not relate to the evolutionary notion of change, however for his time and context, his classification of species was a substantial idea. In fact, Aristotle’s notion that species are fixed became a widely regarded theory within western philosophy for a number of centuries after his death, developing into the current idea known as the Doctrine of Fixed Species. It was Aristotle’s non-evolutionary view of nature and biology that allowed for a movement away from this idea into a more distinctly differing view of the natural world – the evolutionary view.

Aristotle’s theory and concept of “The Great Chain of Being” was developed upon philosophical thought alone, and had no justifiably tangible evidence. It was a theory not grounded and supported by observable evidence and empirical data and therefore theoretically does not constitute as “science”.

Evolutionary Theory:

The historical development of the theories of evolution dates all the way back to the archaic times in Greece. The word “evolution” provides reference to changes within living organisms and species over a long period of time. This type of evolution is known as biological evolution and ideas and theories concerning these biologically related evolution-like ideas existed since the archaic times of the Greeks and have developed and been altered to the currently accepted theory of evolution by natural selection.

Over centuries these differing ideas and theories concerning biological evolution have shared some common basic criteria. This includes the notion that all living organisms arose from a common ancestor/life form and have changed and developed over time, differences that occur within groups of living organisms indicate that living things change over time and that similarities that occur within groups of living things suggest common ancestry.

Aristotle’s “The Great Chain of Being” Theory

Describe the history of evolutionary theories, highlighting the contributions of Aristotle, Lamarck, Wallace, Darwin and any other you think played a vital role.

Jean-Baptiste Lamarck was a French naturalist living between 1744 and 1829. Lamarck is considered one of the earlier scientists to propose an evolutionary theory based on observable evidence. Through observing various species of fauna and through the studying of the developing fossil record, Lamarck was led to the conclusion that life was in fact not fixed – as suggested by Aristotle, but was rather changing over time. This introduction of the possibility of life changing and developing contrasted to the widely accepted notion of the Doctrine of Fixed Species and was one of the initial historical stages for the development of the theory of evolution.

Lamarck was the first person to formulate and propose a mechanism by which evolution and the gradual change of species may take place. Lamarck suggested two critical ideas concerning evolution: 1. The inheritance of acquired characteristics based on use and disuse of body parts and 2. Organisms driven to greater complexity. These two notions were the underpinning of Lamarck’s theory of evolution, and were “supported” by his observations of various animal species. Lamarck’s idea of use and disuse suggested that environmental changes caused organisms to change and develop, and that these changes determined the usage or misusage of various organs, with the amount of usage leading to organs developing or conversely diminishing. Lamarck had the theory that the developed organs were now an “acquired characteristic” within organisms and that the acquired characteristic was now hereditary and could be passed down through offspring. An example used by Lamarck to demonstrate his mechanism for evolution was the elongated neck of the giraffe. According to Lamarck, a giraffe had the capability of developing an elongated neck over its lifetime through the constant straining in reaching for higher branches. This elongated neck was then an ‘acquired characteristic’ and could be passed down to further generations. An addition to Lamarck’s theory was that organisms were gradually but constantly evolving into more complex forms. That is, he suggested that as nature constantly changed, so too did organisms, and these resulted changes was constantly leading to a more advanced, complex form.

Thus, Jean-Baptiste Lamarck’s contribution to the evolutionary theory is substantial, as he was the first person to propose a mechanism by which such a system worked. His theory was also fundamental as it shifted away from the idea proposed by Aristotle, into a distinctly differing view of the natural world. Although Lamarck’s theory is currently dismissed, his contribution to the history of evolutionary theories is heavily noted with the idea known as Lamarckism being generated and with his idea being one of the first evolutionary theories based upon “observable evidence” and the first given serious scientific consideration, opening the way for the proposal of other new ideas.

Charles Darwin was an English naturalist living between 1809 and 1882, whilst Alfred Wallace was also an English naturalist and biologist living between 1823 and 1913. Both men played major roles within the development of the evolutionary theory through the proposal of the idea known as evolution by natural selection, with both men developing the theory independently before jointly combining and presenting their findings within a seminar in London.

