Flight has evolved no less than four separate times in the history of life on Earth as we know it, in four distinct lineages. The four animal groups to have evolved ‘true’, powered flight’ are, in roughly chronological order, (1) insects, (2) pterosaurs, (3) dinosaurs/birds, and (4) mammals.
The advantages offered by flight are many, though almost all of them can be lumped under increased mobility. Flight allows an animal access to the vertical world, increasing the range of available habitats dramatically; it enhances foraging ability and predator evasion; it allows travel over otherwise uncrossable terrain to colonize new territories or engage in long-distance season migrations. The allure is unmistakable, and if it weren’t for the sheer mechanical difficulty and energetic expensiveness of flight, we might expect it to have evolved more frequently in the history of life. Let’s take a closer look at the lineages that have evolved powered flight.
You’ll hardly find a group with a greater variety of flying styles than the insects. Dragonflies (order Odonata) pluck other insects out of the air, buzzing like miniature bi-planes; flies (order Diptera) hover around with aerial dexterity far in excess of our nimblest helicopters; monarch butterflies (order Lepidoptera) flutter erratically yet somehow travel thousands of miles every fall to Mexico to overwinter.
Dragonflies are the fighter jets of the insect world
Contrary to popular belief, pterosaurs are not a type of dinosaur, rather they are a distinct line of flying reptiles which evolved around the same time as the dinosaurs. They were masters of the sky in the Jurassic and Cretaceous periods, and still hold the record for largest flying vertebrate. Quetzalcoatlus, aptly named for the Aztec’s winged serpent god, had a wingspan approaching 40 feet. One species in this genus was so large, in fact, that some scientists think they may represent the upper limit of body size for flying animals.
A pterosaur skeleton
In general, paleontologists now agree that birds evoled from small theropod dinosaurs, such as Microraptor. The specifics of this evolution, however, form the basis of one of the oldest debates in the field. Archaeopteryx is often held up as the earliest known bird and the clarest link between dinosaurs and their modern descendants, but the question of whether or not Archaeopteryx was capable of true flight remains up in the air (pun absolutely intended).
Modern birds are arguably the masters of flight
Mammals are latecomers to the game of flight, with only one order capable of powered flight: the bats (order Chiroptera). Bats didn’t evolve until after the age of dinosaurs had passed and mammals were able to flourish in the wake of their sudden departure. That said, in their short time bats have been very successful. Wikipedia references an impressive statistic from Colin Tudge’s The Variety of Life: “There are about 1,100 bat species worldwide, which represent about twenty percent of all classified mammal species.”
Bats are the only modern mammals to have evolved powered flight
For every animal capable of powered flight, there are a handful more who come close, mainly by gliding. The groups of animals which have evolved some sort of gliding capability are very diverse, which goes to show just how useful a bit more hangtime can be.
Several species of flying squirrel use folds of skin between their hands and feet to make long leaps from tree-to-tree. Sugar gliders, a type of possum found in Australia, glide via a similar mechanism to the squirrels, though they are not closely related. Even further away in the animal tree, there are also snakes which flatten out their bodies using their ribs, and frogs which use huge webbed feet, to make similar arboreal gliding leaps.
Sugar gliders are a species of possum from Australia that use flaps of skin to glide like our flying squirrels
All of the above animals are united in the fact that they are primarily arboreal, and they use their gliding abilities to make longer jumps and improve their mobility among the treetops. In fact, the use of gliding to help arboreal animals is one of the pimary theories to explain how dinosaurs/birds evolved flight.
In fact, all of the above represent fantastic examples of convergent evolution, and really highlight the way environmental pressures can produce similar results in many unrelated groups.
This is a great list, although I’d add another honorable mention. The flying fish are capable of gliding for 50 m (160 ft). With a convinient updraft they have been known to cover as much as 200 m; with a possibility of gliding 400 m (1,300 ft) in one jump. The jump duration was measured to reach 30 seconds and flying fish were known to sometimes glide high enough to end up on ship decks. Their distinct features are the huge pectoral fins, which unfold as the fish propels itself out of the water with tail movements.
Great call! Flying fish are soooo cool. I’ve always wondered what is the evolutionary advantage of this feature?
The idea is to use it to escape a predator, as no other fish can follow them out of the water and it would be difficult to predict a landing spot. Plus there will probably be easier prey well before the limits of the gliding distance.
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