Would you believe me if I said that insects such as flies and bees were originally evolved from crustaceans to which crabs and lobsters belonged?
At first glance, it sounds strange, but when you think about it, it feels very reasonable. Both belong to the same arthropod phylum, and many of the animals of other classes are mistaken for insects by some people, such as scorpions and spiders, which are arachnoids, and tide insects belong to the crustacean, which is as disgusting as other insects. Of course, today we are not talking about these animals, but another branch of the arthropod phylum, crustaceans.
It turns out that these crustaceans are indeed somewhat "related" to insects. The latest research suggests that the vast families of insects that spread across the globe today evolved from crustaceans.
Scientists now generally believe that the earliest insects on Earth appeared about 480 million years ago and evolved from crustaceans living in water. They first gradually left the sea, tried to live on land, and enjoyed the benefits of land, settling down for a long time.
After about 80 million years, as more and more organisms began to develop onto land, terrestrial ecosystems became more and more complex, and the ancestors of insects had to jump up and take to the skies. Considering that the dinosaur age of pterosaurs began about 225 million years ago, birds evolved from dinosaurs, and mammals appeared about 200 million years ago, then insects are indeed the earliest flying animals on Earth, at least twice as long as any other flying animal.
So the question arises: How did the first flying insect get into the sky? Where did its wings come from?
This question has plagued scientists for hundreds of years. We all know that the evolution of species stems from genetic mutations plus natural screening, which are untargeted. For a century, many people attributed the appearance of insect wings to random new organizational structures. In recent years, it has become increasingly believed that insect wings change from the existing organizational structure of crustaceans.
Initially, the focus was on the gills, which had both joints and muscles and met the wing requirements. What's more, some crustaceans have gills that resemble insect wings in their infancy.
Recent studies have suggested that the source of insect wings may not be gills, but legs. Strangely, the wings seem to be on the back of the insect, and the legs are under the body, why do scientists have such ideas? Two studies have given evidence.
The first study came from a study of a shrimp called parhyale hawaiensis, and through gene knockout techniques, the researchers discovered that it had a genetic network similar to insect wings in its body, and this gene controlled its carapace and legs closest to the body. This means that crustacean legs may be squeezed out of the body wall and eventually evolve into wings.
Similarly, the second study also used gene knockout techniques to study insects such as fruit flies. The results show that the three pairs of feet of the insect and the first three pairs of feet of the crustacean are almost perfectly matched. That is, in the evolution from crustaceans to insects, the first three pairs of feet did not change at all.
So the question arises: where did the fourth pair of feet go?
Heather Bruce, a molecular biologist at the Woods Hole Institute of Oceanography, went through a wealth of sources to explore the answer to this question. In a paper published in 1893, the authors pointed out that this pair of feet of insects had been integrated into the body wall, and some even fused together during the embryonic period.
She was not satisfied with this answer and continued to consult the information. In a paper published in the 1980s, she seemed to have found the answer she wanted. A fresh idea is presented in the paper: not only do the two legs melt into the body wall, but the leaves on the legs slowly move to the back, forming the wings of the insect.
Bruce was intrigued by this claim and immediately tested it with her colleagues using genomic and embryo data. It turned out that what the paper said was exactly right: first, the blades of the proximal leg would merge into the body wall, and then the nearest part would gradually move upwards, all the way to the back, and eventually become wings.
The two papers, published in Natural Ecology and Evolution by different research teams, disagree on some aspects but agree on the origin of insect wings. After reading the two papers, experts in the field commented: "The view of the complementarity of genes in the legs and wings allowed the two teams to reach a consensus in answering some key questions about the transformation of crustaceans into winged insects." They agreed that the lateral body wall of the insect was of the same origin as the proximal leg of the parhyale shrimp, and the theory that the legs of crustaceans formed wings after they were integrated into the body wall. ”
Of course, the two sides are not highly consistent on all issues.
Scientists in the first study believe that insect wings evolved in a dual-origin pattern. That is, they believe that not only the legs that blend into the body wall, but also the body wall are involved in the formation of wings.
For the second group of researchers, they believe that in the process of forming wings, basically only those two legs are involved. The legs first blend into the body wall and then squeeze out from behind to form wings.
In any case, at least in the claim that the insect wings came from the legs of crustaceans, there was a consensus between the two sides.
For many years, it was thought that insect wings were newly evolved body parts, and it was very interesting because of it. It turns out that nothing is completely new, and through the comparison of genomes we already know that the wings of these insects have only evolved from existing body parts, but this source is still somewhat unclear.
Fortunately, through the study of the genome, these puzzles are being solved little by little. After this study, we are also more aware of the close relationship between insects and crustaceans in the phylum of arthropods. By looking at the crustaceans of the world today and various parts of their bodies, we can better study their and the history of insects.
Anyway, we're getting closer and closer to the real answer. About 400 million years ago, it has become clearer how the first flying animal on Earth ascended to the heavens. Even though we didn't show up until 400 million years after this happened, we're close to seeing the truth.