Tuesday, November 15, 2005

Deriddling evolution - III

Now, the problem at hand is this: Mutation is a random process.Fine. And adaptation involves changes in the organism, either physically or behaviourally, that improves its chances of survival. Fine. How could a purely random process give rise to a mutation at exactly that part of the genetic material that leads to the adaptation!

The answer is that you have overlooked two rather important features of evolution

  • Evolution does not mean survival of the fittest. It means survival of the sexiest.
  • Mutation is heriditary


Survival of the sexiest means that organisms that are most successful in getting a mate, not necessarily the fittest, or the strongest or the fastest are the ones that propogate their genes to the next generation. A classic example of this is the peacock. The feathers of the male peacock is a nuisance to carry around and make the peacock an easy meal for many of the big cats. But evolution has favoured the long tail because the peahens are most attracted to the peacock with the longest feathers. If it was the feathers for peacock, it was brain (intelligence) for humans.

Now, the genetic material of living organisms is very long, and most of it does not serve any apparent purpose. Most of the mutations occur in this dysfunctional part of the DNA and hence its effects aren't observed. Mutation isn't really as rare as people think it is.

Among the mutations that occur in the active part of the DNA, most are harmful in various degrees. These are the mutations that lead to cancer, third nipple and the sixth finger,for example. And obviously these freaks don't get to mate. Since these mutations don't pass on to the next generation. On the other hand, those mutations that are favourable, despite the fact that they occur very rarely, are successful in attracting a mate, and hence gets passed on to the next generation, and from there it is an exponential growth in numbers.

A random process can indeed lead to evolution.

To be continued...

11 comments:

Sundar said...

In my experience, a supernumerary nipple has not been harmful. I'm sure your reference was either a joke or a misinformation.

Ishwar said...

Sundar, this is what you had commented on one of my first posts-
Survival of the fittest doesn't always mean that only fit individuals are born by Eugenics. Rather the selection happens at many levels, viz social(during courtship), precoital(before sex), post coital, pre-natal(before birth) and post-natal.

It took me a year to truly appreciate this.

Parii said...

Maybe mutation is nature's trial and error process. Whatever works is carried forward.

Nilu said...

I wonder when humans started "appreciating" intelligence as a good trait in their partners.

As in when, I mean - do any of the apes have such behaviour? Or is it strictly human?

Ambar said...

"But evolution has favoured the long tail because the peahens are most attracted to the peacock with the longest feathers."

Quite out of context and shallow. I suggest you read Matt Ridley's "The Red Queen".
If you've already read it, read it again till you get the reason behind the entire long tail encumbrance.

Ishwar said...

aekta, mutation IS nature's trial and error process.

ambar, you don't need a freaking Ph.D in evolutionary sciences to analyse the reason behind a peacock's tail.

Point #1: Peacock's tail doesn't give it any edge over other birds and other organisms in the same ecosystem. If anything, it is a bloody burden to carry around making it an easy prey for tigers, and an easy hiding place for parasites. It takes a lot of energy to preen it.

Point #2:Peacock's tail is a case of sexual dimorphism.If it is not an organ of sexual courtship, it would not a case of sexual dimorphism.

No, I haven't read 'The red queen', but i guess things are pretty clear w./o it.

The point I was trying to make was that the evolutionary path that an organism takes is not always due to the environment. Survival of the sexiest also holds good, and that was the context.

nilu, no idea.

Ambar said...

Ishwar, I'm not disputing the fact that the peacock's tail is a burden. But it began as "look peahens, i can survive very well with one hand tied behind my back all the time/ inconveniently long tail".

Peacocks with long tails got to breed more, and tails kept getting longer. It reached a point where even though the length of the tail was near suicidal, *not* having a long tail ensured that you wouldn't get to breed.

I'm thinking, maybe the entire metrosexual bullshit is going to lead humans down this path soon? :D

Ishwar said...

ambar uncle, courtship is the key.

venusian_observer said...

i agree that in order for a species to propagate, the genes must be passed 'forward' via sexual means. but one inconsistency in your argument is that you assume that courtship and sexism (being sexy) are characteristics that are vital and have ignored that we don't start courting and acting sexy right from the time we're born.
what i'm trying to imply is that one has to make it to a certain stage in life (in case of humans, past puberty) to be able to pass the genes on forward. in order to get past this stage in life, one has to survive and doesn't have to be sexy. one has to be fit.
ok. my concepts maybe blurry but i'm interested in what you think.v

Ishwar said...

venus,
what i'm trying to imply is that one has to make it to a certain stage in life (in case of humans, past puberty) to be able to pass the genes on forward.

True. This has two reasons.
#1. This where parental care comes into picture. There are two strategies here(probably more). One is to spawn so many children that there is a good probablilty that a few survive. Lower vertebrates(not all) adopt this mechanism. Second is to give birth to a limited no. of children and have post-natal care(birds, mammals and some reptiles).

Either case, the organism has to be fit enough to make it to the mating stage. You wouldn't want a heamophilic animal to propogate its genes to the next generation, do you?

Well, this is slightly different with humans. We do propogate bad genes to our next generation. but it still works. will explain this in a later post.

Pinch of salt: These explanations arise out of my understanding of evolution.

Sundar said...

Sundar, this is what you had commented on one of my first posts-

Survival of the fittest doesn't always mean that only fit individuals are born by Eugenics. Rather the selection happens at many levels, viz social(during courtship), precoital(before sex), post coital, pre-natal(before birth) and post-natal.

It took me a year to truly appreciate this.


Did you mention this in the context of my earlier comment in this post?

Pinch of salt: These explanations arise out of my understanding of evolution.
A huge pinch this. ;)