Genetic assimilation finally proven?

[ecologist88]

"Genetic assimilation" was a mechanism termed by Conrad Hal Waddington in the 1950s which he wrote operated as a Darwinian mechanism that allows certain acquired characteristic to become heritable.

Waddington attempted to explain the mechanism in Darwinian terms, but the neo-Darwinian synthesis rejected his mechanism as being "Lamarckian" and based on the heresy of acquired characters, they would not accept it and the theory was neglected for over 40 years.

However there has been a recent interest in this mechanism in the field of evo-devo and as recent scientists have written the theory of genetic assimilation is actually a form of phenotypic plasticity and should not be confused as Lamarckian.

In 2009 there is now some evidence that "genetic assimilation" may exist:

Two scientists Aubret and Shine have found evidence for a 67-year-old concept in evolution called “genetic assimilation“ which may explain the large head of tiger snakes.

Big-headed tiger snakes support long-neglected theory of genetic assimilation : Not Exactly Rocket Science

Its name might conjure up images of science-fiction and DNA-stealing aliens, but genetic assimilation simply describes a means of adaptation. It was proposed in 1942 by Conrad Waddington, who suggested that species initially cope with fresh environments by being flexible – through plasticity. All species have a certain amount of variation built in to their developmental program, which they can exploit according to the challenges they face. In this case, the tiger snakes can grow larger heads if they encounter bigger meals.

But as populations face constant evolutionary pressures, natural selection eventually favours genes that produce the same results, the ones that plasticity once achieved. This is the crux of Waddington’s theory – in time, natural selection eliminates plasticity by fixing genes for the same traits. Such genes as said to be “canalised”.
Back in the 1950s, Waddington demonstrated this using fruit flies. He exposed developing flies to ether vapour and found that some developed a second thorax (the middle segment between the head and abdomen). By anyone’s standards, that’s a radical change, but one that was triggered by an unusual environment. Over time, Waddington selectively bred the double-thorax individuals and exposed each new generation to ether. After 20 rounds of this, he found that some flies developed a second thorax naturally, without being exposed to ether. The double-thorax trait, which was initially induced by the environment, eventually became governed by the fly’s own genes.

It was a neat idea, but finding other natural examples has been very tricky. Aubret and Shine thinks that genetic assimilation tends to happen over such short timescales (geologically speaking) that you can only really detect it under unusual circumstances. And the spread of tiger snakes across Australia certainly fits that bill.

Aubret and Shine’s experiments show that snakes from newly colonised areas had the greatest degree of plasticity when it comes to head size while those from the longest-colonised islands had the least. These differences become abundantly clear when you compare snakes from three populations.

Further reading:

Conrad Hal Waddington - RationalWiki

You won't read about any of this in creationist books

 

[Revoltingest]

I was curious about Rational Wiki, having never used it. It seems a bit like Wikipedia, so I wondered what Rational Wiki had to say about them....

Wikipedia, "The Encyclopedia Any Teenager Can Vandalize", is overly verbose and full of liberal bias, porn, gossip, slander, smear, bias, and atheist propaganda.[1] What's even worse, they occasionally use "BCE" instead of "BC", denying the historical achievements of Christianity.

Hmmm......"atheist propoganda"?
I'll pass on Rational Wiki.

 

[ecologist88]

I was curious about Rational Wiki, having never used it. It seems a bit like Wikipedia, so I wondered what Rational Wiki had to say about them....

Hmmm......"atheist propoganda"?
I'll pass on Rational Wiki.

The "atheist propaganda" is a joke. Rationalwiki is an atheist website. It was set up to debunk the absurd creationist/christian claims of conservipedia and other pieces of pseudoscience.

 

[Revoltingest]

Rationalwiki is an atheist website.

You expect me to trust some godless jerks?
I'll bet they even have puppy recipes!

