Dolphin sonar (still) far better than man’s
We have long known about the exquisite echolocation technology of both bats and dolphins. It is like man-made sonar, yet superior, as it uses sound echoes to calculate the distance and speed of objects. Now Dr Josefin Starkhammar, of the Department of Biomedical Engineering at Lund University, Sweden, has studied what makes dolphins so “phenomenally good” at echolocation.1
Dolphins generate their sound beam with ‘phonic lips’ below the blowhole. Then this beam, lasting only 70 microseconds, passes through the fatty ‘melon’ in the front of the skull. This acts as a sound lens, producing a conical sound beam. While a Ph.D. student, Dr Starkhammar built a measurement system with 47 hydrophones to record differences within the beam. But the signals were so complex that she required the help of her colleagues in mathematical statistics to develop a signal processing algorithm.
The main discovery was that the beam comprises “two intertwined beam components”, one low pitched and the other higher pitched, producing a beam with overlapping pulses.2,3 And the beam has a frequency gradient from bottom (low pitched) to top (higher pitched). This means prey can be located more accurately in the beam: the higher the pitch of the prey’s echo, the higher the prey is physically located in the sound beam.
Dr Starkhammar hopes that analyzing dolphin echolocation will help build better ultrasound scanners, improving resolution of scans of thin layers in the body.4 She explains that low-frequency sounds can spread further under water, while high-pitch sounds can provide more information about the object’s shape. So their new signal processing method “works almost like a magic formula! Suddenly we can see things that remained hidden with traditional methods. We could copy the principle of using sound beams whose frequency content changes over the cross-section.”5 The analysis could also improve the design of ship sonars.1
Dr Starkhammar attributes this to “millions of years of evolution”.1 I would argue that one problem with explaining echolocation with evolution is that dolphins and bats both have complex echolocation systems. And they are each built by about 200 genes that are incredibly similar in both species. However, they have no common echolocating ancestor in evolutionary theory. So evolutionists, including Dr Starkhammer,6 argue that this is a case of convergent evolution. That is, similar environments (in this case, poor visibility and complex surroundings) produce similar selection pressures that drive similar solutions to the navigation problem. However, the fossil record doesn’t document evolution of either dolphin or bat sonars. One evolutionary article admitted:
“that the ancestors of today’s dolphins had an ear structure that suggests they could echolocate as well as their modern relatives can,” and that the “oldest bat fossils” had extensive coiling of bony structures in the inner ears, a sign that they were capable of detecting the high-frequency chirps used in echolocation.”7
A better explanation would incorporate the principle of analogy—to which Darwin himself appealed frequently. That is, since the man-made sonars are the result of intelligence, how much more are the vastly superior dolphin sonars?
References and notes
- .Goodyer, J. (ed.), “Dolphins are phenomenally good at using echolocation, much better than man-made devices”, BBC Focus, Summer 2018, pp. 18–10. Return to text.
- Starkhammar, J., Moore, P.W., Talmadge, L., and Houser, D.S., Frequency-dependent variation in the two-dimensional beam pattern of an echolocating dolphin, Biology Letters 7(6): 836-839, 2011 | doi:10.1098/rsbl.2011.0396. Return to text.
- Lund University, Dolphins use double sonar: Researchers discover that dolphins can generate two sound beam projections simultaneously, sciencedaily.com, 8 June 2011. Return to text.
- Reinhold, I., Sandsten, M., and Starkhammar, J., Objective detection and time-frequency localization of components within transient signals, J. Acoustical Society of America 1434):2368–2378, 1 April 2018 | doi:10.1121/1.5032215. Return to text.
- Medimaging International staff writers, Dolphin echolocation could advance medical ultrasound, medimaging.net, 11 June 2018. Return to text.
- Sarfati, J., Echolocation ‘evolved in the same way’, creation.com/echolocation-homoplasy, 3 October 2013. Return to text.
- Perkins, S., Learning to listen: How some vertebrates evolved biological sonar, Science News 167(20):314, 2005. Return to text.