Workers in the field of evolutionary biology are using microcomputed tomography (micro-CT) scanning to create precise images of the inner ear of echolocating and non-echolocating bats ”in hopes of understanding some of the differences among them.” Evolutionary biology is the ultimate ‘whodunnit’ game for deciding where a particular character like echolocation came from and why it appeared when it did. In the case of bats, the study of flight didn’t necessarily include echolocation. The 3D imaging used for this study enabled scientists to determine that a tiny common mammalian bone called the stylohyal bone physically connects the larynx to the ear (tympanic) bone. January 24 in Nature.

Detailed 3-D images of individual bats representing 26 species were possible because of the micro capabilities of this technology which is close to those commonly used in hospitals but with much higher resolution. Because of it workers were able to avoid dissecting or damaging the specimens studied. As with most anatomical inferences, the stylohyal bone seems to connect only in echolocating bats, though there are no clear answers as to why that is so. There is also no clear evidence that all echolocating bats are represented in the sample. Yet, Brock Fenton, a biology professor at Western Ontario, and senior study author claims, that if you find a fossil with such a bone connecting to the tympanic bone, you have an echolocator. “researchers suggested that [the connection] might help both in perceiving the outgoing signal and in dampening the vibrations to prevent the bat from deafening itself with the sound it produces, which can be more than 100 times louder than the reflected echoes. By having a physical connection, Fenton says, it would allow the bats to have a "completely crisp and close-to-the-source representation of the original signal," which is crucial for comparison with incoming signals. “

Here’s some basic common definition of the terms: “Echolocation

Bat echolocation is a perceptual system where ultrasonic sounds are emitted specifically to produce echoes. By comparing the outgoing pulse with the returning echoes the brain and auditory nervous system can produce detailed images of the bat’s surroundings. This allows bats to detect, localize and even classify their prey in complete darkness. At 130 decibels in intensity, bat calls are some of the most intense airborne animal sounds.[17]

To clearly distinguish returning information, bats must be able to separate their calls from the echoes they receive. Microbats use two distinct approaches.

1.Low Duty Cycle Echolocation: Bats can separate their calls and returning echos in time. Bats that use this approach time their short calls to finish before echoes return. This is also important because these bats contract their middle ear muscles when emitting a call to avoid deafening themselves. The time interval between call and echo allows them to relax these muscles so they can clearly hear the returning echo.[18]

2. High Duty Cycle Echolocation: Bats emit a continuous call and separate pulse and echo in frequency. The ears of these bats are sharply tuned to a specific frequency range. They emit calls outside of this range to avoid self-deafening. They then receive echoes back at the finely tuned frequency range by taking advantage of the Doppler shift of their motion in flight. These bats must deal with changes in the Doppler shift due to changes in their flight speed. They have adapted to change their pulse emission frequency in relation to their flight speed so echoes still return in the optimal hearing range.[19]

Yet while echolocation would have allowed bats to quickly radiate and fill the nocturnal skies left empty by birds, there is no clear evidence that echolocation evolved prior to or simultaneously with flight. One can only imagine the skies filled 24/7 and every conceivable strategy attempted to exploit a burgeoning mammalian clade. If you watch migrating birds today in some of the more populated areas, they seem as a blizzard, and you wonder how might they all seem to do this without practice? Or you wonder is the idea that evolution proceeds in an improving of the species, as obtuse as we were told it was.

A biochemical analysis by Jones and Teeling of the genomes revealed back in 2006 that:

“Recent molecular phylogenies have changed our perspective on the evolution of echolocation in bats. These phylogenies suggest that certain bats with sophisticated echolocation (e.g. horseshoe bats) share a common ancestry with non-echolocating bats (e.g. Old World fruit bats). One interpretation of these trees presumes that laryngeal echolocation (calls produced in the larynx) probably evolved in the ancestor of all extant bats. Echolocation might have subsequently been lost in Old World fruit bats, only to evolve secondarily (by tongue clicking) in this family. Remarkable acoustic features such as Doppler shift compensation, whispering echolocation and nasal emission of sound each show multiple convergent origins in bats. The extensive adaptive radiation in echolocation call design is shaped largely by ecology, showing how perceptual challenges imposed by the environment can often override phylogenetic constraints.”

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It has always seemed more plausible that sophisticated systems such as predation and navigation via sound, and to the extent this must work flawlessly, that there must have been an abundance of traits that contained this, and possibly other capabilities coupled together and perhaps no longer apparent or fitness enhancing. Surely we know that traits were lost for the most ephemeral conditions imaginable. Others were re-invented in new ways that science may never come close to guessing correctly. But it is amazing to see how the biological sciences are apparent in our all our studies of complex systems.