Recent scientific discoveries have led some scientists to the conclusion that it is necessary to make adjustments and additions to the synthetic theory of evolution.
Kevin Lalande toured the conference room, which had gathered several hundred people to discuss the future of evolutionary biology. One of the colleagues sat down with him and asked how he thought things were going in this area.
“Everything seems to be going well,” Laland replied. "There have been no serious disputes yet."
Kevin Lalande is an evolutionary biologist at the University of St Andrews in Scotland. On a cold, cloudy November afternoon, he traveled to London to co-host a meeting of the Royal Scientific Society on New Trends in Evolutionary Biology. The hall was filled with biologists, anthropologists, doctors, computer scientists and self-proclaimed ideologues. The Royal Society of Science is housed in a stately building overlooking St James's Park. The only thing Lalande could see from the high-rise windows of the conference room today were the scaffolding and façade mesh for renovation work. Inside, Lalande hoped, there would also be a modernization today, but of a different type.
In the mid-1900s, biologists supplemented Darwin's theory of evolution with new findings from genetics and other areas of science. The result of this was the so-called "synthetic theory of evolution", which has been setting the direction of evolutionary biology for 50 years. At that time, scientists learned a lot of facts about how life works, and can now sequence entire genomes, watch how genes turn on and off in developing embryos, and how animals and plants respond to changes in the environment.
As a result, Lalande and a group of biologists who share the same opinion with him came to the conclusion that the synthetic theory of evolution needs to be revised. It became necessary to give it a new form of vision of evolution, which they dubbed the concept of "extended synthesis". Other biologists have expressed their disagreement, arguing that there is insufficient basis for such a paradigm shift.
This meeting at the Royal Society of Science was the first public conference where Lalande and his colleagues had the opportunity to present their views on the issue. But Lalande was not in the mood to just preach his views to like-minded people, so prominent evolutionary biologists who were skeptical about the principles of extended synthesis were also invited to the conference.
Both sides expressed their points of view and criticism in a civilized manner, but sometimes there was tension in the audience, expressed by clinking, rolling eyes and meager applause.
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But it never came to fights. At least for now.
Evolution as usual
For any science, there comes a time of transformation and a time when things go on as usual. After Galileo and Newton pulled physics out of old misconceptions in the 1600s, it began to move forward from one humble achievement to the next until the 1900s. Then Einstein and other scientists laid the foundations of quantum physics, presented the theory of relativity and other new ways of knowing the universe. None of them argued that Newton was wrong. But it turns out that the universe is actually not only matter in motion.
Evolutionary biology has had its own revolutions. The first certainly began in 1859 with Charles Darwin's The Origin of Species. Darwin combined information from the fields of paleontology, embryology and other sciences to show the common origin of all living organisms. He also introduced the concept of natural selection, a mechanism for managing these long-term changes. Each generation of the species showed great variability. Sometimes it helped organisms to survive and reproduce, and, thanks to heredity, was passed on to the next generations.
Darwin inspired biologists around the world to study animals and plants from a new perspective, interpreting their biology as adaptations from previous generations. And he succeeded in this, despite the fact that he had no idea about genes. It wasn't until the 1930s that geneticists and biologists joined forces and reformulated evolutionary theory. Heredity has come to be seen as the transmission of genes from generation to generation. The changes were due to mutations that could be intermixed to create new combinations. New species emerged when mutations were formed in populations that made interspecies crossing impossible.
In 1942, British biologist Julian Huxley described this emerging concept in his book Evolution: Modern Synthesis. Scientists still use this name. (They sometimes refer to it as neo-Darwinism, although the term is actually misleading. The term neo-Darwinism was coined in the 1800s and was used by biologists who promoted Darwin's ideas during his lifetime.)
The synthetic theory of evolution has proven to be a powerful tool in the field of nature-related issues. Scientists have used it for a variety of life-history discoveries, such as why some people are prone to genetic diseases like sickle cell disease, or why pesticides sooner or later stop working on pests. But soon after the formation of the concept of modern synthesis, various biologists began to periodically complain about its excessive categoricality. However, it is only in the past few years that Lalande and other scientists have been able to unite and coordinate efforts to develop the principles of an extended evolutionary synthesis that could replace him.
