Biological evolution is the change in heritable characteristics of populations over generations. Its main mechanisms: mutations (DNA changes), gene recombination during sexual reproduction, gene flow (exchange of individuals between populations), genetic drift (random fluctuations in gene variant frequencies), and natural selection. Natural selection directs evolution: traits that increase fitness (the ability to survive and reproduce) gradually spread. Population separation (geographic barriers) can lead to speciation.
History
The idea of species transformation dates back to antiquity, but scientific substantiation emerged in the 19th century. Charles Darwin and Alfred Russel Wallace independently formulated the concept of natural selection; Darwin published it in 1859 in 'On the Origin of Species.' Gregor Mendel discovered the laws of heredity in 1865, which later formed the basis of genetics. In the early 20th century, the synthesis of Mendelism and Darwinism led to the formation of the synthetic theory of evolution (S.S. Chetverikov, J.B.S. Haldane, R. Fisher, S. Wright). The discovery of the DNA structure (1953) and the development of molecular biology provided a direct mechanism for heredity and mutations.
How it works
The evolutionary process is based on four main factors: mutations, recombination, genetic drift, and natural selection. Mutations randomly change the DNA sequence; most are neutral or harmful, but some confer an advantage. Recombination during meiosis shuffles paternal and maternal chromosomes, creating new allele combinations. Genetic drift causes random changes in allele frequencies, especially in small populations. Natural selection increases the frequency of alleles that enhance fitness in a given environment. Mathematically, this is described by the Hardy-Weinberg law, which shows equilibrium in the absence of evolutionary forces. Speciation often occurs through geographic isolation, where accumulated differences lead to reproductive incompatibility.
In practice
Understanding evolution helps create vaccines against rapidly mutatingviruses and explains bacterial resistance to antibiotics. Plant and animal breeding is accelerated evolution under human control.
Fun fact
The octopus eye and the human eye are structured very similarly but developed independently — this is an example of convergent evolution: similar conditions produce similar solutions.
Picture every blood test as a dot on a large map. Plot thousands of those dots and they won't scatter at random: they line up along two main roads. One road separates men from women, the other stretches from youth to old age. Follow these roads and you can see how a person grows up, lives and grows old.
In a rubber band stretched in the lab, three different elasticity mechanisms operate simultaneously. At small strains, Hooke's law prevails; at intermediate strains, entropic chain elasticity; at large strains, strain-induced crystallization.
In a psychologist's quiet office, a fourteen-year-old fills out a questionnaire about childhood. The scores climb, and on the MRI scans the amygdala climbs with them: a small node deep in the brain that teaches us to fear and to remember danger. In a rat held in a narrow tube for three hours a day, the same structure grows faster than in its calm counterparts.
Picture a wind map over a mountain range. The wind mostly blows downhill, following elevation changes. But if you look closely, in some valleys the air swirls into little eddies that keep the wind from simply flowing down. That is exactly what the mutation field in human DNA looks like.
A harbor lives by the tide schedule. Water rises and falls, and with it everything changes: the level at the dock, the composition of the sediment on the bottom, even the salinity in the far corners. A galaxy works similarly, except instead of water it has gas, and instead of the Moon, it has its own stars and neighboring clouds.
Two runners start a race on a course with changing incline. One starts earlier, the other later, and the judge measures their speeds without knowing about the staggered starts. So it is with virus variants: data arrive with delays, and if those delays are unequal, estimates of competitive advantage can be badly wrong.
Picture a flock of birds gathering around a feeder that no one built. Each bird searches for food on its own, yet they all end up together. Usually, such behavior is explained by social instinct: birds want to be near their kin. But what if the flock is simply a side effect of greed?
An old city gains new suburbs. In the center, narrow streets where life has nearly stopped, while on the outskirts construction is booming. That is what a spiral galaxy looks like when its core stars have long aged and new stars are still being born in the outer disk.
Life begins with a bubble. In a warm puddle on ancient Earth, fat molecules could gather into tiny spheres — prototypes of cells. Inside such a sphere, a polymer happened to be present that accelerated the uptake of new fats from the surrounding water. The bubble grew, divided, and passed its composition to offspring.
A forest does not live in a static world. Between winter and summer, day and night, conditions shift, and each fluctuation is like a rhythm that all its inhabitants must keep pace with. Yet until now, ecologists have mostly studied how communities of living beings persist in an unchanging environment, like testing a bridge's strength only in calm weather.
Rare species in a large community are like thin branches on a tree: a random gust can easily snap them. Even if conditions are stable, a small population simply lacks enough individuals to survive a bad season. In a new study, scientists added this factor to an ecosystem model and watched the community clean itself out.
Every winter, hospitals fill up, and by summer they seem to empty. Epidemics breathe like the tide. But why do waves of disease keep rolling in, even without new mutations? Mathematicians found an answer in a tug-of-war between two strains.
Within a single epidemic, two virus variants often coexist.
A forest does not live in a static world. Between winter and summer, day and night, conditions shift, and each fluctuation is like a rhythm that all its inhabitants must keep pace with. Yet until now, ecologists have mostly studied how communities of living beings persist in an unchanging environment, like testing a bridge's strength only in calm weather.
An ant the size of a grain of rice lives longer than its neighbor half its size. But when heat strikes, the bigger one isn't necessarily tougher. Researchers in Australia collected 18 species of ants and checked three things: how long workers live, how quickly they deteriorate, and at what temperature they start to die.
Rare species in a large community are like thin branches on a tree: a random gust can easily snap them. Even if conditions are stable, a small population simply lacks enough individuals to survive a bad season. In a new study, scientists added this factor to an ecosystem model and watched the community clean itself out.