The theory presented by Darwin and Wallace known as the theory of evolution by natural selection was based upon an abundance of observations and on deductions that followed from these observations. Darwin and Wallace each independently identified natural selection as the cause of evolution by gathering evidence that species were not fixed, but rather constantly changing. Darwin’s voyage to the Galapagos Islands and Wallace’s voyage to the Moluccas Islands provided significant amounts of evidence to support their theory.

Darwin & Wallace’s Theory of Natural Selection

Lamarck’s Theory of Inheritance of Acquired Characteristics

Mendel’s Theory of Inheritance

Gregor Mendel was an Austrian monk and scientist living between 1822 and 1884. Mendel is renown and prominent today for his work within the field of genetics and his study of inheritance. Mendel’s work on genetics and inheritance was fundamental to the history of evolutionary theories as it played a highly significant role in the scientific acceptance of the evolutionary mechanism proposed by Darwin and Wallace. The problem that arose within Darwin and Wallace’s theory of natural selection was the lack of knowledge available at the time as to how characteristics could be inherited and the cause of the differing “adaptations” that living organisms possessed. It was the work of Mendel and his experiments with garden pea plants that provided the hereditary mechanism that provided credibility to Darwin and Wallace’s theory.

Through experimental work, Mendel formulated two highly important laws that are currently used as the underpinning within the field of genetics and inheritance. These two laws contributed significantly to the history of evolutionary theories, providing an explanation of how characteristics may be passed down. His two laws were: 1. Mendel’s law of dominance and segregation and 2. Mendel’s law of independent assortment.

Mendel’s two laws accounted for the notion that advantageous characteristics/features could be inherited and passed down to future generations. Together, both the theory/mechanism of inheritance of genes formulated by Gregor Mendel and the theory of evolution by natural selection proposed by Darwin and Wallace form the basis on which people may understand the process of evolution and how living things may change and develop over time.

The Darwin-Wallace theory of evolution proposed that populations of one species living in varying places and under different environmental conditions could evolve over time in different ways and directions. They suggested that it was the process of natural selection that was the mechanism for which accounted for the survival of organisms within the changing environments. Darwin and Wallace suggested that individuals within populations naturally possessed features within their structure or behavior that could become advantageous to the changing environment. These features are now known as adaptations and enable organisms to better survive a change within the environment. Resulting from this is the survival of the organisms with the favorable characteristic – these organisms then survive to reproduce and would pass on the favorable characteristic to the future generation.

The extension of this evolutionary theory is that over many generations, populations of similar species may become increasingly different due to a continuous chain of differential reproduction. Natural selection refers to any environmental change/agent that is present upon a population – resulting in differential reproduction. Differential reproduction occurs when one inherited characteristic is more advantageous in producing survivable offspring than other characteristics. Over many generations, this results in the proportion of the advantageous variety increasing relative to the other species.

Therefore the mechanism known as natural selection is based upon two underpinning concepts: 1. Survival of the fittest (through an advantageous adaptation) and 2. Differential reproduction.

The contribution and theory presented by Darwin and Wallace was the most significant and substantial in regards to the history of evolutionary theories. Their theory, presented in the 1800’s still holds scientific relevance and utmost importance within the field of biology and within biological evolution. The theory of natural selection is the now the widely accepted theory to account for evolution. On the basis of the proposal of Darwin and Wallace, many following scientists have continued their work on evolution through the researching of new technologies which reveal more evolutionary links and which further solidify their theory of natural selection.

Stephen Jay Gould was an American evolutionary biologist and paleontologist living between 1941 and 2002, whilst Niles Eldridge was similarly, an American paleontologist who was born in 1943 and still living today. These two men proposed the theory known as punctuated equilibrium in 1972. This theory was a refinement and extension to the current evolutionary theory of natural selection proposed by Darwin and Wallace.

The theory of punctuated equilibrium proposes that evolution occurs in relatively short bursts of rapid change, followed by extended long periods of stability within populations. This theory differs to the theory presented by Darwin and Wallace of evolution being a gradual change from one species to another.

The theory presented by Gould and Eldridge is one that is supported heavily by fossil evidence and the fossil record. Many fossil species show little or no change over long periods of geological time and these periods are interrupted by much shorter periods during which new species appear and rapidly replace the ancestral species. This therefore supports the idea that evolution occurs in short bursts rather than at a continuous and gradual pace, as suggested by Darwin and Wallace.

