Evolutionary theories are fundamental to understanding the diversity and complexity of life on Earth. Various thinkers throughout history have contributed to the development of these theories, each with their own ideas and concepts. In this context, figures such as Aristotle, Leclerc, Lamarck, Wallace, and Darwin stand out, making important contributions to the understanding of the evolution of species. Their theories and observations helped lay the foundation for the theory of evolution, which is widely accepted and studied today.
3 evolutionary theories that explain the origin and diversity of species over time.
There are several evolutionary theories that attempt to explain the origin and diversity of species over time. Notable among them are the theories of Aristotle, Leclerc, Lamarck, Wallace, and Darwin.
For Aristotle, species arose spontaneously and immutably, according to a hierarchical scale of complexity. This idea persisted for centuries, until new discoveries and observations refuted this hypothesis.
Leclerc, in turn, proposed the idea that species could transform over time through a process called transformism . He believed that changes in the environment could lead to the evolution of species, directly influencing their characteristics.
Lamarck developed the theory of use and disuse , which stated that characteristics acquired throughout an organism's life could be passed on to its offspring. He also defended the idea that species adapted to their environment, which directly influenced their evolution.
Wallace and Darwin, in turn, proposed the theory of natural selection , where species best adapted to the environment would have a greater probability of survival and reproduction, passing their characteristics on to subsequent generations. This theory revolutionized the field of biology and became the basis of the theory of evolution.
Main theories of evolution: learn the main ideas about the origin of species.
Evolutionary theories have been the subject of study and debate throughout history, with various thinkers contributing to the development of knowledge about the origin of species. From Aristotle to Darwin, various ideas have been proposed to explain how living beings have transformed over time.
One of the first evolutionary theories was put forward by Aristotle, who believed in the "natural scale," where living beings were organized hierarchically, with simpler forms evolving into more complex ones. However, this idea was later challenged by Georges-Louis Leclerc, who argued that species were not fixed and could transform over time.
Jean-Baptiste Lamarck was another important thinker who contributed to the development of evolutionary theories. He proposed the idea that organisms could acquire characteristics throughout their lives and pass them on to the next generation, a process known as inheritance of acquired characters. Although this theory was later refuted, Lamarck was instrumental in the advancement of evolutionary thought.
Alfred Russel Wallace was another naturalist who contributed significantly to evolutionary theories. He independently developed the idea of natural selection, which was later introduced by Charles Darwin. Darwin is known for his work "On the Origin of Species," in which he proposed the idea that species evolved through natural selection, a process of adaptation to the environment.
Each thinker brought their ideas and arguments to explain how living beings have transformed over time, providing a solid basis for understanding the diversity of life on Earth.
Main evolutionary theories of Lamarck and Darwin: understand the differences and similarities between them.
The evolutionary theories of Lamarck and Darwin are two of the most important and influential in the study of species evolution. Jean-Baptiste Lamarck proposed the theory of inheritance of acquired characters, which suggests that organisms acquire characteristics throughout their lives and pass them on to their offspring. On the other hand, Charles Darwin developed the theory of natural selection, which postulates that species undergo change over time due to the selection of traits most favorable for survival and reproduction.
A fundamental difference between Lamarck's and Darwin's theories is how they explain the mechanism of evolution. While Lamarck believed that changes occurred due to the transmission of acquired characteristics, Darwin argued that changes were the result of natural selection.
Despite their differences, Lamarck's and Darwin's theories also share some similarities. Both recognized the importance of the environment in the evolution of species and the idea that populations change over time. Furthermore, both scientists contributed significantly to the development of evolutionary theory and to understanding the diversity of life on Earth.
While Lamarck emphasized the inheritance of acquired traits, Darwin emphasized the importance of natural selection. Both scientists left a lasting legacy in the field of evolutionary biology and continue to be studied and discussed to this day.
Darwin and Wallace's theory: how they explain the evolution of species in nature.
Darwin and Wallace's theory, known as the theory of natural selection, revolutionized how we understand the evolution of species in nature. According to this theory, species develop over time through a process of natural selection, where the organisms best adapted to the environment survive and reproduce, passing their characteristics on to subsequent generations.
This theory explains how species adapt to environmental changes over time, resulting in a diversity of life forms. Darwin and Wallace observed that genetic variations among individuals of the same species can confer advantages or disadvantages in certain environments, which influences their ability to survive and reproduce.
Thus, species with more favorable characteristics are more likely to survive and reproduce, passing these characteristics on to future generations. Over time, these accumulated changes lead to the evolution of species, resulting in new life forms adapted to their environment.
Evolutionary theories: Aristotle, Leclerc, Lamarck, Wallace and Darwin
Evolutionary theories are all those that have been put forward by the great thinkers of humanity throughout history to provide plausible explanations for the evolution of living beings on Earth.
Since the beginning of human societies, man has wondered where living beings come from and where they come from; therefore, evolution has been the subject of intense debate for many centuries, strongly influenced by philosophical and religious beliefs, and, more recently, scientific.
However, as a current of scientific thought, evolutionism probably began with the theories of Charles Darwin (1809-82), an English scientist who dedicated an important part of his life to studying the effects of “natural selection” and “adaptations” on species.
What is evolution?
Evolution is the biological process by which species in the biosphere (regardless of their type) originate, diversify, and become extinct. Through fossil evidence, evolution seeks to explain the changes and transformations that different species undergo throughout their history.
Because Darwin set a revolutionary precedent in the scientific world (he is considered the “father of evolutionism”), today we list evolutionary theories as “pre-Darwinist” and Darwinist, suggesting the historical and scientific context in which they were formulated.
Pre-Darwinian theories
There were many “pre-Darwinian” thinkers who, in their time, dedicated themselves to the study of living beings and the search for answers to the many questions related to their evolution.
