Evolution, from a contemporary point of view, is a matter that worries zoologists, geneticists and phylogeny specialists. It is clear that planet Earth is in a period of profound change and, therefore, the rates of genotypic and phenotypic variability of species are no longer limited to the theoretical parameters traditionally postulated, at least to a certain extent.
For example, many may not know that, today, as these lines are written, we are in the middle of the sixth mass extinction (or Anthropocene extinction). The current extinction rate is on the order of 100 to 1,000 times higher than that expected in a natural environment and, therefore, we are not surprised to learn that one in every 8 birds, one in every 4 mammals and one in every 3 amphibians are in Danger of extinction. The plants are not far behind, since 70% of all of them are at risk.
With these preliminary data we want to show a reality: rapid evolution processes that respond to environmental variations could be essential for the permanence of certain taxa over time in such a changing and unstable world. If you want to know all the secrets locked in this little-explored concept, keep reading.
Laying the foundations of evolutionary mechanisms is the first step to adequately explore the topic that concerns us here. In a simple way, evolution can be defined as the set of changes in genetic characters (encompassed in the genome) and phenotypic characters (the expression of said genome) of biological populations through generations. There are two broad types of evolution: divergent and convergent.
Divergent evolution is one in which a species, over time, separates into two different ones These types of adaptive processes are included in the term “speciation”, where living beings from the same population acquire diverse traits in the face of different challenges, whether due to physical, physiological or chromosomal barriers (among many others) until they become different species that do not They can reproduce with each other.
On the other hand, a species can also appear where another existed before, without the need for two populations to separate. Simply put, the genetic changes in a specific taxon may be enough for us to say that one species has evolved into another.
In convergent evolution, two (or more) different species acquire similar traits because they have been subjected to similar evolutionary pressures For example, the bodies of a whale and a fish have comparable characteristics with analogous functions (swimming and preying underwater), but their evolutionary history and ancestors are completely different.
Finally, it is necessary to note that the most powerful mechanism when describing the evolution of species is natural selection, that “force” that promotes the permanence of the fittest and causes the least viable to end up disappearing from the “pool.” genetic. Even so, this is not the only one: processes such as genetic drift cause the loss and variation of genes in populations, although these are random and do not respond to the biological fitness of living beings.
What do we mean by “rapid evolution”?
Framing rapid evolution in the current definition of evolution is extremely complex, since it is assumed that genetic changes in animal species (not so much in viruses and bacteria) occur slowly, over thousands of years.
The term “rapid evolution” is used in scientific publications to describe the changes in allele frequencies (gene variations) within a specific population over a few generations These changes within the same species can arise from the appearance of new genotypes (mutations), gene flow between populations or genetic mixtures between individuals and/or species.
Some authors postulate that rapid evolution must entail a change in the ecological trajectory of the populations that experience it, that is, that it must be translated into a series of tangible observations that demonstrate that the living being has “changed”, simplifying the language as much as possible. . Meanwhile, other researchers argue that this does not necessarily have to be the case: sometimes, rapid evolution can occur to maintain the status quo of a population in the ecosystem in which it proliferates, without requiring ethological or food chain changes. of it, for example.
The potential for local adaptation by a population (and therefore its potential for rapid evolution) depends on several factors Among them, we find the following:
So, we see that an accelerated rate of evolution depends on both the environment and the intrinsic characteristics of the species analyzed For example, if we look at a taxon that has hardly changed in the last 1,000 years and has extremely low genetic variability, it is difficult to think that it could suddenly accumulate tangible genotypic changes in a few generations.
In addition to this, it should be noted that there are accelerated growth DNA regions (ARs) in many animal species, that is, they undergo much faster mutation rates than expected. One could imagine that the greater the proportion of ARs, the more likely rapid evolution would be, but, again, at this point we can only speculate.
Darwin’s finches: a book example
To talk about rapid evolution today is, in many cases, to be untrue, since Although it occurs in a shorter time window than normal evolutionary processes, it is still too wide an interval for one (or several) studies to cover
On the other hand, there are examples that demonstrate to a certain extent the ideas postulated here. A clear event that shows this is that of one of Darwin’s finches (inhabitant of the Galapagos Islands) which, according to a study, decreased the average size of its beak in 22 years due to the introduction of another competing species.
It turns out that finches with larger beaks were introduced into their habitat and, therefore, they displaced the original finches with the large beaks as they were more effective in destroying hard seeds. So that, Birds with smaller beaks that exploited a niche increasingly prospered (the smallest seeds) where there were no competitors. For this reason, little by little the proportion of individuals in the original population with small beaks increased.
Don’t believe everything you see in certain media. Arguing the presence of a rapid evolutionary process is extremely complex, since it does not occur in one or two generations. There are many factors that must be taken into account and, therefore, we ask you the following questions: did the favored character in the population already exist before the supposed “rapid evolution”? Has it been fixed over time or is it a sporadic observation? Is the variation significant?
For example, some media argue that certain species have “learned” to metabolize the venom of a species introduced into their habitat within a few years. Fascinating, right? We dare say that this is practically impossible. It is one thing that there are mutations in a population that alter the composition of a toxin and the individuals that present it are favored, and another thing that this character appears out of nowhere in response to a given selective pressure. If rapid evolution were so simple and effective, how come almost 150 species become extinct every 24 hours?
Summary
In these last lines we have not intended, by any means, to dismiss the concept of rapid evolution. What is necessary is a critical and analytical perspective. Evolution, in all cases, is a slow process that requires a fixation of characters over time We simply cannot know if a population trend is sporadic or definitive until many years after its documentation and, therefore, demonstrating rapid evolution in complex beings is a real headache.
