[From the diaries by susanhu.] The following are selections from an article from the Seattle Post-Intelligencer entitled: STARTLING STUDY ON TOXINS’ HARM WSU FINDINGS SHOW THAT DISORDERS CAN BE PASSED ON WITHOUT GENETIC MUTATIONS
I’m trying to get a handle on this but anyway you look at it this is stunning and exciting news. If this is supported by further experimental evidence implications start with a revolution in evolutionary biology and go on from there.
Read the link and be prepared for a shock. Teaser quotes follow:
It’s just a study involving a few rats with fertility problems in Pullman, but the findings could lead to fundamental changes in how we look at environmental toxins, cancer, heritable diseases, genetics and the basics of evolutionary biology.
Skinner’s team at WSU and colleagues from several other universities report in today’s Science magazine on what they believe is the first demonstration and explanation of how a toxin-induced disorder in a pregnant female can be passed on to children and succeeding generations without changes in her genetic code, or DNA.
The report in Science, entitled “Epigenetic Transgenerational Actions of Endocrine Disruptors and Male Fertility,” also sounds like an attempt to avoid attention. That’s unlikely to work. The findings prompt serious and, in some cases, disturbing questions about a number of basic assumptions in biology.
The standard view of heritable disease is that for any disorder or disease to be inherited, a gene must go bad (mutate) and that gene must get passed on to the offspring.
What Skinner and his colleagues did is show that exposing a pregnant rat to high doses of a class of pesticides known as “endocrine disruptors” causes
an inherited reproductive disorder in male rats that is passed on without any genetic mutation.
It’s not genetic change; it’s an “epigenetic” change. Epigenetics is a relatively new field of science that refers to modifying DNA without mutations in the genes.
“It’s not a change in the DNA sequence,” Skinner explained. “It’s a chemical modification of the DNA.”
… the common wisdom has been that any artificially induced epigenetic modifications will remain as an isolated change in an individual. Because no genes get altered, the changes cannot be passed on.
“We showed that they can be,” Skinner said.
The standard view is that the environment has no direct influence, except in how it may favor or discriminate against the creatures with the latest genetic mutations.
The WSU study, Skinner said, suggests the possibility that environmental factors such as toxins may also directly cause heritable changes in creatures. “Epigenetics may be just as important as genetics in evolution,” he said.
I can’t find a copy of _Science_ nor can I get a hold of anybody. But let me give a couple of links to help put this in perspective.
The Endrocrine system is comprised of the glands that produce hormones. See here for a discussion.
Endocrine _disruptors_ are a group of pesticides containing choline, among other man-made chemicals. See here for more information.
Epigenetic Inheritance is the transmission of information (broadly defined) to descendents *without* being encoded in the DNA sequence of a gene. You will find explication here.
I note, from this reference, “…epigenetic heredity seems to exist transgenerationally in complex organisms can be explained by allowing for minor epigenetic changes not affecting totipotency. This puts some constraints on the extent to which epigenetic changes can be brought upon DNA, but it allows for EISs to play direct evolutionary roles.”
I’m just going to give a short precis of what this all means.
From the Seattle Post-Intelligencer article, “If a pregnant woman is exposed to a pesticide at the wrong time, the study suggests, her children, grandchildren and the rest of her descendants could inherit the damage and diseases caused by the toxin — even if it doesn’t involve a genetic mutation.”
In short, the use of Endocrine disrupting pesticides potentially affect _the rest of human existence_!
A study conducted at Dartmouth Medical School suggests low levels of arsenic exposure may may also trigger Endocrine disruption. Is this, too, Epigenetically transmitted? Who knows?
In Evolutionary Theory there is a problem in describing how to allow for the production of specific beneficial (and unbeneficial) heritable variation in response to environmental signals. Epigenetic Inheritance fits the bill perfectly. I want to stress Epigenetic Inheritance is an expansion of – addition to – the current Theory of Evolution *NOT* a replacement *of* the current Theory.