Is evolution limited to natural selection?

[too-open-minded]

Does evolution require selective breeding to move forward?

 

I've read articles about stress changing DNA and how in an individual lifetime DNA can be impacted by environment.

 

So what I'm asking is, is it possible to adapt without selective breeding?

[swansont]

Yes, there are other mechanisms. Genetic drift is one. http://en.wikipedia.org/wiki/Genetic_drift

[chadn737]

Selective breeding, aka "artificial selection", refers specifically to selective changes imposed by humans. Evolution has proceeded for millions of years without this (aka "natural selection") and certainly does not need selective breeding to continue as nature already does this constantly.

 

Stress and the environment can induce various effects through gene-environment interactions, but these are typically not heritable and therefore its long term effects on the evolution of species is questionable. That being said, the concept of gene-environmental interactions is not new....it goes back at least to one of the fathers of populations genetics, R. A. Fisher, in the early 20th century. For some reason in the last few years the effects of the environment on modulating the phenotypic outcome of the gene has been rebranded as some brand new discovery. Typically when you see this, it is not coming from geneticists, but rather other fields of biology that seem to have not paid much attention to the history of genetics....that and people wanting to jump on the epigenetics bandwagon.

 

Is it possible to adapt without some sort of "selection", whether natural or artificial? Thats kind of a complicated and vague question. First, what is meant by adaptation? Are we referring specifically to a positive adaptive response to some sort of external factor that negatively impacts the reproduction of a species? Then by that definition, all such adaptations will be the result of "selection" by that factor and hence either natural or artificial selection. Its rather tautological. On the other hand if we define "adapt" purely in a sense of changes in phenotype or allele frequency...which really isn't an adaptation per se....then there are three other mechanisms: mutation, genetic drift, and gene flow.

 

In evolutionary and population genetics, four mechanisms driving changes in allele frequency are recognized: natural/artificial selection, mutation, genetic drift, and gene flow.

Edited June 27, 2014 by chadn737

[Endy0816]

I actually think the capability for what are essentially temporary traits is what is of value to evolution in terms of epigenetics.

 

Saw it once in a simulation where it worked wonders. One of my best species used an epigenetic trait to determine kinship, this trait would eventually semi-randomly change.

 

Resulted in multiple competing epigenetic lines. Any genetic mutant lacking the kinship recognition code would only be successful against a limited number, while suffering a disadvantage in terms of reproduction.

 

The species would have actually been worse off if the trait were hard coded, rather than passed along by the parent and subject to eventual deviation.

Edited June 28, 2014 by Endy0816

[chadn737]

I actually think the capability for what are essentially temporary traits is what is of value to evolution in terms of epigenetics.

 

Saw it once in a simulation where it worked wonders. One of my best species used an epigenetic trait to determine kinship, this trait would eventually semi-randomly change.

 

Resulted in multiple competing epigenetic lines. Any genetic mutant lacking the kinship recognition code would only be successful against a limited number, while suffering a disadvantage in terms of reproduction.

 

The species would have actually been worse off if the trait were hard coded, rather than passed along by the parent and subject to eventual deviation.

 

How was it determined to be "epigenetic"?

[too-open-minded]

I used selective breeding without even knowing what it meant..... DOH!!!

 

Not so much is it possible to adapt without selection, but is it possible to adapt without "who lives long enough to reproduce" being the say so? For instance is it a wild idea to think that our Genes and DNA can alter hereditary while being transmitted to our offspring without the need of reproductive selections. Reproductive selections as in natural selection or selective breeding? For example something like this - http://www.iflscience.com/health-and-medicine/exposure-stress-child-can-permanently-affect-your-dna

 

If this studies hypothesis is correct, lets say we have two groups with the control being children who have relatively normal childhoods. The other group of children having stressful childhoods. Lets say these groups have offspring and the same offspring follow as their parents. Lets say 10 generations deep and the variable group of children now have a normal childhood, would we be able to notice a difference in their telomere length? Even though they themselves didn't have a stress induced change, could it end up being hereditary from the DNA? That's the best example I could come up with, as I'm sure there are many variables in this.

 

Epigentics, never even knew what that was either. I love you guys on SF! So helpful, all of you

[Endy0816]

 

How was it determined to be "epigenetic"?

 

Mostly that was just how that particular location in their program memory worked. The parent would pass their value on to their child at birth. At the point that the location was set in the child's memory, the child's own 'DNA' code hadn't run yet.

 

You could also freeze the simulation, pop the proverbial hood and directly verify the value for yourself though.

[chadn737]

 

Mostly that was just how that particular location in their program memory worked. The parent would pass their value on to their child at birth. At the point that the location was set in the child's memory, the child's own 'DNA' code hadn't run yet.

 

You could also freeze the simulation, pop the proverbial hood and directly verify the value for yourself though.

 

So it was a simulation and not an actual case? While its certainly possible for these things to work in simulation, the real question is whether this plays out in reality. In animals, the typical epigenetic mechanisms, namely DNA methylation, is reset every generation. In plants this works somewhat differently resulting in more known cases of true epigenetic inheritance in plants.

[Endy0816]

I agree, need to be careful assuming equivalencies. I just think it suggests a need to consider the short term.

[chadn737]

I agree, need to be careful assuming equivalencies. I just think it suggests a need to consider the short term.

 

In the short term it certainly can have an effect and I think the consequences of these short-term effects could be quite interesting. For instance, epigenetic mechanisms may enable the transition of an organism from one genetic fitness peak to another. For example, lets say you have a gene duplicate gene that over long term evolution, obtains new functionality. However, the transition to this new functionality may require a sequence of mutations that at intermeditate points reduces fitness if this gene is expressed. Silencing of the gene by DNA methylation could allow it to acquire mutations without these mutations affecting fitness as the gene is unexpressed. At some later point, should DNA methylation be lost, the mutated gene maybe re-expressing novel phenotypes. In this case, the transgenerational inheritance of the DNA methylation could allow this transition, even if intermediate steps were potentially lethal.

 

Why I caution overemphasis of epigenetics in evolution is:

 

1) Its completely unknown what role it plays in evolution.

2) Epigenetics has been touted by everyone from neo-Lamarkists, Creationists, Journalists who think they know everything, and even health-fad scam artists as overturning the importance of genetics and disproving Darwinian evolution. None of this is true.

Edited June 30, 2014 by chadn737