Echolocation calls in bats "have parallels with methods that engineers have adopted in commercial and military uses of sonar and radar." In other words, they appear to be "remarkable examples of 'good design'". The authors of a recent review article start by quoting Richard Dawkins: "In 'The Blind Watchmaker', Dawkins (1986) uses bat echolocation to illustrate features of 'good design' through evolution by natural selection." The whole paper is concerned with "adaptive aspects of call design" and it may be surprising to some that the findings will not be regarded as controversial by ID advocates. Adaptive change does occur in the natural world and there is no reason to think that the calls of bats are exempt.
However, there have always been issues about the origin of complex specified information, and this is to be found in the echolocation apparatus possessed by the bat. There are two completely different questions here: one relates to the design of echolocation calls and the other relates to the origin of the echolocation system. When the authors write: "Bat echolocation calls provide remarkable examples of 'good design' through evolution by natural selection," they are referring to the first question. It can be questioned whether the word "evolution" is appropriate (where it actually means adaptation) and it can be questioned whether natural selection is part of the story (for which no evidence is provided).
Picking up the point about natural selection, it should be noted that bats have brains that process and respond to sensory information. This introduces additional factors to the adaptation story. The significance of what is going on here can perhaps best be grasped by this comment:
"We suggest that engineers can learn from breakthroughs in our understanding of adaptive design in echolocation signals used by bats. For example, autonomously guided vehicles could use speed-dependent sonar signal designs that minimize localization errors, offering advances over the simple signals used in many current robotics applications".
Bat echolocation calls: adaptation and convergent evolution
Gareth Jones and Marc W. Holderied
Proceedings of the Royal Society B - Biological Sciences, Volume 274, Number 1612 / April 07, 2007: 905 - 912 | DOI: 10.1098/rspb.2006.0200
Abstract: Bat echolocation calls provide remarkable examples of 'good design' through evolution by natural selection. Theory developed from acoustics and sonar engineering permits a strong predictive basis for understanding echolocation performance. Call features, such as frequency, bandwidth, duration and pulse interval are all related to ecological niche. Recent technological breakthroughs have aided our understanding of adaptive aspects of call design in free-living bats. Stereo videogrammetry, laser scanning of habitat features and acoustic flight path tracking permit reconstruction of the flight paths of echolocating bats relative to obstacles and prey in nature. These methods show that echolocation calls are among the most intense airborne vocalizations produced by animals. Acoustic tracking has clarified how and why bats vary call structure in relation to flight speed. Bats using broadband echolocation calls adjust call design in a range-dependent manner so that nearby obstacles are localized accurately. Recent phylogenetic analyses based on gene sequences show that particular types of echolocation signals have evolved independently in several lineages of bats. Call design is often influenced more by perceptual challenges imposed by the environment than by phylogeny, and provides excellent examples of convergent evolution. Now that whole genome sequences of bats are imminent, understanding the functional genomics of echolocation will become a major challenge.
In 'The Blind Watchmaker', Dawkins (1986) uses bat echolocation to illustrate features of 'good design' through evolution by natural selection. Since the design of the echolocation calls determines the type and quality of information contained in returning echoes, bats have evolved different signals to meet a diversity of sensory demands. Dawkins poses problems that echolocating bats experience, considers solutions that sensible engineers might consider and then arrives at solutions that bats have achieved. Often the solutions adopted by bats, for example, the use of broadband chirps for ranging, and the exploitation of Doppler shifts to calculate relative velocity, have parallels with methods that engineers have adopted in commercial and military uses of sonar and radar. Bat echolocation provides rich examples of good design because echolocation performance can be predicted from theory developed in acoustics and in sonar (and radar) engineering.
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