Researchers do not consider the synthetic theory of evolution to be an erroneous concept - it is simply not capable of reflecting all the richness of evolution. Organisms inherit more than just genes - they can inherit other cellular molecules as well as the behaviors they learn and their ancestral habitats. Lalande and his colleagues also dispute the overriding role of natural selection in explaining how life came to be as we know it today. The course of evolution can be influenced by other processes, from the rules according to which species develop, to the external conditions of their habitation.
“It's not about screwing more and more machines to what we already have,” Lalande said. "We need to look at causation from a different angle."
Complementing Darwin
Tel Aviv University biologist Eva Jablonka in her speech tried to analyze the evidence that not only genes can determine the forms of inheritance.
Our cells use a number of molecules to recognize which genes make proteins. For example, in a process called methylation, cells restrict their DNA to keep certain genes closed. When cells divide, they can use the same principle, thus controlling new DNA. Certain signals received from the environment can cause cells to change the so-called "epigenetic" control, allowing organisms to adapt to new conditions.
Some studies show that under certain circumstances, epigenetic changes in the parent can be passed on to offspring. And they, in turn, can pass on this altered epigenetic code to their children. This is a type of inheritance outside genes.
This principle of inheritance is especially clearly seen in plants. In one study, scientists were able to trace an altered methylation pattern up to 31 generations using a plant called Arabidopsis. This type of inheritance can significantly alter the functioning of the body. In another study, scientists found that inherited methylation patterns could change the flowering time of Arabidopsis and affect the size of its roots. The variability caused by these patterns was greater than that caused by ordinary mutations.
After presenting the evidence, Ms. Yablonka argued that epigenetic differences could determine the maturity of organisms for procreation. “Natural selection could have an impact on this system,” she said.
Since natural selection has a significant impact on the course of evolution, conference participants presented evidence of how it can be limited or displaced in a different direction. University of Vienna biologist Gerd Müller cited an example from his own research on lizards. Some species of lizards have lost their toes on their hind legs during evolution. Some species only had four toes, others only one, and some lost their limbs entirely.
According to Mueller, the synthetic theory of evolution leads scientists to view these mechanisms as simply the result of natural selection, which favors one option due to its advantages in survival. But this approach will not work if you wonder what is the advantage for a certain species of individuals in the loss of the first and last fingers, and not any others.
“The answer to that question is that there is no real selective advantage,” Mueller said.
The key to understanding why lizards lose certain toes is primarily how lizards' toes develop in their embryonic state. Processes first appear on the sides, and then five fingers develop from them, always in the same sequence. And they lose them in the course of evolution in the reverse order. Müller suggests that such limitations are caused by the inability of mutations to reproduce all possible changes in a trait. Certain finger combinations are thus unavailable and natural selection cannot select them at all.
Development can limit evolution, and on the other hand endows animals and plants with high plasticity. Sonia Sultan, an evolutionary ecologist at Wesleyan University, gave an interesting example in her speech, talking about the herb of the buckwheat family she was studying, the peppermint.
Within the framework of modern synthesis, Sultan said, the adaptation of the mountaineer will seem to you a fine-tuned result of natural selection. If it grows in low light conditions, natural selection will favor plants with altered traits that allow them to thrive in the environment, for example by developing wider leaves for photosynthesis. And those that grow in bright sunlight develop adaptations for successful growth in different conditions.
“This speaks in favor of the point of view that our meeting is dedicated to opposing,” said Sultan.
If you grow genetically identical Knotweed plants under different conditions, you end up with plants that appear to belong to different species.
For starters, the peppermint adjusts the size of its leaves to the amount of sunlight it receives. In bright light, their leaves become narrow and thick, and in low light, they become wide and thin. In dry soil, these plants take root deep into the ground in search of water, and in well-moisturized soil, the roots become short, hairy and shallow.
Scientists at the meeting argued that such plasticity can contribute to the course of evolution by itself. It allows plants to spread in different habitats, for example, to which natural selection then adapts their genes. Among the speakers was Susan Anton, a paleoanthropologist at New York University, who argued that plasticity could play a significant role in hitherto underestimated human evolution. This is because in the last half century, modern synthesis has significantly influenced its study.
