Not only are they the only mammals that can fly, but bats also show off with their immunity to viruses and other diseases. What gives?

Well, according to a recent study in Science, these two abilities—flight and immunity—might be related in the winged animals.

A group of international researchers sequenced the entire genomes of two species of bats—the fruit bat Pteropus alecto and the insectivore Myotis davidii. These two species are from the two distinct sub-orders of bats—P. alecto is a megabat and M. davidii, a microbat. By comparing and contrasting the two species’ genomes and those of other mammals (human, rhesus macaque, mouse, rat, dog, cat, cow, and horse), the scientists could refine bats’ place in the tree of life as well as determine the evolution of some of their bat-traits.

Study co-author Chris Cowled, of the Australian Animal Health Laboratory, describes how remarkable these traits are. “Bats are a natural reservoir for several lethal viruses, such as Ebola and SARS, but they often don’t succumb to disease from these viruses. They also live a long time compared to animals similar in size.”

It turns out the trick for this trait is flight. Flying is a very energy intensive activity that also produces toxic by-products, and bats have developed some novel genes to deal with the toxins. Some of these genes are implicated in the development of cancer or the detection and repair of damaged DNA.

“What we found intriguing was that some of these genes also have secondary roles in the immune system,” says Cowled. “We’re proposing that the evolution of flight led to a sort of spill over effect, influencing not only the immune system, but also things like aging and cancer.

“A deeper understanding of these evolutionary adaptations in bats may lead to better treatments for human diseases, and may eventually enable us to predict or perhaps even prevent outbreaks of emerging bat viruses,” says Cowled.

Sounds bat-tastic.

Image: James Niland/Wikipedia

But here’s an interesting twist to the tale. A recently designed robot at the Biomimetic Millisystems Lab at UC Berkeley is now shedding light on flight evolution.

A research team, led by Ron Fearing—we highlighted some of his early biomimicry work a few years ago here—wanted their robotic cockroach, DASH, to move faster. DASH is a lightweight, speedy robot made of inexpensive, off-the-shelf materials first launched in 2009. Its small size makes it a candidate for deployment in areas too cramped or dangerous for humans to enter, such as collapsed buildings.

But compared with its biological inspiration, the cockroach, DASH had certain limitations as to where it could scamper. Remaining stable while going over obstacles is fairly tricky for small robots, so the researchers affixed DASH with lateral and tail wings borrowed from a store-bought toy to see if that would help.

The researchers ran tests on four different configurations of the robotic roach, now called DASH+Wings. The test robots included one with a tail only and another that just had the wing’s frames, to determine how the wings impacted locomotion.

With its motorized flapping wings, DASH+Wings’ running speed nearly doubled, going from from 0.68 meters per second with legs alone to 1.29 meters per second. The robot could also take on steeper hills, going from an incline angle of 5.6 degrees to 16.9 degrees.

“With wings, we saw improvements in performance almost immediately,” says Kevin Peterson, a Ph.D. student in Fearing’s lab. “Not only did the wings make the robot faster and better at steeper inclines, it could now keep itself upright when descending.

The engineering team’s work caught the attention of animal flight expert Robert Dudley, a UC Berkeley professor of integrative biology, who noted that the most dominant theories on flight evolution have been primarily derived from scant fossil records and theoretical modeling.

He referenced previous computer models suggesting that ground-dwellers, given the right conditions, would need only to triple their running speed in order to build up enough thrust for takeoff. The fact that DASH+Wings could maximally muster a doubling of its running speed suggests that wings do not provide enough of a boost to launch an animal from the ground. This finding is consistent with the theory that flight arose from animals that glided downwards from some height.

“The fossil evidence we do have suggests that the precursors to early birds had long feathers on all four limbs, and a long tail similarly endowed with a lot of feathers, which would mechanically be more beneficial for tree-dwelling gliders than for runners on the ground,” says Dudley.

Dudley said that the winged version of DASH is not a perfect model for proto-birds – it has six legs instead of two, and its wings use a sheet of plastic rather than feathers – and thus cannot provide a slam-dunk answer to the question of how flight evolved.

“It’s still notable that adding wings to DASH resulted in marked improvements in its ability to get around,” Fearing adds. “It shows that flapping wings may provide some advantages evolutionarily, even if it doesn’t enable flight.”

Their research was published online today in the journal Bioinspiration and Biomimetics.

Image by Kevin Peterson, Biomimetic Millisystems Lab