April 11, 2022 | David F. Coppedge

“Probably Evolved” Is Batty Science

Some bats echolocate but don’t have to. Saying that
they “probably evolved” echolocation makes no sense.

 

The Egyptian fruit bat uses echolocation but is active at day and night. Israeli scientists predicted they would not use this skill while flying during daylight hours. They were wrong. Observations showed that these bats, even though they have keen vision, still use echolocation in broad daylight. Their open-access paper in appeared in Current Biology on April 11, 2022.

We hypothesized that fruit bats would rarely use echolocation in broad daylight.

We will refer to bats that are active during daytime as ‘diurnal bats’. We conducted video and acoustic recordings of bats while they emerged from their colony, foraged at fruit trees and drank from an artificial pool. Contrary to our prediction, bats regularly used echolocation as they emerged from their colony and when flying near fruit trees. The bats increased their click rate while landing on trees and descending to drink from the pool, and they reduced it when ascending from the pool, showing that echolocation is functional even in broad daylight.

> Source: Eitan et al., Functional daylight echolocation in highly visual bats. Current Biology, Volume 32, Issue 7, PR309-R310, April 11, 2022.

Making predictions and testing them with observations is good scientific practice. Often, nature surprises the naturalist with unexpected things. This is all fine and good. But did their work “shed light on evolution” at all? How did echolocation originate? Did Darwinian theory assist them in coming to an understanding of this phenomenon? Notice two uses of the word “probably” in their answers:

Despite their visual abilities, Egyptian fruit bats use lingual echolocation clicks, which probably evolved independently of laryngeal echolocation….

Lingual echolocation has probably evolved independently in Egyptian fruit bats after the loss of laryngeal echolocation by their common ancestor.

Flying foxes are among the largest bats.

Lingual and laryngeal echolocation only differ by the distance in the mouth or throat of the clicks and the alleged longer duration of lingual clicks. The latter is assumed to be more “primitive” than the laryngeal echolocation used by nocturnal bats. This perception is mistaken, however; a paper in 2011 found that lingual echolocation was just as good as the other kind, and in some cases might even be superior, comparable to that in dolphins. Dolphin sonar is known to be exceptionally good, as was demonstrated in Illustra’s film Living Waters. The 2011 paper says also studied the Egyptian fruit bat.

We show experimentally that in tasks, such as accurate landing or detection of medium-sized objects, click-based echolocation enables performance similar to laryngeal echolocators. Further, we describe a sophisticated behavioral strategy for biosonar beam steering in clicking bats. Finally, theoretical analyses of the signal design–focusing on their autocorrelations and wideband ambiguity functions–predict that in some aspects, such as target ranging and Doppler-tolerance, click-based echolocation might outperform laryngeal echolocation. Therefore, we suggest that click-based echolocation in bats should be regarded as a viable echolocation strategy, which is in fact similar to the biosonar used by most echolocating animals, including whales and dolphins.

> Source: Yovel et al., Click-based echolocation in bats: not so primitive after all. J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2011 May;197(5):515-30. doi: 10.1007/s00359-011-0639-4. Epub 2011 Apr 5.

The first bats were 100% bat.

Do evolutionists know how bat echolocation evolved? Another paper in Current Biology from April 2021 not only fails to explain the origin of echolocation, but appeals to “convergent evolution” (Darwin Flubber).

Here, we present developmental evidence in support of laryngeal echolocation having multiple origins in bats. This is consistent with a non-echolocating bat ancestor and independent gain of echolocation in Yinpterochiroptera and Yangochiroptera, as well as the gain of primitive echolocation in the bat ancestor, followed by convergent evolution of laryngeal echolocation in Yinpterochiroptera and Yangochiroptera, with loss of primitive echolocation in pteropodids. Our comparative embryological investigations found that there is no developmental difference in the hearing apparatus between non-laryngeal echolocating bats (pteropodids) and terrestrial non-bat mammals. In contrast, the echolocation system is developed heterotopically and heterochronically in the two phylogenetically distant laryngeal echolocating bats (rhinolophoids and yangochiropterans), providing the first embryological evidence that the echolocation system evolved independently in these bats.

> Source: Nojiri et al., Embryonic evidence uncovers convergent origins of laryngeal echolocation in bats. Current Biology, Volume 31, Issue 7, 12 April 2021, Pages 1353-1365.e3.

But the “primitive echolocation” by tongue clicks, as the previous paper showed, is not primitive. It is highly effective.

Making noises with the tongue and throat is easy. The hard part is not making the clicking sound but using the echoes for navigation. This involves the ears and the brain, not just the vocal apparatus. The ears need to pick up tiny echoes. The brain must be able to perceive differences in them. Then the brain has to activate nerves and muscles rapidly to allow course correction for obstacle avoidance or prey detection. Clicking is the easy part!

The terms “convergent origins” and “evolved independently” with appeals to some theoretical “bat ancestor” provide no scientific information, since there are no bat ancestors in the fossil record. Such terms only serve to affirm the authors’ philosophical beliefs about the origins of complex phenomena.

 

 

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