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Author Topic:   Evolution of Echolocation
Rei
Member (Idle past 7013 days)
Posts: 1546
From: Iowa City, IA
Joined: 09-03-2003


Message 1 of 7 (65414)
11-09-2003 5:16 PM


Echolocation has long been one thing that creationists show incredulity as to the ability for it to evolve.
I was watching a show the other day called "More than Human", in which they show people who can do unusual feats. One person that they had on was completely blind - and yet, they showed him mountain biking. The amazing thing was how he was doing it: echolocation.
As soon as I saw this, my initial reaction was disbelief. However, they set up a scenario to test him. They sat him down outside, and placed some objects near him - a tall metal pole, supporting what looked like a thin pane of cloth or plastic at the top over him - and asked him to identify his surroundings. He started off by recognizing the pole, describing it as a tall, thin metal object, and then went on to describe the boom mike that they were holding up to record the interview. He then identified a nearby tree, and then, turning upward, got confused... "is there a tent over me?"
Intrigued, I started researching the subject, and found this. Apparently, a minimal level of echolocation is not only teachable to even non-blind people, but is part of our everyday senses. Most people are completely unaware of it. In one test, they had a number of blind people, and blindfolded sighted subjects, and asked them to approach as close to a board as possible without touching it. The blind people immediately were able to get within inches of it without touching; the sighted people took about 30 tries before they could get this level of accuracy. However, as they steadily removed their abilities to make and receive sounds, they steadily lost their ability to find the object, until everyone collided with the board every time.
So, I decided to run some tests for myself. I tried going to different rooms of my house, then spinning around until I had no clue where I was pointing, and then trying to orient myself with echolocation. However, I was continually frustrated. There was always at least some sort of faint sound in the house, and I could instinctively orient myself based on that sound, no matter how faint, without having to try and make echoes.
Then, that clued me in - if humans can orient themselves easily based on even faint sounds, then the only issue is whether humans can make echoes from objects strong enough to clue in on, and to separate multiple reflections. Quick tests in my bedroom showed that, with a proper clicking sound, you can get pretty clear echoes from most walls (I'm sure it would be a lot harder outdoors, though). So, there's only the complexity of the room to be able to learn to factor in.
If blind humans develop this ability even subconsciously on their own - and blind humans who actively use it (making clicking and snapping sounds with their mouths) can do things as dramatic as mountain biking - it seems quite clear that such a system can evolve from an organism which steadily moves to a niche or environment in which sight is no longer as effective. Furthermore, it appears to evolve from an already present system - namely, our ability to do direction finding on sound.
------------------
"Illuminant light,
illuminate me."

Replies to this message:
 Message 2 by Silent H, posted 11-09-2003 6:23 PM Rei has not replied
 Message 3 by judge, posted 11-09-2003 11:29 PM Rei has not replied
 Message 5 by judge, posted 12-01-2003 4:35 AM Rei has not replied

  
Silent H
Member (Idle past 5819 days)
Posts: 7405
From: satellite of love
Joined: 12-11-2002


Message 2 of 7 (65440)
11-09-2003 6:23 PM
Reply to: Message 1 by Rei
11-09-2003 5:16 PM


I agree with this assessment of how echolocation could evolve.
On a personal note I was in a martial art which at later levels involved fighting with a blindfold. It was surprising to me to find out it wasn't a trick. While much of it involved touching an opponent so one could recognize shifts in movement, I could also fight without that physical connection. I could "see" just from the simple ruffling of clothing or shifting of feet.
The most interesting part is that I gained this ability before they ever put on the blindfold. I don't know, maybe my mind realized my eyes were more of a hindrance (too easily deceived), and so stopped using them during fights.
I noticed most of the upper students and the master had this weird far off look, not even looking at you while they fought. After a week or so of everyone telling me I was now fighting like that (I hadn't noticed), the master said for me to try a blindfold. I couldn't believe it, but it made no real difference.
After that experience I started recognizing that in fact I didn't really use my eyes in a fight anymore. It was touch and sound.
This ability does raise the question however: Did ancestors of humans use echolocation? Maybe its still with us to some degree and so all we are doing is bringing out that latent potential, rather than growing a new one.
------------------
holmes

This message is a reply to:
 Message 1 by Rei, posted 11-09-2003 5:16 PM Rei has not replied

  
judge
Member (Idle past 6443 days)
Posts: 216
From: australia
Joined: 11-11-2002


Message 3 of 7 (65498)
11-09-2003 11:29 PM
Reply to: Message 1 by Rei
11-09-2003 5:16 PM


How was it preserved in people?
So how was the ability to use echolocation preserved in people if only blind people need it?
I can underdstand how it would provide an advantage that could be selected for in bats but it seems it would have become redundant in humans.
Waddya think?

This message is a reply to:
 Message 1 by Rei, posted 11-09-2003 5:16 PM Rei has not replied

Replies to this message:
 Message 4 by NosyNed, posted 11-10-2003 1:00 AM judge has not replied

  
NosyNed
Member
Posts: 8996
From: Canada
Joined: 04-04-2003


Message 4 of 7 (65515)
11-10-2003 1:00 AM
Reply to: Message 3 by judge
11-09-2003 11:29 PM


Re: How was it preserved in people?
Well, given the frequent darkness that I assume descended regularly on our ancestors I would think that some such skill would be of some value.
Besides, hearing and "binocular" hearing is of value even when we are sighted. For example, in a dense jungle. This then is co opted for echolocation. I don't see anything very hard about this question?

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judge
Member (Idle past 6443 days)
Posts: 216
From: australia
Joined: 11-11-2002


Message 5 of 7 (70216)
12-01-2003 4:35 AM
Reply to: Message 1 by Rei
11-09-2003 5:16 PM


seeing with sound

This message is a reply to:
 Message 1 by Rei, posted 11-09-2003 5:16 PM Rei has not replied

  
Minnemooseus
Member
Posts: 3941
From: Duluth, Minnesota, U.S. (West end of Lake Superior)
Joined: 11-11-2001
Member Rating: 10.0


Message 6 of 7 (70309)
12-01-2003 2:20 PM


Discover magazine article
I'll also point out that the December 2003 issue ofDiscover magazine has the article "Blast from the Vast" (page 50) on sound production and use by whales and such. Also man's attempts to reproduce and use this methodology.
There's probably some or all of this to be found somewhere at Discover Credit Cards, Banking & Loans
Moose

  
lpetrich
Inactive Member


Message 7 of 7 (70407)
12-01-2003 9:08 PM


Over in the thread "A Most Promising Anti-Evolutionist" over at the Evolution/Creation section of Internet Infidels Discussion Board there was a creationist who called himself "Charles Darwin" who responded only to that thread.
He had maintained that echolocation is unevolvable, and he maintained that creationism could be considered refuted only by presentation of a "compelling" naturalistic alternative. And about echolocation, he demanded the presentation of all the details of how it had evolved before he could accept that it had evolved.
He'd present details like how echolocating bats have middle-ear muscles that muffle their ears as they chirp (it's rather difficult for a bat to cover its ears with its wings, let alone stick its fingers in its ears, as it flies).
However, such muscles are a common feature of mammalian middle ears, and many species of bats simply make more use of them. All that is necessary is for a "make a chirp" brain command to also command temporarily muffling the ears.

  
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