Login

Join for Free!
118317 members


Questions about evolution and epigenetics

Discussion of everything related to the Theory of Evolution.

Moderator: BioTeam

Questions about evolution and epigenetics

Postby mgustavsson » Tue Sep 29, 2009 5:18 pm

Some background:
I'm a computer science major so my understanding of genetics and biology in general is pretty limited; anyhow, I'd like to share with you some simple thoughts I have had regarding if the theory of evolution could use some adjustments. If any of you with more knowledge in this area could provide some insight on the following topics I would be very grateful.

Basic premise:
It seems much more powerful if environmental factors during the lifetime of individuals could affect offspring in a way that plays an important part of the evolutional process. This more powerful process seems more likely to be potent enough to give rise to the immense diversity, specialization and complexity of the species present on earth.

Questions and statements:
1. Has there been any mathematical analysis made regarding if the random mutation processes of classical evolutionary theory could give rise to the diversity that we see given the time frame of life on earth?

2. If a deer continually stretches his neck during it's lifetime, then:
a) It will get a longer neck.
b) It's offspring has a higher chance of having a longer neck.

3. If a dark man moves to a colder climate, then:
a) He will get lighter skin.
b) His offspring will have a higher chance of having lighter skin.

4. If a human travels to colder climates (inuits, samis..), then:
a) He will during his lifetime(!) get shorter and thicker limbs.
b) His offspring will have a higher chance of having shorter and thicker limbs.

5. If we put a bacterial culture in a box, and slowly over many months raise the temperature, then:
a) We will evolve bacteria with higher resistency to heat.
b) This evolution is not just a matter of mutation and survival of the fittest, but the environment actually directly affects the offspring of the bacteria.

6. If a person during his lifetime does a lot of thinking, then:
a) He will become smarter.
b) His offspring has a higher chance of being smarter.

7. If I walk around barefoot all the time I will get really thick skin under my feet. Is this epigenetics at work?

All of the above examples seem possible to do research upon. So my question is, have these things been researched and what was the results?

Also, I'm not saying that all of the points above are necessarily true, I'm just suggesting that at least some of them might be.

Some thoughts about how this could possibly work:
1. We should extend the theory of evolution from individuals to also apply to cells within an individual. Since cells in an organism is continually replaced, there could be evolutionary forces at work within the organism; this would allow cells carrying DNA that gives the organism advantages in the current environment to slowly replace other less 'fit' cells.

2. The DNA machinery of cells is able to process input from the environment and use this feedback to modify themselves and thus adapt to the environment.

3. These changes to the cells will propagate through the organism; at least to the sperm in males and possibly also to the eggs in females.

Some further supporting thoughts:
1. How does a baby grow? How does the body know to heal itself? Clearly the cell machinery is already able to gather input from the environment and act on it in complex ways.
2. We clearly do adapt to the environment during our lifetimes; we grow bigger muscles adapted for the tasks that we often do, we adjust our skin color and we develop immunity to viruses. Why wouldn't evolution find a way for our bodies to use this information to produce fitter offspring?
3. It just seems more likely to work. For example, how did the inuits get shorter limbs? Random mutation and survival of the fittest? How likely is such a mutation to happen shortly after people move to colder places? And if it doesn't happen by a freak mutation and instead by many small gradual changes; then how can those small changes be enough to make a evolutionary difference in a social species as homo sapiens? If I have 1 mm shorter arms, how much more likely am I to pass on offspring in a cold climate? If instead there somehow was some system in place that could translate "I'm really cold" to "let's decrease the surface area of my offspring" then it's easy to see how such a change could gradually happen over as little as a few generations. The big questions then are, of course, how does such a system work and how did it evolve?
mgustavsson
Garter
Garter
 
Posts: 2
Joined: Tue Sep 29, 2009 3:10 pm

Postby robsabba » Tue Sep 29, 2009 8:36 pm

A few thoughts:

1. As you noted, changes to non-germline cells will have no effect on offspring.

2. There are now known examples of epigenetics where modifications of DNA in response to environmental stimulai life are passed down to offspring. An example of this is methylation of specific nucleotides that have phenotypic effects. These can be passed down to offspring who will maintain these modifications and pass them down. However, if the stimulus is removed, these modifications are lost after a few generations.

3. There are no known epigenetic modifications to DNA that are permanent.

4. Evolution by natural selection can actually occur quite fast. For example, the diverisfication of 14 Cichlid fish species in Lake Victoria took only 12,000 years, since the lake was dried up for 5,000 years, until about 12,000 years ago.
http://hagblomfoto.com/article_evolution.htm

5. The occurance of genotypes that provide even a small increase in fitness will increase in frequency in a population.
User avatar
robsabba
Coral
Coral
 
Posts: 106
Joined: Tue Aug 25, 2009 6:53 pm
Location: North Dakota State University

Postby canalon » Tue Sep 29, 2009 8:37 pm

About your thought experiments:
1. Probably, there is a lot of modeling done, but I could not give you any pointers
2 to 6. The provided answer are not really good. The selection of new traits happen only if said trait improve the chance of the organism to reproduce. So your organisms arriving in a new environment will have a descent where all the considered traits could be different from the parent (shorter or longer limbs, smarter or dumber, darker or lighter...) and if one variation provide an advantage as in lighter skin = more vitamin D hence an healthier individual which would be more likely to have numerous offspring, then it will spread in the population, however if said trait is at no advantage (say intelligence and reproductive power) then it will never be selected for.
7. No, just the ability of your body to protect itself.

About your thoughts:
1. some people are working about extending the evolution not only within cells (organisms as populations of cells) but to the gene level. Still very much a concept, but I think a very interesting thing. Getting rid of teleology in biology is probably the way to go. Not necessarily easy.