The main, fundamental problem with the evidence for punctuated equilibrium is the fact that the fossil record is incomplete. An incomplete fossil record makes it difficult to come to a substantial, scientific agreement on the rate of evolutionary change, as there is a possibility of missing links within the fossil record which could provide more evidence.

The theory of punctuated equilibrium by Gould and Eldridge is therefore a theory that does not question the theory of evolution by natural selection, but rather questions the rate at which evolutionary change occurs. Punctuated equilibrium suggests that evolution occurs at short bursts, followed by long periods of stability whilst Darwin and Wallace believed that evolution occurred gradually over long periods of time.

Gould and Eldridge provide an extension to the evolutionary theory and thus are an important aspect in the historical development of evolution. They contributed by using “old knowledge in the light of new evidence” to provide a theory which is supported by their findings and studies. Their contribution is significant as it indicates that the theory presented centuries ago may still be adjusted accordingly to newfound evidence and to improved technology that may present new and differing evidences.

Gould & Eldridge’s Theory of Punctuated Equilibrium

Timeline Showing the Historical Development of Evolutionary Theories

Lamarck lived during the mid 1700’s to the earlier 1800’s within his birthplace of France. During this time the French revolution was a prominent aspect within Lamarck’s society and culture and thus had very influential effects on his life and on his evolutionary theory. The French revolution was a period of intense, radical social and political upheaval, with an abrupt transformation taking place within the French society. The revolution permeated all aspects of life, primarily within religion and the economy. This disturbance within France, affected the work of Lamarck, with Lamarck adjusting the way he operated. An example of this is Lamarck changing the name of the Royal Garden in which he worked, to a name that did not hold relations with the King of France. Other societal and cultural influences on Lamarck’s work were the lack of knowledge of evolutionary relationships at the time of his proposal. At that time, the majority of people believed in the Doctrine of Fixed Species and not the possibility of evolution and change, and so it was only during this time that Lamarck presented his evolutionary theory based upon observable evidence to the general public. His theory was the first to be widely acknowledged and given consideration. His theory challenged the general misconception that species were created independently and did not change over time. Therefore, the reception of his work was impacted by the societies lack of knowledge and by the impacts from the French revolution.

Jean-Baptiste Lamarck

Therefore, Mendel’s contribution to the history of evolutionary theories is one that is as important as any other scientific figure. His work on inheritance and the study of genetics provided the means by which evolutionary relationships could be identified. Without his work on inheritance and the presence of his laws regarding the inheritance of characteristics the theory of evolution may not have progressed to the stages that it has reached today. It was his work and his contribution that provided the relevance and credibility to the work of others, and it is through his experimental work that we may understand how living things change over time and evolve.

Mid 1800 AD –

Charles Darwin and Alfred Wallace propose their theory of evolution by natural selection.

Gregor Mendel experiments on pea plants and develops his laws on genetics and inheritance.

Early 1800 AD –

Jean Baptiste Lamarck proposes his mechanism for evolution – his theory of inheritance of acquired characteristics.

1970’s AD –

Stephen Jay Gould and Niles Eldridge propose their theory of punctuated equilibrium.

300 BC –

Aristotle proposed his theory of “The Great Chain of Being” and suggested that species could not change and were ‘fixed’.

Aristotle lived during 300’s BC within archaic Greece. At this time Greece was highly advanced and drew heavily off the influences from the culture of Ancient Rome. This period was an era of abundance within the development of scientific thought and philosophy, with the historical figures of Plato and Aristotle presenting new revolutionary philosophies and ideas. Aristotle’s work on “The Great Chain of Being” and his philosophical and scientific work in general, was highly influenced by his context within archaic Greece. Archaic Greece was highly influenced by religion, that is, religion played a fundamental role within the development of ideas, literature, philosophy and scientific thought. Aristotle’s ideas concerning relationships between species and “The Great Chain of Being” was also highly influenced by religion. Religion influenced his work greatly – as his “The Great Chain of Being” includes a hierarchical link between the most basic and lowest to the most complex and highest, with the pinnacle of the most high being divinity or God. Aristotle also depicts through his theory that each living organism is fixed within his hierarchical scale, with each organism being created independently. His notion of creation and of a God is reflected in his work concerning relational links between living organisms and therefore the archaic Greece society and culture highly influenced his theory and his own persona as a philosopher. Aristotle’s work was also impacted by the work of other philosophers, namely Plato, his teacher.

