What is Free Evolution?
Free evolution is the concept that the natural processes of organisms can cause them to develop over time. This includes the emergence and development of new species.
This has been demonstrated by many examples, including stickleback fish varieties that can live in saltwater or fresh water and walking stick insect species that are apprehensive about specific host plants. These typically reversible traits do not explain the fundamental changes in the body's basic plans.
Evolution by Natural Selection
The development of the myriad living creatures on Earth is an enigma that has intrigued scientists for centuries. The most widely accepted explanation is that of Charles Darwin's natural selection, an evolutionary process that occurs when individuals that are better adapted survive and reproduce more effectively than those less well-adapted. Over time, a community of well-adapted individuals expands and eventually becomes a new species.
Natural selection is an ongoing process and involves the interaction of three factors: variation, reproduction and inheritance. Variation is caused by mutation and sexual reproduction both of which enhance the genetic diversity of the species. Inheritance is the passing of a person's genetic traits to the offspring of that person, which includes both recessive and dominant alleles. Reproduction is the production of fertile, viable offspring, which includes both sexual and asexual methods.
Natural selection only occurs when all these elements are in equilibrium. If, for instance an allele of a dominant gene causes an organism reproduce and survive more than the recessive allele, then the dominant allele is more prevalent in a population. If the allele confers a negative advantage to survival or reduces the fertility of the population, it will disappear. The process is self reinforcing, which means that the organism with an adaptive trait will live and reproduce much more than one with a maladaptive characteristic. The greater an organism's fitness which is measured by its ability to reproduce and survive, is the more offspring it can produce. People with desirable characteristics, such as having a long neck in the giraffe, or bright white patterns on male peacocks are more likely than others to survive and reproduce and eventually lead to them becoming the majority.
Natural selection is an element in the population and not on individuals. This is an important distinction from the Lamarckian theory of evolution which claims that animals acquire characteristics by use or inactivity. For instance, if the giraffe's neck gets longer through stretching to reach prey, its offspring will inherit a larger neck. The difference in neck length between generations will persist until the neck of the giraffe becomes so long that it can not breed with other giraffes.
Evolution through Genetic Drift
Genetic drift occurs when alleles from a gene are randomly distributed within a population. At some point, only one of them will be fixed (become widespread enough to not longer be eliminated through natural selection) and the rest of the alleles will drop in frequency. This could lead to dominance at the extreme. The other alleles are eliminated, and heterozygosity decreases to zero. In a small population it could result in the complete elimination of recessive gene. This is known as a bottleneck effect and it is typical of evolutionary process that takes place when a lot of individuals move to form a new population.
A phenotypic bottleneck may also occur when the survivors of a catastrophe like an outbreak or mass hunt incident are concentrated in a small area. The survivors will have a dominant allele and thus will have the same phenotype. This situation could be caused by war, earthquakes or even a plague. The genetically distinct population, if it remains susceptible to genetic drift.
Walsh Lewens, Walsh, and Ariew define drift as a deviation from the expected values due to differences in fitness. They cite the famous example of twins who are both genetically identical and share the same phenotype. However, one is struck by lightning and dies, while the other lives to reproduce.
This kind of drift could be very important in the evolution of the species. But, it's not the only way to develop. Natural selection is the primary alternative, in which mutations and migration maintain the phenotypic diversity of the population.
Stephens claims that there is a major difference between treating the phenomenon of drift as a force, or a cause and considering other causes of evolution such as selection, mutation and migration as forces or causes. Stephens claims that a causal process explanation of drift lets us separate it from other forces, and this distinction is essential. He further argues that drift has a direction, i.e., it tends to reduce heterozygosity. It also has a size, that is determined by the size of the population.
Evolution through Lamarckism
Students of biology in high school are often introduced to Jean-Baptiste Lamarck's (1744-1829) work. His theory of evolution is often referred to as "Lamarckism" and it states that simple organisms develop into more complex organisms through the inheritance of traits which result from an organism's natural activities use and misuse. Lamarckism is usually illustrated with the image of a giraffe stretching its neck further to reach higher up in the trees. This would result in giraffes passing on their longer necks to offspring, which then grow even taller.
Lamarck was a French zoologist and, in his inaugural lecture for his course on invertebrate zoology at the Museum of Natural History in Paris on the 17th of May in 1802, he introduced a groundbreaking concept that radically challenged the previous understanding of organic transformation. In his opinion living things evolved from inanimate matter through a series of gradual steps. Lamarck was not the first to suggest that this could be the case but his reputation is widely regarded as giving the subject its first general and comprehensive analysis.
The predominant story is that Charles Darwin's theory on natural selection and Lamarckism were competing during the 19th century. Darwinism eventually triumphed and led to the development of what biologists refer to as the Modern Synthesis. This theory denies the possibility that acquired traits can be inherited, and instead, it argues that organisms develop by the symbiosis of environmental factors, like natural selection.
Although Lamarck endorsed the idea of inheritance by acquired characters and his contemporaries spoke of this idea however, it was not a central element in any of their evolutionary theories. This is partly due to the fact that it was never validated scientifically.
But it is now more than 200 years since Lamarck was born and, in the age of genomics there is a vast body of evidence supporting the heritability of acquired traits. This is referred to as "neo Lamarckism", or more commonly epigenetic inheritance. This is a model that is just as valid as the popular Neodarwinian model.
Evolution by adaptation
One of the most commonly-held misconceptions about evolution is its being driven by a struggle to survive. This is a false assumption and overlooks other forces that drive evolution. The fight for survival can be more accurately described as a struggle to survive in a specific environment, which may be a struggle that involves not only other organisms, but also the physical environment itself.
Understanding the concept of adaptation is crucial to understand evolution. It refers to a specific characteristic that allows an organism to live and reproduce in its environment. It could be a physiological feature, like feathers or fur or a behavioral characteristic such as a tendency to move into shade in hot weather or stepping out at night to avoid cold.
The ability of an organism to extract energy from its surroundings and interact with other organisms, as well as their physical environment, is crucial to its survival. The organism must possess the right genes for producing offspring and to be able to access sufficient food and resources. Moreover, evolutionkr.Kr the organism must be capable of reproducing in a way that is optimally within its niche.
These factors, in conjunction with mutations and gene flow can cause an alteration in the ratio of different alleles in a population’s gene pool. Over time, this change in allele frequency can result in the emergence of new traits and eventually new species.
Many of the characteristics we find appealing in plants and animals are adaptations. For instance the lungs or gills which extract oxygen from the air feathers and fur for insulation and long legs to get away from predators and camouflage for hiding. To understand adaptation, it is important to differentiate between physiological and behavioral characteristics.
Physiological adaptations like thick fur or gills, are physical traits, whereas behavioral adaptations, such as the desire to find friends or to move into the shade in hot weather, are not. In addition, it is important to note that a lack of forethought does not make something an adaptation. Failure to consider the consequences of a decision, even if it appears to be rational, could make it unadaptive.