2. Separation of the germ and somatic lines. No information is passed from the body to the germ line. But this is also a protection from environmental damages to the germ line. So no way to pass the information down fro some Lamarckian style selection.

3. The 1mm shorter, might help. Or and that is another thing, gene expression is also regulated by the environment in some measure (food available, temperature, sun exposure,...). And add to the mix the powerful agent that is mate selection. So it is just a very complicated set of interactions between genes, the environment, mate choices that can drive evolution in some ways quite fast.
Patrick

Science has proof without any certainty. Creationists have certainty without
any proof. (Ashley Montague)
User avatar
canalon
Inland Taipan
Inland Taipan
 
Posts: 3909
Joined: Thu Feb 03, 2005 2:46 pm
Location: Canada


Re:

Postby robsabba » Tue Sep 29, 2009 8:47 pm

canalon wrote:About 2. Separation of the germ and somatic lines. No information is passed from the body to the germ line. But this is also a protection from environmental damages to the germ line. So no way to pass the information down fro some Lamarckian style selection.

This is a very good point, that should be emphasized. How would an organism differentiate those changes to non germline cells that are beneficial (longer neck in your example) from those that are not (loss of a limb from an accident, for example)?
User avatar
robsabba
Coral
Coral
 
Posts: 106
Joined: Tue Aug 25, 2009 6:53 pm
Location: North Dakota State University

Re: Questions about evolution and epigenetics

Postby mgustavsson » Sun Oct 11, 2009 5:32 am

Sorry everyone for my lack of replies; it was a discussion with a friend which sparked me to post this topic last week, but then I left the day after for a sweet internet-less holiday.

Robsabba:
1. If changes are not propagated from normal cells to germline cells, perhaps there is underlying mechanisms which simultaneously causes the germline and non-germline cells to change? Anyhow, if such changes are not propagated; how does the "there are now known examples of epigenetics.." happen?

2,3. I'd argue that this precise mechanism might be what I'm talking about when I say that "environmental factors during the lifetime of individuals could affect offspring in a way that plays an important part of the evolutional process". A proposal for how it could work:
As a protection mechanism, epigenetics doesn't influence the DNA directly; but merely enables/disables certain genes.
This enabling/disabling is hereditary, but only persists while the outer stimulus is present.
However, if the outer stimulus is present for many generations, this 'drives' evolution by making mutations in disabled genes insignificant.

4. I perfectly trust that evolution happens and works. But it seems to me more plausible that 'natural selection' is boosted by epigenetics somehow.

Robsabba,Canalon:
As for my questions in the original post, I was actually hoping for answers like 'yes, this has been proved in this paper..' or 'no, this has been disproved in this paper..'.

Let's take another example instead, skin color:
How did the white skin of Europeans come about? As you know, white skin is genetically weaker than black; so it seems to me that whenever a 'whiter skin' mutation did happen in the early European Africans that mutation would not have been able to spread throughout the entire group as it did. (Actually, Europeans seem to be many distinct groups rather than one; and in all of these the 'white skin' mutation became dominant.)

I would argue that epigenetics somehow 'drive' the occurrence of whiter skin.
An example:
If some dutch families moved to south africa; and lived there for several generations without mixing with Africans - and then moved back to Holland; would their skin be darker?
How much darker after 1, 10 or 100 generations in Africa?

There has to be existing research about these very specific questions, right?
mgustavsson
Garter
Garter
 
Posts: 2
Joined: Tue Sep 29, 2009 3:10 pm

Re: Questions about evolution and epigenetics

Postby Dougalbod » Sun Oct 11, 2009 10:32 pm

mgustavsson wrote:
I would argue that epigenetics somehow 'drive' the occurrence of whiter skin.
An example:
If some dutch families moved to south africa; and lived there for several generations without mixing with Africans - and then moved back to Holland; would their skin be darker?
How much darker after 1, 10 or 100 generations in Africa?


I'm not convinced by your suggestion that white skin in europeans is caused by epigenetics,, perhaps you could explain your reasoning?

If your dutch family moved back to Holland after 1 generation, they would soon lose their suntan, probably the same after 10 generations. After 100 generations, where the white skin would have made them more susceptible to skin cancer there might have been some selection for darker skin......


Dougal
Last edited by JackBean on Mon Aug 01, 2011 1:28 pm, edited 1 time in total.
Reason: quotes fixed
Dougalbod
Garter
Garter
 
Posts: 37
Joined: Wed Oct 07, 2009 8:55 am

Re: Questions about evolution and epigenetics

Postby sara135 » Tue Jul 12, 2011 7:46 am

History has the habit of creating heroes and anti-heroes, and so Darwin triumphed while Lamarck bore the brunt of ridicule and obscurity. The reason is that the theories of the two men are logically diametrically opposed. Darwin's theory is natural selection, and selection entails a separation of the organism from its environment. The organism is thus conceptually closed off from its experience, leading logically to Weismann's barrier and the central dogma of the genetic paradigm, which is reductionistic in intent and in actuality. Lamarck's theory, on the other hand, is of transformation arising from the organism's own experience of the environment. It requires a conception of the organism as open to the environment - which it actually is - and invites us to examine the dynamics of transformation, as well as mechanisms whereby the transformation could become 'internalized'. Hence it leads logically to the epigenetic approach, which embraces the same holistic, systems thinking that Lamarck exemplifies.
sara135
Garter
Garter
 
Posts: 21
Joined: Mon Jul 11, 2011 2:10 pm


Return to Evolution

Who is online

Users browsing this forum: No registered users and 2 guests