Snakes are common and diverse reptiles that are very close to lizards and are descended from them in the process of evolution. Among the more than four thousand species of snakes, there are inhabitants of almost all continents and large islands, which dominate a wide variety of ecological niches and can feed on almost anything. The authors of a new article in the journal Science analyzed the genomes of more than a thousand scaly species (snakes and lizards), data on their diet, and explained how snakes’ unique diversity emerged.

Approximately 40,000 species of vertebrate animals are known, and one tenth of them are snakes. An impressive number, if you remember that these are just a suborder of the order scaly reptiles (Squamata), which also includes lizards and several divorced animals. Lizards were the ancestors of snakes, but their paths diverged sharply more than 150 million years ago, and the two groups subsequently evolved in their own ways. Although snakes are officially just one type of lizard, they are very different from their scaly counterparts in ecology, morphology, and biogeography.

Snakes have demonstrated the ability to rapidly create new species and larger systematic groups. As a result, they dominated all continents of the Earth (except Antarctica) and even settled on many islands. Ireland and New Zealand remain rare exceptions that do not contain snakes in their native fauna. Snakes have also acquired a complex of unique adaptations, such as the absence of limbs, an elongated body, a developed sense of smell and, of course, their unique venom.

This is how snakes have mastered various ecological niches: they swim in the seas, dig in the ground, climb on branches, live in deserts and equatorial forests, where they poison, strangle and swallow their victims. Snakes have become accustomed to different types of food, except, of course, plant foods that are not of interest to resident predators. Also, unlike lizards, they usually specialize in a single type of food.

The authors of a new publication in a leading scientific journal Science We set out to learn the secret of snakes’ evolutionary success and extraordinary diversity. They analyzed fragments of 1,018 crustacean genomes, as well as fossils and data on the food preferences of almost 70,000 individuals (using museum specimens). This is how biologists reconstructed the evolutionary history of scaly reptiles.

It turns out that snakes are evolving at a very high rate, about three times faster than lizards. They also have special genetic and molecular adaptations: an increase in the number of transposons and a change in the functions of proteins involved in metabolism. At the same time, the selection of snakes into a separate group at the time of the dinosaurs (about 150 million years ago) was accompanied by their rapid and radical transformation. Snakes almost immediately acquired all the characteristic adaptations: a legless, elongated body, a deformable skull for swallowing large prey, and extraordinary sensitivity to odors.

Separately, such devices also appeared in other vertebrates. For example, more than 25 groups of lizards (spines, scales, etc.) and amphibians, such as modern worms and long-dead storks, have independently evolved to the “legless structure” at various points in time. However, snakes especially successfully combined all these adaptations, which appeared almost simultaneously (on the evolutionary scale of time), changed very dynamically and enabled a sharp acceleration of speciation and growth of ecological diversity.

Scientists have called the situation before such a “serpent explosion” a macroevolutionary singularity, by analogy with the cosmological term describing the universe that was in an infinitely compressed and heated state before the Big Bang. After the singularity, everything began to change rapidly and unexpectedly, but the nature of the changes largely determined the initial state of the animals. One can only guess what events triggered the rapid evolution of the first snakes.