Creatures evolve to fit the world around them, but if the changes don't fit, can the creature reverse the process?
Creatures evolve to fit the world around them, but if the changes don't fit, can the creature reverse the process? For example, an insect that originally ate leaves from different types of plants, but evolved to eat a certain type of leaves, and then the tree it hangs on became extinct, can the insect reverse the process and go back to eating a variety of types of leaves? More than a hundred years ago, the French paleontologist Louis Dollo proposed that evolution is unable to retrace its steps to restore a lost trait, an idea that remains controversial to this day.
Dullo's law receives support from cases such as whales and snakes that never re-evolved legs, or birds that did not re-evolve teeth, even though these features existed in the evolutionary past of the animals. But recently, studies have shown that silenced genes and dormant developmental programs can be reactivated, leading many evolutionists to think that evolution can indeed retrace its steps. New research From Nature tries to shed some light on these kinds of questions. In the article in question, researchers tested "Dollo's Law" at the molecular level, by examining a protein that is a glucocorticoid receptor, which binds the The hormone cortisol In the process of regulating stress responses. One of the researchers, Joseph Thornton, says that at least in the case of the protein he studied, new mutations make it virtually impossible for evolution to go back. According to him, "they are burning the bridge that evolution has currently crossed".
To understand what they did, one must first understand how a protein is built: every protein is actually a sequence of amino acids. In living things there are 22 types of amino acids and the arrangement of their sequence determines the properties of the protein. The order in which the amino acids will appear in the protein is determined by information in the DNA. A change of one letter in DNA can lead to several results: a. No change in the amino acid will occur, b. A code for another amino acid will be obtained c. The teacher code will be received to stop reading the sequence and actually to cut the protein. It is possible to find out what changes have occurred in the sequence of a protein by comparing sequences from different animals. According to the theory of evolution, all creatures that contain the particular gene came from a single ancestor. After they diverged from each other, each branch of the evolutionary tree accumulated different changes in the gene sequence. Comparison of many sequences leads to obtaining the original sequence. For example: if in 90% of living things amino acid A appears as second in the protein sequence, and in 10% three other amino acids appear, it can be concluded that in the original sequence amino acid A was in second place.
In previous publications, the team of researchers showed that the protein in its early version evolved about 400 million years ago from a receptor activated by three hormones: cortisol, aldosterone and deoxycorticosterone. Over the course of 40 million years, the receptor underwent 37 amino acid changes leading to the receptor known today that binds only cortisol. The researchers examined the sequence of the cortisol receptor and analyzed the effect of each of the 37 changes on the protein's activity. They discovered that only seven changes are responsible for the ability to bind cortisol, and in the next step they reversed these seven changes. But the received receptor was "dead", it simply did not work. In order to determine whether other changes had an effect on the activity of the receptor, the researchers examined changes in the three-dimensional structure of the protein, and found five additional mutations. These mutations were not important for the purpose of binding cortisol, but they did affect the receptor's ability to perform its function. After the researchers reversed these mutations as well, they got a receptor that functions like the ancient receptor capable of binding all three hormones.
In summary: before the seven essential mutations could be reversed, five additional mutations related to the protein structure had to be reversed. But these five mutations had no role in the way the receptor bound hormones. So there is no way in which natural selection can favor individuals with the opposite mutation. That is, the receptor could, theoretically, go through a series of mutations that would allow it to bind a variety of hormones, but this would have to be a new path, it would not be able to return to the path it had already taken.
Despite the impressive demonstration, the fact that the phenomenon would hold true for such long periods of time is what any evolutionary biologist would expect. After all, if the change was not successful, he would not have survived 360 million years. But in the short term the selection can be reversible - In a study published at the beginning of the year In Nature genetics, researchers showed that fruit flies that underwent selection in the laboratory for decades returned to their original state after only two years of reverse selection. Here it is important to note that the initial selection was in favor of traits that do not constitute an advantage in nature, while the second (return) selection actually brought back traits that had evolved in flies over millions of years. Another criticism of the article claims that the study does not prove that it is impossible to reverse the evolutionary direction, but only strengthens the claim that if a successful change has been made, it will receive more and more reinforcements over time to prevent it from changing again.
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thanks Michael
white blood:
The article sends one message but the research described sends a slightly different message.
In the interpretation, it is possible for the animal to readapt to itself features that it has lost and there are even examples of this in nature.
For example the dolphins and whales are creatures that made the way from the sea to the land and back to the sea.
On the way they replaced fins with legs and later replaced the legs with something that looks very similar to fins.
This is an example of how a similar phenotypic result can be obtained in different genotypic ways.
Another example of obtaining similar traits through different genes can be seen in all cases of convergent evolution.
In this sense - of features - there is no doubt that the message of the article is inaccurate.
What else? In the study they tested something else.
They tested it to see if it was possible to reproduce exactly the same genes (ie - to go back in evolution - not in the phenotypic sense, but in the genotypic sense) and in the specific case they tested it turned out to be very unlikely.
The truth is that even in the Gutifi matter - the difficulty from one case to the others seems problematic to me, and therefore the blanket conclusion would not be justified.
Even if it is not possible, hypothetically, to restore a lost feature, does that mean that it is not possible to redevelop it, like the first time?
It is simply a matter of how much time the agent has to adapt to the change...
For example, the change that the dinosaurs underwent was so violent in its essence that the absolute majority of them became extinct before they could adapt
But the more time a factor has to adapt, evolution has shown that it has a better chance of survival. At least from what we have discovered so far about our past.
After all, nature will adapt quite a bit.
It is necessary to distinguish between mutations in genes (such as a 1 for 0 exchange), which are phenomena with defined individual states and low information changes, and structural changes in the chromosome (when the number of molecules in the DNA itself changes) which are usually of great complexity.