Two daughter cells receiving equal shares from the mother: that's the familiar picture of division. But what if one gets almost everything and the other just crumbs? Stochastic modeling shows that sometimes unequal division is more advantageous.
Each cell stores a protective reserve that helps it weather hardships. During division, this reserve is distributed between daughters.
Two daughter cells receiving equal shares from the mother: that's the familiar picture of division. But what if one gets almost everything and the other just crumbs? Stochastic modeling shows that sometimes unequal division is more advantageous.
Each cell stores a protective reserve that helps it weather hardships. During division, this reserve is distributed between daughters.
When an antibody meets a virus, it doesn't latch on with a single death grip. Rather, it's like two bunches of grapes tumbling in water, catching each other with dozens of short tendrils. Each tendril is weak on its own, easily torn by the thermal jitter of water molecules, but together they hold tight.
A protein chain folds into a working tool in a fraction of a second, and almost never makes a mistake. For a long time, it was thought that evolution specifically polishes amino acid sequences so that a protein not only works but also easily finds its unique shape. New work turns this idea on its head.
A protein chain folds into a working tool in a fraction of a second, and almost never makes a mistake. For a long time, it was thought that evolution specifically polishes amino acid sequences so that a protein not only works but also easily finds its unique shape. New work turns this idea on its head.
A jazz ensemble: at first, a cacophony of random notes. Then — a catchy riff that plays over and over. Such is the riddle of the origin of life — only in the language of chemistry.
In 1970, mathematician John Conway invented the Game of Life — a cellular field where just three rules generate surprisingly complex patterns. Forty years later, SmoothLife appeared: a version where space is no longer cellular but smooth, like a blurred patch. The authors of the new study took an even simpler variant of this continuous game: now everything changes smoothly in time as well.
A web where lions eat zebras and hyenas finish the leftovers is not just a list of dinners. It's a survival map for an entire region. When the climate shifts, animals move, and the map tears. To understand where it will tear and where it will hold, you need to find its unchanging 'skeleton'—the connections that repeat across different places.
A planet in the habitable zone is no guarantee of life. Like a conductor leading an orchestra, a star dictates the tempo and character of planetary atmosphere evolution over billions of years.
The human mind is like a construction set that builds itself. New ideas don't die with their creators: they are passed on, mixed, and selected. This process is called cultural evolution: useful inventions stick, useless ones are forgotten. That's how a ratchet works — a mechanism that only turns forward.
But what exactly happens in the head when one thought displaces another?
A bacterial biofilm is like a city made of slime. The houses are the microbes themselves. The streets and bridges are long polymer molecules that bacteria secrete outside. This whole construction is not static: the bridges are constantly breaking and re-forming.
The authors built a "toy" computer model of such a city.
A perfume bottle is not just glass with liquid. It is a snapshot of its time, a frozen melody of fragrant notes. From 1900 to 2024, tens of thousands of such 'melodies' have accumulated, and now they can be studied as a single organism.
Imagine a cookbook that gets rewritten from generation to generation. One day, the borscht recipe receives a secret ingredient from a pastry chef, and from that moment, the taste remembers not only ancestors but also a neighbor. In the Standard Model of evolution, genes behave the same way.
Two gardeners haggle over water from a magical well. One proposes how many buckets to take, the other can agree or refuse. If the deal goes through, the water decreases; if not, the well gradually refills. This haggling repeats hundreds of times, and the gardeners' habits sometimes change randomly, as if they're trying new tactics.
For a long time, biologists argued: if a herd of animals stably maintains a mix of aggressive and peaceful individuals, does each one alternately change behavior, or do some always fight while others always yield? In classical equations, these options are indistinguishable.
The cells of an organism are like twin chefs sharing a kitchen. They have the same cookbook (DNA), but when copying the recipe to a cheat sheet and assembling the dish, random errors occur. This unpredictability, entropy, means that in identical cells, protein levels are sometimes high, sometimes low.
Ecosystems are not chaos but a complex dance where every species plays its part. Scientists modeled such a dance: two prey compete for carbon and water (the building blocks of cells), while a predator eats both. Sixteen scenarios emerged — from predator extinction to a steady rhythm for all three species.
Evolution resembles not just a tree with diverging branches, but a woven tapestry. Threads of ancestry cross when species exchange genes — for example, bacteria pass drug resistance to each other, and plants crossbreed to produce hybrids.
Every tumor writes its own cosmology. Its cells are galaxies, and mutations are stellar flares marking the branches of a genealogical tree. The key to its history is the rhythm of accumulating genetic typos.
A family tree becomes a tangle if you account for adopted children and remarriages. Evolution often resembles such a tangle: although the Standard Model, the traditional view of divergent evolution where species branch like a tree, paints a neat tree of species, in reality genes travel not only by inheritance but also directly between unrelated organisms — a process…
Evolution flows like water. In a wide river, changes are smooth and slow, while a mountain stream churns with every stone. Population size and mutation rate set the channel: broad and calm, or narrow and rapid-filled.
A desert where every step reshapes the terrain. Dunes settle, new slopes emerge, and the next step is dictated by what you've just trampled. That's roughly how "sandscapes" work — a mathematical model inspired by living systems.
In a world where Reynolds numbers are minuscule, water turns into thick syrup, and the swimming tricks we know stop working. Here reigns the insidious scallop theorem: reciprocal motions produce no net displacement. Microorganisms found a way out: they grow polymer tails.
A runner loses on both a smooth track and sticky sand. Seems hopeless. But if the surface underfoot starts changing every few seconds (track, then sand) the runner suddenly stops falling behind. He doesn't get faster; the environment just doesn't get a chance to 'crush' his weakness.
That's exactly what the authors found when studying a simple predator–prey model.