Aristotle and the immutability of organisms
Aristotle (384-322 BC) was perhaps one of the first thinkers to implement a hierarchical system of classification for living beings.
This insisted on the “immutability” and eternal perfection of the species, as well as the existence of a progressive, that is, ascending, hierarchical order, at whose “peak” man was.
Aristotle stated that the order thus proposed responded to a “vital force” and that there was nothing that led to fundamental changes in individuals, hence the theory of immutability, that is, of living beings created and not prone to change.
James Ussher and the Day of Creation
Other great philosophers began to investigate life and the human being as a fabulous spectator. Acceptance of theories of biological evolution slowly penetrated society, with religious figures being its main detractors.
Today religion is not completely closed to discussion, but in the past many popular creationist thinkers tried to reinforce the version of the origin of the universe, the earth and living beings in the hands of a “creator” of a superior nature, to exclude any atheistic thought.
Among them was the Irish Anglican Archbishop James Ussher (1581-1656) who, from the analysis of biblical texts, deduced that creation occurred on an exact date: October 23, 4004 BC.
His statements, therefore, proposed that the Earth was no more than 6.000 years old and that God created infinite creatures, each one “outdoing” the next (simple and complex forms), including human beings as we know them today, that is, unchanging.
The strong influence of religion on scientific thought was evident until the 19th century.
This is demonstrated in history by the fact that the thinkers of the late 17th and early 18th centuries clearly devoted themselves to the description of plants and animals and not to any attempt to explain how they acquired their characteristics and forms.
Carolus Linnaeus (1707-78), for example, was a naturalist (botanist) who devoted immense effort to describing nature, seemingly "revealing" the immutable order of life that had been created by God.
Georges-Louis Leclerc and spontaneous generation
Also known as “the Count of Buffon”, Leclerc (1707-88) favored the idea of the origin of life through spontaneous generation and the existence of a “master plan” inherent in nature.
In a way, he refuted the Aristotelian conception of immutability, as he went so far as to propose that species had the capacity to change over time, perhaps due to the influence of the environment or mere chance.
Furthermore, as part of his speculations, Leclerc proposed that the Earth was at least 75 years old and even suggested in his notes that man and apes were related in some way.
Jean-Baptiste Lamarck and the theory of acquired characters
Perhaps the first true pre-Darwinian evolutionist was Lamarck (1744-1829), a French naturalist who published an evolutionary theory generated from observations of invertebrate fossils deposited in the Natural History Museum in Paris.
According to this character, all organisms had an “internal progressive tendency” that forced them to “climb” the natural scale, that is, that living beings actually changed over time, always tending towards an “improved version of themselves”.
More specifically, Lamarck proposed that if an organism (his examples were based on animals) had not yet reached the “top” of its development, consecutive use of any organ could give it a “potency” proportional to the duration of that use, and otherwise, disuse made it disappear.
In short, Lamarck established that, for example, if a giraffe could not reach the highest leaves on a tree branch, its neck would gradually increase and these small changes due to use would be passed on to the next generation and then to the next and so on, until one of the individuals managed to reach that food.
Georges Cuvier and the theory of catastrophism
Soon after Lamarck published his theories, some scientists made a major effort to discredit them. Among them was George Cuvier (1769–1832), a French naturalist who was the first to document the extinction of ancient animals (he was a dinosaur expert).
His ideas were summarized in the doctrine of catastrophism, in which evolution was explained through violent catastrophes (floods, mountain formations, etc.) that caused the loss of numerous species and the development of new ones.
With this theory, Cuvier and other adherents sought to explain the abrupt differences between fossil records and the sudden changes that were observed in extinct species.
Charles Lyell and uniformitarianism
Cuvier's catastrophism was refuted by Lyell (1797-1875), who proposed an evolutionary theory known as uniformitarianism, according to which the evolution of species has been strongly influenced by slow and gradual changes that have occurred since the beginning of time on the Earth's surface and that are imperceptible to the human eye.
Alfred Russell Wallace and Natural Selection
Wallace (1823-1913) was a British naturalist who, around 1858, reached the same conclusions as Darwin, explaining the evolution of species thanks to natural selection.
Since Wallace and Darwin made their findings public to the Linnean Society of London at the same time, many authors believe that the theory of natural selection should actually be known as the Darwin-Wallace theory.
Charles Darwin and natural selection
As the “father of evolutionism,” Darwin was the first of all naturalists until the mid-1800s to establish a connection between evolutionary thought (usually only conceptual) and the “real world.”
This means that Darwin demonstrated with facts (gathered and explained in On the Origin of Species ) the process of evolution through selection and natural adaptation.
According to his theory, natural selection allows individuals with the most favorable characters to survive in a given environment and, in addition, to reproduce more, passing on these characters to their offspring (survival of the fittest).
Consistent with this, Darwin also proposed that nature produces more individuals than are “necessary” for each species in order to allow natural selection to occur.
Thus, survival of the fittest is nothing more than a result of “nature’s own instinct for preservation,” to ensure that only the best-adapted individuals survive and spread in the changing environment.
Darwin also proposed that the new species observed are the product of the accumulation of small successive changes (gradualism), produced by different types of adaptations.
The post-Darwinian era
Darwinian theories of evolution had much support in the scientific community, as did Mendelian theories of character inheritance and chromosomal inheritance theory later on.
However, for many years these approaches seemed “divorced” or “incompatible”, until the emergence of the synthetic theory of evolution, also known as the modern synthesis or neo-Darwinism.
Thanks to the contributions of scientists such as S. Wright, J. Haldane, R. Fisher and T. Dobzhansky, this theory now has the molecular basis to explain the effect of natural selection on the variability of species (of their populations) or rather, on the allele frequencies of a population.
References
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