Paleoanthropologists tended to treat the traits found in the fossils as the result of genetic differences. This allowed them to recreate the evolutionary tree of man and extinct forms close to him. Adherents of this approach have achieved significant results, Anton admitted. By the 1980s, scientists had figured out that about two million years ago, our early relatives were small and had small brains. Then representatives of one of the lines of inheritance became taller and developed a large brain. This transition marked the origin of our kind, Homo.
But sometimes paleoanthropologists found variations that were difficult to understand. The two fossils may appear to belong to the same species in some ways, but very different in others. Scientists tend to ignore such environmental-induced differences. “We wanted to get rid of it all and get to the point,” said Anton.
But “all this” is too much to ignore. Scientists have found a staggering variety of humanoid fossils dating back to between 1.5 and 2.5 million years ago. Some are tall and some are not, some have large brains, and some have small brains. All of their skeletons share Homo traits, but each has a confusing combination of differences.
Anton believes that the principles of extended synthesis can help scientists understand this confusing story. She, in particular, believes that her colleagues should take plasticity seriously as an explanation for the strange diversity of early human fossils.
In support of this idea, Anthon noted that living people have their own kind of plasticity. The quality of food a woman receives during pregnancy can affect the growth and health of the baby, and the impact can be traced back to adulthood. Moreover, the size of the woman herself, which depends in part on her own mother's diet, can affect her children. Biologists have found, for example, that the children of women with long legs are generally taller than their peers.
Anthon suggested that the strange changes from the paleontological archive could be even more dramatic examples of plasticity. All of these fossils date from a time when Africa's climate was undergoing extreme fluctuations. Droughts and heavy rains could change food resources in different regions of the world, causing early humans to develop in a different direction.
Extended evolutionary synthesis theory can also help us deal with another chapter in our history - the emergence of agriculture. In Asia, Africa and the Americas, people have domesticated crops and livestock. Smithsonian archaeologist Melinda Zeder gave a talk about the problematic understanding of how this transformation could have happened.
Before people started farming, they had to get their own food and hunt game. Zeder explained how many scientists interpret gatherer behavior in the context of modern evolutionary synthesis: as something superbly regulated by natural selection to get better rewards for their efforts to find food.
It is hard to imagine how such gatherers could have switched to agriculture at all. “You don't get immediate pleasure from grabbing food and putting it in your mouth,” Zeder told me.
Some scientists have suggested that the transition to agriculture may have occurred during a climate change, when finding wild plants became much more difficult. But Zeder and others have found no evidence at all of a crisis in which agriculture could have arisen.
Zeder argues that there is another point of view on this matter. People are not obedient zombies trying to survive in a constant environment, but creative-minded individuals who can change the environment itself and direct evolution in a new direction.
Scientists call this ecological niche building, a process that involves many species. Among the classic cases, beavers are worth noting. They cut down trees and build a dam, creating a pond. In these new conditions, some species of plants and animals will be better than others. And they will adapt in new ways to their environment. This is true not only of the plants and animals living around the beaver pond, but also of the beavers themselves.
According to Zeder, her first acquaintance with the concept of building an ecological niche was a revelation for her. “It was like little explosions in my head,” she told me. The archaeological finds collected by her and other scientists will help to understand how people managed to change environmental conditions.
Early gatherers appear to have moved wild plants away from their natural habitats so that they can always be found at hand. By watering plants and protecting them from herbivores, humans helped them adapt to their new environment. Weed species also changed their habitat and became independent agricultural crops. Some animals have also adapted to their environment, becoming dogs, cats, and other domestic species.
Gradually, from chaotically scattered patches of land inhabited by wild plants, the environmental conditions changed to densely located arable fields. This contributed not only to the evolution of plants, but also to the development of culture among the peasants. Instead of wandering around the world like nomads, they settled in villages and got the opportunity to cultivate the land around. Society has become more stable as children receive ecological inheritance from their parents. This is how civilization began.
Building an ecological niche is just one of many advanced evolutionary synthesis concepts that can help us understand the domestication process, Zeder said. During her speech, she presented a variety of predictions slide by slide, ranging from the movements of early gatherers to the pace of plant evolution.
“It felt like a commercial for the principles of extended evolutionary synthesis,” Zeder told me later, laughing. - But that is not all! You can get a set of kitchen knives!"
The return of natural selection
Among those in the room was a biologist named David Schacker, a researcher at the University of St Andrews. He calmly listened to the discussions for a day and a half, and now decided to take the floor himself and raised his hand.
