Friday, March 02, 2007

With human thought came stuttering (Part II)

Of course, this evolution of a second auto-pilot pathway took thousands and thousands of years. Genes that built or support the stability such a pathway spread out, and genes that hinder or render unstable such a pathways die out more and more. So over the years, more and more humans carried genes that developed such a pathways, and fewer and fewer had genes that blocked this pathway. The point is that I believe that the stuttering genes are the left over from this evolution. We carry genes that have not been selected out yet due to their devastating effect on speech fluency, but will eventually. So I argue that in the past a greater proportion of the population stuttered, and slowly the genes are selected out. (Of course, there is evidence that some stuttering is not genetic. There I argue that you can have an unstable pathways due to genes or due to an incident. And I argue that the genes part will decline more and more, and the incident part will stay unless there are genes that increase the probability of such incidents while not having any other benefits to the human being).

Please note: These arguments only make sense if the dual pathway theory advocated by Per Alm is correct: see here for a discussion. Also, theses are conceptual arguments, and the details are definitely more complicated.


Anonymous said...

Hi Tom,

Interesting theory. But I disagree with your assertion that the genes for stuttering will select out of the gene pool over time.

Survivial of the fittest, at this point in human evolution, does not solely depend on communication. For example, a stutterer can hold down a job and make a good living in fields that may not lean heavily on speech e.g. Information Technology. This and other personal qualities can still allow a stutterer to attract a mate and pass on his/her genes to the next generation.

BTW - Let's meet up again when you are in NYC.

Tom Weidig said...

Hi Lloyd,

yes, my argument rests on the assumption that the conditions in which humans lived for 100'000s of years is the same now and will be the same in the next 100'000s of years.

In my post, I was really only interested in how stuttering became what it is now. I havent looked at the future YET, but that's a good post, too. :-)

1) Do you not think stuttering still makes it a tiny bit harder to attract the opposite sex, have off-spring, and care for them?

There is no doubt stutterer do attract the opposite sex and have off-spring. However, the key is that stuttering does not help you. Therefore, your competitors have a a tiny advantage. So even if our chance to have off-spring might be a bit smaller like 49.9999% to 50.00001%. After 1000 generations, the genes are not present anymore in the population. (of course, this is a simplified model).

2) Many people who stutter live in poor regions where stuttering is a real handicap, and the conditions are similar to our ancestor's environment.

3) Modern society and advances in sciences have completely and utterly changed the evolution ball game. For example, many women used to die during birth, now it is very rare. (Of course, there is no genetic selection anymore for genes that make childbirth successful, like wider hips for a wider birth channel.) Or teenage mums have now more babies than intelligent women due to career and inability to find a male who has the same or higher status than themselves.

You might be right that it will be different, but I dont think you can claim that you understand what is going to happen in the future with humans and how it will affect stuttering, if you were to claim this knowledge! :-) My guess is that verbal communication will become less and less important and selection might well slow down dramatically.

Anonymous said...

Have you ever tried homeopathic remedies?