Why Didn't Dinosaurs Evolve Into Intelligent Beings?

[Rive]

The word "randomness" in the same sentence as evolution usually implies a misconception.

In the same time, forgetting about the randomness involved is a bit dangerous given the situation of some species with decreased population.

 

[BillTre]

Randomness and evolution, as already mentioned, are intertwined in a few different ways.

One is that mutations are often considered to happen randomly.
Usually they do, but not always:

• rates of mutations can be increased in times when an organism is stressed, but not as much as was previously thought
  
• in some specific cases, the occurrence of particular mutations can be increased in probability (antibody gene recombination, mutation within a single organism's cells; yeast mating type locus, changes by directed movement of DNA sequences to determine which mating type a yeast cells is)

Both are based upon mechanisms that have most likely been selected for because they yield better survival.

Selection vs. Random Drift:
Selection (natural or human driven) can impose a non-random direction to changes.
The always present alternative to selection is change that happens randomly.
This can be due to the lack of strong selective values (usually at a molecular level) of one allele vs. another.

Another way random changes can have more impact on a population depends on the size of the population in question.

forgetting about the randomness involved is a bit dangerous given the situation of some species with decreased population.

As an evolving population's size goes down it becomes more likely to change randomly and the rate of adaptive change in a population's gene frequencies is decreased for a number of reasons. A large population reduces the likelihood that a population's gene frequencies will change randomly and increases the strength of natural selection on population.
Extreme examples:
Small population: The gene changes in an inbred population of mice being maintained through brother sister crosses. This is explained by the random inheritance of the same allele of a particular gene by a limited number of offspring.
Large population: a global population of interbreeding bacteria.

 

[pinball1970]

Hi pinball:

I confess this confuses me. I tried to locate in this thread (with a quick search) an instance of "randomness" and "evolution" in the same sentence so I could evaluate whether there was also a misconception. Unfortunately, I failed to find it. I also tried to find "the process is mostly random", and I could not find that either. Would you please post the post numbers where you found these texts?

Regards,
Buzz

Don't be confused the words are not there I just looked back myself
The subject was evolution and the phrase included "random/mostly random" which I thought was not a great way to describe it.
Bill has pointed out that random can be used describing evolution and he used random/ly/ness ten times in all in the last post and all perfectly valid.

 

[lavinia]

We try to avoid those here at the PF.

BTW, have you read through the thread that is stickied at the top of the Biology forum (this forum where we are) about Evolution?

https://www.physicsforums.com/threads/learn-about-evolution-evolution-introduction.543950/

It is a good introduction, and has links to more information.

Much of this thread is speculation and often discussions of Evolution are speculative. You might demand scientific discussions of technical questions rather than broad discussions of such things as how humans became intelligent. Or maybe reroute this thread to General Discussion.

 

[jim mcnamara]

@lavinia is correct. Posts here need to move off of waffly topics or moved to general discussion.

So, Moved to GD.