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Letters to the editor, March 2012

This a traditional letter column. You are encouraged to write a letter of comment on anything that you find worthy of comment. It will (may) be published in this column along with my reply. As editor I reserve the right to delete material; however I will not alter the undeleted material. E-mail to me that solely references the contents of this site will be assumed to be publishable mail. All other e-mail is assumed to be private. And, of course, anything marked not for publication is not for publication. Oh yes, letters of appreciation for the scholarly resources provided by this site will be handled very discreetly. This page contains the correspondence for March 2012.

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From: Ben Turner
Date: 15 February 2012
Subj: [snipped email address]

Sent from my iPhone

I'm answering on the off hand chance that this email was something real from a real person that didn't get out right.

(Apparently it wasn't real or from a real person.)

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From: Lesia Noble
Date: 15 February 2012
Subj: Well ...

Knowing a friend like you would make me happy in a million ways and if ever I have to let you go I'm sure there are many things that will make us stick together I can send a pic to you directly compose me your minds

Alesia

Alesia, Alesia, such a beautiful name. It sounds like the name of one of those small European principalities on the edge of the Alps. Alas, your mother tells me that you actually a 43 year old Nigerian with bad teeth and a nasty tobacco habit. Would she lie to me?
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From: Neill Bartlett
Date: 21 February 2012
Subj: question

Hello Richard Harter, if you're still out there?

Can you help me with a query or question about evolution which I don't find answered directly in your excellent site, largely because in all probability I don't understand sufficiently yet.

I do understand about mutation as the driving force for evolution and I'm very much settled in my own mind on the question of how the world is how it is. What I'd like to ask is whether behaviour has an impact on genes and how this is traceable in biology.

Two examples for clarity's sake -

1) 7 million years ago a primate stood to reach for the fruit at the top of the canopy; did those with a slightly longer reach prevail where food was limited and therefore pass on their genes, or did this adaptive behaviour in itself have an effect?

2) Whales have little bones on their skeleton where their back legs used to be. Did lack of usage (ie an adaptive behaviour) mean that the legs became redundant? How did this interact with their genes?

Your understanding of this would be very welcome!

Thank you for writing; my apologies for not having responded sooner.

Let me talk about your (2) first. Whale legs are a good example of a vestigial organ. Classic examples include the blind eyes of cave fish and our own vermiform appendix. There are two main factors at work in the evolution of vestigial organs.

The first is that there is no longer any selective pressure to keep the organs working. What happens is that "bad" mutations occur; these are mutations that damage the effectiveness of the organ. If the organ is in use these are harmful mutations; if it is not they are not. As a result the organ becomes more and more useless over time.

The eyes of cave fish are a good example. Over time not only are the fish blind, their eyes fail to work in different ways. However the eyes are still there. Structural genes seldom completely disappear. Chickens still have the genes for dinosaur teeth. Blind cave fish still have eyes. Whales still have vestigial leg bones.

The second is that there can be selection against investing development energy in the vestigial organ. Whale legs are a good example here. First of all it takes a lot of energy to grow legs. Cutting the growth short is an advantage. Secondly, legs are cumbersome if you are not using them. This goes to your question; a change in behaviour can make for negative selection.

Now onto your first question. Basically it is those with the genes for a longer reach that prevail. However it isn't quite that simple. Your DNA is programmed with attached methyl groups that alter the behaviour of your genes. (That' at least sort of right.) You inherit some of this programming from your mama. Now what this means is that if some behaviour is adaptive and if it can be favored by a change in the DNA programming then that change can happen and will be inherited. Understand that this is not genetic inheritance; the genes haven't changed. If you inherit some DNA programming from your mama you can undo it.

Another related phenomenon is that learned behaviour can eventually become instinctual. What happens over time is that genetic changes that make it easier to acquire the learned behaviour are now selected for.

I hope that this at least a little help.

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This page was last updated March 4, 2012.

Richard Harter's World
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March 2012
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