The speaker in front of him was Denis Noble, a physiologist with a shock of gray hair and a blue jacket. Noble, who spent most of his career at Oxford, said that he started out as a traditional biologist, who believed that genes were the ultimate cause of everything in the body. But in recent years, he changed his mind and began to talk about the genome not as a basis for life, but as a sensitive organ that detects stress and is able to rebuild to overcome problems. “It took me a long time to come to this conclusion,” Noble said.
To illustrate this new view, Noble talked about a variety of recent experiments. One of them was published last year by a team at the University of Reading and was the study of bacteria that move through the environment using long, rotating tails.
First of all, scientists isolated a gene from the DNA of bacteria that is responsible for growing a tail. Then they placed the resulting tailless individuals in a petri dish with a meager supply of food, which they soon consumed. Without the ability to move, they died. In less than four days in these dire conditions, the bacteria started swimming again. Upon close inspection, it was discovered that they had grown new tails.
“The strategy is to create rapid evolutionary changes in the genome in response to adverse external influences,” Noble explained to the audience. "It is a self-sustaining system that allows certain properties to manifest independently of DNA."
Shaker did not find it convincing, and after the applause subsided, he decided to enter into a discussion with Noble.
"Could you comment on the mechanism behind this discovery?" - asked Shaker.
Noble began to stammer. “The mechanism in general terms, I can, yes…” he said, and then began talking about networks and rules and the feverish search for a way out of the crisis. “You need to refer to the original text of the report,” he then said.
As Noble struggled to answer, Shaker glanced at the lecture open on his clipboard. And he began to read out one of the paragraphs aloud.
“Our findings demonstrate that natural selection can quickly change regulatory networks,” Shaker read and put down his iPad. “This is a wonderful, just wonderful example of rapid neo-Darwinian evolution,” he said.
Shaker got the very essence of the feelings of a considerable number of skeptics with whom I was able to speak at the conference. The ambitious rhetoric about the paradigm shift was mostly unfounded, they said. However, these skeptics did not remain in the shadows. Some of them decided to take the floor in person.
“I think I'm expected to talk about Jurassic evolution,” said Douglas Futuima, taking the podium. Futuima is a fluent biologist at Stony Brook University in New York and the author of a major textbook on evolution. During the meeting, he was inundated with complaints that textbooks paid little attention to such things as epigenetics and plasticity. In fact, Futuima was just invited to explain to colleagues why these concepts were ignored.
“We have to admit that the basic tenets of the synthetic theory of evolution are strong and valid,” said Futuima. Not only that, he added, but the varieties of biology discussed at the Royal Society are not really all that new. The creators of the synthetic theory of evolution mentioned them more than 50 years ago. To understand them, many studies based on modern evolutionary synthesis have been carried out.
Take plasticity. Genetic variation in animals or plants regulates the range of forms an organism can develop into. Mutations are able to change this range. And the mathematical models of natural selection show how it can promote certain types of plasticity at the expense of others.
If the theory of extended evolutionary synthesis is not needed by anyone, how is it that an entire meeting at the Royal Society of Science was devoted to it? Futuima suggested that this interest was emotional rather than scientific. Its principles made life a driving force, not a dormant weapon of mutation.
“I think science cannot be based on what we find emotionally or aesthetically more attractive,” said Futuima.
Yet he went to great lengths to show that the research discussed in the session could lead to some interesting conclusions about evolution. But these conclusions can arise only as a result of hard work, which entails the emergence of reliable data. “Enough essays and reports have been written on this topic,” he said.
Some members of the audience started bickering with Futuima. Other skeptical speakers were freaked out by arguments they thought were meaningless. But the meeting was still completed on the third day without any fights.
“This is probably the first of many, many meetings,” Lalande told me. In September, a consortium of scientists in Europe and the United States received funding of $ 11 million (of which $ 8 million from the John Templeton Foundation) to conduct 22 studies on the principles of advanced evolutionary synthesis.
Many of these studies will test the predictions that have emerged from the synthetic theory of evolution over the past few years. They will, for example, find out if species that build their own habitat - cobwebs, hornets' nests, etc. - can grow into more species than those that don't. They will also consider whether high plasticity allows for faster adaptation to new conditions.
“Doing this research is what our critics are asking for,” Lalande said. "Go and find evidence."