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Previous research has shown that bad rat mothering can be passed down through this kind of DNA modification--but those changes are thought to be triggered specifically by maternal behavior. In the new study, researchers also had healthy mothers raise the offspring of stressed mothers, and found that the problems were only partially fixed. That suggests that the changes "were not due to their neonatal experience," says David Sweatt, a neuroscientist at the University of Alabama at Birmingham, who oversaw the study. "It was something that was already there when they were born." The research was published online last month in Biological Psychiatry.
The results of both studies are likely to be controversial, perhaps resurrecting a centuries-old debate. "It's very provocative," says Lisa Monteggia, a neuroscientist at the University of Texas Southwestern Medical Center, in Dallas. "It goes back to two schools of thought: Lamarck versus Darwin."
In contrast to natural selection, in which organisms that are born well adapted to their environment survive and reproduce, passing down those successful traits, Lamarckian evolution suggests that animals can develop adaptive traits, such as better memory, during their lifetimes, and pass on those traits to their offspring. The latter theory was largely abandoned as Darwin's, and later Mendel's, theories took hold. But the concept of Lamarckian inheritance has made a comeback in recent years, as scientists learn more about epigenetics.
"I didn't set out to come up with findings that support neo-Lamarckian inheritance," says Sweatt. "But the research now makes it more plausible that these things may be real and may be based in molecular mechanisms."
Feig, on the other hand, argues that while the findings are "a Lamarckian kind of phenomenon it's still Darwinian, because the changes don't last forever." In Feig's study, the offspring of enriched mice lost their memory benefits after a few months.
Sweatt and others say that this type of inheritance may in fact be much more common than expected. Improving technologies are now providing a broader look at the epigenetic changes linked to environment and behavior. Scientists are starting to use DNA microarrays, which over the past few years have become widely employed in genetic studies of disease, to look at one specific type of change, known as DNA methylation. "The changes we see are not limited to a small number of genes," says Szyf, who is using the technology to study epigenetics and cancer. "Whole circuitries are changed."
DNA sequencing, which is rapidly dropping in price, can also be used to study DNA methylation. But epigenetics studies require high-volume sequencing, which has been prohibitively expensive. "In contrast to the genome, every epigenome is different in different types of cells," says Sweatt. "A human epigenome project would be the equivalent of 250 human genomes, because there are at least 250 cell types in the body." Cheap sequencing may soon make that type of study possible, he says.
The actual mechanism underlying these patterns of inheritance is somewhat mystifying to scientists. Feig theorizes that environmental enrichment triggers a long-lasting hormonal change: when the animal becomes pregnant, the hormone would somehow modify the DNA of the fetus, ultimately causing it to have improved memory and LTP as an adolescent. However, he cautions, there is no direct evidence of this, and no specific evidence that the behaviors are transmitted through epigenetic mechanisms.
Worms given life-span-enhancing mutations produce offspring that lack the responsible genes but live longer anyway.
A startup is targeting diseases including cancer using epigenetic approaches.
I was reading an article about "Black-White Gap Widens Faster for High Achievers" and, based on a commentary done by someone named Mikke on the site http://hip.weblogs.hopkins.k12.mn.us/, I belive it would be very interesting to the authors to read the paper and the comment. They are both related with the experiment.
Lamarckian evolution is still Darwinian
Even if Lamarckian evolution happens, it is still hierarchically under Darwinian rule. This is because all the molecular machinery involved in epigenetic changes is still encoded by genes. And all these genes are ultimately under Darwinian "rule".
So epigenetic/Lamarckian changes only serve to temporarily nuance the phenotype.
Think of Darwinian selection as the big brush, which paints 90% of the picture. Then think of the epigenetic changes, as the small, finishing brush that fills in the small details, and brings nuance to the picture.
last year in other magazine, Science News I think.
Basically saying that environment of the genes / cells can activate certain cellular machinery (RNA) in the parent as part of everyday living, i.e. better nutrition or certain bio-chemicals or state of the body.
And, as the article says, this has large consequences on the offspring. This makes sense because we know intuitively and by examples that health of the mother animal or parent plant produce healthier babies / non-stunted or more seed.
Now we see that genes get a jump start depending on state of the parent. Not exactly the same but similar in principle.
This is by no means a setback for Darwinian theory, as I'm sure some will posit. Check, recheck, adjust...it's all the nature of the beast. I have long believed in my gut that Lamarck would eventually regain some cred, but alas, I can find no place where I have said so publicly. Guess I don't have "told you so" bragging rights.
Just for the record, I found it from Feb. of 2007: http://bit.ly/4nZJLL
Darwinism is not synonymous with evolutionary theory. Evolutionary theory has progressed since Darwin and will continue to evolve. The common sort of simple-minded pseudo-scientific dogmatism that believes that all past and future observations are already explained by current theories is a principal impediment to scientific progress. Much more is inherited than a just the sequence of DNA bases. Selection operates on more than one level. Inheirited attributes are not always passive or simple, but may be patterns of coordinated epigenetic response.
I first learned the term "epigenetic" reading "Neural Darwinism - The Theory of Neuronal Group Selection" by Nobelist Gerald Edelman some 20 years ago. Then he wrote of an high-dimensional "epigenetic landscape" with branching paths such that the developing organism's state would roll down one or another branch at each of many forks according to chance and environmental influences. The genetic code is not a fixed linear tape, but rather a library of code which can be called in many different orders and patterns of simultaneous activation. The newer concepts of epigenetics such as methylation patterns add to rather than replace that point of view.
It has long seemed odd to me that girls are born with all the eggs that they will ever have. Each of our cells traces its lineage back to a single cell which developed in our maternal grandmother's womb. The development of our mothers' ova could potentially be affected by the environment of our grandmothers' wombs. I can see no evolutionary reason for this curious arrangement other than to ensure that such influences actually happen.
As everyone should realize as interesting as this is, novel research is often inaccurate or misinterpreted. I would really like to see this research continued and built upon. Until that time it should be treated carefully before we claim too much from it.
How does this differ so much from the studies that support acquired resistant mutations by fruit flies to, say, DDT--which is passed on to offspring? The fact is, genes learn. They memorialize adaptations. One also suspects that an unchanged archival blueprint for genes may exist as well, perhaps in all the so-called latent DNA material. Although it may sound unrelated, Sheldrake's morphic resonance may have a biologic basis in this regard.
Manufacturing in the United States is in trouble. That's bad news not just for the country's economy but for the future of innovation.
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1 Comment
It's not Lamarck vs Darwin
We should stop thinking of it (and reporting it) as a fight between the ideas and concepts of Lamarck *versus* Darwin. These are simply two different but complementary methods of increasing the fitness of a line of individuals. Tech Review could help lead us to this new way of thinking by promoting their complementarity rather than their competition.
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