Aristotle

Influence of society and culture:

Society and culture, as well as context are highly significant when considering the historical development of the evolutionary theories. The society and culture at the time at which the evolutionary theories were proposed impacts the reception of the theory as well as the content of the theory. Within ancient times, theories were highly influenced by religion and traditional culture, whilst in more modern times, within the post-modern era, opinion is more widely exposed and as such theories are accepted more widely, if they have tangible and observable evidence and proof. It is the impact of one’s context and society and culture that determines the shape and form of the ideas and scientific work.

Assess how each scientists and his theory was influenced by society/culture and the knowledge available at the time.

Stephen Jay Gould and Niles Eldridge were born in the mid to late 1900s. At this point in time, they had an abundance of knowledge concerning the evolutionary theory, with the presence and work of Darwin and Wallace, Mendel, Lamarck and Aristotle before them. Gould and Eldridge also had the accessibility to more recent technologies and scientific methods. An important feature of evidence supporting the theory of punctuated equilibrium is fossil evidence and the fossil record. During the mid to late 1900s paleontology had increased dramatically in its effectiveness and study, as a whole. This means that the information and studying of the fossils was done at a more intricate and critical level, which means that Gould and Eldridge’s theory is supported by the developing technology at the time. The fact that the society and culture had already been exposed to the evolutionary theories of Darwin, Wallace, Lamarck and others, also provided Gould and Eldridge with a foundational starting point to their own theory. Their theory of punctuated equilibrium was just an extension onto the already widely accepted theory of natural selection. They did not challenge the Darwin-Wallace theory, but rather challenged the rate at which evolution occurred. Using new information that was available during their context, they were able to propose a theory concerning the rate of evolution.

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Gregor Mendel was born and lived in Austria during the 1800s. Mendel was highly affected by society and culture as his work was relatively unrecognized until some time after it was published. Mendel published his work on genetic inheritance in 1866, however it was only until 1900 that his work was rediscovered and its value recognized, this was primarily due to the influence of society and culture and the lack of knowledge available at the time. During this time very little was known in regards to genetics and inheritance – and about cellular life, including chromosome, mitosis etc., because of this the work of Mendel was viewed as radically different from previous research and thus the scientists that received his work did not understand the significance of his research. The common belief was that during inheritance there was a ‘blending’ of characteristics in the offspring, however Mendel suggested that it was due to the laws of dominance and segregation that accounted for the offspring’s characteristics. Mendel’s research was too “new” and distinctly different to anything the culture and society had been exposed to before, thus his research was largely ignored and his theories dismissed.

Stephen Jay Gould & Niles Eldridge

Gregor Mendel

Charles Darwin & Alfred Wallace

Darwin and Wallace lived primarily throughout the 1800’s and during that time were influenced by a range of social and cultural changes that impacted their development of their theory of evolution. The main influences included the: age of enlightenment, the industrial revolution and the rise of Great Britain as a world power. The Age of Enlightenment was the time within the 18th century when a particular focus was centered upon reason and proof, and thus a shift occurred to a stronger belief in rationality and science. This was an ideal time for the proposal of the Darwin-Wallace theory, as it was based upon scientific proof and observable evidence, which catered to the Age of Enlightenment’s shift to reason and science. Similarly, the industrial revolution had an impact within the lives of Darwin and Wallace and their theory of evolution. The industrial revolution was a time of change within technology, and this had a profound effect on the culture and society at the time. With the various innovations and developments with technology becoming apparent, Darwin and Wallace’s theory became another scientific innovation – in the form of a new mechanism to explain evolution and the change of species. Darwin’s theory was not yet seen before by the general public, however his theory gained significant support from Wallace, as the two figures, coincidentally independently developed the same theory. The rise of Great Britain as a world power also aided in the reception of the Darwin-Wallace theory as it allowed their theory to become more accessible to other nations. Therefore, a range of social and cultural circumstances influenced the theory proposed by Darwin and Wallace of natural selection.

Punctuated Equilibrium

Punctuated equilibrium is another form in which evolutionary thought has changed and developed since the time of Darwin and Wallace. In the light of new evidence, Gould and Eldridge proposed the theory of punctuated equilibrium to suggest that evolution occurs in short rapid bursts of change, followed by long periods of stability within populations. This differs to the idea presented by Darwin and Wallace, that evolution occurs gradually over long periods of time.