 

[painted wolf]

Interesting, but I'm having a hard time with figuring out how this is different from what we already know about phenotypic plasticity and eppigenetics.

wa:do

 

[tumbleweed41]

Interesting, but I'm having a hard time with figuring out how this is different from what we already know about phenotypic plasticity and eppigenetics.

wa:do

Pop-science and headlines.

 

[Iti oj]

I did not know this needed any proving. Still real cool experiment, but i don't think it fundamentally changes anything. I do wonder what causes the loss of plasticity... or perhaps the flies could adapt back to their single thorax form in the right conditions?

 

[Simurgh]

Concerning the OP, the theory was taken up by Dean H. Hamer in his book “The God Gene”. His book was later discredit since it was based on shoddy scholarship and lacked basic scientific value. But that did not stop right many religious people from proclaiming it the TRUTH!!. Although, religious leaders too stated in their critiques that the scholarship was questionable and they did not agree with his findings.

PS: BCE has been used for a couple of decades to indicate Before Common Era and CE is used in the same way to denote Common Era. This was done, primarily by the anthropological community to render dating less Christianity-centric. Apparently, anthropologist noticed that there are other religious communities out there that are not exactly eager to go by someoen elses religious calendar and the scientific community agreed that we all would be able to use a more religion-neutral way to count years.

 

[painted wolf]

I was curious about Rational Wiki, having never used it. It seems a bit like Wikipedia, so I wondered what Rational Wiki had to say about them....

Hmmm......"atheist propoganda"?
I'll pass on Rational Wiki.

I think you need to read further to find the humor. Some subjects are allowed a rather light tone.

You may actually find much of the site quite amusing as well as informative.

wa:do

 

[FunctionalAtheist]

Tiger snakes have only been on Trefoil Island for 30-40 years and the jaws of their hatchlings are still small. However, they’re also plastic – if they eat big meals, they’ll grow bigger. On Carnac Island, tiger snakes have been around for 90 years and there, the hatchlings have moderately sized jaws and a relatively high degree of plasticity. On Williams Island, the tiger snakes have been cut off from the mainland for 9,100 years and their jaws are not only large from birth but their growth has very little plasticity.

I find very little if anything I wasn't taught 30 years ago. The development of a second thorax by flies may seem odd. But consider that insects undergo metamorphosis, where their entire body is turned to liquid and then reformed into a new body, and really is not that strange.

Lamarkism? I'm not seeing it. Yes Lamark's theory was that aquired characteristics could be inherited. To test his theory, he chopped the tail off of rats for generation after generation, and predicted that before long rat's would be born without tails.

What we have here is not an aquired trait in this sense. In fact it is an existing trait. It is already in the genotype, and was merely not expressed in the phenotype.

When we talk about plasticity, there are two frames of reference. Both can be seen here. The fact that a 'young' snake's head could grow is phenotypic plasticity. The fact that there are genes for different sizes of heads (even if phenotypic plasticity was not present) is genotypic plasticity.

Humans show phenotypic plasticity. Humans have traveled the earth and been all over. Then number of sweat glands they have is dependent on where they were raised. Think of it like this, just because a human has been born, does not mean they are completlely develooped. This should be obvious looking at any baby. Part of the continued ontological develpment of the human includes 'turning on' the optimum number of sweat glands for the environment in which they live out their first 6 or 8 years of life. People in hot clilmates have more sweat glands because they need them. People in cold cimates would lose excess body moisture and would have to spend more metabolic energy to maintaine body temperature with too many sweat glands. Once the person is older, that number of glands is fixed. Moving has no effect after about age 8.

(Hem, that explains why children who spend all their time indoors as youngsters complain about the heat so much.)

After 9,000 years you can expect the snake's heads to all be big and even genetic plasticity to be lost. Genetic plasticity, which is nothing more than genetic variability, serves the purpose of allowing each generation to tap into different traits as the envionment changes or they move to different environments. Every generation, the frequency of the genes not currently needed decrease little by little. After enough generations of that version not being useful, it has disappeared.