You’ve probably heard of the phrase, “evolve,” but you may not know exactly what it means. Evolution is a process in which a species’ genetic makeup changes in order to become more like other species. The changes can be seen in the gaps in the fossil record and in the way a species’ genetic makeup shifts from one generation to the next.
Genetic drift is a process in which genetic variations change from one generation to the next because of random chance. Specifically, this process results in allele frequency and inbreeding coefficient changes. It is considered to be a major factor in evolution.
Genetic drift is a term used by biologists to describe the phenomenon of random variation of gene frequencies in populations. It also describes how the allele frequency of one species is influenced by the population’s size.
Genetic drift can occur in small populations as well as in large ones. Small populations are more prone to drift and tend to be less stable than larger ones. The probability of fixation of an allele in a population depends on the number of alleles and the initial frequency of each allele. In large populations, however, there is little to no natural selection pressure on genes.
Genetic drift has been the subject of many controversies in evolutionary biology. Some scientists argue that it plays a minor role in evolution. Others assert that it is the single most important factor.
A key question is whether drift should be treated as a chance phenomenon, or as a result of a natural condition. For instance, if a population is subject to severe reductions, the alleles can decrease in frequency.
If a population is subject to frequent recolonization, drift can play an important role in its evolution. However, when a new population is established, the effects of drift are not so clear.
Genetic drift is a significant source of controversy in the philosophy of biology. It is also a hot topic in population genetics textbooks.
Various models have been developed to explain the phenomenon of drift. One model was developed by Sewall Wright. He postulates a scenario in which some species migrate from a different region to a new area. As a result, a new group of individuals will diverge from the original population to a point where they cannot interbreed.
Gaps in the fossil record
There are various gaps in the fossil record, some of which are more important than others. These gaps can be within the same species, between two or more species, or between the fossil record and the living world.
One of the most obvious gaps in the record is between plants and animals. While there are some gaps between mammoths and modern elephants, there are far more gaps between plant and animal lineages.
Another gap in the fossil record is the Cambrian Explosion. In this period, which occurred roughly 360-345 million years ago, the earth was filled with complex marine fossils. The lack of transitional forms made this event difficult to explain, as it was impossible to imagine why so many such organisms were suddenly on the scene.
Other stratigraphic gaps are caused by changes in habitat and the distribution of sedimentary rock. These changes are evident in fossiliferous strata, as they indicate the changing nature of the environment at a given time.
Some creationists assert that the fossil record is not sufficient for a complete picture of life. They believe that the rock record preserves a more thorough sampling of life than the fossil record. This view is often akin to the creationist belief that the earth has been young since creation.
Regardless of whether or not gaps in the fossil record are true, they are a fact of life. Several large gaps in the record have been found and studied, including the aforementioned Cambrian Explosion. However, most of these gaps are unlikely to be fully remedied.
Nevertheless, there are several examples of transitional fossils that have provided fillers for the gaps once thought unbridgeable. These include Archaeopteryx, coelurosaurians and Compsognathus.
Co-adapted meme-complexes are no new thing. In fact, they’re still going strong today. Whether it’s a celebrity or an embryological mechanism, they’re all about the same finite resources, such as time and space. Hence, there is more to them than meets the eye.
A meme is a cultural artifact that’s replicable and can spread from one person to another. Some even get so clever as to replicate themselves. This phenomenon is akin to genetic self-copying, and it’s not limited to mammals. It can also be found in fungi and protozoans. Depending on how you look at it, you can see why the human brain has a hard time keeping up with the latest and greatest in the digital realm.
In the real world, memes compete for attention with everything from newspaper column inches to billboard space. These are not always funny though. They can be commensal or parasitic. However, it’s their ability to spread and multiply that’s worthy of note. There’s a reason this is called the meme-meme.
One of the more obvious aspects of this corollary is that it’s not just about recursive replication. Memes are symbiotic and are also subject to blending. The most successful ones are those that capitalize on their environment. For example, a phallic image from Kilroy was here graffiti has been around for years, but it’s only been re-appeared in recent years thanks to a re-appearance by a renaissance man.
While the latest internet craze will likely fade away soon enough, the meme-meme is here to stay. It’s also a good time to take stock of the co-adapted trends of our time, and the way we consume and create culture.
Evolutionary biology vs species-level or group-level selection
The theory of evolutionary biology is the crowning intellectual achievement of the biological sciences. Charles Darwin laid careful foundations in the 19th century, and other evolutionists elaborated on his ideas during the first half of the 20th century. During the mid-1960s, most biologists disbelieved group selection as a key force in the history of life.
It was only during the 1970s that the positive literature began to expand. Multiple overviews of group selection have been published in influential review papers and books.
Group selection is a theory that claims that natural selection acts at a higher level than individual selection. This is based on the concept that the genetic locus of a trait spreads through a population of individuals. However, it is possible that a trait could have an effect on the survival of the individual, but not on the gene.
In contrast, the individualistic view of natural selection assumes that social organization is a by-product of self-interest. Natural selection acts at the individual level and, therefore, favors traits that are suited to the survival of the individual.
One important difference between individual selection and group selection is that the latter operates at the level of the population as a whole. In other words, it works against genic selection and favors traits that increase the fitness of the entire population.
As a result, the concept of group selection was rejected by most evolutionists. Their emphasis on genes as “replicators” influenced this stance.
On the other hand, many philosophers and biologists have supported group selection, arguing that the logic of natural selection at the organism level can be applied to the entire group. They have used numerous examples as corroborating evidence.
Evolutionary explanations for altruism
If you have an interest in altruism, you’ve probably come across many different evolutionary explanations of the phenomenon. It’s a subject that has fascinated scholars for decades.
A recent survey of the empirical evidence on the subject has yielded a dual pathway model. The first pathway, based on kin selection, suggests that altruism helps to promote the survival of genetic relatives.
However, the evolutionary explanations for altruism may not be as straightforward as you might think. In fact, a number of heuristic strategies have been developed to encourage individuals to accept a single explanation for a set of seemingly similar events.
One of the most common heuristics is to assume that a particular event – such as the act of helping – requires a similar explanation to other similar events. This is a useful way to reduce the possibility of an incorrect assumption being made about a complex phenomenon.
Another heuristic is to use the concept of “cheating detectors”. These are individuals who are willing to cooperate, but don’t pay a price for it. As a result, they are vulnerable to being exploited by cheaters.
For years, biologists have tried to explain altruism using group selection models. However, the question of how this mechanism actually works remains unresolved.
One answer to this puzzle may be a combination of kin selection and group selection. Groups that split into daughter groups have a smaller chance of re-reproducing their traits. Whether or not this mechanism is efficient has been debated.
Interestingly, the “altruists” have an advantage in promoting the survival of their kin and society as a whole. But altruists are also at a disadvantage in reproduction.