Fossil evidence and the fossil record was analyzed and studied to act as the backbone for the proposal of punctuated equilibrium. Many fossilized remains indicate millions of years of stability without any signs of evolutionary change, before being interrupted by much shorter periods during which new species appear and rapidly replace the ancestral species.

This theory of punctuated equilibrium is therefore a development upon the earlier theory proposed by Darwin and Wallace. It suggests that evolution occurs in a different rate to the previously proposed, occurring in short bursts rather than gradually over extended periods of time.

The concept coined Neo-Darwinism refers to the Darwinian evolution based on Mendel’s work on modern genetics. It is the addition of Mendelian genetics to support and explain Darwin and Wallace’s theory of genetic variation leading to the formation of a new species. Previous, to the knowledge of Mendel’s work, Darwin could not satisfactorily explain what caused variations within species or how variations could be passed down to future generations. Darwin’s theory of descent with modification posed a number of problems and it was Mendel’s research and work on genetics and inheritance that enabled the solution to those problems. It was during the early twentieth century that scientists combined the works of Darwin and Mendel to produce the ideas known today as Neo-Darwinism.

Darwin and Wallace had identified the mechanism of natural selection to account for how species evolved. They believed that species evolved through the slow and gradual accumulation of inherited differences through natural selection. However, through the Neo-Darwinism ideas, other processes have been recognized that have the capability of producing new species. These include: random or chance events, termed genetic drift and changes in the number of sets of chromosomes, known as mutation. Therefore, evolutionary thought changed into Neo-Darwinism, which accounted for the initial problems involved with Darwin’s theory of natural selection.

Neo-Darwinism

Describe how evolutionary thought has changed/developed since Darwin proposed his theory of natural selection.

The “old” technologies used to consider the evolutionary relationships between humans and other primates comprised of areas which did not rely on complex technologies and the like, but rather were dependent on observation and human analysis. The “old” technologies that were used when considering the evolutionary relationships were comparative anatomy, comparative embryology, and comparative behavior. Scientists such as Darwin utilized these technologies when analyzing the evolutionary relationships between humans and other primates.

Comparative anatomy is the study of similarities and differences in the structure of living organisms. Within earlier times, this was a substantial means of determining possible evolutionary relationships between organisms. An example of this is that within the 1860’s a German biologist, Ernst Haeckel classified a number of primates including the orangutans, gorillas and chimpanzees in one family and placed humans in a separate family. He made this separation between the two based upon evidence derived from the comparison of the structural anatomies of both the humans and the primates. Haeckel determined that because of the similarities present between gorillas and chimpanzees with the structure of their hind limb and the enamel on their teeth, gorillas and chimpanzees were more closely related to each other in comparison to humans or orangutans, which were absent of such anatomical features.

The use of comparative embryology and the comparison of behavioral features between humans and primates was also a means by which former scientists and biologists gathered information as to the evolutionary relationships between humans and primates. Comparative embryology is the study and comparison of the developmental stages of different species. Within the study of comparative embryology it is quite clear that there are a number of distinct similarities between humans and primates. Both humans and primates show the presence of gill slits and tails with distinct muscle blocks. This indicates that embryos of closely related organisms – such as humans and primates – have homologous features and characteristics, which indicates the possibility of a shared, common ancestor. The other form in which humans and primates were compared was behaviorally. Scientists utilized observations of human behavior and compared it to that of primal behavior, to attempt to determine any behavioral links that may indicate evolutionary relationships between the two separate species.

From the information, it is clear that the old technology used was based primarily on observations and physical analysis rather than life at the chemical level. These old technologies revealed information concerning the evolutionary relationships between humans and primates in a more physical sense.

Old Technology

Technology:

Advances within technology provide scientists with a greater capability of understanding the evolutionary relationships between humans and other primates. The study of chemicals found in cells, in biochemistry, allows for a deeper exploration of the evolutionary links between humans and other organisms. Amino acid sequencing, DNA-DNA hybridization and DNA sequencing are relatively newly developed forms of technology that have enabled a more thorough consideration of the evolutionary relationships.

 

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